REPORT D-27 B-VHF Deployment Scenario · Project co-funded by the European Community within the 6th Framework Programme (2002-2006) REPORT D-27 B-VHF Deployment Scenario

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Project co-funded by the European Community within the 6th Framework Programme (2002-2006)

REPORT D-27 B-VHF Deployment Scenario

PROJECT NUMBER: AST3-CT-2003-502910

PROJECT ACRONYM: B-VHF

PROJECT TITLE: BROADBAND VHF AERONAUTICAL COMMUNICATIONS

SYSTEM BASED ON MC-CDMA

INSTRUMENT: SPECIFIC TARGETED RESEARCH PROJECT

THEMATIC PRIORITY: AERONAUTICS AND SPACE

PROJECT START DATE: 01.01.2004

DURATION: 33 MONTHS

PROJECT CO-ORDINATOR: FREQUENTIS GMBH (1) (FRQ) A

PRINCIPAL CONTRACTORS: DEUTSCHES ZENTRUM FÜR LUFT UND RAUMFAHRT E.V. (2) (DLR) D

NATIONAL AIR TRAFFIC SERVICES (EN ROUTE) PLC (3) (NERL) UK

LUFTHANSA GERMAN AIRLINES (4) (LH) D

BAE SYSTEMS (OPERATIONS) LTD (5) (BAES) UK

SCIENTIFIC GENERICS LTD (6) (SGL) UK

UNIVERSITEIT GENT (7) (UGent) B

UNIVERSIDAD POLITECNICA DE MADRID (8) (UPM) E

PARIS LODRON UNIVERSITAET SALZBURG (9) (UniSBG) A

DEUTSCHE FLUGSICHERUNGS GMBH (10) (DFS) D

UNIVERSIDAD DE LAS PALMAS DE GRAN CANARIA (11) (ULPGC) E

DOCUMENT IDENTIFIER: D-27

REVISION: 1.0

DUE DATE: 02.06.2006

SUBMISSION DATE: 03.10.2006

LEAD CONTRACTOR: FREQUENTIS

DISSEMINATION LEVEL: PU - PUBLIC

DOCUMENT REF: 04A02 E507.10

Contract number: AST3-CT-2003-502910 Report number: D-27 Issue: 1.0

File: D-27 Deployment Scenario_10.doc Author: Frequentis

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History Chart

Issue Date Changed Page (s) Cause of Change Implemented by

DRAFT 01 14.06.2006 All sections New document Frequentis

DRAFT 02 01.08.2006 Added section 1, 3, 6, 8, 14 Modified section 5, 7, 13

Frequentis

1.0 26.09.2006 Added section 2, 12

Modified section 4, 5, 6, 7, 10

Frequentis

Authorisation

No. Action Name Signature Date

1 Prepared M. Sajatovic 2006-09-26

2 Approved B. Haindl 2006-10-03

3 Released C. Rihacek 2006-10-03

All rights reserved.

The document is proprietary of the B-VHF consortium members listed on the front page of this document. No copying or distributing, in any form or by any means, is allowed without the prior written agreement of the owner of the proprietary rights.

Company or product names mentioned in this document may be trademarks or registered trademarks of their respective companies.

CCMU

Dokumentenfreigabe



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Contents

1. Introduction .................................................................1-1

2. Executive Summary.......................................................2-1

3. Scope..........................................................................3-1

4. Pre-requisites ...............................................................4-1 4.1. General Pre-requisites .................................................................... 4-1 4.2. Required B-VHF RF Performance ...................................................... 4-1

5. B-VHF System Parameters..............................................5-1 5.1. Parameters of the B-VHF Radio Chain ............................................... 5-1 5.2. Signal Constellations ...................................................................... 5-3 5.2.1. B-VHF � Narrowband Signal Constellations ........................................ 5-3 5.2.2. Frequency Spacing......................................................................... 5-4 5.3. Parameters of the B-VHF System Operating in the VHF Range .............. 5-5 5.3.1. B-VHF PHY Simulations................................................................... 5-7 5.3.2. Laboratory Measurements ............................................................... 5-9 5.4. B-VHF RX Protected Signal Level .................................................... 5-11 5.5. B-VHF TX Power .......................................................................... 5-11 5.6. B-VHF TX Signal Power Variation with Frequency Range .................... 5-13 5.6.1. VHF COM Range .......................................................................... 5-13 5.6.2. VOR Range ................................................................................. 5-13 5.6.3. DME Range ................................................................................. 5-13 5.6.4. MLS Range.................................................................................. 5-14 5.7. Spectra of Signals ........................................................................ 5-15 5.7.1. DSB-AM...................................................................................... 5-15 5.7.2. VDL ........................................................................................... 5-16 5.7.3. Signal Spectra of Narrowband VHF Systems..................................... 5-16 5.7.4. B-VHF Spectrum (VHF Range) ....................................................... 5-17 5.7.5. B-VHF Spectrum (DME Range)....................................................... 5-19



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5.7.6. B-VHF Spectrum (MLS Range) ....................................................... 5-21 5.7.7. B-VHF Spectrum (VOR Range) ....................................................... 5-21

6. Spectrum Management Guidelines ...................................6-1 6.1. Separation Distances...................................................................... 6-1 6.1.1. B-VHF Interference Scenarios .......................................................... 6-2 6.2. Interference Environment of a B-VHF Cell.......................................... 6-3 6.3. Approach for B-VHF Frequency Planning............................................ 6-6 6.3.1. General Procedure ......................................................................... 6-7 6.3.2. DSB-AM Victim Receiver � B-VHF Interferer....................................... 6-8 6.3.3. VDL Victim Receiver � B-VHF Interferer............................................. 6-8 6.3.4. B-VHF Victim Receiver � DSB-AM or VDL Interferer............................. 6-9 6.3.5. B-VHF Victim Aircraft Receiver � Interfering B-VHF GS ........................ 6-9 6.3.6. B-VHF Victim GS Receiver� Interfering B-VHF Aircraft ....................... 6-10 6.4. Interaction of DSB-AM and B-VHF Signals........................................ 6-11 6.5. Results of B-VHF Laboratory Tests.................................................. 6-12 6.6. B-VHF System Deployment in the DME Range .................................. 6-13 6.6.1. B-VHF System Interaction with UAT/DME/MIDS/JTIDS Systems.......... 6-13 6.7. B-VHF System Deployment in the MLS Range .................................. 6-14 6.8. B-VHF System Deployment in the VOR Range .................................. 6-14

7. Initial B-VHF System Deployment Scenarios......................7-1 7.1. Common Aspects ........................................................................... 7-1 7.1.1. B-VHF Operational Scenarios and Functional Scope............................. 7-1 7.1.2. Applicable Spectrum Ranges............................................................ 7-2 7.1.3. Aircraft Capabilities ........................................................................ 7-2 7.1.4. Airspace Regimes........................................................................... 7-3 7.1.5. Spectrum Usage Options................................................................. 7-4 7.1.6. System Configuration Options.......................................................... 7-5 7.1.7. Ground B-VHF System Architecture .................................................. 7-5 7.1.8. Airborne B-VHF System Architecture................................................. 7-7 7.1.9. B-VHF Cellular Concept................................................................... 7-9 7.1.10. Size of B-VHF Cells....................................................................... 7-10 7.2. B-VHF System Deployment in the VHF COM Range ........................... 7-15 7.2.1. Common Aspects of VHF Deployment Scenarios ............................... 7-15



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7.2.2. Option 1 �Introduction in B-VHF-supported Airspace (APT) ................ 7-19 7.2.3. Option 2 �Introduction in B-VHF-supported Airspace (TMA)................ 7-23 7.2.4. Option 3 � Introduction in B-VHF-supported Airspace (ENR)............... 7-26 7.2.5. Option 4� Introduction in B-VHF Airspace (ENR HIGH) ...................... 7-29 7.3. B-VHF System Deployment in the DME Range .................................. 7-31 7.3.1. B-VHF System Data-only Deployment in the Target DME Range.......... 7-33 7.3.2. Integrated B-VHF System Deployment in the Target DME Range......... 7-38 7.4. B-VHF System Deployment in the MLS Range .................................. 7-39 7.5. B-VHF System Deployment in the VOR Range .................................. 7-41

8. Transition Scenarios ......................................................8-1 8.1. Common Aspects ........................................................................... 8-1 8.1.1. B-VHF Operational Scenarios and Services Provided............................ 8-1 8.2. Transition in the VHF COM Range ..................................................... 8-2 8.2.1. B-VHF System Spatial Expansion...................................................... 8-2 8.2.2. Change in the Spectrum Availability.................................................. 8-4 8.2.3. Adding New Services ...................................................................... 8-5 8.2.4. Ground Infrastructure Evolution ....................................................... 8-6 8.2.5. Airborne Equipage Evolution ............................................................ 8-7 8.3. Transition in the non-VHF COM Ranges ............................................. 8-8 8.3.1. B-VHF System Spatial Expansion...................................................... 8-8 8.3.2. Change in the Spectrum Occupancy.................................................. 8-9 8.3.3. Adding New Services ...................................................................... 8-9 8.3.4. Ground Infrastructure Evolution ..................................................... 8-10 8.3.5. Airborne Equipage Evolution .......................................................... 8-10

9. Final B-VHF System Deployment Scenarios .......................9-1 9.1. Common Aspects ........................................................................... 9-1 9.1.1. B-VHF Operational Scenarios and Functional Scope............................. 9-1 9.2. Final B-VHF System Deployment in the VHF COM Range...................... 9-2 9.2.1. B-VHF System Spatial Expansion...................................................... 9-2 9.2.2. Change in the Spectrum Availability.................................................. 9-4 9.2.3. Adding New Services ...................................................................... 9-4 9.2.4. Ground Infrastructure Evolution ....................................................... 9-5 9.2.5. Airborne Equipage Evolution ............................................................ 9-6



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9.3. B-VHF System Deployment in the non-VHF COM Ranges ..................... 9-7 9.3.1. B-VHF System Spatial Expansion...................................................... 9-7 9.3.2. Change in the Spectrum Availability.................................................. 9-7 9.3.3. Adding New Services ...................................................................... 9-8 9.3.4. Ground Infrastructure Evolution ....................................................... 9-8 9.3.5. Airborne Equipage Evolution ............................................................ 9-8

10. Non-B-VHF Aeronautical Communications Systems ..........10-1 10.1. Introduction ................................................................................ 10-1 10.2. Current and Future VHF Communication Systems ............................. 10-1 10.2.1. Current VHF Communication Systems ............................................. 10-1 10.2.2. Future VHF Communication Systems .............................................. 10-3 10.3. Current and Future non-VHF Systems ............................................. 10-4 10.3.1. Current non-VHF Systems............................................................. 10-4 10.3.2. Future non-VHF Systems .............................................................. 10-5 10.3.3. Applicability of Communication Systems for CoS Classes ................... 10-7 10.4. Distribution of Services between B-VHF and Other Systems ............... 10-8

11. B-VHF Standardisation Concept.....................................11-1 11.1. Introduction ................................................................................ 11-1 11.2. General Approach for Certification of Airborne Systems ..................... 11-1 11.2.1. ICAO.......................................................................................... 11-2 11.2.2. EUROCAE/RTCA........................................................................... 11-3 11.2.3. JAA/EASA/FAA............................................................................. 11-4 11.2.4. ARINC........................................................................................ 11-5 11.2.5. ETSI .......................................................................................... 11-5

12. Conclusions ................................................................12-1

13. References .................................................................13-1

14. Abbreviations .............................................................14-1



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Illustrations

Figure 1-1: -VHF Project Work Breakdown Structure Overview.............................. 1-3 Figure 5-1: B-VHF Radio Chain......................................................................... 5-1 Figure 5-2: Relative Position of B-VHF and Narrowband Signals ............................ 5-3 Figure 5-3: Results of B-VHF PHY Simulations [B-VHF D23]................................ 5-10 Figure 5-4: Explanation of the DSB-AM and VDL Spectra.................................... 5-15 Figure 5-5: Signal Spectra of Narrowband VHF Systems..................................... 5-16 Figure 5-6: Explanation of the B-VHF Spectrum ................................................ 5-17 Figure 5-7: Estimated B-VHF Spectrum ........................................................... 5-18 Figure 5-8: Spectra of Signals in the DME Range .............................................. 5-20 Figure 6-1: B-VHF Cell and Interference Zones ................................................... 6-3 Figure 6-2: Distance d_S................................................................................. 6-6 Figure 6-3: B-VHF to B-VHF Interference ......................................................... 6-10 Figure 6-4: DSB-AM and B-VHF Signals ........................................................... 6-11 Figure 7-1: Airspace Regimes........................................................................... 7-4 Figure 7-2: Ground B-VHF System.................................................................... 7-6 Figure 7-3: Airborne B-VHF Sub-system ............................................................ 7-7 Figure 7-4: B-VHF Cell DOCs (CDOCs)............................................................. 7-10 Figure 7-5: London Airports� Coverage at 500 ft................................................ 7-12 Figure 7-6: London TC Coverage at 500 ft ....................................................... 7-12 Figure 7-7: London TC Coverage at 1500 ft...................................................... 7-13 Figure 7-8: London ACC Coverage at 4500 ft.................................................... 7-14 Figure 7-9: Coupling of DSB-AM and B-VHF Voice System via VCS ...................... 7-18 Figure 7-10: Constellation of Local Channels at Heathrow Airport.......................... 7-20 Figure 7-11: Ground Measurements � Heathrow Tower ....................................... 7-21 Figure 7-12: Spectrum Availability at 2500 ft above GND (1 MHz BW, -80 dBm) ..... 7-22 Figure 7-13: Spectrum Availability at FL 250 (1 MHz bandwidth, -75 dBm)............. 7-24 Figure 7-14: Spectrum Availability at FL 245 (1 MHz, -80 dBm, ENR high) ............. 7-30 Figure 7-15: Usage of ARNS Band 960 � 1215 MHz............................................. 7-32 Figure 7-16: Single RF Channel B-VHF Operation Based on TDMA ......................... 7-37 Figure 9-1: B-VHF Airspace Expansion............................................................... 9-3



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Tables

Table 5-1: VHF Signal Parameters ................................................................... 5-6 Table 5-2: Constellation of Interferers as Used for Simulations ............................ 5-7 Table 5-3: Results of B-VHF Laboratory Measurements ....................................... 5-9 Table 5-4: Transmitted B-VHF TX Power......................................................... 5-14 Table 6-1: Minimum DSB-AM - VDL Separation Distances (m) ............................. 6-1 Table 6-2: B-VHF - NB Interference Cases ........................................................ 6-2 Table 6-3: B-VHF � Calculated Separation Distance d_W for f= 118 MHz............... 6-4 Table 7-1: Typical Coverage of Narrowband GSs.............................................. 7-11 Table 10-1: Mapping of Services onto Communication Systems ........................... 10-8



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1. Introduction

Air transport has been identified as dominant factor for sustainable economic growth of the European Union. The "Vision 2020" clearly points out the cornerstones of a future air transport system and the Advisory Council for ATM Research in Europe (ACARE) elaborates these requirements in depth in their "Strategic Research Agenda".

A/G communication is the key enabler for achieving an Air Transport System that is capable of meeting future demands. The communications in the VHF aeronautical communications (COM) band (118 - 137 MHz) are particularly attractive as they provide adequate coverage with moderate equipment power and acceptable price.

Today, an analogue VHF voice communications system is still used for tactical aircraft separation and guidance. This communications technology has been introduced in the '40s and generally utilises the available VHF spectrum in an inefficient and inflexible manner. A small part of the COM spectrum is used by several types of aeronautical data links (ACARS, VDL Mode 2, and VDL Mode 4) for safety-related data link communications.

After 2010, the VHF COM band in Europe is expected to become progressively saturated. This is expected to happen in spite of the recent introduction of the 8.33 kHz DSB-AM voice system and the VDL Mode 2 data link that both use the VHF spectrum in a more efficient manner than the "old" solutions. The main reason for the saturation is the traditional ATM operational concept based on the tactical control of aircraft that generates increased demand for voice communications channels proportional to the increase in air traffic itself.

The problem can only be solved by adopting new ATM concepts. Strategic European documents and recent studies indicate that a relief after 2010 may be achievable with intensive usage of the aeronautical data link. The tactical Air Traffic Control (ATC) will shift towards strategic Air Traffic Management (ATM), and at the same time the demand for new VHF voice communications channels would be reduced.

Today�s VHF solutions � including VDL Mode 2 data link - cannot fulfil performance and capacity requirements of future data link applications.

As there are no plans to deploy VDL Mode 3 system in Europe, VDL Mode 4 remains as only European option to replace VDL Mode 2 data link in the future. VDL Mode 4 as a pure data link technology without support for voice communications is capable to solve only a part of the congestion problem. In order to provide expected data link capacity, VDL Mode 4 would require multiple VHF channels that are difficult to find and co-ordinate. As there are still some unresolved architectural issues, there is no guarantee that VDL Mode 4 airborne radio can be operated without interference with analogue VHF voice radios.

EUROCONTROL�s Communications Strategy clearly points out the need for alternative communications systems. Air Traffic Service Providers (ATSPs) prefer keep on using their existing ground communications facilities, so an integrated voice-data system in the VHF range would be highly appreciated, being capable of using same physical locations of ground stations and same interconnecting infrastructure as the current VHF system. Therefore, more and more attention in Europe is directed towards broadband VHF technologies.

Within the course of the B-VHF project bottom up research on multi-carrier technology (MC) for aeronautical communications is carried out. This work will result in the definition of a new future MC broadband VHF (B-VHF) system, which is able to support Single




European Sky, Free Flight and other advanced concepts and programmes, leading far beyond 2015 into Vision 2020. The B-VHF project is conducted under Priority #4/ Aeronautics and Space of the Sixth Framework Programme (FP6) of the European Commission (EC).

The target technology is MC-CDMA, a highly innovative, high capacity technology that is also discussed for fourth generation (4G) mobile communications systems. However, the project will investigate possible implementation outside the VHF range, as well as non-CDMA access schemes.

The B-VHF system has the potential to exploit the mobile VHF aeronautical channel better than any currently discussed VHF communication alternative. It increases voice and data capacity and addresses security and safety issues, promising a service level that is today unknown to the aeronautics user. Moreover, it has the potential to preserve the excellent inherent cost-range characteristics of the VHF band. It may eventually be applied as an overlay system and co-exist with the available VHF infrastructure, providing smooth transition and rollout scenarios.

The proposed B-VHF system will support both voice and data link communications. The main expected benefits of the future B-VHF communications system are:

! High spectral efficiency - the broadband B-VHF system uses VHF spectral resources more efficiently than today's narrowband VHF communications systems

! High communication capacity - the total capacity of the B-VHF system is higher than the aggregate capacity of VHF systems deployed today or planned for a near future

! Flexibility - the B-VHF system may be easily adapted to provide support for new operational and communications requirements

! Security - the B-VHF system is inherently resistant against narrowband jamming and provides mechanisms supporting end-to-end data security

! Sound transition path - the B-VHF system uses the knowledge about the current usage of VHF spectrum and may be able to share the VHF spectrum with legacy narrowband VHF systems without adverse interfering effects

The high-level goal of the B-VHF project - proving the feasibility of the broadband MC-CDMA technology and demonstrating its benefits to the aeronautical community - requires a series of interrelated tasks that have been encapsulated as five separate work packages in the B-VHF project:

! WP 0 � "Project Management and Quality Assurance"

! WP 1 � "B-VHF System Aspects"

! WP 2 � "VHF Band Compatibility Aspects"

! WP 3 � "B-VHF Design and Evaluation"

! WP 4 � "B-VHF Testbed"

Figure 1-1 summarises the detailed work breakdown of the B-VHF project, including main work packages and all sub-work packages:




Research, technologicaldevelopment and innovation

ProjectManagement

WP 1B-VHFSystemAspects

WP 2VHF BandCompatibilityAspects

WP 3B-VHFDesign andEvaluation

WP 1.1B-VHFOperationalConcept

WP 1.2ReferenceEnvironment

WP 1.3B-VHFDeploymentScenario

WP 2.1Theoretical VHFBandCompatibilityStudy

WP 2.2VHF ChannelOccupancyMeasur.

WP 2.3InterferenceModelling

WP 3.2PHY LayerDesign & SWImplementation

WP 3.3DLL LayerDesign & SWImplementation

WP 3.5B-VHFEvaluation

WP 3.4Protocol Design& SWImplementation

WP 0ProjectManagementand QualityAssurance

WP 0.1ProjectManagement

WP 0.2Validation andQM

WP 0.3KnowledgeManagement

WP 3.1VHF ChannelModelling

WP 4B-VHFTestbed

WP 4.1BasebandImplementation

WP 4.2VHF FrontendDevelopment

WP 4.3B-VHF TestbedEvaluation

Figure 1-1: B-VHF Project Work Breakdown Structure Overview

WP 0 "Project Management and Quality Assurance" comprises all activities that are essential to all work packages. It takes care of achieving high quality results throughout the whole project. It covers all management activities on Consortium level, in particular the information exchange and co-ordination with the European Commission and with the partners. A separate sub-work package has been destined for the validation and quality control which reflects the importance of maintaining high quality outputs in all project phases. Another sub-work package is dedicated to manage new knowledge generated within the B-VHF project in terms of intellectual property rights and dissemination strategies.

WP 1 "B-VHF System Aspects" establishes the necessary connection between the scope and goals of the B-VHF project and the high-level objectives of the EC, European and global aeronautical community. Starting at the very beginning of the B-VHF project, this work package will produce high-level requirements for the B-VHF system, describe the reference aeronautical environment and produce the B-VHF Operational Concept document. By the end of the B-VHF project, the WP 1 will produce the B-VHF Deployment Scenario document, describing technological, operational and institutional issues of the B-VHF initial deployment, transition and operational usage.

WP 2 "VHF Band Compatibility Aspects" assesses by theoretical (modelling) and practical (measurements) means probably the most critical aspect of the future B-VHF




broadband channel: its capability to be installed and operated "in parallel" with legacy narrowband channels, sharing the same part of the VHF spectrum, but remaining robust against interference coming from such legacy narrowband VHF systems. The investigations will also address the conditions for interference-free operation of the B-VHF system towards legacy narrowband VHF systems. The Theoretical VHF Band Compatibility Study developed in the WP 2 will provide inputs to the WP 1 required for the development of the B-VHF Deployment Scenario. Together with the B-VHF Interference Model developed in the WP 2, the Theoretical VHF Band Compatibility Study will also be used as input for the B-VHF system design and evaluation (WP 3).

WP 3 "B-VHF Design and Evaluation" covers B-VHF system design tasks, starting with developing the model of the broadband VHF channel, and proceeding with the development and implementation of the SW representing the physical (PHY) B-VHF layer, DLL layer, higher protocol layers and representative aeronautical applications. The design and implementation tasks will be augmented by the development of detailed evaluation plans and corresponding simulation scenarios. The B-VHF Evaluation Reports produced in the WP 3 will provide necessary feedback to the B-VHF Deployment Scenario task of the WP 1. The WP 3 will also produce as a deliverable a complete set of the B-VHF System Design and Specification documents.

The prime objective of the B-VHF project - demonstrating the capabilities of the MC-CDMA technology - will be achieved within the scope of the WP 3 by using intensive and layered simulation trials. This task will start with investigating the capabilities and performance of the B-VHF physical layer and will proceed by adding/integrating the DLL and upper protocol layers, respectively. The "generic" B-VHF technology validation will be concluded by considering specific requirements coming from the aeronautical environment and applications. The WP 3 will develop and implement a SW set of representative communications applications and verifies by simulation means that the B-VHF system can support a mix of such applications under nearly-realistic loading, while fulfilling the Quality of Service (QoS) and other requirements of each particular application.

WP 4 "B-VHF Testbed" covers the baseband implementation and evaluation of a first B-VHF testbed for both the forward- and the reverse-link. The implementation is carried out in DSP technology and is restricted to the physical layer, which is the most critical part of the B-VHF development. The B-VHF baseband implementation is interfaced to the low-power broadband VHF frontend, thus, enabling testbed evaluation not only in the baseband but also in the VHF band. Testbed evaluation in the baseband is performed using channel and interference models, which are also implemented in DSP technology. The VHF band evaluation is carried out in the laboratory using actual VHF systems as interference sources and victim receivers, respectively.

----------- END OF SECTION -----------




2. Executive Summary

This document � �B-VHF Deployment Scenario� � describes different scenarios for the deployment of the B-VHF system in both the VHF COM range as well as in other spectrum ranges anticipated to be used by new aeronautical communications systems.

The B-VHF project is investigating the feasibility of a new aeronautical communications system based on MC-CDMA. Many tasks have still to be fulfilled, including the refinement of the B-VHF system design and more precise specification of the system parameters.

Chapter 4 identifies some requirements that should be considered in the future work. Developing representative mature radio hardware was clearly outside scope of the B-VHF project, hence the RF front-end performance had to be assumed, as it may be critical for the system deployment.

Chapter 5 provides an initial estimate of parameters of the B-VHF system that are relevant for frequency planning and co-existence with other systems in the VHF COM range, and therefore directly influence the system deployment. These parameters are based on the results of different simulations and laboratory measurements performed under different constraints and shall be regarded as the best possible estimate instead of a mature set of parameters.

As it is expected that an airborne B-VHF transmitter operating in the VHF range will become an extension of the existing airborne VDR standards, it has been proposed to limit the maximum allowed total signal power of an airborne B-VHF transmitter to the same level as already applied for existing VDR 750 radios operating in the DSB-AM mode (25 W respectively +44 dBm). It can be concluded that with assumed number of carriers and -100 dBm minimum detectable per-carrier signal power at the RX input the above limit would not be reached for cell sizes up to 60 nm, but it would be exceeded (+48 dBm) for large ENR cells (175 nm radius).

Estimates of the required transmitted power in non-VHF ranges allow the conclusion that in the VOR range even very large ENR cells (175 nm) could be deployed without overlay. In the MLS range only airport services could be reasonably deployed. In the DME range the operation with cells of up to 60 nm may be possible, but with increased power (+52 dBm) that, however, remains compatible to the UAT power levels [RTCA DO-282]. Knowing the spectrum of the B-VHF signal in space is of extreme importance. Unfortunately, it could not be fully derived from the laboratory measurements as not all spectrum-shaping techniques have been implemented. Therefore, only an estimate could be offered for a B-VHF TX operating in the VHF range, based on isolated simulation results combined with known relevant characteristics of narrowband systems (e.g. phase noise spectrum). Based on the VHF-estimate, similar estimates have then been constructed for the other spectral ranges (DME, MLS) under investigation.

Developing frequency planning criteria for the broadband B-VHF system is a challenging task. The procedure normally starts, as for other VHF systems, with laboratory measurements using representative B-VHF and narrowband equipment. The current results of the laboratory measurements cannot be considered as representative for the mature B-VHF system. For that reason, in Chapter 6 of this document only an outline of the frequency planning approach is given, together with some explanatory material about basic interactions between DSB-AM and B-VHF systems.

The clear focus of this deliverable is put on the development of deployment scenarios for an initial B-VHF system deployment, as well as for the system transition towards �full� deployment. In all scenarios it is assumed that an aircraft is either fully equipped with B-




VHF radios (�B-VHF aircraft�) or it continues to carry narrowband equipment (�NB aircraft�). In addition to the current situation where the entire airspace is �narrowband-one� (NB airspace), in the B-VHF scenarios two other options have been identified: one where B-VHF equipage is mandatory for all aircraft (�B-VHF airspace�) and another one (�B-VHF-supported airspace�) where B-VHF equipage is voluntary and mixed B-VHF/NB aircraft population may exist.

The initial deployment is outlined in Chapter 7 both for the VHF- and non-VHF ranges (DME, MLS and VOR). These scenarios and associated airborne and ground B-VHF system architectures are well aligned with the B-VHF operational concept [B-VHF D7]. Therefore, the B-VHF system in the early deployment phase provides support for basic voice services and an ATN-compatible air-ground data link (selective voice services, surveillance data link and downlink of aircraft parameters have been postponed to the transition/final deployment phases).

All VHF scenarios are based on overlay, as it has been assumed that this is the only feasible option in the densely populated VHF spectrum. On the contrary, all non-VHF scenarios are based on the usage of dedicated channels that are not used by other systems. This was dictated by the fact that even if overlay would be principally possible, e.g. in the DME range, the broadband nature of the existing signals-in-space makes it difficult to �port� an overlay concept developed for the narrowband systems in the VHF range.

Additionally, in all VHF scenarios an integrated voice/data B-VHF system is assumed. Airborne co-location of B-VHF and other narrowband DSB-AM systems in the VHF range, that would be the consequence of a data-only B-VHF concept, is considered to be very difficult or even impossible to realize. Radiated out-of-band noise floor and/or intermodulation products of the broadband B-VHF transmitter could e.g. prevent DSB-AM reception when the airborne B-VHF system is transmitting.

The feasibility of three generic B-VHF cell sizes, with Designed Operational Coverage (CDOC) set to 25, 60 or 175 nm, respectively, has been investigated in each scenario. While airport cells (25 nm coverage) are perceived to be easily deployable, TMA and ENR coverage seems to be only reasonable with maximum cell sizes restricted to about 60 nm. In that case aggregate TMA/ENR coverage for operational services with service DOC beyond 60 nm is achieved by implementing the corresponding service at multiple cells and using the B-VHF-internal seamless handover between such cells. For off-shore sectors with coverage requirements beyond 60 nm the ground B-VHF stations may implement high-gain antennas or beamforming in order to provide �extended� coverage.

In scenarios with mixed B-VHF/NB population a so called �gateway� feature must be realised between the B-VHF voice channel and DSB-AM voice channel. In that case the Voice Communications System (VCS) would have to get access to both B-VHF- and DSB-AM systems and route the pilots� voice messages between them.

The preferred options for the initial B-VHF system deployment in the VHF range under overlay conditions are:

! Introduction in the B-VHF-supported airspace (APT/TMA/ENR_Low)

! Introduction in the B-VHF airspace (ENR_High)

While other combinations are not precluded, the above scenarios are the preferred combination because it may become very difficult or impossible to mandate B-VHF equipage for small aircraft in APT/TMA/ENR_Low airspace from the very beginning of the B-VHF system deployment, while it may be easier to apply such a mandate for transport




aircraft flying above certain FL (similar policy could be applied for the B-VHF system as for the 8.33 kHz system introduction or for ATN/VDL Mode 2 equipage). A side benefit from conversion to the B-VHF system in ENR_High airspace would be the relieved spectrum occupancy situation, i.e. narrowband channels converted to B-VHF operation could be immediately re-used by the B-VHF system both within- and outside the converted airspace.

Similar scenarios based on data-only B-VHF system usage have been proposed for the DME and MLS range. In that case, voice services remain in the VHF range, sufficiently isolated from the data-only B-VHF system operating in non-VHF ranges. As most systems deployed in these ranges are broadband ones, the focus has been put onto deployment scenarios based on dedicated broadband channel allocations for the B-VHF system (without overlay). Sub-banding could be applied to achieve increased isolation between a B-VHF system operating in the VOR range and DSB-AM systems operating in the VHF COM range.

With a data-only approach the airborne B-VHF avionics reduces to just a single B-VHF radio with an ATN-compatible external interface. The ground B-VHF system architecture also becomes simplified, as all voice-relevant functions and components may be omitted.

Scenarios for an initial B-VHF system deployment have been used as a starting point for further discussion in Chapter 8 where transitional aspects are discussed.

The transition scenarios in the VHF COM range assume that the B-VHF system has been initially mandated for the ENR High airspace and installed on voluntary basis in ENR_Low airspace, in TMAs and at selected airports. During the transition the initial system expands and more and more airspace will be converted to either B-VHF airspace or B-VHF-supported airspace. At the same time new services are successively added to the system (e.g. selective voice for AOC usage, downlink of aircraft data or powerful ATS services for trajectory-based ATM). The impact of B-VHF system expansion in all applicable ranges upon spectrum availability in the VHF range has been discussed. Scenarios for the evolution of airborne and ground system architectures have been described, including e.g. an option for reducing the vertical boundary between the B-VHF airspace and the B-VHF-supported airspace. Similar aspects have been described for non-VHF ranges, too.

At the end of the transition phase a significant part of the narrowband spectrum resources formerly used by NB systems within the selected region has been abandoned and now these resources are used by the B-VHF system. In the final deployment phase, described in Chapter 9, the functional scope of the B-VHF system will further improve as the change in the spectrum occupancy would now allow the air-air data link and broadcast surveillance services to be deployed (ADS-B, TIS-B), as well as possibly other broadcast services (e.g. FIS-B).

In that phase a significant percentage of aircraft has already been equipped with the B-VHF radios, so the mandate for the B-VHF equipage may eventually be extended to selected TMAs and APTs (again, similar policy has been anticipated for the B-VHF system expansion as for the 8.33 kHz system). Even in that phase some parts of the European airspace still will be operated as narrowband (NB) airspace, so there will be always some boundary to other �NB regions� outside Europe.

Both transition and final B-VHF deployment scenarios assume that the B-VHF system capacity and performance would steadily increase due to the improvement in the spectrum availability. As not all services can be immediately offered by the B-VHF system, it is important to know which other systems are available during the initial B-VHF




system deployment, because such systems could relieve the B-VHF system by taking-over some services foreseen in the operational scenarios. Such systems are described in Chapter 10, comprising DSB-AM and VDL systems in the VHF range. These will remain in use within the B-VHF-supported airspace, therefore relieving the B-VHF system that shall provide same services for the equipped B-VHF aircraft. However, existing and emerging non-VHF systems like Mode S, AMSS or SDLS have significant potential to relieve the B-VHF system in the sensitive phase of its initial deployment. In particular, it is expected that the Mode S technology would provide operationally required support for downlink of aircraft parameters and surveillance link at the time where B-VHF system will not be able to provide these services.

Apparently, additional work will be needed after this initial feasibility study to establish the B-VHF system as a fully validated, mature technology that can be deployed and operationally used for safety-related aeronautical communications. It is expected that this remaining work will be done in the course of system standardisation. One chapter of this document (Chapter 11) is dedicated to the standardisation activities, identifying the most important actors and actions on the roadmap towards a mature B-VHF system.

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3. Scope

This document � �B-VHF Deployment Scenario� � describes different scenarios for the deployment of the B-VHF system in both the VHF COM range as well as in other spectrum ranges anticipated to be potentially used by new communications systems [ACPF14-WP14]. These alternative ranges are:

! Lower part (960 � 1024 MHz) of the �L� band - �DME band�

! �C� band (5091 � 5150 MHz) � �MLS band�

! VHF NAV band (108 � 118 MHz) - �VOR band�

In the following, these three candidate ranges are being called DME band, MLS band and VOR band.

This document comprises following chapters:

! 1. Introduction

! 2. Executive Summary

! 3. Scope (this chapter)

! 4. Assumptions

! 5. B-VHF System Parameters

! 6. Spectrum Management Guidelines

! 7. Initial B-VHF System Deployment Scenarios

! 8. Transition

! 9. Final B-VHF System Deployment

! 10. Non-B-VHF Aeronautical Communications Systems

! 11. B-VHF Standardisation Concept

! 12. Conclusions

! 13. References

! 14. Abbreviations

The focus of the B-VHF project has been put on checking the feasibility of a broadband aeronautical communications system, which is based on MC-CDMA. No mature representative RF hardware could be produced within this project. Thus, one chapter of this document is dedicated to the assumptions upon expected performance of this hardware. Another chapter captures the most important system parameters that are relevant for the frequency planning and system deployment decisions. Again, as these parameters are also dependent on the performance of �real� radio hardware, only estimates could be provided during this phase.

It is not realistic to expect that the B-VHF system could be simultaneously globally deployed in a single step. It is also highly probable that after an initial installation the B-VHF system upgrades - towards its full functionality - would occur on a local rather than on a global basis (the changes would not occur at the same time in different regions). Three chapters of this document are dedicated to the system initial deployment, transition and final deployment both in the VHF COM and in alternative ranges (DME, MLS, and VOR).




One chapter describes the possible impact of other aeronautical communications systems. Some of these systems will already be in operation during the B-VHF initial deployment and transition phase and could relieve/supplement the B-VHF system.

Finally, an outline of a standardisation procedure is presented, indicating different international bodies involved with standardisation of aeronautical communications systems and their specific roles.

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4. Pre-requisites

This chapter captures pre-requisites and assumptions for the B-VHF system deployment. Some of these pre-requisites are of general nature, while the others are related to the performance of the B-VHF RF front-end. Where applicable, a rationale is provided along with the assumption.

4.1. General Pre-requisites

The deployment scenarios are based on following general assumptions:

[A 1] Initial B-VHF deployment scenarios describe real initial system introduction in a given airspace (no B-VHF cells have already been deployed within or outside the selected airspace, so the �best� RF channel with the lowest occupancy can be selected for a given cell).

[A 2] Local VHF channel occupancy and interference situation is known for the target deployment area.

[A 3] B-VHF RF channel bandwidth has been fixed.

NOTE: Bandwidth of 1 MHz has been used in the most of B-VHF simulations and is � as long as not otherwise stated � assumed in this document. The determination of the optimum bandwidth requires further work within the system standardisation.

[A 4] System design of the B-VHF system has been refined, system-wide B-VHF parameters described in Chapter 5 have been fixed in the course of B-VHF system standardisation and remain stable during entire deployment cycle.

[A 5] The existence of the ground B-VHF infrastructure is a pre-requisite for any B-VHF deployment scenario. It is assumed, that such an infrastructure has already been deployed on ground in B-VHF airspace and B-VHF-supported airspace (see section 7.1.4).

[A 6] An aircraft is either completely equipped with B-VHF-capable radios or completely remains a NB aircraft (see section 7.1.3).

[A 7] The total transmitted power of an airborne B-VHF transmitter is limited to +44 dBm in all scenarios and all environments.

The last-mentioned assumption is necessary to allow an airborne B-VHF transmitter to be designed as extension of existing airborne VDR standards. As these transmitters should fit into existing airframes and would continue to be operated as DSB-AM and/or VDL2 radios, the maximum total B-VHF transmitted power shall be limited. The actual used total power may be lower, in particular in TMA and APT environments.

4.2. Required B-VHF RF Performance

NOTE: Developing representative mature radio hardware was not a goal of the B-VHF project, but the RF front-end performance � in particular large signal handling capability and spectral shaping of the signal - turned out to be an important factor for estimating the overall system performance. The assumptions in this chapter can be used to define requirements for the B-VHF RF front-end operating in the VHF COM range.




NOTE: Possible constellations of narrowband signal to the B-VHF signal (�O�, �W�, �S�) are described in section 5-3

[A 8] The B-VHF signal out-of-band spectral mask is as described in section 5.7.4.

[A 9] Except for the emergency channel, no other VHF narrowband voice channel (DSB-AM, ACARS, VDL Mode 2 and/or VDL Mode 4) is operated on the B-VHF capable aircraft when at least one radio is switched into the B-VHF mode.

Current DSB-AM radios have relatively low noise floor and out-of-band products, but if installed on the same aircraft they still require [ARINC 716] 2/6 MHz frequency separation (for antennas installed on the opposite/same side) for really independent operation. The safety is preserved due to the fact that the simultaneous usage of two radios remains human-controlled all the time (the communicating pilot may monitor two channels, but does not simultaneously transmit over non-ATC radio during an ongoing reception on the ATC radio and vice versa).

It is unlikely that the total power level of in-band or out-of-band side-lobes, noise and intermodulation products of a multi-carrier B-VHF transmitter could be reduced below the corresponding level achievable with the single-carrier DSB-AM transmitter. With an integrated voice/data airborne system it would also be impossible for the pilot to continue managing communications in such a way that local interference between two radios would always be prevented. The above assumption is made to exclude from initial deployment scenarios signal constellations (see section 5.2.1) of airborne radios that are unrealistic from the physical point of view. This reduces the total number of scenarios.

[A 10] Emergency NB channel (121.5 MHz) - that would appear in an �S� (in-band) constellation when one broadband channel (121-122 MHz) is used by the B-VHF cell - can be still supported in the DSB-AM mode on the same aircraft that uses B-VHF mode radios due to the special handling within the RF front-end of the B-VHF radio.

The reception of the emergency DSB-AM channel during B-VHF transmissions is supported by e.g. inserting a narrowband crystal band-rejection filter centred on 121.5 MHz between the B-VHF TX exciter stage and the power amplifier. This filter additionally reduces the level of already suppressed in-band side-lobes and also suppresses the broadband TX noise power radiated over an emergency channel. As this filter cannot remove intermodulation products produced in the power amplifier itself, it is essential to use amplifiers with sufficient back-off.

The B-VHF signal reception during (rare) �own� transmissions on the emergency channel is preserved by inserting another 121.5 MHz crystal notch-filter in the B-VHF RX front-end. This filter should reduce very strong (+8 dBm) local 121.5 MHz signal to the level comparable with the level of �S� signals coming from other aircraft (-22 dBm). The required filter attenuation is about 30 dB.

[A 11] Airborne B-VHF RX can operate reliably if one single STRONG in-band narrowband interferer that is a-priori not known to the system and has not been removed via filtering is received in �S� constellation with -22 dBm level at the RX input.

This assumption is necessary for safety reasons. It is theoretically possible that the pilot of a NB aircraft at the closest operationally just allowed distance from the B-VHF aircraft enters a wrong NB channel that is �unknown� to the B-VHF system. Hence, the notches in the B-VHF RX front-end could not be properly configured (this was done for the �known� �S� channels). Such misconduct shall not block B-VHF communications for the




B-VHF population that is close to that NB aircraft. The closest possible distance is 210 m at an airport, yielding (with LOS propagation model) -22 dBm of interference power at the input of the B-VHF RX. If this assumption is fulfilled at an airport, it would automatically allow that flying aircraft at 600 m distance also makes a communication error and starts to transmit on the �wrong� frequency.

Without that assumption no B-VHF-supported airspace or NB airspace would be allowed closely below/above/around the B-VHF airspace or B-VHF-supported airspace. The entire airspace from GND to UNL would have to be converted into B-VHF airspace, with mandatory equipage and clearly defined external boundary to the NB airspace across all flight levels.

[A 12] B-VHF aircraft and NB aircraft at the airport at 210 m distance can operate simultaneously without interference in �O� constellation (see section 5.2.1).

This is a pre-requisite for an airport to be configured as a B-VHF-supported airspace, with mixed aircraft population. Without above assumption, the entire airport would have to become B-VHF airspace, with mandated B-VHF carriage for all aircraft that would like to visit that airport or the minimum spacing between B-VHF and NB aircraft would have to be locally increased to 600 m.

[ARINC 716] indicates that a NB airborne RX should tolerate up to + 3 dBm of interfering signal coming from the same aircraft with a frequency spacing of 2 � 6 MHz. With increased path attenuation (25 dB more if the signal comes from another aircraft) the required frequency spacing for independent operation would reduce as well. The same standard indicates that an airborne radio operating close to the protected signal level (-87 dBm) must be able to tolerate up to -27/-21 dBm continuous wave (CW) power at ± 25/50 kHz spacing, respectively (cross modulation criterion). As the total maximum RL power of an airborne TX is assumed [A 6] to be limited to +44 dBm (distributed over many OFDM carriers), an airborne NB RX would be affected by only a fraction of this power and would with high probability operate within its performance specifications.

The maximum NB signal level received by a B-VHF aircraft with 210 m spacing is -22 dBm. The B-VHF RX RF front-end should be able to handle such a signal level (as it is comparable to today�s performance of a NB RX). The interference can be further reduced by applying notch filters and/or interference suppression techniques.

The �S� constellation has been excluded mainly because of concerns about increased in-band phase noise radiated by the multi-carrier B-VHF TX. The assumption is believed to be valid not only for DSB-AM, but also for the VDL2 system.

[A 13] Flying B-VHF aircraft and NB aircraft at 600 m distance can simultaneously operate without interference in either �S� or �O� constellation.

This assumption allows a single ATC sector to be configured as B-VHF-supported airspace, with mixed aircraft population. Otherwise, as it cannot be prevented that another aircraft appears at this distance, entire airspace from GND to UNL would have to be converted into B-VHF airspace, with mandatory equipage and clearly defined external boundary to the NB airspace for all flight levels.

Due to the increased distance (600 m) - the isolation is 10 dB higher than for 210 m distance - it is believed that the �S� constellation may be applicable (in addition to the �O� constellation). The assumption is believed to be valid not only for DSB-AM, but also for the VDL2 system.

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5. B-VHF System Parameters

The purpose of this chapter is to provide initial estimates of parameters of the B-VHF system that are relevant for frequency planning and co-existence with other systems in the VHF COM range, and therefore directly influence the system deployment.

Probably the most important parameter from that point of view is the protected signal power level at the input of the B-VHF receiver that in turn is derived from the minimum detectable signal under specified conditions (noise, interference). Once these parameters are known, transmitted B-VHF signal power can be calculated for different distances between the B-VHF transmitter and receiver.

In order to determine realistic parameters for the B-VHF receiver, systematic laboratory measurements would be required under �real� interference conditions. The pre-requisite for such measurements is mature B-VHF radio hardware. During laboratory measurements with B-VHF test-bed [B-VHF D34] some problems have been experienced with prototype B-VHF radio hardware. Additionally, the test-bed B-VHF transmitter has operated at a power level that was far below the realistic expected power of an airborne or ground transmitter. Finally, only windowing was applied as the interference suppression technique (neither filtering, nor leakage compensation have been implemented) within the test-bed receiver. As a consequence, the results of these laboratory measurements cannot be taken as representative for the �mature� B-VHF system.

Therefore, the [B-VHF D23] simulations have been used as a main source when estimating the B-VHF parameters. These simulations have been performed by using interference patterns that obey some statistical rules and have produced results for average BER over all configured OFDM carriers. Moreover, the most scenarios did not include advanced interference mitigation methods (TX side-lobe suppression, RX leakage compensation).

Based on these inputs, best possible current estimates of the B-VHF parameters are captured in Table 5-1, with explanatory details provided in the subsequent sub-chapters.

Additionally, spectral mask must be defined for the B-VHF transmitter. The B-VHF TX spectral mask has been estimated by combining the results for side-lobe suppression [B-VHF D23] with the known characteristics (e.g. phase noise) of the state-of-the-art narrowband VHF systems.

5.1. Parameters of the B-VHF Radio Chain

The general topology of a B-VHF radio chain between the transmitter (TX) and receiver (RX) with signal power levels at different points is shown in Figure 5-1.

TX Af_T = 3 dB

Lp

EIRP

pr_A

PT

pr

PR

pt

PR_A

eirp

Ga_T = 2/0 dB (G/A)

Af_R = 3 dB

Ga_R = 2/0 dB (G/A)

RX

Figure 5-1: B-VHF Radio Chain




The meaning of the parameters depicted in Figure 5-1 is as follows:

1. TX output power (PT = Nc á pt): Total B-VHF signal power averaged over frame duration with Nc active carriers, measured at the output of the B-VHF TX within 1 MHz bandwidth.

2. Number of carriers (Nc): Maximum number of carriers simultaneously used by the B-VHF TX in FL/RL, respectively, within assumed RF channel bandwidth of 1 MHz.

3. TX per-carrier output power (pt): Average signal power of a single OFDM carrier measured at the output of the B-VHF TX during RL/RA/FL/BC frame duration.

4. Feeder Loss (Af_T/Af_R): Loss (in dB) of a transmitting/receiving antenna feeder, respectively.

5. Antenna gain (Ga_T/Ga_R): Antenna gain for a transmitting/receiving antenna respectively.

6. Total EIRP: Effective isotropic radiated total B-VHF signal power PT with Nc active carriers, measured at the output of the TX antenna within a bandwidth of 1 MHz.

7. TX per-carrier EIRP (eirp): Per-carrier EIRP measured at the output of the TX antenna.

8. Propagation Loss (Lp): Free-space loss (in dB) between isotropic airborne/ground antennas.

9. Protected power at RX antenna (PR_A): Protected level of total received B-VHF signal power (1 MHz bandwidth) in front of the receiver antenna.

10. Protected per-carrier power at RX antenna (pr_A): Protected level of received single-carrier B-VHF signal power in front of the receiver antenna.

11. Protected power at RX input (PR): Power of the entire B-VHF signal measured at RX input required for �satisfactory� system operation.

12. Protected single-carrier power at RX input (pr): Power of a single B-VHF carrier measured at RX input required for �satisfactory� system operation.

The meaning of the other parameters used in this chapter is as follows:

13. Minimum Detectable Signal at RX input (MDS): Minimum level of a total B-VHF signal at RX input sufficient for achieving the minimum required BER performance

NOTE: [ACPF14-WP5] proposes as a measure of performance uncorrected voice BER of 10-3 for VDL3 radios and corrected data BER of 10-4 for VDL2 radios. These values could probably be also used as a criterion for testing the B-VHF receiver. However some B-VHF simulations have been done by assuming corrected BER of 10-6 for data.

14. Minimum per-carrier detectable signal at RX input (mds = MDS/Nc): Minimum level of a single B-VHF OFDM carrier at RX input sufficient for achieving the minimum required BER performance.

15. System Margin (M): difference (in dB) between the protected signal power value (PR/pr) and the minimum detectable signal (MDS/mds) value.

16. Total RX noise power (N).

17. RX noise figure (NF).

18. RX thermal noise power (N0).




5.2. Signal Constellations

NOTE: Signal constellations described in this section are only applicable to the VHF COM range and the VOR range where narrowband systems are used.

5.2.1. B-VHF � Narrowband Signal Constellations

Signal constellations depicted in Figure 5-2 apply to the input of the victim B-VHF- or narrowband (NB) receiver. The signal level for the B-VHF signal (both desired and undesired) is expressed as per-carrier signal power pt, while the level of narrowband signal (both desired and undesired) is expressed as total narrowband signal power Pn.

According to Figure 5-2, there are three possible constellations of narrowband VHF signals with respect to the B-VHF channel:

! �S� constellation denotes a STRONG NB in-band signal (channel) that operates within the B-VHF RF bandwidth under overlay conditions and is received with a power above some pre-defined WEAK/STRONG threshold.

! �W� constellation denotes a WEAK in-band NB signal (channel) that operates within the B-VHF RF bandwidth under overlay conditions but which is received with a power level below the WEAK/STRONG threshold.

! �O� constellation denotes a NB signal (channel) that operates outside the B-VHF RF bandwidth.

Figure 5-2: Relative Position of B-VHF and Narrowband Signals

�S� and �W� constellations apply to the overlay concept, where different signals (parts of signals that carry significant energy) may overlap in the spectral domain.

NOTE: In the broader sense, the overlay concept also comprises cases where systems operate in �O� constellation where the parts of signal spectra that carry most of the energy do not overlap.




Narrowband channels classified as �S� are not effectively used by the B-VHF system. In order to protect �S� NB receivers, the B-VHF TX shall never place its OFDM carriers into these channels. A B-VHF RX must apply notch filters to suppress received interference coming from NB �S� transmitters.

�W� channels are considered to be �available� and are effectively used by the B-VHF system in a �real� overlay mode (B-VHF TX may put its carriers into �W� channels). The B-VHF RX does not apply filtering, but must use interference suppression techniques (e.g. windowing) to reduce the received interference coming from NB �W� transmitters.

�O� channels are not affected by the WEAK/STRONG threshold (may be either STRONG or WEAK, with the received power above or below the threshold). For �O� constellation classic frequency protection reasoning applies, based on the required spatial distance to achieve satisfactory performance at a given frequency spacing ∆f between involved signals (Figure 5-2).

5.2.2. Frequency Spacing

When investigating mutual interference impact, the narrowband signal virtually �slides� over a broadband B-VHF signal and the measurements are performed according to the selected protection criterion for different values of the relative frequency offset ∆f between the two involved signals.

The frequency spacing ∆f is calculated in a different way. For narrowband VHF systems it is usually specified as a number of required 25 kHz guard channels (see Figure 5-2 and also Figure 5-4 - Figure 5-8). In the B-VHF context, it is proposed to use following definitions (TBC) for different constellations:

! For �O� constellation ∆f denotes the distance (expressed as a number of 25 kHz channels) between the nominal centre frequency of a narrowband signal lying on the 25 kHz grid and the �middle� B-VHF OFDM carrier from the outermost 25 kHz sub-band in the spectrum of the B-VHF signal.

NOTE: Another possibility would be to specify ∆f as the distance between the nominal frequency of the narrowband signal channel and the nominal centre frequency of the outermost active OFDM carrier in the spectrum of the B-VHF signal.

NOTE: When dealing with 8.33 kHz DSB-AM system, it may be more appropriate to express ∆f as a number of 8.33 kHz channels.

! For �W� constellation ∆f denotes the distance (expressed as [n á OFDM carrier spacing/2] ) between the nominal centre frequency of a narrowband signal and the nominal centre frequency of the selected in-band OFDM carrier (see Figure 5-2).

NOTE: Increasing ∆f in such small steps shall allow for investigating e.g. leakage effect [B-VHF D18].

! For �S� constellation ∆f denotes the distance (expressed as [n á OFDM carrier spacing/2]) between the nominal centre frequency of a narrowband signal and the nominal centre frequency of the closest active OFDM carrier (see Figure 5-2).

NOTE: Increasing ∆f in such small steps shall allow for investigating e.g. effect of side-lobe suppression or leakage caused by �S� signals [B-VHF D18].




5.3. Parameters of the B-VHF System Operating in the VHF Range

The relevant parameters for investigating interference between narrowband VHF systems are captured in [ACP_F14-WP5] and Table 6-1 of [B-VHF D9]. Similar parameters must be defined for the B-VHF system.

Estimated B-VHF system parameters are captured in Table 5-1 together with parameters of narrowband VHF systems that are relevant for frequency planning. The purpose of Table 5-1 is just to give the reader an impression about what could be achievable based on the completed B-VHF system investigations � some of these parameters may have to be changed when more information becomes available.

In particular protected B-VHF signal power level at the input of the B-VHF receiver must be agreed as it represents the starting point for further frequency planning activities.

Ground DSB-AM transmitter power was in all environments (ENR/TMA/APT) set to +47 dBm to cover cases where an interfering TMA/ENR DSB-AM transmitter may be located at an airport. Fixed cable losses (3/3 dB) and fixed antenna gains (0/2 dB) have been assumed for airborne and ground installations, respectively.

NOTE: Aircraft DSB-AM transmitters operate at a constant maximum power (+44 dBm) in all environments.

From Table 5-1 it can be concluded that, with assumed number of carriers and -100 dBm minimum detectable per-carrier signal power at the RX input the required transmitted power for the airborne transmitter would remain within assumed limit (+44 dBm, the same as for current VDR operating in the DSB-AM mode) for cell sizes up to 60 nm, but the limit would be exceeded (+48 dBm) for large ENR cells (175 nm radius). It can also be seen that the ground TX power is about 10 dB higher than the airborne power due to the larger number of used carriers.




Parameter

APT TMA ENR APT TMA ENR

B-VHF cell size (nm) 25 60 175 25 60 175

Nr. Of carriers (Nc) 1 1 1 1 1 1 384 384 384 32 32 32

TRANSMITTER AIR GND AIR GND AIR GND

TX output power (PT, dBm) 44 47 42 44 43 45 42 50 59 31 39 48

TX per-carrier output power (pt = PT/Nc, dBm) 44 47 42 44 43 45 16 24 33 16 24 33

TX feeder loss (Af_T, dB) 3 3 3 3 3 3 3 3 3 3 3 3

TX antenna gain (Ga_T, dB) 0 2 0 2 0 2 2 2 2 0 0 0

Total EIRP (EIRP, dBm) 41 46 39 43 40 44 41 49 58 28 36 45

TX per-carrier EIRP (eirp, dBm) 41 46 39 43 40 44 15 23 32 13 21 30

PROPAGATION loss (f = 108 MHz) between isotropic antennas (Lp, dB) 107 115 124 107 115 124

RECEIVER GND AIR GND AIR GND AIR

Protected power at RX antenna (PR_A = PR + Af_R - Ga_R, dBm) -93 -82 -93 -82 -88 -88 -66 -66 -66 -79 -79 -79

Protected per-carrier power at RX antenna (pr_A = pr + Af_R - Ga_R, dBm) -93 -82 -93 -82 -88 -88 -92 -92 -92 -94 -94 -94

RX antenna gain (Ga_R, dB) 2 0 2 0 2 0 0 0 0 2 2 2

RX feeder loss (Af_R, dB) 3 3 3 3 3 3 3 3 3 3 3 3

Protected power at RX input (PR = MDS +M, dBm) -94 -85 -94 -85 -89 -91 -69 -69 -69 -80 -80 -80

Protected per-carrier power at RX input (pr = mds + M, dBm) -93 -82 -93 -82 -88 -88 -95 -95 -95 -95 -95 -95

System Margin (M, dB) 5 5 5 5 5 5

Available SNR = MDS - N (dB) 30 30 30 19 19 19

MDS at RX input (MDS, dBm) -74 -74 -74 -85 -85 -85

Per-carrier MDS at RX input (mds = MDS/Nc, dBm) -100 -100 -100 -100 -100 -100

Total RX input noise power (N, 1 MHz, dBm) -104 -104 -104 -104 -104 -104

Total RX NF (dB) 10 10 10 10 10 10

RX input thermal noise power (N0, 1 MHz, dBm) -114 -114 -114 -114 -114 -114

DSB-AM VDL-M2 VDL-M4

GND

GND

AIR

AIR

B-VHF

Table 5-1: VHF Signal Parameters




5.3.1. B-VHF PHY Simulations

This chapter briefly summarises the findings in [B-VHF D23] that are relevant for specifying B-VHF system parameters.

The performance of the B-VHF system has been assessed by simulations. Each simulation scenario uses the corresponding propagation channel model (parking/take-off/en-route).

Table 5-2 shows the distribution of idle (green), strong (red) and weak (yellow) NB channels within the bandwidth of 1 MHz as used as interference pattern during simulations. The data carriers used for BER simulations are either idle or weak channels. During the simulations strong and weak interferers have been configured to be at certain positions within the 1 MHz channel and their power over a particular B-VHF frame has been selected from the power distributions previously derived in [B-VHF D12]. It is important to note that in FL scenarios, white channels have not been used for data transfer or BER calculation and that number, position and power distribution of interferers in all RL scenarios is based on the FL-ANR-WC scenario.

Scenario Simulation Availability-Interference Pattern

FL-PARK

FL-PARK S=W

FL-TAKEOFF

FL-ENR

FL-ENR-WC

RL-PARK

RL-TAKEOFF

RL-ENR

Table 5-2: Constellation of Interferers as Used for Simulations

The maximum possible number of carriers within 1 MHz bandwidth is 40 á 12 = 480. In all FL scenarios, except FL-ENR-WC (a worst case scenario for en-route environment), 116 data carriers (of 156 free carriers) have been used for transmitting data and BER calculations. The remaining 40 �available� carriers were considered to be required as side-lobe cancellation carriers and were not used for calculating the BER. In FL-ENR-WC scenario and all RL scenarios 384 data carriers were effectively used for data transmission and BER measurements (72 carriers are occupied by strong interferers, 24 of 408 free carriers are considered to be cancellation carriers for side-lobes). In RL scenarios BER was measured over 64 carriers of a single user (it was assumed that 384 RL carriers are shared by 6 aircraft, each using 64 carriers).

The simulation results in [B-VHF D23] have been presented as BER curves for voice and data vs. total B-VHF signal power Ps.

In all scenarios only windowing has been applied within the B-VHF RX as a method for interference suppression. Strong �S� signals have generally not been notched-out at the B-VHF RX, so their contribution to the leakage is significant. In one (FL-PARK S=W) scenario the power of a single involved �S� interferer has been set according to the �W� power distribution while retaining the original �S� duty-cycle.




Fixed number of carriers Nc and fixed constellations of interferers - as depicted in Table 5-2 - have been assumed, with separate interference power distributions for strong and weak interferers.

All FL scenarios except FL-ENR-WC used the �typical� interference picture with one or two active �S� and �W� interferers (Table 5-2). Such �typical� interference picture corresponds to the practical results of VHF occupancy measurements conducted within the WP 2 of the B-VHF project. The measurements have been performed during peak traffic hours in the most congested European area and may be considered as representative for the �realistic� current interference situation in Europe.

On the contrary, FL-ENR-WC and all RL scenarios use the worst-case ENR interference picture (6 STRONG and 7 WEAK interferers) that has been artificially constructed by placing involved aircraft and ground stations at the same time at worst possible positions, without taking operational separation minima or probability of such simultaneous occurrence into account. In other words, the �worst-case� situation would probably never occur in the real world. The total average �S� and �W� powers in the FL-ENR-WC scenario are about 5 dB higher than in the FL-ENR scenario. This explains why the [B-VHF D23] results for the �worst-case� RL scenarios are significantly worse the results for �typical� FL scenarios.

Figure 5-3 indicates for each simulated scenario the average powers of strong and weak interferers, their duty-cycles, average powers that take these duty-cycles into account, total average powers of all strong/weak interferers, their ratio as well as the total average interference power as applicable to a given scenario. Additionally, the required minimum signal power (MDS) required for target voice (10-3) and data services (10-4) BER has been indicated for each scenario, as derived from [B-VHF D23]. Finally, per-carrier (mds) values have been calculated by dividing total signal power by the number of used data carriers applicable to the particular scenario.

From [B-VHF D23] figures the total signal power Ps required to achieve target BER for voice and data (10-3/10-4, respectively) has been derived for each scenario and per-carrier power ps has been calculated taking Nc into account. In Figure 5-3 windowing was still the only method for interference suppression.

After the power of �S� interferer in the FL-PARK W=S scenario was set according to the �W� power distribution, simulating the effect of notching-out the single strong interferer, the mds values for both voice and data BER have dramatically improved (to -102 dBm). The �worst case� mds to achieve both voice and data target BER figures was around � 100 dBm across all FL scenarios that are based on �typical� rather than �worst-case� interference scenarios. Therefore the mds value of -100 dBm is proposed (and included in Table 5-1) for an airborne B-VHF receiver.

The required mds to achieve both voice and data target BER figures was between -77 and -90 dBm across all RL scenarios that are based on the �worst-case� interference scenario.

Although only limited simulations were performed (only FL-ENR-WC scenario/voice BER was considered), additional results from [B-VHF D23] with respect to leakage compensation are very encouraging. While with windowing without leakage compensation total signal power (MDS) of -66 dBm was required to achieve a target voice BER of 10-3, when windowing was combined with leakage compensation only -88 dBm were required. This corresponds to the mds reduction from -92 dBm to -114 dBm.

This allows for a conclusion that with leakage compensation similar results would be achieved in all RL scenarios (that are also based on FL-ENR-WC interference scenario).




Further improvements are expected from RX filtering (notching-out �S� signals within the B-VHF receiver) as this would both remove direct interference caused by such signals and reduce leakage effect. RX filtering can easily be combined with other methods (windowing and leakage compensation).

Therefore, the mds value of -100 dBm is also proposed (and included in Table 5-1) for a ground B-VHF receiver.

In order to obtain the protected signal level some system margin M should be applied to the above mds values. Estimated value of 5 dB was assumed (and included in Table 5-1) as a system margin M for airborne and ground B-VHF receivers.

5.3.2. Laboratory Measurements

In [B-VHF D34] the results of B-VHF sensitivity measurements in the presence of single DSB-AM interferer have been presented. Prototype B-VHF radio hardware (�front-end�) was combined with the prototype baseband system.

During measurements two B-VHF signal constellations were used, one (�Frame 1�) used all (128) OFDM carriers, another one (�Frame 7�) used 104 active carriers (24 carriers in the middle of the B-VHF signal spectrum have not been used for data transmission).

Table 5-3 shows the values for maximum tolerable DSB-AM power (as measured) to preserve B-VHF voice BER of 10-3 for specified protected B-VHF signal power PR (including system margin). The table also indicates the number of carriers Nc and the per-carrier protected power pr. Taking into account that pr values also include system margin (that has in [B-VHF D34] been selected to be greater than 10 dB), the corresponding mds values would lie below -100 dBm.

Constellation PR (dBm) Nc pr (dBm) P_DSB-AM (dBm)

Frame 1 -80 128 -101 -95

Frame 7 -70 104 -90 -90

Table 5-3: Results of B-VHF Laboratory Measurements




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FL-PARK -55,20 0,1843 -62,54 1 -62,54 -83,98 0,0415 -97,80 1 -97,80 35,25 -62,54 -58 116 -78,64 4-14/Isync -52 116 -72,64 4-17/IsyncFL-PARK S=W -83,98 0,1843 -91,32 1 -91,32 -83,98 0,0415 -97,80 1 -97,80 6,47 -90,44 -87 116 -107,64 4-14/Isync + -82 116 -102,64 4-17/Isync + NotchFL-TAKEOFF -71,77 0,1872 -79,05 1 -79,05 -88,52 0,0505 -101,49 2 -98,48 19,43 -79,00 -83 116 -103,64 4-22/Isync -80 116 -100,64 4-24/Isync, F= FLOSFL-ENR -78,36 0,2528 -84,33 2 -81,32 -83,57 0,0747 -94,84 2 -91,83 10,50 -80,95 -80 116 -100,64 4-28/Isync -81 116 -101,64 4-30/Isync, F= FLOSFL-ENR-WC -78,36 0,2528 -84,33 6 -76,55 -83,57 0,0747 -94,84 7 -86,39 9,84 -76,12 -66 384 -91,84 4-33/Isync -73 384 -98,84 4-35/Isync, F= FLOSRL-PARK -78,36 0,1843 -85,70 6 -77,92 -83,57 0,0415 -97,39 7 -88,94 11,02 -77,59 -68 64 -86,06 4-38/Ich -59 64 -77,06 4-40/IchRL-TAKEOFF -78,36 0,1872 -85,64 6 -77,86 -83,57 0,0505 -96,54 7 -88,09 10,23 -77,46 -70 64 -88,06 4-43/Ich, F= FLOS -64 64 -82,06 4-45/Ich, F= FLOSRL-ENR -78,36 0,2528 -84,33 6 -76,55 -83,57 0,0747 -94,84 7 -86,39 9,84 -76,12 -72 64 -90,06 4-48/Ich, F= FLOS -66 64 -84,06 4-50/Ich, F= FLOS

-110,00

-105,00

-100,00

-95,00

-90,00

-85,00

-80,00

-75,00

-70,00

-65,00

-60,00

Per-carrier mds (dBm) for BER =10-3 -78,64 -107,64 -103,64 -100,64 -91,84 -86,06 -88,06 -90,06

Per-carrier mds (dBm) for BER=10-4 -72,64 -102,64 -100,64 -101,64 -98,84 -77,06 -82,06 -84,06

TOTAL Average "W" Power (dBm) -97,80 -97,80 -98,48 -91,83 -86,39 -88,94 -88,09 -86,39

TOTAL Average "S" Power (dBm) -62,54 -91,32 -79,05 -81,32 -76,55 -77,92 -77,86 -76,55

FL-PARK FL-PARK S=W FL-TAKEOFF FL-ENR FL-ENR-WC RL-PARK RL-TAKEOFF RL-ENR

Figure 5-3: Results of B-VHF PHY Simulations [B-VHF D23]




5.4. B-VHF RX Protected Signal Level

The B-VHF receiver will be able to demodulate a desired signal in presence of a certain amount of noise and interference. The minimum detectable signal (MDS) is defined as that signal level at the demodulator input that would produce an acceptable minimum output BER for voice and data services, respectively.

The noise power N is composed of the thermal noise power Nt and the internal receiver noise contribution expressed as receiver Noise Figure (NF).

N = Nt + NF

Without interference, MDS must be several dB (SNR_min) above the total RX noise power N.

MDS = Nt + NF + SNR_min

With that input signal level still only a minimum acceptable BER is obtained, therefore some system margin of M dB must be added to the MDS, resulting in the protected signal level PR at the receiver input.

PR = MDS + M

Assuming overlay conditions in the VHF COM range strong interference can be expected, so the B-VHF RX performance � MDS, PR - is determined mainly by the interference power I and not by the noise power N. The parameter PR is defined at the RX input. The corresponding value at the receiver antenna input (PR_A) can be calculated by adding the cable loss Af_R = 3 dB and subtracting the receiver antenna gain Ga_R (0 dB/2 dB for airborne/ground antenna, respectively).

During the simulations, MDS has been expressed [B-VHF D23] as a total B-VHF signal power when a specified number of OFDM carriers Nc is used for transmitting/receiving voice or data packets. Knowing the total MDS, it is possible to calculate the average �per-carrier� minimum signal power (mds) required for satisfactory RX performance (MDS = Nc ● mds).

5.5. B-VHF TX Power

Minimum required per-carrier transmitted total signal power pt for a given B-VHF cell size will be determined by the protected B-VHF signal level pr required for the satisfactory OFDM carrier demodulation performance at the input of the B-VHF RX. The protected level pr is in turn derived by applying the system margin M to the minimum per-carrier detectable signal (mds). The mds values have been estimated from the simulations.

Per-carrier pt, pr and mds power values have been listed in Table 5-1. The same table also indicates the total signal powers that have been obtained by multiplying per-carrier values by the number of used carriers Nc.

An airborne B-VHF transmitter is anticipated to become an extension of the existing airborne VDR standards. As these transmitters should fit into existing airframes and the multi-mode B-VHF radio should continue to operate with DSB-AM and VDL power ratings in NB airspace, the maximum allowed total signal power of an airborne B-VHF transmitter should be limited to the same level as applicable to an existing VDR 750 radio operating in the DSB-AM mode (25 W or +44 dBm) and should not be exceeded under any operating circumstances. The power limit is valid for aircraft transmissions in both




RACH/sRACH and RL slots and should be preserved independently of the number of OFDM carriers that are actually used on RL.

NOTE: The explanation of B-VHF frame structure (slots) can be found in [B-VHF D18].

The limit for the total airborne TX power, proposed above, is expected to be only reached at the boundary of the largest possible cell, representing the maximum possible airborne transmitted power in an ENR environment (PT_ENR). As TMA/APT cells are smaller than ENR cells, lower actual total transmitted power (PT_TMA < PT_ENR, PT_APT < PT_ENR) is required for these cells.

NOTE: For aircraft being within TMA and APT the GS further reduces actual total airborne transmitting power PT by applying power regulation mechanisms. Dependent on the aircraft distance to the GS, PT is kept at the amount that is just sufficient for good quality communications.

In order to guarantee interference-free operation towards close DSB-AM and other narrowband receivers the maximum radiated per-carrier power (due to the broadband nature of the B-VHF signal) of a B-VHF transmitter pt must be specified and limited. This corresponds to limiting the power spectral density of the radiated B-VHF signal. The same per-carrier power pt has been assumed for all frame types in a given direction (FL/RL). The total actual power PT per frame may be different as different frames may use different number of carriers (PT = Nc ● pt).

NOTE: The FL per-carrier power is averaged over the FL frame by assuming maximum carrier loading (four voice users simultaneously active on that carrier). As the spreading is applied on FL, this produces the same per-carrier power as if a single user is active on RL without spreading.

Assuming constant per-carrier RL power pt, the total RL transmitted power PT can only be limited by limiting the maximum number of OFDM carriers (Nc) used on RL.

It is proposed to consider Nc = 32 as the maximum number of RL carriers (this value has been included in Table 5-1). The total power PT of an airborne B-VHF transmitter is equally distributed among these carriers (B-VHF signal has a �flat spectrum� over carriers used on RL).

NOTE: In [B-VHF D6] and [B-VHF D7] it was assumed that an airborne radio would use all available RL carriers during RACH/sRACH transmissions. Later inspection of the data payload for these transmissions has shown that the required number of data carriers can be reduced to 32. Additional 16 �cancellation carriers� are transmitted together with each RL frame in order to improve the spectrum shape of the B-VHF signal. When CCs are inserted the resulting TX signal is normalized such that the power with and without CCs is the same. Therefore, at most 32 OFDM carriers can be assumed to be used by any single aircraft radio during any RL transmission, regardless of CCs are used or not.

The B-VHF GS transmitting power PT remains constant, at the fixed configured level that depends on the selected cell size.

As the B-VHF GS simultaneously provides multiple services to all aircraft within the cell and uses more carriers (Nc = 384 has been assumed in Table 5-1) than any aircraft radio, its total transmitted power PT will be in general significantly higher than the maximum total power of an aircraft transmitter.




5.6. B-VHF TX Signal Power Variation with Frequency Range

Maximum total B-VHF radiated power values in different ranges (VHF COM, DME, MLS, VOR) are captured in Table 5-4. In non-VHF ranges interference-free operation of the B-VHF system was assumed by using dedicated channels FDM separated from other systems (B-VHF system is operated as a noise-limited- rather than interference-limited system).

Total transmitting powers have been calculated applying following assumptions:

! Cable loss/antenna gain are 3 dB/2 dB for B-VHF GS TX/RX

! Cable loss/antenna gain are 3 dB/0 dB for an airborne B-VHF TX/RX

! B-VHF RF bandwidth is 1 MHz

! B-VHF RX NF is 10 dB

! EB/N0 = 7 dB for BER = 10-3 (QPSK, voice, no coding, Rice channel with k=15 dB)

! System margin M = 10 dB

With these assumptions, the protected signal level at the RX input is -87 dBm. This corresponds to -84/-86 dBm at the input of the airborne/ground antenna, respectively. From these values the EIRP has been calculated for different CDOC values, assuming that free-space propagation model applies.

NOTE: Cell Designed Operational Coverage (CDOC) is explained in section 7.1.10.

5.6.1. VHF COM Range

Table 5-4 shows the required TX power if interference-free conditions could be established (dedicated B-VHF channels found) in the VHF COM range for the purpose of B-VHF system deployment. Such a scenario is completely improbable, so the presented values are only for comparison purposes with other scenarios.

5.6.2. VOR Range

Operation in the VOR band (108 � 118 MHz) under non-overlay conditions requires for the same CDOC approximately the same transmitted power as required for the operation in the VHF COM range. As expected, VOR transmitted power values are acceptable in all scenarios. Therefore, it is proposed, with respect to the required transmitting power, to consider deploying the B-VHF system in the VOR range in all environments/CDOCs.

5.6.3. DME Range

Table 5-4 shows estimated the expected transmitted B-VHF signal power for airborne and ground B-VHF transmitters operating under non-overlay conditions in the DME range in cells with different CDOC. In the DME range, 18 dB more transmitting power than in the VHF range is generally required for covering the same area due to the higher operating frequency. However, the strong interference would in the VHF range probably lead to transmitted power levels approaching those required without interference in the DME range.

This raises an integration problem within the airborne architecture, as in TMA/ENR domain the airborne transmitted power is higher than the power of currently used airborne transmitters in the VHF range (+41 dBm EIRP). As in large airspace blocks old




narrowband modes of operation will continue to be used, the backward-compatibility of airborne B-VHF radios is required. However, too high required transmitter power may preclude the B-VHF radio deployment in form of multi-mode/multi-range radios.

The problem may be solved by limiting the maximum total power an airborne B-VHF transmitter may use for any transmission. The total power may in turn be reduced by reducing the number of OFDM carriers available for any RL transmission and/or applying spreading in order to reduce the total power over such frames (RACH, sRACH) that use all available OFDM carriers.

Transmitter CDOC PR_A (dBm) Range (nm) Lp (dB) EIRP (dBm)

APT_CDOC -84 25 107 23

TMA_CDOC -84 60 115 31

ENR_CDOC -84 175 124 40

APT_CDOC -86 25 107 21

TMA_CDOC -86 60 115 29

ENR_CDOC -86 175 124 38

APT_CDOC -84 25 125 41

TMA_CDOC -84 60 133 49

ENR_CDOC -84 175 142 58

APT_CDOC -86 25 125 39

TMA_CDOC -86 60 133 47

ENR_CDOC -86 175 142 56

APT_CDOC -84 25 140 56

TMA_CDOC -84 60 147 63

ENR_CDOC -84 175 157 73

APT_CDOC -86 25 140 54

TMA_CDOC -86 60 147 61

ENR_CDOC -86 175 157 71

APT_CDOC -84 25 107 23

TMA_CDOC -84 60 115 31

ENR_CDOC -84 175 124 40

APT_CDOC -86 25 107 21

TMA_CDOC -86 60 115 29

ENR_CDOC -86 175 124 38

GND_TX

VOR Range

AIR_TX

GND_TX

AIR_TX

GND_TX

MLS Range

AIR_TX

VHF COM Range

AIR_TX

GND_TX

DME Range

Table 5-4: Transmitted B-VHF TX Power

5.6.4. MLS Range

Operation in the MLS band (5 GHz) under non-overlay conditions requires for the same CDOC 33 dB more power than operation in the VHF range. Transmitted power values in the MLS range shown in Table 5-4 are prohibitive (non-realistic transmitter powers are




required) in all scenarios except for an airport deployment. Therefore, it is proposed, with respect to the required transmitting power, to consider deploying B-VHF system in the MLS (5GHz) range only in the airport environment (APT_CDOC). In order to retain acceptable transmitting power values for airborne equipment the scope of offered services should be preferably restricted to ground services with coverage requirements below 25 nm.

NOTE: Other environments/CDOCs can be served by the same B-VHF system, but operating in other ranges (DME, VOR, VHF) with correspondingly modified radio part.

5.7. Spectra of Signals

Knowing out-of-band spectra of signals-in-space is important for determining safe separation distances when several systems are simultaneously used within the same part of the spectrum or in spectrum areas that are adjacent to each other. This section captures the specifics of out-of-band spectra of the DSB-AM signal, VDL Mode 2 signal and the B-VHF signal in the VHF range.

5.7.1. DSB-AM

Out-of-band spectral density of a DSB-AM signal is measured within specified bandwidth versus frequency distance ∆f from the nominal DSB-AM carrier frequency (Figure 5-4). The offset ∆f from the DSB-AM carrier frequency can be expressed as an absolute offset in kHz and alternatively as a number of 25 kHz channels. �X� in Figure 5-4 denotes the reference (carrier) power (0 dBc). The measurement bandwidth is in most cases set to 25 kHz.

Figure 5-4: Explanation of the DSB-AM and VDL Spectra




5.7.2. VDL

Out-of-band spectral density of a VDL signal is measured within specified bandwidth versus frequency distance ∆f from the nominal VDL frequency (Figure 5-4). The offset ∆f from the nominal VDL frequency is expressed as a number of 25 kHz channels and alternatively as absolute offset in kHz. �X� in Figure 5-4 denotes the reference VDL signal power (0 dBc). The measurement bandwidth is also in most cases set to 25 kHz.

5.7.3. Signal Spectra of Narrowband VHF Systems

-160

-140

-120

-100

-80

-60

-40

-20

0

Distance f rom carrier (Nr. of 25 kHz channels)

Spec

tral m

asks

(d

Bc/H

z or

dBc

& 2

5 kH

z)

vs. n

umbe

r of 2

5 kH

z ch

anne

ls

D (dBc & 25 kHz) C (dBc & 25 kHz) A (dBc/Hz)B (dBc & 25 kHz) E (dBc & 25 kHz)

D (dBc & 25 kHz) -60,00 -70,00 -80,00 -85,00 -90,00 -95,00 -95,00 -95,00

C (dBc & 25 kHz) -40,00 -65,00 -70,00 -75,00 -92,00 -107,00 -107,00 -107,00

A (dBc/Hz) -120,00 -125,00 -130,00 -132,00 -135,00 -140,00 -145,00 -148,00

B (dBc & 25 kHz) -78,00 -83,00 -88,00 -90,00 -93,00 -98,00 -103,00 -106,00

E (dBc & 25 kHz) -40,00 -65,00 -70,00 -75,00 -92,00 -98,00 -103,00 -106,00

1 2 4 8 16 32 64 128

Figure 5-5: Signal Spectra of Narrowband VHF Systems

Figure 5-5 shows exemplary out-of-band spectra for narrowband aeronautical VHF systems.

The series "A" represents the DSB-AM TX out-of-band phase noise density (dBc/Hz) derived from [EUROCAE WG47]. The series "B" represents the same [EUROCAE WG47] spectrum expressed as the total noise power in 25 kHz bandwidth relative to the carrier power (dBc & 25 kHz), assuming that the noise density is approximately flat within the 25 kHz bandwidth.

Series "C" represents the out-of-band spectral [NEXCOM MDR] for the ground NEXCOM multimode radio operating in DSB-AM mode. This spectrum is specified as a total noise power measured in 25 kHz bandwidth at a specified offset relative to the carrier power (dBc & 25 kHz).




Series "D" is derived from the VDL out-of-band spectral mask [ACP_F14-WP5]. The original VDL mask is defined as an absolute VDL power that is received at a specified offset within 25 kHz bandwidth (except for the adjacent channel where 16 kHz bandwidth is used). This absolute power has been re-calculated by assuming +42 dBm reference airborne VDL power and expressed as out-of-band power received in 25 kHz bandwidth relative to above reference power (dBc & 25 kHz).

The representative DSB-AM out-of-band spectrum (Figure 5-5, series �E�, in dBc & 25 kHz) has been derived by combining the masks �B� and �C� (higher of two values has been retained at a given offset from the DSB-AM carrier).

5.7.4. B-VHF Spectrum (VHF Range)

In addition to knowing the required transmitter power, it is also necessary to specify undesired out-of-band spectral components that are radiated together with the desired B-VHF signal and may affect the operation of other VHF systems.

NOTE: Normally, the declaration of the out-of-band spectral density requires that mature radio hardware is available, which was not the case within the B-VHF project. Therefore, only an estimate of such a spectrum can be given in this document.

The B-VHF TX out-of-band spectrum (Figure 5-6) can be described as a ratio �A� of out-of-band power density of the B-VHF signal to the in-band power density, dependent on the distance ∆f from the �edge� of the B-VHF signal. The parameter �A� remains constant for any �relatively small� bandwidth of the measurement receiver, e.g. 1 Hz, 4 kHz, 8.33 kHz, 16 kHz, 22 kHz or 25 kHz. The frequency distance ∆f is expressed in kHz and alternatively as a number of 25 kHz channels.

In Figure 5-6 �X� denotes the reference in-band power density (0 dB), while �A� describes the B-VHF signal power density measured at a given frequency offset ∆f. Parameter �Y� represents the average power density of notched-out in-band areas relative to the reference in-band power density.

Figure 5-6: Explanation of the B-VHF Spectrum

Detailed spectra for the B-VHF GS and the transmitting B-VHF aircraft are expected to be different because an aircraft normally uses for its transmissions in the RL slot significantly less carriers than the GS.




NOTE: When an aircraft transmits in RACH/sRACH slot, it uses the same carrier constellation (maximum number of available OFDM carriers) as the B-VHF GS and therefore may produce signal with spectrum which is similar to that of the transmitting B-VHF GS. The interference impact of increased carrier number in RACH/sRACH slot can be reduced by applying spreading (therefore reducing the per-carrier transmitted power). This case has not been separately considered so far (only aircraft transmissions in RL slots have been assumed).

For the B-VHF GS transmitter the worst-case (with respect to the phase noise within-/close to the B-VHF RF channel) would probably occur if the GS uses all OFDM carriers within 1 MHz RF channel bandwidth. In that case, the maximum (nearly constant) level of in-band phase noise would be produced, dependent on the number of active carriers. At the same time, the maximum level of out-of-band phase noise (starting at the edge of the RF channel and ending at several MHz distance from the channel edge) would be produced.

Figure 5-7 shows several hypothetical out-of-band spectrum of a B-VHF transmitter as well as the out-of-band spectrum of the DAB transmitter.

-160

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-100

-80

-60

-40

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Spec

tral m

asks

(d

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"x" k

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chan

nels

R (dB & 4 kHz) S (dB & 25 kHz) T (dBc & 25 kHz)U (dBc & 25 kHz) W (dBc & 25 kHz) X (dBc & 25 kHz)

R (dB & 4 kHz) -5,6 -11,3 -22,5 -45,0 -53,8 -71,3 -80,0 -80,0

S (dB & 25 kHz) -55,0 -78,0 -100,0 -115,0 -130,0 -150,0 -160,0 -160,0

T (dBc & 25 kHz) -44,2 -67,2 -89,2 -104,2 -119,2 -139,2 -149,2 -149,2

U (dBc & 25 kHz) -76,0 -81,0 -86,0 -88,0 -91,0 -96,0 -101,0 -104,0

W (dBc & 25 kHz) -61,0 -63,0 -65,0 -66,0 -69,0 -72,0 -78,0 -93,0

X (dBc & 25 kHz) -44,2 -63,0 -65,0 -66,0 -69,0 -72,0 -78,0 -93,0

1 2 4 8 16 32 64 128

Figure 5-7: Estimated B-VHF Spectrum

Series "R" represents the [ETSI-DAB] DAB out-of-band spectrum limits (spectral mask) expressed as in-band/out-of-band power ratio (dB & 4 kHz) measured in 4 kHz bandwidth (intermediate values for some frequency offsets have been calculated by respecting the original spectral mask shape). It can be observed that the DAB out-of-band floor due to noise, intermodulation etc. is around -80 dB.




Series "S" has been derived from [B-VHF D18]. It represents the results of side-lobe suppression (D18 V0.4 Fig. 8-22, combined case 2 CC + rc window) expressed as out-of-band power density (averaged over 25 kHz) relative to the in-band power density (dB & 25 kHz). As both in- and out-of-band densities are flat, the series �S� also describes the ratio of total in-band/out-of-band powers within 25 kHz bandwidth or any other narrow bandwidth.

Series "T" has been derived from the series "S". It denotes the total out-of-band power of TX side-lobes (that was measured in 25 kHz BW and expressed as �dBc & 25 kHz�), that is now referred to the (reference) power of a single in-band OFDM carrier instead of a total B-VHF signal power. The single carrier reference power has been calculated from the series "S" by assuming that 12 in-band OFDM carriers are contained within 25 kHz bandwidth (reference single carrier power is 10,8 dB below composite power of 12 carriers). As for series �S�, series �T� only includes effects of side-lobes, excluding aspects of phase noise or intermodulation.

Series "U" represents estimated B-VHF phase noise power measured in 25 kHz relative (dBc & 25 kHz) to the maximum power of a single active carrier (appearing at the edge of the RF channel).

NOTE: It was assumed that the OFDM carrier phase noise density (single carrier) is the same as the phase noise density of the DSB-AM carrier described by the series �A� of the corresponding figure.

Series "W" represents the estimated B-VHF phase noise power measured in 25 kHz relative (dBc & 25 kHz) to the maximum power of a single active carrier, however with contributions of 512 active carriers occupying entire B-VHF RF channel. All B-VHF carriers are assumed to have the same power level.

Finally, series "X" represents the estimated total out-of-band B-VHF spectrum (dBc & 25 kHz) derived as a worst-case between series �T� and �W�. The impact of side-lobe suppression is expected to dominate only at small offsets (<25 kHz), while phase noise would probably dominate at larger offsets (> 25 kHz).

NOTE: It is assumed that the B-VHF out-of-band spectral mask could be made much better than the DAB mask due to B-VHF specific side-lobe suppression techniques (as demonstrated within the B-VHF project) and due to the assumed usage of power amplifiers with very high IP3 (technically feasible, but with corresponding cost impact).

5.7.5. B-VHF Spectrum (DME Range)

One candidate B-VHF channel bandwidth is 1 MHz, which is comparable to the required bandwidth for the UAT system. Brief inspection of UAT transmitter mask [RTCA DO-282] has shown that the main energy of an UAT signal is contained within 1.3 MHz bandwidth, but outside that bandwidth the radiated power decays relatively slowly.

The UAT mask (expressed as the ratio of the out-of-band power to the in-band power measured in 100 kHz bandwidth) is shown as series �M� in Figure 5-8.

Series �N� represents the estimated out-of-band spectrum of the B-VHF system that is operating in the VHF range (as described in section 5.7.4). This spectrum is described as a power measured in 25 kHz (dBc & 25 kHz) relative to the maximum power of a single active OFDM carrier.




Series �O� represents an estimate for the out-of-band spectrum of the B-VHF transmitter that would operate in the DME band. It has the same shape as the spectrum of the transmitter operating in the VHF range, except that the original phase noise values have been increased by 18 dB due to the higher operating frequency. For ∆f = 25 kHz where the contribution of the phase noise is not dominating the same value of � 44,2 dBc has been retained as in the VHF case.

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M (dB & 25 kHz) N (dBc & 25 kHz) O (dBc & 25 kHz)

M (dB & 25 kHz) 0 0 0 0 0 -10,8 -33,36 -60

N (dBc & 25 kHz) -44,2 -63,00 -65,00 -66,00 -69,00 -72,00 -78,00 -93,00

O (dBc & 25 kHz) -44,2 -45 -47 -48 -51 -54 -60 -75

1 2 4 8 16 32 64 128

Figure 5-8: Spectra of Signals in the DME Range

It is expected that the B-VHF spectral mask for the system operating in the DME range is completely contained within the UAT mask, at least for the following reasons:

! B-VHF-specific side-lobe suppression techniques provide rapid decay of out-of-band side-lobes at close distances from the outermost OFDM carrier in the B-VHF spectrum. Such detailed side-lobe management (particularly important at moderate relative power levels between 0 dB and -50 dB) is not possible with the UAT system.

! B-VHF system design enables that any number of OFDM carriers can be left-out at any position within the broadband RF channel. In case incompatibility problems with a DME, UAT or MIDS system that operates in an out-of-band (�O�) constellation with respect to the B-VHF system, the required number of �boundary� carriers can be intentionally left-out. This would further optimise the B-VHF spectral mask.




5.7.6. B-VHF Spectrum (MLS Range)

The out-of-band spectrum for the B-VHF transmitter operating in the MLS range (5 GHz) is expected to have similar shape as the spectrum of the system operating in the DME range (Figure 5-8) except for the further increase of the noise floor for additional 15 dB at all offsets.

5.7.7. B-VHF Spectrum (VOR Range)

The spectrum of a B-VHF transmitter operating in the VOR range (116-118 MHz) is expected to have same shape as the spectrum of the B-VHF transmitter operating in the VHF COM range.

----------- END OF SECTION -----------




6. Spectrum Management Guidelines

6.1. Separation Distances

Each radio receiver can only cope with some maximum amount of external interference. In order to achieve safe operation, the antennas of the victim receiver and the interfering transmitter must be sufficiently spatially separated.

On the other side, the involved aircraft and ground stations may appear in different constellations, constrained by the minimum separation distances that are considered as �safe� in a given environment.

Case Interference Scenario Separation (m)

Isolation (dB)

Max. Signal Power at RX Input (dBm)

1 GND Aircraft !" GND Aircraft 210 60 -22

2 GS !" GND Aircraft 750 71 -33

3 Flying Aircraft !" GS/GND Aircraft 600 70 -32

4 Flying Aircraft !" Flying Aircraft 600 70 -32

5 Aircraft !" same Aircraft (co-site) - 30 +8

6 GS !" GS (incl. co-site) - 30 +8

Table 6-1: Minimum DSB-AM - VDL Separation Distances (m)

Table 6-1 summarizes the minimum operationally allowed distances [ACP_F14-WP5] between the transmitting and receiving antennas of narrowband communications systems (flying and ground DSB-AM/VDL x aircraft and GSs) operating in the VHF COM range. The table also indicates the isolation between isotropic antennas as well as the maximum power that would be received by the victim receiver from a narrowband interferer operating with +41 dBm EIRP at 118 MHz at indicated distance.

In [ACP_F14-WP5] the calculation of required protection distances between VDL and DSB-AM systems has been done considering these operational separation distances, based on selected protection criteria. This method [ACP_F14-WP5] has yielded some results that cannot be easily achieved in the practice:

! In case 1 (two aircraft on the ground) the minimum possible actual aircraft spacing is between 50 and 100 m, but the minimum specified VDL2/DSB-AM received signal level of -85 dBm (as specified in ICAO Annex 10) can only be kept protected if the interferer is at an increased distance (210 m).

! In case 2 the minimum possible spacing between the GS and an aircraft on GND to achieve the protected signal level from ICAO Annex 10 at the GS RX input is between 100 and 150 m, but the protection distance had to be increased to 750 m.

! In case 5 (airborne co-location) the distance between two aircraft antennas has not been specified in [ACP_F14-WP5]. The value of 30 dB has been selected as representative for small aircraft [B-VHF D11].

! In case 6 (ground co-location) the minimum separation has not been specified in [ACP_F14-WP5]. It is assumed that the minimum isolation between GS antennas is similar (30 dB) to the airborne co-location case.




6.1.1. B-VHF Interference Scenarios

Due to the B-VHF FL/RL asymmetry, an increased number of detailed interference cases is possible in the B-VHF context (Table 6-2).

Case Interference Scenario Separation (m)

Isolation (dB)

1 BN GND B-VHF Aircraft " GND NB Aircraft 210 60

2b BN GND B-VHF Aircraft " NB GS 750 71

3d BN GND B-VHF Aircraft " Flying NB Aircraft 600 70

3b BN Flying B-VHF Aircraft " GND NB Aircraft 600 70

3a BN Flying B-VHF Aircraft " NB GS 600 70

4 BN Flying B-VHF Aircraft " Flying NB Aircraft 600 70

2a BN B-VHF GS " GND NB Aircraft 750 71

3c BN B-VHF GS " Flying NB Aircraft 600 70

5 BN B-VHF Aircraft Radio " NB Aircraft Radio (co-site) not specified 30

6 BN B-VHF GS " NB GS (incl. co-site) not specified 30

1 NB GND NB Aircraft " GND B-VHF Aircraft 210 60

2b NB GND NB Aircraft " B-VHF GS 750 71

3d NB GND NB Aircraft " Flying B-VHF Aircraft 600 70

3b NB Flying NB Aircraft " GND B-VHF Aircraft 600 70

3a NB Flying NB Aircraft " B-VHF GS 600 70

4 NB Flying NB Aircraft " Flying B-VHF Aircraft 600 70

2a NB NB GS " GND B-VHF Aircraft 750 71

3c NB NB GS " Flying B-VHF Aircraft 600 70

5 NB NB Aircraft Radio" B-VHF Aircraft Radio (co-site) not specified 30

6 NB NB GS " B-VHF GS (incl. co-site) not specified 30

7a BB B-VHF GS " Flying B-VHF Aircraft of other GS TBD TBD

7b BB Flying B-VHF Aircraft " other B-VHF GS TBD TBD

Table 6-2: B-VHF - NB Interference Cases

Cases �xBN� denote interference from the B-VHF broadband system towards the narrowband receiver, while cases �yNB� denote interference in the opposite direction.

Last two cases (7a BB, 7b BB) in Table 6-2 cover the �B-VHF to B-VHF� interference, covering both co-channel and adjacent channel sub-cases.




6.2. Interference Environment of a B-VHF Cell

r_C

h_C

d_W

d_W

d_S

d_S

�S� NB A/C

�W� NB GSB-VHF GS

�S� NB A/C

�W� NB A/C

�W� NB A/C

B-VHF A/C

�S� NB GS

Figure 6-1: B-VHF Cell and Interference Zones

Each B-VHF cell is allocated a dedicated B-VHF RF broadband channel. That channel can be re-used only beyond some distance from the first cell, according to the �co-channel protection criteria� described in section 6.3. A B-VHF aircraft is authorised (by using existing operational procedures) to use the RF channel of a particular cell only if it is within the cylindrical CDOC of that cell defined by (r_C, h_C).

NOTE: Normally, the relation r_C >> h_C applies. Hence, in the following only r_C is considered.

The B-VHF receiver of an aircraft flying at the CDOC boundary shall receive the signal from the controlling GS with a level not less than the protected B-VHF signal level PR (as applicable to an aircraft receiver in a given environment). The EIRP for the GS and the cell size (r_C, h_C) are adjusted in such a way that this condition is fulfilled. At the same time, the GS shall adjust the PR for the aircraft transmitter in such a way that the B-VHF signal power at the GS receiver is above the protected B-VHF signal level PR (as applicable to the GS). The B-VHF PR values for several representative CDOCs are captured in Table 5-1.

Around the CDOC of a particular cell there is a cylindrical area defined by (r_C + d_W, h_C + d_W).




WEAK NB interferers are those transmitters outside the (r_C + d_W, h_C + d_W) area that would always be received by the B-VHF aircraft flying at the CDOC boundary with a power below the STRONG/WEAK threshold (I_t) value that is applicable to that cell.

WEAK NB interferers that operate within/outside the selected B-VHF RF channel would appear in the �W�/�O� constellation with respect to the B-VHF signal, respectively. The B-VHF receiver must be able to operate properly when multiple �W� interferers are simultaneously active within the RF broadband channel. Interference power from �W� channels is further reduced prior to the OFDM demodulator by applying internal interference suppression mechanisms.

NOTE: The threshold value I_t must be known in order to identify STRONG signals within the broadband B-VHF channel that require specific handling within the B-VHF receiver. Once the representative B-VHF radios become available, the �real� I_t value will probably be determined via laboratory measurements and will depend upon the �real� B-VHF receiver ability to suppress STRONG narrowband interference. As the effectiveness of such measures within the B-VHF RX is still unknown, in [B-VHF D9] and in this document a range of I_t values was used.

Knowing the (fixed) maximum EIRP of a narrowband (DSB-AM) transmitter (EIRP_N = +41 dBm), the selected interference threshold value (I_t) and the combination of cable losses and antenna gain of a the B-VHF receiver (a_R), it is possible [B-VHF D9] to calculate the total propagation loss (Lp) between the NB transmitter and the B-VHF receiver

Lp = EIRP_N � I_t � a_R

From Lp the required separation distance d_W between the �W� NB transmitter and the B-VHF receiver can be derived by applying free-space propagation law.

NOTE: The d_W value has been derived by observing �unilateral� NB " B-VHF interference. In order to declare interference-free B-VHF�NB condition the d_W value must be validated against results of laboratory measurements with real representative B-VHF radio hardware, for both directions ( B-VHF " NB and NB " B-VHF). The worst-case result should be retained for frequency planning purposes.

In order to get an impression about physical separation between systems, Table 6-3 shows calculated distance d_W for operating frequency f = 118 MHz and different threshold values I_t (with 25 kHz bandwidth) applicable to the B-VHF aircraft at the cell boundary.

STRONG/WEAK Interference Threshold I_t (dBm)

EIRP_N (dBm)

Prop. Loss (dB)

Calculated Separation Distance d_W (nm)

-90 +41 128 270

-85 +41 123 157

-80 +41 118 86

-75 +41 113 49

-70 +41 108 28

Table 6-3: B-VHF � Calculated Separation Distance d_W for f= 118 MHz




Preliminary calculations of spectral availability [B-VHF D9] have shown that the spectrum availability rapidly decreases with decreasing I_t. On the other side, very high I_t values lead to high B-VHF transmitting power that may jeopardise operation of NB receivers. Therefore, only the I_t range between -85 dBm and -75 dBm is considered to be realistic.

STRONG NB interferers are those operating within the (r_C + d_W, h_C + d_W) area that may eventually be received by the victim B-VHF receiver with a power above the threshold I_t. Dependent on whether they operate within/outside the selected B-VHF RF channel, such interferers would appear in the �S�/�O� constellation with respect to the B-VHF signal, respectively.

Wherever possible, the number of local �S� interferers shall be reduced by applying frequency management methods to the narrowband systems � existing �S� allocations shall be removed from the B-VHF RF channel to become �O� interferers or, if such moving is not possible, another broadband RF channel shall be selected.

NOTE: In the practice this means that the existing �S� NB GSs should be converted to an �O� constellation � this conversion automatically removes airborne �S� interferers on these channels.

Remaining narrowband �S� channels that could not be moved out of the B-VHF RF channel must be specially handled by the B-VHF system. These channels are not used by the B-VHF TX (are suppressed in the B-VHF signal spectrum) and must be notched-out in the B-VHF RX.

The depth of B-VHF RX notch filters must be sufficient to attenuate even the strongest possible �S� signal to appear as a WEAK in-band signal (�W�) to the OFDM demodulator. From there on, these signals are handled as �W� signals, e.g. by applying interference suppression mechanisms.

NOTE: The depth of the B-VHF RX notch filters for �S� signal suppression will be a fixed parameter (dB) that can currently be only estimated as 53-63 dB, by considering the difference between the maximum possible STRONG NB signal level (-22 dBm, coming from another aircraft on the airport surface) and the assumed range for STRONG/WEAK threshold (-75 dBm � -85 dBm).

As �S� channels cannot be used for voice and data transmission by the B-VHF TX and the shape of notch filters is never ideal, each �S� channel reduces the number of �usable� OFDM carriers and therefore the system capacity. Hence, the B-VHF system can only tolerate a certain maximum number N_S of �S� interferers. Additionally, the maximum total received power of all �S� interferers must be limited as the entire B-VHF receiving chain between the B-VHF RX input up to and including the A/D converter must be able to cope with that power.

Dependent on the local situation, STRONG interferers may be located either within the cell radius r_C or outside the cell, up to the (r_C + d_W) limit (Figure 6-1).

Even with advanced B-VHF-specific interference mitigation methods in the B-VHF transmitter (side-lobe suppression) and receiver (interference mitigation) it will not be possible to completely eliminate interference to- and from �S� narrowband channels. Moreover, narrowband receivers have only limited strong signal handling capability, including strong local B-VHF signals, so a minimum protection distance (d_S) between the B-VHF GS/airborne radio and the closest narrowband GS/airborne radio will be always required.




The distance d_S is obtained as worst-case from NB " B-VHF and B-VHF " NB interference cases (assuming �S� constellation) and must be carefully checked against the minimum possible operationally allowed distances between the aircraft in a given environment (as reducing aircraft spacing below d_S may jeopardise communications safety).

NOTE: The protection range d_S is expected to be significantly smaller than d_W (as B-VHF TX reduces its power density over �S� channels and B-VHF RX applies filtering and interference mitigation measures over such channels).

The protection distance d_S depends on the effectiveness of the implemented B-VHF-specific measures for interference mitigation in the B-VHF transmitter and receiver. It includes multiple RF issues and mechanisms and can only be determined by laboratory measurements with representative narrowband systems once mature �representative B-VHF radio hardware� becomes available.

NOTE: Once obtained, the �representative� d_S value must be verified against operationally required/allowed minimum distances between aircraft and/or GSs, respectively.

Figure 6-2: Distance d_S

6.3. Approach for B-VHF Frequency Planning

[ACP_F14-WP5] provides an overview of protection parameters and criteria applicable to the interaction of currently used narrowband systems (DSB-AM, VDL2, VDL3 and VDL4).

The procedure for defining B-VHF-specific frequency planning criteria would start as for other VHF systems with laboratory measurements on representative B-VHF and narrowband equipment. The measurements should be repeated for both directions (both B-VHF- or narrowband receiver can be the victim) and for all possible B-VHF-NB combinations. The measurements aim to determine the level of susceptibility of a victim receiver that is receiving a weak desired signal to the strong interference signal produced by the undesired signal source.




6.3.1. General Procedure

The characteristics of both desired and undesired signal must be carefully specified. The entire procedure must be repeated for each pair of interfering systems.

During measurements the level of a desired (B-VHF or narrowband) signal Pd is kept constant, corresponding to the required protected (Pd = PR) value (Table 5-1). The level of an undesired (narrowband- or B-VHF-) signal Pu is increased � starting from some very low value � until the specified degree of degradation of a desired signal is observed.

The degradation itself may be due to direct interference power that is received within the bandwidth occupied by the desired signal (e.g. SNR reduction due to the radiated phase noise, side-lobes or intermodulation products) or due to different non-linear effects within the victim receiver that effectively transfer out-of-band signal energy into the reception bandwidth (e.g. reciprocal mixing due to the LO phase noise).

The protection parameter value shall be met with the specified minimum desired signal level (Pd) at the receiver input according to Table 5-1 and also with an undesired signal at a maximum level (Pu) that does not cause yet exceeding the protection parameter.

NOTE: [ACP_F14-WP5] power levels are related to the input of the victim receiver antenna, but can easily be converted to corresponding values at the input of the victim receiver by considering the fixed (and known) receiver antenna gain and cable loss.

The protection criteria are used with variable frequency separation ∆f between involved systems. Pd/Pu ratio measurements are performed for a case where both systems are tuned to the same narrowband VHF channel (�co-channel� interference) and for a case where the desired source and interferer are offset by ∆f = 1, 2, 3, 4, 5, 10, 20 and 40 (25-kHz channels).

NOTE: Where a broadband B-VHF system is involved the traditional �co-channel� approach must be replaced by B-VHF-specific in-band measurements, considering both �W� and S� constellations.

For each offset ∆f the level of the undesired signal level Pu is increased until the protection parameter value is achieved and the corresponding Pd/Pu power ratio is noted. Knowing the Pu value and the EIRPu of the undesired signal transmitter, the protection distance d (in km) can be calculated for a given frequency f (in MHz) as:

20log(d) = EIRPu � Pu � 20 log(f) � 32.4 (dB)

Afterwards, the obtained distances d are compared with the minimum operationally required/allowed separation distances in each environment (section 6.1) and the conclusions about the required ∆fmin (number of required guard channels) are drawn (∆fmin is obtained from the minimum tabulated d value that is smaller than the minimum operational distance in that environment/scenario).

The procedure is repeated for the interference in the opposite direction (where a former interferer becomes a victim) as well as for other applicable protection criteria and the worst-case ∆fmin value is retained.

NOTE: As the B-VHF FL/RL transmitting per-carrier power may be different in different environments (APT/TMA/ENR), the spatial protection distance d and the required minimum frequency separation ∆fmin depend on the current B-VHF operating environment.




6.3.2. DSB-AM Victim Receiver � B-VHF Interferer

6.3.2.1. Protection Criteria

In case where a DSB-AM receiver is the victim following protection criteria have been defined [ACP_F14-WP5]:

1. Squelch opening (the level of undesired signal Pu where squelch opens is noted, without desired signal Pd)

2. Subjective evaluation of the voice quality (with specified desired signal Pd and interference signal Pu and therefore with fixed Pd/Pu ratio)

3. (S+N)/N degradation (with specified desired signal Pd and variable undesired signal Pu)

4. S/P ratio (calibrated by the desired signal Pd, measured with only undesired signal Pu without desired signal Pd)

6.3.2.2. Measurements

For all measurements except (1) � squelch opening � the desired DSB-AM signal should be modulated (m=30%) with a 1 kHz sinusoidal tone, producing the required signal strength at the input of the victim DSB-AM receiver according to Table 5-1.

For S/P measurements the B-VHF signal should be adjusted according to realistic B-VHF duty-cycle (framing). For S/P measurements with B-VHF interferer, the target S/P value is TBD yet.

Separate measurements are required for airborne/ground victim DSB-AM receiver, including appropriate ground/air interfering B-VHF transmitter. All measurements should be performed in different constellations (�O�, �W�, �S�), for different frequency offsets ∆f and with closely specified B-VHF signal spectrum (yet TBD, e.g. with maximum applicable number of carriers).

6.3.3. VDL Victim Receiver � B-VHF Interferer


According to [ACP_F14-WP5], the impact of DSB-AM transmitter onto VDL receiver is assessed by a using single criterion � BER degradation of the desired signal D (with fixed specified level) under presence of an undesired signal U (with variable level).

This criterion � BER degradation � is also considered as appropriate for the case of B-VHF � VDL interference.


Separate measurements are required for airborne/ground victim VDL receiver, including appropriate ground/air interfering B-VHF transmitter. Independent measurements are required for each type of VDL equipment (VDL2, VDL4).

Out-of-band measurements in �O� constellation and in-band measurements (separately for �W� and �S� constellation) with a VDL receiver should be performed for different frequency offsets ∆f.




6.3.4. B-VHF Victim Receiver � DSB-AM or VDL Interferer


While the protection criteria for NB systems are relatively mature and have only to be enhanced by adding some B-VHF-specific methods, protection criteria for the B-VHF receiver have to be developed from scratch.

Two separate criteria, acceptable uncorrected BER for voice and corrected BER for data, seem to be applicable to a digital B-VHF receiver. These values should not be exceeded for all types of narrowband interferers.

For the B-VHF receiver following BER degradation criteria are proposed:

! Maximum acceptable uncorrected BER for voice channels should be 10-3

NOTE: This value has been required [ACP_F14-WP5] for the VDL Mode 3 voice operation. B-VHF system uses the same vocoder as VDL Mode 3 and like VDL Mode 3 provides no internal coding protection for voice packets, so the same acceptance criterion is considered to be applicable for both systems.

! Maximum acceptable corrected BER for data channels (incl. FEC) is 10-4

NOTE: This value has been required [ACP_F14-WP5] as corrected data BER for VDL Mode 2 and is also considered as a possible acceptance criterion for B-VHF data system.

In an integrated B-VHF system both criteria must be fulfilled at any time, so the worse result has to be considered.


Separate measurements are required for ground/airborne B-VHF receiver, including appropriate airborne and ground interfering NB transmitters for each type of NB equipment (DSB-AM, VDL2 and VDL4). All measurements should be performed in different constellations (�O�, �W�, �S�) for different frequency offsets ∆f.

The characteristics of undesired signals should be kept comparable to these described in [ACP_F14-WP5]:

! Voice with 30% modulation depth for DSB-AM interfering transmitter, corresponding to 90% peak amplitude modulation with ATC phrases

! VDL2 transmitter with 2% channel loading

! VDL4 transmitter with various channel loading

6.3.5. B-VHF Victim Aircraft Receiver � Interfering B-VHF GS

In the scenario 7aBB in Table 6-2, a victim B-VHF aircraft flying at the range of CDOC of its controlling GS1 is interfered by the distant non-controlling B-VHF GS2 that uses the same (�co-channel�) or adjacent RF channel (Figure 6-3).

All B-VHF GSs are mutually synchronised to the same reference. The interference can occur during airborne reception of BC or FL frames of the controlling GS1. Unless a victim aircraft is exactly in the middle between two GSs the symbols contained in corresponding desired/undesired FL or BC frames would be offset because of different propagation delay (1.,.3 ms frame offset per 200 nm difference in the propagation distance).




Both GSs are assumed to have the same CDOC defined by the maximum usable distance �d� and use all available carriers over BC frames and FL frames with exactly the same carrier constellation within the common RF channel.

Figure 6-3: B-VHF to B-VHF Interference


The uncorrected BER degradation criterion for voice and corrected BER criterion for data, as specified in section 6.3.4.1, are considered to be applicable to the victim B-VHF receiver in this scenario.


The required separation distances should be determined via laboratory measurements using representative B-VHF radio equipment for different frequency offsets ∆f.

6.3.6. B-VHF Victim GS Receiver� Interfering B-VHF Aircraft

Scenario 7bBB in Table 6-2 describes the case where a flying A/C2 controlled by GS2 transmits (dashed lines in Figure 6-3) RA or RL frames operating on the same (co-channel) or adjacent RF channel to that used by GS1 that cause interference at the victim GS1 (that normally receives RA/RL frames from the �own� aircraft A/C1).

The worst �co-channel� case would occur during RA transmissions as both GSs would probably advise their aircraft to use the same sub-set of available carriers by applying similar rules. The probability of collisions during RL transmissions is lower than for RA slots as two GSs may allocate different sets of RL carriers to their aircraft and could be further reduced if the GSs used the knowledge about aircraft position when allocating RL carriers to the aircraft.


The uncorrected BER degradation criterion for voice and corrected BER criterion for data, as specified in section 6.3.4.1, are applicable to the victim B-VHF receiver.





The required separation distances should be determined via laboratory measurements using representative B-VHF radio equipment for different frequency offsets ∆f.

6.4. Interaction of DSB-AM and B-VHF Signals

The amplitude spectrum of a DSB-AM signal modulated with a single-tone is represented in Figure 6-4 together with a part of the B-VHF signal that may span the 25 kHz bandwidth. Figure 6-4 also shows real reception bandwidths (22/7 kHz) of a 25/8.33 kHz DSB-AM receiver, respectively.

Figure 6-4: DSB-AM and B-VHF Signals

In case of single-tone modulation, the relation between the sideband power PSB (single sideband) and the carrier power Pc of a DSB-AM signal is given by:

PSB(dB) � Pc(dB) = 10 log (m2/4)

It can be seen from Figure 6-4 that the power of each of 12 B-VHF sub-carriers within 25 kHz bandwidth would have to be set to 10,8 dB below the DSB-AM signal power (m = 30%) in order to produce the same received power within the 25 kHz bandwidth.

6.4.1.1. Impact of DSB-AM Signal onto B-VHF RX

With single-tone modulating signal and m = 1, the power in each of the two sidebands would be ¼ of (6 dB below) the carrier power. With m = 0,3 the power in each of the two sidebands would be 16,5 dB (Figure 6-4) below the carrier power.

This indicates that in a typical case the DSB-AM sideband power may be almost completely neglected compared to the DSB-AM carrier itself.

Any single 25/8.33 kHz DSB-AM transmitter signal occupies at most 7 kHz of RF bandwidth and would therefore theoretically directly affect at most 4 successive OFDM carriers. However, even if the power of a strong interfering DSB-AM signal is constrained to a narrow bandwidth (7 kHz), such a signal can still indirectly (via leakage effect) influence B-VHF OFDM carriers that lie outside that bandwidth.




If the carrier of a DSB-AM interferer could be eliminated by interference mitigation techniques within the B-VHF receiver the total direct interference power would be significantly reduced (13 dB). It is apparent that if the DSB-AM carrier power were reduced, the leakage effect would be reduced as well.

6.4.1.2. Impact of B-VHF Signal onto DSB-AM RX

From the standpoint of a victim DSB-AM RX the worst case occurs when the B-VHF TX simultaneously transmits with the maximum specified per-carrier power over all carriers that lie within the DSB-AM bandwidth. Maximum effective bandwidth of a 25/8.33 kHz DSB-AM victim receiver is 22/7 kHz, respectively (Figure 6-4). Therefore, with assumed flat B-VHF spectrum the 25 kHz DSB-AM receiver would receive about 5 dB (22/7) more interference power than the 8.33 kHz receiver due to the contributions of up to 11 successive OFDM carriers, instead of 3 � 4 carriers that would only be �seen� by the 8.33 kHz DSB-AM receiver.

NOTE: 25 kHz DSB-AM RX is more susceptible to the B-VHF interference than the 8.33 kHz RX. B-VHF system deployment in the �8.33 kHz airspace� above FL 245/FL195, respectively, may be easier than in lower airspaces as according to the DSB-AM RX susceptibility criterion the separation distance between the B-VHF TX and the 8.33 kHz RX could be halved compared to the case with the 25 kHz RX.

B-VHF GS transmitting in the BC slot (�broadcast� slot at the beginning of the super-frame) always uses all available carriers (Nc). B-VHF GS transmitting in the FL slot typically may also use all carriers.

Transmitting B-VHF aircraft would use only a relatively small number (at most 48) of OFDM carriers for RA/RL transmissions, scattered (due to frequency interleaving) over multiple 25 kHz channels within the B-VHF RF bandwidth. Due to the interleaving and resource allocation policy it can be assured that any B-VHF aircraft would simultaneously use at most 2-3 OFDM carriers within any 25 kHz channel.

6.5. Results of B-VHF Laboratory Tests

Within the WP 4 of the B-VHF project laboratory measurements have been conducted by using commercially available narrowband radios as well as B-VHF demonstrator. The results have been captured in [B-VHF D34].

The B-VHF demonstrator comprised the prototype RF front-end and the baseband implementation of the B-VHF physical layer. During measurements the B-VHF transmitter could be configured either to use or to exclude OFDM carriers that fall over the narrowband channel used by the DSB-AM system. Additionally, windowing has been applied at both B-VHF TX and RX in order to reduce the level of transmitted side-lobes and the leakage effect at the receiver. However, advanced B-VHF-specific measures for interference mitigation proposed in [B-VHF D18] like side-lobe suppression within the B-VHF transmitter, filtering or leakage compensation within the B-VHF receiver, could not be implemented.

In order to measure the interference imposed by the B-VHF system on a DSB-AM victim receiver different tests have been carried out, comprising squelch opening, SINAD reduction, perceptual evaluation of speech quality and signal-to-pulse measurements.

NOTE: These measurements are described in detail in section 6.3.2.1




The performance of the B-VHF receiver under DSB-AM interference conditions has been investigated by bit error rate measurements.

During measurements the B-VHF radio transmitter has operated at relatively low power level. Some problems have been experienced with the RF hardware - spurious signals have been observed in the up- and down-conversion stages, different results have been obtained for B-VHF receiver sensitivity during subsequent measurements and for different system configurations, accompanied by the synchronisation problems. This indicates that the current results of the laboratory measurements � in particular those related to the spectrum of the B-VHF signal-in-space - should not be considered as representative for the mature B-VHF system and that continuation of the work on the B-VHF demonstrator and further test measurements are needed in order to provide more reliable conclusions.

The current results show that an additional B-VHF interference reduction is necessary at transmitter and also at receiver of B-VHF system. There are strong indicators that the results of interference investigations would be significantly improved if advanced interference mitigation measures were in place.

With respect to the B-VHF interference on DSB-AM legacy systems, a proposal for an acceptance criterion has been made. Subjective perceptual measurements have indicated that the level of an interfering B-VHF signal shall be 10 dB below the value that leads to a 6 dB SINAD reduction of the DSB-AM receiver output signal.

6.6. B-VHF System Deployment in the DME Range

6.6.1. B-VHF System Interaction with UAT/DME/MIDS/JTIDS Systems

The bandwidth of DME and UAT signals is larger than the bandwidth of the B-VHF RF channel and the duration of DME transmission is significantly shorter than B-VHF FL/RL bursts. The B-VHF receiver would probably experience only short interference over parts of FL/RL bursts. It is possible that this interference could be completely recovered by appropriate mitigation mechanisms.

The impact of the interference in the opposite direction, from the B-VHF system towards other systems operating in the DME band, is completely unknown. Therefore, the currently preferred B-VHF system deployment concept in the DME range is based on dedicated B-VHF channel allocations, without overlay.

In any B-VHF deployment scenario in the target DME range, UAT channel (978 MHz) is considered to be unavailable for the B-VHF system (with or without overlay concept, the B-VHF system will avoid that channel). A number of dedicated 1 MHz channels required for the B-VHF system deployment is selected and allocated within the 63 MHz range that remain �available� in the target DME range after the UAT channel was deemed unavailable.

Frequency planning criteria must be developed prior to the B-VHF system deployment, with precise separation rules for any combination of the B-VHF system and any other system operating in the DME target band.

Existing DME frequency planning criteria may eventually be used as a first estimate for the system interoperability and as a starting point for the development of B-VHF-specific planning criteria, supplemented by the UAT planning criteria.

Detailed investigation of B-VHF interaction with MIDS/JTIDS system would be required.




6.7. B-VHF System Deployment in the MLS Range

The currently preferred B-VHF system deployment concept in the MLS range is based on dedicated B-VHF channel allocations, without overlay. Frequency planning criteria must be developed prior to the B-VHF system deployment, with precise separation rules for any combination of the B-VHF system and any other system operating in the MLS target band.

6.8. B-VHF System Deployment in the VOR Range

As in other non-VHF COM ranges, the currently preferred B-VHF system deployment concept in the VHF VOR range is based on dedicated B-VHF channel allocations, without overlay. Frequency planning criteria must be developed prior to the B-VHF system deployment, with precise separation rules for any combination of the B-VHF system and any other system operating in the VHF VOR and VHF COM band.

----------- END OF SECTION -----------




7. Initial B-VHF System Deployment Scenarios

This chapter provides scenarios for the initial B-VHF system deployment in the VHF COM range and non-VHF COM ranges.

As the B-VHF system introduction is linked to significant costs for all actors, prior to the B-VHF system deployment a roadmap should be developed similar as for the LINK 2000+ deployment, in order to get a commitment of all involved parties.

7.1. Common Aspects

This section captures aspects that are common to all B-VHF deployment scenarios and defines some terms that will be used in the following sections and chapters of this document.

7.1.1. B-VHF Operational Scenarios and Functional Scope

The scope of B-VHF services is described in [B-VHF D7] Table 8-1 and in the chapter 8.1- Scenario for 2011-2015. A detailed overview of operational applications and data link services applicable to that scenario is given in Table 7-1 (column �2011�) of the same document.

In this scenario, voice is still a primary means for tactical exchanges and serves as a back-up for the loss of data link. Voice services are restricted to the �traditional� party-line service (B-VP) and broadcast service (B-VB); selective voice service (B-VS) is not supported in that phase. Ground-supported pilot-pilot voice communications and AOC voice communications are provided by using party-line (B-VP) service.

Data link is used as a primary means for non-tactical purposes. Initially supported data link services comprise air-ground ATN data link services for different ATS and AOC purposes:

! Pilot-ATCO dialogue (e.g. ACL, Auto-CPDLC, AMC, D-TAXI, D-SIG, DCL, DSC, ARMAND, GRECO, D-ALERT)

! ATM automation (DLL, FLIPCY, FLIPINT)

! FIS provision (D-ORIS, D-OTIS, D-RVR, D-SIGMET, D-FLUP)

! AOC data link (sub-set of all services)

All these air-ground data link services are expected to use an ATN-compatible interface of the B-VHF system, using internal B-VHF service (B-DA). More sophisticated air-ground services like DYNAV, COTRAC or services with expected high QoS demands like URCO are not supported in the initial phase.

Similarly, no support within the B-VHF system is initially foreseen for automated provision of aircraft data and broadcast data link services (internal B-DB and B-DN services are not supported).

NOTE: These are marked as applicable to 2011 in Table 7-1 of [B-VHF D7], but will not be provided via B-VHF system in its initial deployment phase. At the time of B-VHF introduction automated aircraft parameters will be provided via extended surveillance Mode-S data link, while 1090 ES technology will be used as a surveillance broadcast data link. This means that no B-VHF system access to




surveillance networks will be required in the initial phase (such access can be organised either centrally at the GNI, or at each radio site GSC).

7.1.2. Applicable Spectrum Ranges

The main focus of the B-VHF project was the feasibility of the overlay deployment concept in the VHF COM range. [ACPF14-WP14] identifies frequency bands 960 � 1024 MHz (DME) and 5091 � 5150 MHz (MLS) as suitable candidates for the implementation of future Aeronautical Mobile (Route) Services - AM(R)S. [ACPF14-WP21] indicates a possibility to deploy a new AM(R)S system in the upper part of the VOR range (116- 118 MHz).

Taking these additional opportunities into account, the B-VHF system may be deployed in:

! VHF COM range (118 � 137 MHz)

! VOR range (target range: 116 � 118 MHz)

! DME range (target range: 960 � 1024 MHz)

! MLS range (target range: 5091 � 5150 MHz)

The new system � B-VHF - shall operate in accordance with international aeronautical standards subject to the conditions that the new AM(R)S system(s) and shall not cause harmful interference to, claim protection from, or otherwise impose constraints on the operation and future development of other co-band aeronautical systems operating in accordance with international aeronautical standards.

7.1.3. Aircraft Capabilities

Two aircraft types can be defined with respect to the B-VHF system deployment:

! B-VHF aircraft represents an aircraft that is equipped by B-VHF radios (that can be operated in the B-VHF mode or backward-compatible NB mode). Multi-mode VHF radios are not allowed to be operated in narrowband modes if at least one multi-mode radio is used in the B-VHF mode

! NB aircraft represent an aircraft that is not yet equipped by B-VHF radios (only NB radios are available on board).

In order to be capable to cover all possible deployment scenarios, airborne B-VHF radios are considered to be multi-mode/multi-range radios, with a common baseband kernel and dedicated RF part for each particular frequency range, including receiver front end, transmitter output stage and up/down converters. Moreover, due to differing propagation conditions and interference environment, such multi-range transmitter would operate with different powers in different ranges and different operational environments (APP/TMA/ENR).

B-VHF aircraft would use B-VHF capabilities only within B-VHF airspace or B-VHF-supported airspace.

It is expected that the interest for B-VHF equipage will be generally higher for transport aviation than for general aviation as the benefits offered to the equipped aircraft � high performance data link - are also higher for that category.




7.1.4. Airspace Regimes

Three airspace regimes with corresponding rulemaking options for ground and airborne equipage are possible with respect to the B-VHF system deployment:

! B-VHF-supported airspace, where the B-VHF ground infrastructure must be deployed, but the airborne deployment of the B-VHF system is voluntary.

Within B-VHF-supported airspace a mixed ground NB/B-VHF infrastructure and mixed NB/B-VHF aircraft population would exist. B-VHF system would be operated in parallel to existing narrowband DSB-AMx and VDLy systems, providing some additional B-VHF services in parallel to existing narrowband services. No �rapid scheduled overnight switchover� to the new system would be required � new services would just have to be announced to the users and would be used at user�s discretion. For some services special precautions must be taken on the ground (gateways) to assure interoperability between NB and B-VHF aircraft.

! B-VHF airspace, where the B-VHF ground infrastructure must be deployed and the deployment of the B-VHF system is mandatory for all aircraft that intend to enter such airspace.

B-VHF airspace would be segregated from B-VHF-supported airspace or NB airspace. With this option, a �rapid scheduled overnight switchover� to the new system would be required.

Moreover, after the switchover, B-VHF system would remain as sole terrestrial air-ground communications system operated within that airspace, replacing all services that were previously provided over DSB-AMx and VDLy.

In case of the deployment in the VHF range, the only exception is the emergency NB channel (121.5 MHz) that shall be further used in parallel to the B-VHF system. As a consequence, the non-B-VHF NB ground infrastructure may be removed, except for the 121.5 MHz channel.

NOTE: This approach is similar to the deployment of the 8.33 kHz DSB-AM system within European upper airspace. Within European 8.33 kHz airspace there is no support for a 25 kHz DSB-AM system anymore, except for the emergency channel 121,5 MHz. It is not yet clear, whether the same exception also applies to the secondary SAR channel (123.1 MHz).

! NB airspace, where no ground B-VHF system is deployed (only NB ground infrastructure exists).

Within NB airspace mixed NB/B-VHF aircraft population may exist, but only NB VHF systems are used to provide communications services. NB airspace may be visited by B-VHF aircraft, but aircraft radios (even if B-VHF-capable) would always be operated in NB mode due to the lack of ground B-VHF support. Therefore, NB airspace is actually out of scope with respect to the B-VHF system deployment, but B-VHF airspace or B-VHF-supported airspace would always be surrounded by the NB airspace.




High ENR B-VHF Airspace

High ENR

NB Airspace

High ENR

NB Airspace

Low ENR

NB Airspace

Low ENR B-VHF-Supported Airspace

Low ENR

NB Airspace

FL 245

UNL

2000 ft

TMA

B-VHF-Supported Airspace

APT B-VHF

Airspace

APT NB Airspace

Figure 7-1: Airspace Regimes

An example of three airspace regimes (vertical view) is shown in Figure 7-1. In this example, it was assumed that an airport and a part of the upper-space have been converted to B-VHF operation. In low ENR airspace and within TMA, mixed B-VHF/NB operations are possible (B-VHF-supported airspace), while the rest of the airspace is a �conventional� NB airspace.

Dedicated B-VHF airspace option can also be seen as a last step of the voluntary equipage in a B-VHF-supported airspace.

B-VHF-supported airspace is the preferred deployment option from the purely technical standpoint as it is less restrictive than the dedicated airspace option - it does not require airspace segregation, mandatory airborne equipage or rapid switchover from the NB to B-VHF mode that may be difficult to co-ordinate. Wherever possible, the B-VHF system deployment shall start in the B-VHF-supported airspace.

Later on, after sufficient level of equipage has been reached, B-VHF-supported airspace can be easily converted to B-VHF airspace.

7.1.5. Spectrum Usage Options

Basically, B-VHF system deployment in any range may be based either on overlay or usage of dedicated channels.

! With dedicated channel approach (without overlay), other systems operate �out-band� with respect to the B-VHF broadband channel, without spectrum sharing. Here, Frequency Division Multiple Access (FDMA) is applied - dedicated 1 MHz/500 kHz channels (optionally also 250 kHz channels) that are not used by any other system are allocated to the B-VHF system. Traditional frequency planning criteria for that range are applied (specific new criteria would have to be developed for the B-VHF system).




! With an overlay approach, the B-VHF system shares the spectrum with other systems (these systems operate �in-band� with respect to the B-VHF broadband channel). It accepts some amount of interference from other systems (DSB-AM, VDL, DME, UAT, MIDS) operating within the same part of the spectrum that is used by the B-VHF system while itself not producing visible interference towards these systems. �Extended� frequency planning criteria must be developed, taking into account all traditional FDMA aspects for that range, as well as specific aspects due to an overlay approach.

NOTE: �Extended� B-VHF Frequency planning criteria must cover both internal rules for allocation of available B-VHF broadband channels and FDMA rules for interference-free operation of B-VHF and other co-located systems (separation distances).

The basic B-VHF cellular concept, developed for the VHF band, requires that B-VHF cells operate within the B-VHF system as frequency-protected service volumes - each cell is allocated a dedicated broadband channel. For a single cell, only one broadband channel is required, for wide-area coverage a certain minimum number of broadband channels must be allocated. Frequency planning criteria assure that with appropriate spatial separation of service volumes no B-VHF-to-B-VHF interference can occur that could jeopardise the required voice and data QoS.

7.1.6. System Configuration Options

B-VHF system has been designed to provide simultaneous support for both voice and data link communications, but it can be configured and practically deployed as an

! Integrated system, providing voice and data link services

! Data-only system, providing only data link services (voice services being provided via legacy DSB-AM system)

An option to deploy B-VHF as a voice-only system � although theoretically possible - is not seen as a realistic one, as the highest communications pressure is expected in the area of data communications and long-term scenarios anticipate that the role (very probably also capacity-) of the voice system will be reduced when compared with today�s situation. Moreover, co-location problems at the airborne platform in the VHF range may preclude any �non-integrated� solution.

7.1.7. Ground B-VHF System Architecture

The architecture of the ground part of the B-VHF system is shown in Figure 7-2. The B-VHF specific blocks (yellow) comprise the following parts:

! Ground Station (GS), comprising the

" Ground B-VHF Transmitter (G_TX)

" Ground B-VHF Receiver (G_RX)

" Ground Station Controller (GSC)

! Ground Network Interface (GNI)

! B-VHF Management System




The ground sub-system interfaces with airborne sub-system over B-VHF air-ground interface. On the other side, GNI interfaces with legacy Voice Communications System (VCS) and Data Link System (DLS).

B-VHF Mgmt.

VCS

GNI

DLS HMI

GND Network

GS

GSCA/C

G TX

G RX

GND Voice/Data Networks

Figure 7-2: Ground B-VHF System

The physical radio units (G_TX, G_RX) are connected to their local GSC via local connection. They comprise the Physical Layer and the parts of the DLL layer (MAC sub-layer) of the B-VHF protocol stack. G_TX acts as timing master for entire aircraft population within a cell and will have to maintain precise internal timing source.

The GSC implements the DLL layer components above MAC sub-layer, the BSS sub-layer and a part of the LME entity that is required for the operation of the B-VHF system on a single RF channel.

NOTE: The details of the B-VHF protocol stack and B-VHF-specific procedures for e.g. net initialisation, handovers or resource allocation are described in [B-VHF D7].

The GNI implements the LME part dealing with multiple cells and multiple broadband RF channels as well as B-VHF sub-network layer functions. GNI interfaces with external ATN and non-ATN Data Link Systems (DLS) as well as with an external VCS and may comprise Voice Units (vocoders) for B-VHF voice operation (alternatively these may be implemented within the VCS). The GNI is responsible for managing multiple GSs that may be involved with a particular wide-area voice/data service and supports on the ground side rapid switching of voice circuits between cells during cell handover.

The GNI maintains a central repository with ICAO addresses and assigned Local IDs of all aircraft that have logged at any of the attached GSs. Finally, the GNI will implement necessary B-VHF management functions, including the central repository of available VHF resources within an entire region.




NOTE: In some cases (e.g. in B-VHF-supported airspace) gateways are required within the ground architecture, interconnecting the part of the airborne population that uses legacy narrowband systems and the part that uses the B-VHF system. Within the ground architecture (Figure 7-2) these gateways may be allocated to the VCS and DLS, respectively.

7.1.8. Airborne B-VHF System Architecture

The architecture of the airborne part of the B-VHF system for a transport aircraft is shown in Figure 7-3.

This architecture remains stable throughout all deployment scenarios (after an initial B-VHF airborne installation the B-VHF system functionality should further evolve solely due to flexible B-VHF system configuration, without a need for any new component or architecture change).

The entire architecture closely resembles existing airborne architecture with analogue narrowband VHF radios. The B-VHF specific blocks (yellow) comprise the following parts:

! Airborne B-VHF Radio Transceiver (A_TRX)

! B-VHF functions delegated to the Communications Management Unit (CMU)

An airborne B-VHF sub-system has similar functional scope as its ground counterpart, but in order to facilitate equipment certification it would be contained within only two physical units � legacy CMU and the new B-VHF multimode transceiver.

CMU2 (optional) FMS

VHF1

CMU1 AMS

VHF2 VHF3

VoiceA

Data

Figure 7-3: Airborne B-VHF Sub-system

Airborne B-VHF transceivers interface with the ground sub-system over a B-VHF air-ground interface. Airborne radios interface with a local Audio Management System




(AMS), while airborne B-VHF functions that are implemented within CMU would interface with the legacy part of the CMU, including an ATN router.

The basic difference of the B-VHF system with respect to the narrowband systems is its ability to provide simultaneously multiple voice and data link services. However, according to the current practices no more than two simultaneous VHF DSB-AM voice sessions are kept between the aircrew and the ground staff, each running over a dedicated VHF radio unit (corresponding to A_TRX1 and A_TRX2 in Figure 7-3).

Existing voice practices have their roots not only in the technology, but also in the human factors and would/should not change due to the B-VHF system introduction. Moreover, narrowband systems will continue to be used in large parts of the world even if the B-VHF system was deployed in some local areas. An airborne broadband B-VHF radio is expected to be usable for voice operation only if it can be operated by the aircrew in a similar way (by using uniform procedures) as a narrowband DSB-AM radio today.

The constraints for voice communications do not apply to the data link � multiple data link sessions/services are multiplexed via ACARS or ATN data link by using third radio (A_TRX3) in a narrowband mode of operation (VDL Mode 2).

Operationally, each of two B-VHF airborne transceivers (A_TRX1, A_TRX2) could be used for voice services, while the third unit (A_TRX3) could be � as shown in Figure 7-3 - independently used for multiple data link services. Each A_TRX radio is directly connected to its dedicated antenna (typical aircraft have two top and one bottom antennas).

As two independent voice sessions (e.g. one ATC party-line service and one AOC voice session) may in some cases run between an aircraft and two different B-VHF GSs, each B-VHF airborne radio unit shall be independent � with respect to voice operation � from any other radio unit. Three airborne B-VHF radios would be seen by the ground B-VHF system as three independent addressable units which � for voice operation � are NOT combined through some higher layer protocol at the airborne side.

NOTE: With respect to data link, two data radios may be connected either to different CMUs or to the same CMU. In the later case, the CMU would finally merge two physical transceivers into single airborne data link system.

As long as doubled data link equipage is not mandated, the number of required airborne radios may be reduced to two units and the radio that has been selected by the aircrew to provide ATC services (e.g. A_TRX1) could be used for the simultaneous provision of data link services, thus eliminating a need for A_TRX3 radio. Such a concept of operation has been developed for VDL Mode 3. It is enabled by the fact that an aircraft normally remains connected to the ATC voice service (and the corresponding GS) over longer time periods.

NOTE: A second (non-ATC) voice radio (A_TRX2) is required because of doubled voice equipage, but is not suitable to carry data link as it will often be used in an analogue DSB-AM mode (without data link capability) for monitoring the emergency frequency. Therefore, with a mandate for high availability data link equipage expected in the future, a third VHF radio (A_TRX3) becomes inevitable.

A two-radio concept is seen as particularly attractive for general aviation (GA), while three-radio architecture is assumed to be the most probable one for transport aircraft.

With this approach a B-VHF airborne transceiver (A_TRX) could be considered as an extension of existing VHF Digital Radio (VDR) standards, so similar certification procedures could be applied as for ARINC 750-compliant radios.




Each A_TRX implements the PHY layer, MAC sub-layer, BSS sub-layer, a part of the LME entity and the voice unit (vocoder) as required for autonomous voice operation of this particular radio.

NOTE: The details of the B-VHF protocol stack and B-VHF-specific procedures for e.g. net initialisation, handovers or resource allocation are described in [B-VHF D7].

Each A_TRX provides a voice interface to the external Audio Management System (AMS).

NOTE: AMS represents any other on-board voice communications system, e.g. intercom as commonly used for General Aviation (GA).

NOTE: No CMU or other external entity is required for B-VHF voice operation.

The B-VHF functions that are required only for the data link operation (e.g. DLS sub-layer, part of the LME, entire B-VHF sub-network layer) are delegated to the (already existing) CMU that internally implements an ATN router and is connected to various other systems like Flight Management System (FMS), Central Maintenance Computer (CMC), Aircraft Condition and Monitoring System (ACMS) etc.

In Figure 7-3 it was assumed that the Flight Management System (FMS) hosts non-ATN data link services and has a direct access to A_TRX3 over a dedicated non-ATN interface, but this interface can also be used with other non-ATN on-board systems to provide non-ATN services to e.g. General Aviation (GA) or military aircraft.

NOTE: External non-ATN interface is not required if non-ATN services are also hosted within the CMU.

7.1.9. B-VHF Cellular Concept

B-VHF cells (Figure 7-4) may have different sizes and serve different types of continental airspace: APT, TMA or ENR. The Cell Designed Operational Coverage (CDOC) is defined by the cell radius (r_C) and cell height (h_C).

Each cell is assigned a broadband RF channel according to the frequency planning criteria. As long as these criteria are fulfilled, the cell CDOCs may overlap or a CDOC of a cell may even be entirely contained within a CDOC of another cell.

Within a CDOC the cell offers multiple operational services. Each operational service has its own Designed Operational Coverage (DOC) that is independent of the B-VHF CDOC. For some services the service DOC may be entirely contained within the cell CDOC, wide-area services with large DOC volumes are served by deploying the required service channel at several B-VHF cells (in such a case CDOC is smaller than the aggregate DOC required by the service).

TMA/ENR cells (e.g. GS1 from Figure 7-4) will provide their services to different ATC sectors and aircraft flying at different Flight Levels (FL) within TMA/ENR airspace, respectively.

A particular cell placed at an airport (e.g. GS2 from Figure 7-4) may be tasked with APT services like delivery, ATIS, ground control and RWY control, but may also comprise voice party-line circuits for TMA ATC sectors. In such a case, the GS TX per-carrier FL power must be designed for the �maximum service DOC� (TMA services), but in order to reduce interference to APT NB systems the GS TX may use reduced per-carrier power for carriers dedicated to APT services.

NOTE: For �multi-purpose� GSs it may be possible to configure the B-VHF GS TX per-carrier power separately for each M&Q group and make sure that services with




different DOCs use different M&Q groups. This would allow that single physical GS could provide different CDOCs at the same time. Such an approach has not been investigated in-depth within the B-VHF project as it is considered to be a configuration/implementation issue for the B-VHF GS. An aircraft on the airport surface would receive all FL OFDM carriers transmitted by the GS located at the airport while an aircraft beyond some distance from such �composite� GS would effectively receive only a sub-set of all transmitted FL carriers that carry TMA and ENR services. The transmissions over a BC slot that are used by an aircraft radio for detecting available GS carrier constellation would still have to use maximum per-carrier power for the service with the maximum DOC.

Figure 7-4: B-VHF Cell DOCs (CDOCs)

7.1.10. Size of B-VHF Cells

The Designed Operational Coverage (CDOC) of a particular cell is defined by the cell radius (r_C) and cell height (h_C).

Due to the B-VHF wide-area concept, the CDOC of the B-VHF cell is independent from the DOC for a given communications service. These services are currently provided in the narrowband mode, by using a number of GSs placed at appropriate locations. As each GS comprises not only radio equipment, but also other (costly-) infrastructure like buildings, antenna towers or power supplies, the number of currently deployed narrowband GSs is very probably close to the necessary minimum.

Because of these reasons, the service providers would prefer to deploy the new B-VHF GSs at same physical locations as the existing narrowband GSs. In that case the coverage of a particular cell (CDOC) should at least for non-wide-area services be comparable to the coverage provided by existing narrowband GS operating from the same location.




Table 7-1 shows typical coverage of existing narrowband APT/TMA/ENR GSs derived from [B-VHF D8]. It can be seen that for existing GSs r_C is normally much greater than h_C, therefore CDOC is basically determined by its footprint, r_C.

Airspace Type GS Coverage Radius (r_C) GS Coverage Ceiling (h_C)

APT (GND & TWR) 25 nm 2500 ft

TMA (APP & ATIS) 60 nm FL 215

ENR 175 nm FL 660

Table 7-1: Typical Coverage of Narrowband GSs

In some cases several narrowband GSs are combined together to provide required operational coverage for services with large DOC.

Target CDOC values for B-VHF cells are defined as follows:

! APT_CDOC = 25 nm

! TMA_CDOC = 60 nm

! ENR_CDOC = 175 nm

If it proves to be possible to design and deploy B-VHF cells with such CDOCs, the B-VHF GSs could be placed at positions of existing NB GSs, with maximal re-use of existing infrastructure.

7.1.10.1. TMA and ENR Coverage in the UK

For the purposes of this deliverable NERL has provided plots (Figure 7-8, Figure 7-6 and Figure 7-7) of the VHF coverage that is currently provided for TMA and ENR voice services within the London FIR. These plots indicate positions of involved GSs and coverage that can be achieved from each involved GS, therefore also the aggregate coverage for entire airspace. Alternative plots of aggregate TMA and ENR coverage have been produced with reduced number of GSs.

NOTE: TMA and ENR are denoted in figures as �TC�/�ACC�, respectively.




Figure 7-5: London Airports� Coverage at 500 ft

Figure 7-6: London TC Coverage at 500 ft




Figure 7-7: London TC Coverage at 1500 ft




Figure 7-8: London ACC Coverage at 4500 ft

These plots and the supplementary material (frequency tables) provided by NERL in the course of producing [B-VHF D8] allow for the following conclusions:

Airport B-VHF coverage can only be meaningfully provided from a B-VHF GS that is close to the concerned airport (Figure 7-5).

! For each type of airspace � TMA or ENR � the coverage at the lowest applicable flight level is critical (without taking redundancy aspects into account, it determines the minimum number of GSs required for �seamless coverage�).

! As the communication transfer between airports and TC may occur at levels as low as 300 ft, at least one TMA GS must be located very close to the concerned airport (Figure 7-6).

! At 1500 ft (Figure 7-7) the coverage range of a single GS over flat terrain is about 60 km.

! The coverage picture further improves with higher flight levels. The seamless TMA coverage outside airport zones can be easily achieved as the lower TMA boundary in the UK is normally about 2500 ft [B-VHF D8]).

! Without taking redundancy aspects into account, the current number of 8 TMA GSs may be eventually reduced to 6 GSs due to the overlapping at some GSs.




! The transfer between TMA and ENR (TC and ACC) may occur at the level of 4500 ft. In order to provide cumulative ACC coverage at 4500 ft, about 18 GSs are currently used (Figure 7-8). That number could be slightly reduced (15 GSs may be sufficient) due to the overlapping.

! Without significant terrain constraints, the coverage range of each single GS at 4500 ft is about 150 � 200 km. The coverage further improves with increasing FL (at higher FLs the designed coverage of a GS may be 175 nm and more [B-VHF D8]).

All TMA GSs within London FIR are co-located with ENR GSs. The selection of locations for these �combined� GSs was probably guided by the TMA coverage requirements, as these are more restrictive than the ENR coverage requirements. Two GSs are �specialised� TMA GSs, providing back-up for each other and have significant overlapping coverage, but even these GSs host some ENR channels. This leads to the conclusion that a sub-set of B-VHF GSs deployed at existing ENR GS locations would automatically be suitable for TMA services. About 15 B-VHF cells would be sufficient to provide aggregate coverage for both TMA and ENR services in London FIR. According to Figure 7-8, there would be significant overlap in the coverage, therefore a degree of redundancy. Redundancy would be further improved if all 18 GSs were used.

Dependent on the coverage requirements of each particular service, each of involved cells would have to be configured to provide a sub-set of all ENR/TMA services, on the other side, only a sub-set of all cells may be required for a provision of a given service.

NOTE: Implementing a service just at a �necessary� number of cells would avoid unnecessary cell loading and unnecessary handoffs between involved cells. Implementing a service at an increased number of cells (above the minimum required number) degrades cell capacity and increases number of handoffs, but also increases robustness of the service provision due to the overlapping of CDOCs of B-VHF cells (similar to the current CLIMAX practice).

7.2. B-VHF System Deployment in the VHF COM Range

The B-VHF system has been designed based on [B-VHF D5] requirements as an integrated voice/data system that should be preferably deployed in the VHF range. This chapter addresses initial VHF COM deployment scenarios for the B-VHF system in selected parts of the European airspace.

7.2.1. Common Aspects of VHF Deployment Scenarios

7.2.1.1. Aircraft Co-location Constraints

The investigation of existing avionics standards for DSB-AM equipment [ARINC 716] indicates that the narrowband DSB-AM airborne receiver of a transport aircraft is required to operate normally with antenna isolation of 35/45 dB when another 25 W airborne radio is transmitting at frequency spacing of 6/2 MHz respectively. At frequency spacing lower than 2/6 MHz, respectively, interference-free operation of two airborne DSB-AM radios cannot be guaranteed anymore.

The level of out-of-band B-VHF signal components (noise, intermodulation products, OFDM side-lobes) cannot be expected to be better than the spectral masks of legacy NB




systems. This may lead even with �O� constellation to an unacceptable number of guard channels required between the B-VHF channel and the closest DSB-AM voice channel. It is even less probable that the level of in-band B-VHF signal components (in particular side-lobes) transmitted over an in-band NB voice channel used by the same aircraft could be sufficiently reduced to avoid interference with an in-band NB voice radio operating in �S� constellation.

Therefore, it has been assumed in all scenarios [A 9] that the B-VHF radios cannot be simultaneously used from the same aircraft with other VHF radios operating in the COM band without causing intolerable mutual interference. The only exception is the emergency channel (121,5 MHz) where the co-existence is assured by implementing special measures (crystal filters) within the B-VHF radio front-end.

7.2.1.2. System Configuration

A set of [B-VHF D5] requirements identifies an integrated voice/data system as a desired feature of a future radio system (FR-FRQ-G-17, FR-FRQ-G-18 and FR-FRQ-G-19). However, this does not generally preclude system installation as a voice-only or data-only system.

However, as the considerations from the previous section preclude the airborne installation of a data-only B-VHF radio in any constellation, the only feasible concept for the system deployment in a VHF COM range is an integrated voice/data system where all existing VHF communications services for a particular aircraft are ported to the B-VHF system.

With that configuration the closest interfering aircraft carrying narrowband VHF systems can appear at 210/600 m minimum distance from the victim airborne receiver (aircraft on ground/flying aircraft). The path loss is correspondingly increased to 60/70 dB, respectively, relative to the case when two radios are operated from the same aircraft.

7.2.1.3. Spectrum Usage

All VHF deployment scenarios are based on overlay. The B-VHF deployment in the VHF COM range without overlay is not realistic due to the fact that each B-VHF GS requires a separate broadband channel that would have to be completely free from any in-band narrowband channels.

Not even a single broadband VHF channel can be allocated in Europe without overlay. For B-VHF frequency planning multiple broadband channels would be required, each in �O� constellation with respect to any NB signal � no �S� or �W� NB signals should appear within the bandwidth of the B-VHF signal.

NOTE: With an overlay deployment concept, the B-VHF system basically becomes interference-limited � the system performance and important parameters like required transmission power are dictated by the interference received from NB systems rather than the noise produced in the B-VHF receiver.

The B-VHF system deployed in the VHF range as an overlay system remains an overlay system until the last in-band VHF narrowband channel has been abandoned within the implementation area. It is likely that at least the NB emergency channel (121.5MHz) will continue to be operated within the VHF COM range for the foreseeable future. Additionally, there will always be a boundary to the NB airspace where the overlay constraints and specific frequency planning criteria would apply.




7.2.1.4. Airborne Architecture

A B-VHF aircraft is equipped by three B-VHF-capable radios, therefore the basic airborne architecture from Figure 7-3 applies. Within the B-VHF airspace or B-VHF-supported airspace two multi-mode radios with separate antennas (A_TRX_1, A_TRX_2) are operated in B-VHF mode and used for voice operations while the third B-VHF radio (A_TRX_3) with an independent antenna is used for all kinds of data link communications. In the NB airspace the mode is changed and radios are used either as DSB-AM and/or VDL Mode 2 radios.

7.2.1.5. Ground Architecture � Introduction in the B-VHF-supported Airspace

With all deployment options that assume B-VHF-supported airspace with mixed B-VHF aircraft and NB aircraft population the basic architecture from Figure 7-9 applies. Physical B-VHF radio units (G_TX, G_RX) are connected to their local GSC via local connection. The GSC is connected over wide-area network to the GNI. The GNI interfaces with external ATN and non-ATN Data Link Systems (DLS) as well as with an external VCS. The VCS has another interface towards the legacy DSB-AM voice system.

NOTE: When selecting a sub-set of existing GSs for additionally deploying the ground B-VHF radios a clear preference in all scenarios should be given to split transmitter/receiver sites as this would generate les requirements/constraints with respect to the ground co-location of both systems. Ground B-VHF TX equipment would in that case be co-located with existing NB TX equipment, while the B-VHF RX equipment would be co-located with existing NB receivers.

Here, the interoperability problem arises for party-line voice service, as B-VHF aircraft cannot directly monitor conversation between the NB aircraft and the controller and vice versa. The problem can be solved if the VCS is configured (via cross-coupling) to act as a gateway between two systems: controller�s voice is transmitted in parallel over DSB-AM and B-VHF system, any transmission of the NB aircraft is re-directed via VCS to the B-VHF �sub-system� and re-transmitted to be heard by the B-VHF aircraft population. Similarly, RL transmissions of B-VHF aircraft are re-directed to be broadcasted by the DSB-AM ground transmitter. This preserves the party-line between two systems and reduces the probability of an access collision (as both types of aircraft are aware of the �common� channel status).

The interoperability problem does not exist for broadcast voice services � these services are deployed in parallel over both technologies, each part of the aircraft population receives broadcast voice services via the technology they are equipped with.




Figure 7-9: Coupling of DSB-AM and B-VHF Voice System via VCS

Similarly, addressed air-ground data link services are provided by using the VDL Mode2 system in parallel with the B-VHF system. This kind of data link runs between the ground Data Link System (DLS) and selected aircraft, invisible for other aircraft, so no interoperability problem exists. However, the ground data link system must be capable to support both types of data link in parallel.

NOTE: Broadcast data link is out of scope of initial B-VHF deployment scenarios.

7.2.1.6. Ground Architecture � Introduction in the B-VHF Airspace

Basic architecture from Figure 7-2 applies to all scenarios where B-VHF system is introduced in the B-VHF airspace. Physical ground radio units (G_TX, G_RX) are connected to their local GSC via local connection. The GSC is connected over wide-area network to the GNI. The GNI interfaces with external ATN and non-ATN Data Link Systems (DLS) as well as with an external VCS.

NOTE: When selecting a sub-set of existing GSs for additionally deploying the ground B-VHF radios a clear preference in all scenarios should be given to split transmitter/receiver sites. Moreover, wherever possible the B-VHF ground radios should be deployed at �abandoned� NB sites (that do not anymore support NB operation).




7.2.2. Option 1 �Introduction in B-VHF-supported Airspace (APT)

In this scenario a given APT deploys the B-VHF ground infrastructure and accepts mixed B-VHF and NB aircraft population being operated as a B-VHF-supported airspace.

Each APT can be converted from NB airspace to B-VHF-supported airspace independently of any other airspace, including surrounding TMA and ENR airspace.

NOTE: This deployment scenario is perceived as highly probable. It imposes no constraints upon the aircraft equipage as both NB aircraft and B-VHF aircraft can be easily accommodated. There are no constraints with respect to the coverage as basically only one APT B-VHF GS, one GSC and single GNI is required. The additionally required B-VHF ground infrastructure is believed to be affordable at least for large airports. The benefits are expected mainly from the locally improved data link service capacity and quality obtained without the need for additional VHF spectral resources

7.2.2.1. Applicable Signal Constellations

According to 0 the B-VHF aircraft and NB aircraft on the airport surface are in this scenario separated by 210 m. No APT NB GS should be operated closer that 600 m from the B-VHF aircraft (the same is true for any TMA or ENR NB GS that may be located at an APT).

Local APT NB channels can be only operated in the �O� constellation with respect to the local broadband RF channel. This means that no NB aircraft on the APT surface should actively use local NB channels that lie within the broadband B-VHF channel.

.

In order to reach the desired �O� constellation the local B-VHF RF channel for a given APT should be selected in such a way that all locally used STRONG NB channels appear outside that channel. If this is not possible (e.g. B-VHF frequency planning does not allow the preferred broadband channel to be used at a particular APT), all remaining local in-band �S� NB channels should be removed from the allocated APT broadband channel by applying traditional NB frequency re-planning mechanisms.

When selecting the broadband channel for a particular airport it is also important to minimise the number and total power of �S� interferers in the surrounding airspace that may affect that channel.

NOTE: Other active VHF NB systems around the airport (e.g. aircraft flying in TMA airspace, lower ENR sectors, VOLMET/ATIS GSs located at > 600 m from the B-VHF radio) are allowed to appear in the �S� constellation with respect to the selected APT broadband channel due to the increased spatial separation between systems (> 210 m). These channels must be properly handled by the B-VHF system (should be filtered-out within the B-VHF RX and not actively used by the B-VHF TX).




NB 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 1360 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A1 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A2 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A3 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 128,075 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A4 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A5 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A6 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A7 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A8 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A9 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A10 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A11 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A12 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A13 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A14 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A15 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A16 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,400 #N/A #N/A #N/A #N/A #N/A17 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,425 #N/A #N/A #N/A #N/A #N/A18 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,450 #N/A #N/A #N/A #N/A #N/A19 #N/A #N/A #N/A #N/A #N/A #N/A 124,475 #N/A #N/A #N/A #N/A #N/A #N/A 131,475 #N/A #N/A #N/A #N/A #N/A20 118,500 #N/A #N/A 121,500 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,500 #N/A #N/A #N/A #N/A #N/A21 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,525 #N/A #N/A #N/A #N/A #N/A22 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,550 #N/A #N/A #N/A #N/A #N/A23 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,575 #N/A #N/A #N/A #N/A #N/A24 #N/A #N/A #N/A 121,600 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,600 #N/A #N/A #N/A #N/A #N/A25 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,625 #N/A #N/A #N/A #N/A #N/A26 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,650 #N/A #N/A #N/A #N/A #N/A27 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A28 118,700 #N/A #N/A 121,700 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,700 #N/A #N/A #N/A #N/A #N/A29 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,725 #N/A #N/A #N/A #N/A #N/A30 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,750 #N/A #N/A #N/A #N/A 136,75031 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,775 #N/A #N/A #N/A #N/A #N/A32 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,800 #N/A #N/A #N/A #N/A #N/A33 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,825 #N/A #N/A #N/A #N/A #N/A34 #N/A #N/A #N/A 121,850 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,850 #N/A #N/A #N/A #N/A #N/A35 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,875 #N/A #N/A #N/A #N/A #N/A36 #N/A #N/A #N/A 121,900 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,900 #N/A #N/A #N/A #N/A #N/A37 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,925 #N/A #N/A #N/A #N/A 136,92538 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 131,950 #N/A #N/A #N/A #N/A #N/A39 #N/A #N/A #N/A 121,975 #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A #N/A 136,975

Constellation of Local NB Channels - Heathrow Airport

Figure 7-10: Constellation of Local Channels at Heathrow Airport

Figure 7-10 shows the current constellation of ATC, OPC, ACARS and VDL2 channels locally used at Heathrow Airport [UK_AIP]. The columns represent 19 hypothetic B-VHF broadband channels with assumed 1 MHz bandwidth, while the rows represent 40 NB 25 kHz channels contained within each hypothetic broadband B-VHF channel.

Red marked NB channels that are locally used at Heathrow airport would appear as STRONG interferers in the �S� constellation with respect to the corresponding broadband B-VHF channel. It can be seen that the B-VHF channel 131-132 MHz is heavily occupied by the local OPC and ACARS channels � this particular channel should clearly be avoided with this deployment scenario.

However, it can also be seen from Figure 7-10 that even for a large airport like Heathrow many broadband channels are not locally used � such �empty� broadband channels are good candidates for a local B-VHF channel allocation!

This was also confirmed by the ground occupancy measurements campaign [B-VHF D12] at Heathrow control tower (Figure 7-11). The figure indicates the number of idle (green), weak (yellow) and strong (red) channels counted with a 1 MHz window sliding over VHF COM range (118 � 137 MHz).

Two peaks in the red line are related to the OPC frequencies between 131-132 MHz and ATC frequencies in the 121- 122 MHz range.




100 200 300 400 500 6000

5

10

15

20

25

30

35

40IdleWeakStrong

Figure 7-11: Ground Measurements � Heathrow Tower

7.2.2.2. Applicable Cell Size

The achievable B-VHF cell size is generally very dependent on the local interference situation (VHF resource availability, defined by the distribution of STRONG/WEAK interferers). For large CDOCs it may also depend on other factors like maximum available airborne B-VHF TX power and required number of voice channels that must be accommodated within cell.

According to Figure 7-12, the spectrum availability at 2500 ft above ground with STRONG/WEAK threshold set to -80 dBm and cell size of 25 nm is above 50% for all locations except for 3 airports in the UK.

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NOTE: Opposite to the legend in Figure 7-12, the cell size has been constantly kept at 25 nm.

Therefore, the deployment of APT cells under overlay scenario with target radii corresponding to APT_CDOC (25 nm) is not expected to be a problem except for busy locations.




Figure 7-12: Spectrum Availability at 2500 ft above GND (1 MHz BW, -80 dBm)

7.2.2.3. Usability for APT Services

In this scenario, voice services for B-VHF aircraft are restricted to the �traditional� controller-pilot voice communications, pilot-pilot communications and AOC voice communications (OPC) that are provided by using party-line (B-VP) B-VHF internal service. Broadcast service (B-VB) can be used for ATIS service, but it is expected that more and more aircraft will use digital ATIS service. All existing DSB-AM voice APT services � with possible exception of broadcast voice channels � must be replicated within the B-VHF system. Party-line (coupling) between the B-VHF and DSB-AM voice system is provided via the APT Voice Communications System (VCS). Emergency channel (121,5 MHz) is supported in the DSB-AM mode for the entire population (B-VHF and NB aircraft).

Initially supported B-VHF data link services comprise air-ground ATN data link services for different ATS and AOC purposes in an APT environment, according to [B-VHF D7] Table 8-1. All these air-ground data link services use an ATN-compatible internal B-VHF service (B-DA).

The particular attractiveness of this scenario is the opportunity to deploy powerful data link with QoS and capacity that surpasses what can be achieved with multiple VDL2




channels. The number of APT voice services is (and will probably remain-) limited to some 35 channels even for a very large APT like Heathrow and each B-VHF voice channel effectively consumes less than 1% of the total bandwidth of the broadband channel (4 OFDM carriers). Assuming that the B-VHF system was initially deployed at Heathrow, 4*35 = 140 OFDM carriers would be required for voice services.

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Assuming 50% available (WEAK) OFDM channels, the number of FL carriers available for data link would become 432/2 � 140 = 76, so the APT B-VHF system could offer relatively high data link capacity (76*4*21.5/60*39/44= 96 kbps). Comparable capacity can be expected for RL (however, the RL resources and throughput are shared - several aircraft can have separate RL links with the GS at the same time).

It may be generally concluded that B-VHF cells with APT_CDOC = 25 nm are feasible both from the availability and capacity standpoints.

NOTE: DL capacity (FL) has been calculated in all examples by multiplying number of OFDM carriers used for DL by 4 kbps (QPSK). The result has then been corrected by taking B-VHF TDD framing (one 21.5 ms FL frame duration appears within a multi-frame of 60 ms) and FL frame effectiveness (only 39 of total 44 FL frame symbols carry user data) into account.

7.2.3. Option 2 �Introduction in B-VHF-supported Airspace (TMA)

In this scenario a given TMA deploys the B-VHF ground infrastructure and accepts mixed B-VHF and NB aircraft population being operated as a B-VHF-supported airspace.

Each TMA can be converted from NB airspace to B-VHF-supported airspace independently of any other airspace, including surrounding APT and ENR airspace.

NOTE: This deployment scenario is perceived as probable. It imposes no constraints upon the aircraft equipage as both NB aircraft and B-VHF aircraft can be easily accommodated. The physical coverage can be provided by a single GNI and an appropriate number of TMA B-VHF GSs with associated GSCs. The additionally required B-VHF ground infrastructure is believed to be affordable at least for large TMAs. The benefits are expected mainly from the locally improved data link service capacity and quality obtained without the need for additional VHF spectral resources.


According to the assumptions about the B-VHF RF front-end from Chapter 4 of this document [A 13], B-VHF aircraft and NB aircraft separated by 600 m within the TMA airspace are able to operate without interference with appropriate handling of STRONG �S� interferers. The minimum distance to the B-VHF GS and NB GS is 600 m for both aircraft types.

With this topology the B-VHF system under [A 13] can be operated in either �O� or �S� constellation with respect to �local� NB channels. In other words, NB aircraft at 600 m spacing from the B-VHF aircraft can use a NB channel within (�S�) or outside (�O�) the B-VHF broadband channel allocation without further constraints (known �S� channels are internally converted to �W� channels within the B-VHF RX).

Still, in order to minimise interference effects, the local TMA B-VHF RF channel should be selected in such a way to minimise both the number and the total power of �S�




interferers that appear within that channel from both the TMA airspace and the surrounding airspace (APT, ENR).

If required, the number and total power of �S� interferers should be further reduced to an acceptable value by using frequency re-planning in the NB airspace surrounding the B-VHF-supported TMA airspace.


The number/power of WEAK interferers that may be received within the TMA airspace are generally lower than the number/power of interferers that affect B-VHF aircraft flying in an ENR airspace, but simulations [ICNS 2006] suggest that under overlay conditions deploying B-VHF cells with target radii (TMA_CDOC = 60 nm) may become a problem in busy TMAs.

Figure 7-13: Spectrum Availability at FL 250 (1 MHz bandwidth, -75 dBm)

According to [ICNS 2006], for the most European TMAs the availability at FL 250 with STRONG/WEAK threshold set to -75 dBm (Figure 7-13) is above 50% for TMA CDOC (60 nm). However, for two major TMAs in Europe (London, Amsterdam) the spectrum availability with 60 nm radius is below 50%.

NOTE: TMA upper boundary in UK is approximately at FL 215, so actual availability figures may be slightly better than indicated above.




7.2.3.3. Usability for TMA Services

In this scenario, voice TMA services for B-VHF aircraft are restricted to the �traditional� party-line service (B-VP) and broadcast service (B-VB). Controller-pilot voice communications, pilot-pilot communications and AOC voice communications (OPC) are also provided by using party-line (B-VP) service. Broadcast service (B-VB) can be used for VOLMET service, but it is expected that more and more aircraft will use digital ATIS service.

As previously described, party-line functionality (coupling) between the B-VHF and DSB-AM voice system is provided by the TMA Voice Communications System (VCS). Emergency channel (121.5 MHz) is supported in the DSB-AM mode for the entire population (B-VHF and NB aircraft).

Initially supported B-VHF data link services comprise air-ground ATN data link services for different ATS and AOC purposes in a TMA environment, according to [B-VHF D7] Table 8-1. All these air-ground data link services are expected to use an ATN-compatible interface of the B-VHF system, using internal B-VHF service (B-DA). The particular attractiveness of this scenario is the powerful data link with QoS and capacity that surpasses what can be achieved with VDL2.

With this scenario, all existing DSB-AM voice TMA services � with possible exception of broadcast voice channels � must be replicated within the B-VHF system.

The detailed inspection of detailed information about UK frequency usage (as provided by NERL in the course of producing [B-VHF D8]) has shown that about 40 channels are allocated to London TMA voice functions, including 3 broadcast VOLMET channels. The required aggregate voice capacity for the TMA cell (assuming that single cell covers all TMA demands) is therefore 4*40 = 160 OFDM carriers.

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Assuming that single TMA B-VHF GS provides all TMA voice services � very unrealistic scenario - for TMAs with spectrum availability of 80% (345 available OFDM carriers) about 432* 0.8 � 160 = 185 carriers would remain available for data link and the TMA B-VHF system could offer aggregate data link capacity of about 235 kbps (185*4*21.5/60*39/44). Assuming the spectrum availability of 50% and 40 voice channels as in London TMA (situation that may apply to e.g. Frankfurt or Paris TMAs), 56 carriers would be available for data link and the TMA B-VHF system could offer aggregate data link capacity of about 71 kbps (56*4*21,5/60*39/44).

As previously shown (section 7.1.10.1), currently 8 separate ground stations are used for providing voice services for London TMA with required redundancy. Comparable number of physical B-VHF GSs would be required to provide aggregate required TMA coverage, in particular at lower FLs around airports. This reduces the required per-cell voice capacity as not all voice services must be implemented at all cells.

There is a possibility to deploy several TMA B-VHF GSs and to split the voice demands between several cells. This would allow for high-capacity TMA data link even around London and Amsterdam, but would increase the number of required broadband channels. However, it should be noted that there is some lower limit with respect to the acceptable TMA cell size, as with decreasing cell size more and more voice services would have to be implemented at each cell, reducing the remaining capacity for data link. The optimum policy must be determined separately for each TMA.




It may be generally concluded that B-VHF cells with TMA_CDOC = 60 nm may be feasible both from the availability and capacity standpoints.

7.2.4. Option 3 � Introduction in B-VHF-supported Airspace (ENR)

In this scenario a given part of the ENR airspace (e.g. selected FIR) deploys the B-VHF ground infrastructure and is operated as a B-VHF-supported airspace, accepting mixed B-VHF and NB aircraft population.

NOTE: This deployment scenario is perceived as less probable. It imposes no constraints upon the aircraft equipage as both NB aircraft and B-VHF aircraft can be easily accommodated. The physical regional coverage (FIR) can be provided by a single GNI and an appropriate number of ENR B-VHF GSs with associated GSCs. However, due to the poor spectrum availability at higher FLs the cell size (CDOC) would have to be reduced below 175 -200 nm that are typical today. This may require new GS locations beyond the existing ones and may cause capacity/performance problems. With fixed required per-service operational coverage (DOC) and reduced cell size (CDOC) the �wide-area� attribute would apply to more and more services � each such service would have to be implemented at more than one cell, with handoff between cells. This may reduce the available capacity for data link, so the benefits expected from the locally improved data link service would not apply anymore.

Theoretically, each ACC sector may be converted from NB airspace to B-VHF-supported airspace independently of any other airspace, including surrounding ACC sectors, APT and TMA airspace. However, the conversion of a single sector is not believed to be a scenario that could be easily justified � it is more probable that the least quantity of convertible airspace would be a FIR/UIR.

Therefore, two realistic options remain with that scenario:

! Deploy B-VHF system for entire FIR/UIR ENR airspace

! Deploy ENR B-VHF system in an UIR above selected FL


With appropriate handling of STRONG �S� interferers, B-VHF aircraft and NB aircraft separated by 600 m within the ENR airspace are assumed to be able to operate without interference. The minimum distance from the B-VHF GS and NB GS for both aircraft types is 600 m.

With this topology the B-VHF system can be operated in either �O� or �S� constellation with respect to �local� NB channels. In other words, NB aircraft would be able to use a NB channel within the B-VHF broadband without any operational constraints.


The total London FIR coverage is provided from 18 GSs (5 GSs are shared between London ACC and Manchester ACC). These GSs have been designed with 175 nm coverage range.

According to [ICNS 2006], the spectrum availability in Scandinavia and Southern Europe at FL 250 is 80% and more with cell size of 200 nm and STRONG/WEAK threshold set to -75 dBm (Figure 7-13).

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NOTE: VHF occupancy simulations have shown that the occupancy situation does not further worsen with increasing FL above FL 250 (spectrum availability at FL 450 remains basically the same as for FL 250).

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However it is difficult to justify the initial B-VHF system deployment in non-Core area as the most communications congestion problems are experienced over Core area where the VHF spectrum availability is between 50% and 80 % with cell sizes that correspond to the TMA_CDOC (60 nm).

Therefore, under interference conditions it seems to be necessary to use ENR cells with CDOC smaller than 175 nm.

To provide aggregate required seamless B-VHF coverage for London FIR some minimum number of such �small� B-VHF cells - preferably deployed at existing GS locations - would be required (section 7.1.10.1). The exact number would heavily depend on the terrain profiles and GS antenna heights, but with cellular B-VHF principle and seamless service provision between multiple cells should be slightly less than 18 GSs.

NOTE: No significant reduction is possible as multiple GSs are mandatory to achieve ENR coverage at a required minimum level (may be as low as 4500 ft).

With a second option � B-VHF deployment above certain FL � the number of required B-VHF GSs for UIR coverage and associated broadband channels would be further reduced due to reduced terrain impact at higher FLs.

In both cases the coverage for off-shore sectors at larger distances from the GS can be improved by using directional antennas (beam-forming) on the ground side.

7.2.4.3. Usability for ENR Services

In this scenario, voice ENR services for B-VHF aircraft are restricted to the �traditional� party-line service (B-VP) and broadcast service (B-VB). Party-line functionality (coupling) between the B-VHF and DSB-AM voice system is provided by the ACC Voice Communications System (VCS). Emergency channel (121.5 MHz) is supported in the DSB-AM mode for the entire population (B-VHF and NB aircraft).

Initially supported B-VHF data link services comprise air-ground ENR ATN data link services for different ATS and AOC purposes.

A given cell must provide voice support not only for ATC sectors that are entirely contained within its footprint, but also for all �adjacent� sectors that are at least partially contained within that footprint. Therefore, wide-area voice services generate an increased demand for voice channels per cell.

The maximum voice capacity of the B-VHF cell (with 100% availability) is limited to 108 voice channels with 1 MHz B-VHF channel bandwidth (with recent [B-VHF D18] change proposals this was further limited to 88 and 72 voice channels, respectively). While the theoretical peak cell voice capacity is independent of the cell size, actual capacity depends on the spectrum availability and therefore also on the cell size.

The detailed inspection of detailed information about UK frequency usage (as provided by NERL in the course of producing [B-VHF D8]) has shown that about 40 channels are allocated to provide London ACC voice functions within London FIR. Additional 9 channels have been allocated to Manchester ACC.




It can be concluded that the cell voice capacity should be no problem for ENR cells as the aggregate demand is limited to some 50 voice channels for a busy London FIR. Without interference and assuming no coverage constraints that capacity could be theoretically provided even by a single large B-VHF cell.

NOTE: Investigations made by NERL (section 7.1.10.1) show that about 15 B-VHF cells with CDOC of approximately 60 nm may be sufficient to provide aggregate coverage for both TMA and ENR services in London FIR.

As under interference condition the availability figures improve with reduced cell size, several ENR cells with CDOC < ENR_CDOC of 175 nm would be required to increase per-cell spectrum availability and provide seamless FIR coverage in the Core area. Increased availability would in turn increase offered per-cell voice capacity.

The number of voice services that are required per cell would not be linearly reduced when the cell size decreases as with smaller cells more and more voice services would become �wide-area� services that must be instantiated at each involved cell, but with smaller cells the voice capacity should be no problem anymore.

7.2.4.4. Comparison of Options

It can be concluded that a B-VHF system introduction in entire ENR airspace (FIR/UIR) based on overlay is accompanied by several problems:

! With large number of required cells and limited total number of broadband channels the frequency planning becomes difficult

! Data link performance may be degraded due to an increased number of inter-cell handovers between small cells

! With small cells it becomes difficult (beamforming required) to provide long-distance off-shore coverage at low levels, e.g. for sectors over North Sea. With large cells the per-cell capacity may become a problem.

! Motivation for the B-VHF deployment in the lower ENR airspace may be reduced, leading to longer transition phase. In a mixed scenario a high percentage of NB aircraft (small aircraft, GA) is expected in the lower ENR airspace that may be difficult to motivate to use B-VHF equipment.

With the second option the B-VHF system would be deployed on the voluntarily basis (only-) in the upper ENR airspace (e.g. above FL 195, similar to the 8.33 kHz system deployment). The rest of ENR airspace below ENR B-VHF-supported airspace would remain NB airspace and would continue to use the DSB-AM/VDL 2 system.

This option is preferred over the first option at least for the following reasons:

! As with that option only a part of ENR airspace is converted to B-VHF operation, less voice channels are required per cell, leaving more capacity for data link

! The major users of B-VHF benefits (powerful data link) would be transport aircraft that anyway prefers upper airspace � this may speed-up the rate of voluntary equipage

! Total interference is reduced as NB channels used for APT operation are operated at relatively large minimum distance from the B-VHF aircraft using higher FLs.




7.2.5. Option 4� Introduction in B-VHF Airspace (ENR HIGH)

With this option the B-VHF system is introduced as mandatory for all users in entire European ENR airspace or a large part of it (e.g. Core Area) above FL xxx and UNL, with clearly defined outer boundary to the surrounding NB airspace and/or B-VHF-supported airspace that may appear both below and around the B-VHF ENR airspace.

NOTE: Introduction in the ENR airspace above some defined FL is believed to be the only realistic option for initial B-VHF system deployment based on mandated B-VHF equipage. The introduction policy itself would be similar to the introduction of the 8.33 kHz system. Even with that option the system would probably be deployable only after the ongoing deployment of the 8.33 kHz DSB-AM and VDL Mode 2 systems have been completed and the corresponding investments returned.

NOTE: Mandatory initial B-VHF system introduction in an APT or TMA airspace is not believed to be a realistic initial scenario as it raises questions with respect to the NB aircraft - e.g. GA or MIL - that may have to use the �B-VHF airport�. In particular, handling of NB aircraft under emergency condition may be critical. Therefore, it is recommended to consider APTs and TMAs to be B-VHF-supported airspace as described in sections 7.2.2 and 0, respectively.

Emergency channel (121.5 MHz) remains supported in the DSB-AM mode for the entire population (B-VHF and NB aircraft) and can be operated even from the B-VHF aircraft (due to specific handling in the B-VHF RF front-end).




Figure 7-14: Spectrum Availability at FL 245 (1 MHz, -80 dBm, ENR high)


With that scenario both �O� and �S� constellations are allowed.

The minimum vertical distance between the B-VHF aircraft and the closest NB aircraft (therefore to the closest NB system) is 600 m. There may be at most single NB aircraft at that distance below the B-VHF aircraft. The next closest NB aircraft can appear at 1200 m distance below the B-VHF aircraft. Remaining �close� NB aircraft below the B-VHF airspace boundary is subject to lateral ENR separation rules and therefore at least 5 nm away. The minimum vertical distance between B-VHF aircraft and the NB GS is dependent on the minimum FL within the B-VHF airspace. Assuming FL 195, this distance would be about 6 km.

When selecting the local broadband channel for a particular B-VHF ENR GS it is important to minimise the total number of �S� interferers (in the NB- or B-VHF-supported airspace) that operate within that channel.


As no NB interferer can appear within the B-VHF ENR airspace and the corresponding NB GSs that have previously supported upper ENR airspace have been removed, the overall




interference picture with that scenario generally improves (both the number of �S� and �W� interferers and the average received �S� or �W� interference power is expected to decrease) when compared to the scenario where the ENR airspace is operated in a B-VHF-supported mode.

Therefore, it may be possible to deploy with this scenario cells with CDOCs slightly greater than the CDOCs offered in a B-VHF-supported mode.

To provide aggregate required seamless B-VHF coverage for London FIR above some FL some minimum number of �small� B-VHF cells - preferably deployed at existing GS locations - would be required. As it is easier to provide coverage at higher FLs, the upper ENR airspace could be covered by using a sub-set of the GSs that would otherwise be required to cover entire ENR airspace.

The coverage for upper off-shore sectors at larger distances from the GS can be improved by using directional antennas (beam-forming) on the ground side.

7.2.5.3. Usability for ENR Services

In this scenario, initially offered voice ENR services for B-VHF aircraft remain restricted to the �traditional� party-line service (B-VP) and broadcast service (B-VB). Initially supported B-VHF data link services comprise air-ground ENR ATN data link services for different ATS and AOC purposes.

According to [B-VHF D8], the maximum number of voice channels for ACC HIGH sectors within 200 nm distance from large European airport is 70, without taking any further constraints (FIR/UIR boundaries, national borders) into account. As with this scenario only HIGH ACC sectors would be converted to the B-VHF mode of operation, the offered maximum theoretical cell voice capacity would be able to match demands even with cell radius of 200 nm. It can be concluded that with this scenario there are no system constraints that would speak against deploying large cells, but the real cell size and capacity must be determined dependent on the local spectrum availability and specific coverage demands and would be below the maximum theoretical values.

NOTE: Even if theoretical maximum system capacity cannot be reached under interference conditions, an overlay system would with this scenario provide an adequate number of additional voice channels and powerful data link without demanding additional VHF spectrum and would therefore be �perfectly spectrally efficient�.

7.3. B-VHF System Deployment in the DME Range

The ARNS 960-1215 MHz band (DME band) has so far been reserved and protected for aeronautical navigation services. Figure 7-15 - reprinted from [ACPF14-WP12] - shows the current usage of this band.

A large part of ARNS 960 � 1215 MHz band has been allocated to DME channels. DME frequencies are spaced in 1 MHz increments throughout the 962 to 1213 MHz band. Interrogation frequencies are contained within the band 1025 to 1150 MHz, and reply frequencies from the beacon are on paired channels located either 63 MHz below or above the corresponding interrogation frequency. DME occupied bandwidth is several MHz.




Two dedicated allocations (1030 ± 10 MHz, 1090 ± 10 MHz) have been allocated for the SSR and TCAS operations (occupied bandwidth is several MHz). DME channels lying within those ranges and the corresponding ground reply frequencies are not used.

Two dedicated allocations (1176.45 MHZ, 1207.14 MHz) have been allocated for the future GNSS (Galileo) operations (occupied bandwidth is several MHz).

DME and TACAN systems use 1 MHz channel grid, but the bandwidth of these signals exceeds 1 MHz. According to [ICAO EUR 011], the frequency planning criteria comprise both the first and second adjacent channel.

In the frame of the WRC-07 Agenda Item 1.6, the lower part (960 � 1024 MHz) of the DME band (denoted as �target DME range� from now on) has been identified [ACPF14-WP14] as a candidate frequency band to receive the future Air/Ground aeronautical communication system (FCS). Within that part of the DME band (yellow block in Figure 7-15):

! One dedicated 1 MHz channel (978 MHz) has been anticipated for the UAT link. About 99% of the UAT signal power is contained [UAT SARPs] within 1.3 MHz.

! Military TACAN system operates with 1 MHz channel spacing on DME frequencies.

! According to [ACPF14-WP12], only ground DME stations are active (replying) in the target range 960 � 1024 MHz (aircraft uses for interrogations paired DME channels that are 63 MHz above reply channels).

! Military JTIDS/MIDS system (a spread-spectrum frequency hopping TDMA system) operates in the 960 � 1215 MHz band with carriers spaced at 3 MHz intervals. Two exclusion bands (1008 � 1053, 1065 � 1113 MHz) protect the SSR operations. This system has no internationally recognised status in the ARNS band. In order to avoid interference with other systems, operational constraints are set on national basis.

NOTE: JTIDS/MIDS system occupies the lower part (960 � 1008 MHz) of the target DME sub-band (960 � 1024 MHz), using in that area 14 (of totally 51 used) carriers spaced at 3 MHz. The carrier frequency is rapidly changed (once per 13 µs) over a time slot of 7.8 ms duration. SSR interrogators and TCAS operate at 6 MHz spacing from the upper limit of this sub-band (1030 MHz).

Figure 7-15: Usage of ARNS Band 960 � 1215 MHz




The B-VHF system is a candidate FCS technology that could be deployed in the target DME range. Due to higher operating frequency modifications must be done at the physical layer. No changes are expected in other parts of the B-VHF protocol stack.

As no specific investigations have been performed within the B-VHF project with respect to the possible B-VHF system operation in the DME range, it is only possible to draw some conclusions from analogy with other systems operating in this range, in particular the newly standardised UAT system.

7.3.1. B-VHF System Data-only Deployment in the Target DME Range


Some B-VHF system physical layer parameters (e.g. sub-carrier spacing, guard interval) may have to be adapted to different propagation conditions in the DME band.

The preferred B-VHF deployment option in the target DME range is B-VHF as data-only system. Data-only operation becomes particularly attractive on conjunction with the proposed long-term strategy of voice usage [COCR] where beyond some point the data link shall become a primary means of air-ground communications (and existing VHF voice system would be used up to that point).

Opposite to the VHF COM range where B-VHF data-only system would interfere with the co-located DSB-AM systems, a data-only B-VHF system in the DME range would work well from the same aircraft as the voice services provided in the �distant� VHF range would be significantly less susceptible to the interference coming from the DME range than to the interference from the VHF range itself.

7.3.1.2. Airspace Regimes

The entire airspace subject to B-VHF system deployment would the B-VHF supported airspace, with mixed B-VHF and NB aircraft population and voluntary airborne equipage. This approach does not require dedicated B-VHF airspace segregated from other airspace types with mandatory carriage of B-VHF radios. Equipped users would receive B-VHF services with associated benefits via the B-VHF airborne radio (A_TRX3). Other users would be able to continue to use traditional narrowband data link equipment.


B-VHF system deployment concept in the DME range assumes that a number of dedicated 1 MHz channels has been allocated to and is exclusively used by the B-VHF system. These channels can be selected anywhere within the target DME range, with re-use distance according to frequency planning criteria in that range (B-VHF-specific criteria TBD).

NOTE: Relatively stringent DME planning criteria [ICAO EUR 011] may be eventually used as a �first guess� - any channel from the target DME range that can be considered as locally available for a DME assignment automatically becomes a candidate for the B-VHF channel assignment.

NOTE: No specific precautions are taken in [ICAO EUR 011] with respect to the interference coming from the military JTIDS/ MIDS system that effectively operates in an overlay mode with respect to the DME system, using TDMA with time slots of 7,8 ms combined with fast frequency hopping with frequency changes each 13 µs. Operational constraints are set on a national basis [ACPF14-




WP12] to avoid interference with DME and SSR equipment. However, even under similar operational constraints interference freedom between JTIDS/MIDS and the B-VHF system cannot be automatically assumed as these use completely different signals-in-space.

7.3.1.4. Impact on Airborne Architecture

An airborne B-VHF radio for the DME band could be considered as a further integration stage of a VDR multi-mode radio. Within the B-VHF airspace or B-VHF-supported airspace it should use DME-band RF front-end, otherwise it should use VHF front-end and support �standard� VHF modes of operation.

NOTE: This flexibility must be supported by an airborne multi-mode antenna, attached to the B-VHF radio and capable to operate � in an exclusive manner - across VHF and (lower part of the-) DME band. Such antennas are expected to become widely available e.g. due to the UAT deployment.

As long as no doubled data link components are required, airborne architecture (Figure 7-3) could be reduced to just a single airborne transceiver (A_TRX3) supported by a single CMU.

NOTE: Similar airborne data link architecture would apply as used today when providing ATN data link services over VDL Mode 2.

When doubling of data link components becomes mandated (e.g. due to increased availability requirements when data link is used as a primary communication means), second transceiver (A-TRX2), second multi-range antenna and second CMU may be added.

7.3.1.5. Impact on Ground Architecture

With data-only deployment concept, the ground B-VHF system architecture (Figure 7-2) becomes simplified, as all voice-relevant functions and components may be left-out. Voice service would be completely decoupled from the B-VHF system, provided as an �external� DSB-AM service. The B-VHF GNI would only need to interface with external data link systems like ATN routers or local data link servers operating in non-ATN mode.

As data link coverage is completely de-coupled from the voice coverage, similar service provision arrangements between the communications service providers (SPs) and air traffic service providers are possible as existing today. Moreover, due to the relatively large separation between VHF and DME bands, it may be possible to deploy B-VHF ground radio equipment operating in the DME range co-located with the current VDL Mode 2 radios.

B-VHF DME physical radios (G-RX, G_TX) would have to be deployed, with appropriate antennas. Due to the shorter antenna size, beam-forming techniques may be used as a means to increase required operational coverage. The rest of the ground architecture remains unchanged compared to the VHF architecture (Figure 7-2). As ATN does not support air-air communications services, no gateways are required between the B-VHF system and narrowband data link technologies.

All involved B-VHF cells would have to implement the initially required data service � an ATN-compatible data link based on the internal B-DA data service. All cells (GSCs) are attached to the GNI that in turn is connected to an external ATN A/G BIS router.

NOTE: Similar ground data link network architecture would apply as used today by the SPs (SITA and ARINC) when providing ATN data link services over VDL Mode 2.




7.3.1.6. Aircraft Co-location Requirements

As the DME range is sufficiently separated from the VHF range, no interference is expected between the data-only B-VHF radio operating within the DME range and the �classical� DSB-AM voice radio operating in the VHF range. However, care must be taken to assure interference-free operation of the B-VHF DME radio and other airborne systems operating within � or close to DME range.

As only ground DME stations are active (replying) in the target DME range 960 � 1024 MHz, airborne DME interrogations would not disturb FL reception from the B-VHF GS. A close ground DME station is still a concern, but the main airborne co-location concern would be preventing that transmitting B-VHF airborne TX interferes with an ongoing DME reply from the DME GS.


Data-only concept is applicable in all CDOCs (APT_CDOC/TMA_CDOC/ENR_CDOC). Required operational coverage could be achieved in the DME range with reasonable transmitting power (comparable to the UAT system operating in the same range, [RTCA DO-282]) even for ENR_CDOCs, due to the assumed spectrum usage option (dedicated channel, therefore absence of interference).

7.3.1.8. Usability for APT/TMA/ENR Services

As another system (UAT) has been developed to operate in the target DME range and 1090ES system has been selected for an initial implementation of the ADS-B service group, no initial support has been foreseen for these services within the B-VHF system. For the similar reason the downlink of aircraft data has been excluded (these will be provided by using Mode S-specific services).

This scenario is suitable for the provision of data link services in all airspace types (APT/TMA/ENR). The only condition is that for each GS an �empty� DME 1 MHz channel can be found that allows for the GS deployment with desired coverage, according to B-VHF-specific planning criteria (TBD). Between such cells data link service is handed-over in a seamless manner, using B-VHF internal mechanisms [B-VHF D7].

NOTE: In order to reduce the need for dedicated channels and overhead associated with handovers, a minimum number of simultaneously active B-VHF GSs should be used that guarantees desired operational coverage.

7.3.1.9. Data-only Deployment with Single 1 MHz Channel (DME)

In order to achieve a regional data-only coverage, the B-VHF system requires a number of GSs to be deployed and corresponding RF channels to be allocated.

The number of required B-VHF broadband channels could be reduced if several B-VHF cells could be organised (TDMA) to share the same broadband channel by using different TDMA slots. TDMA option was included in the B-VHF system design in the form of DCCH (Dedicated Control Channel) that exists on RL and is intended to carry system and user�s data. However, due to stringent voice timeliness requirements TDMA cannot be used for reducing the number of VHF RF channels as long as B-VHF system is used as an integrated voice/data system.

If the B-VHF system were used as a data-only system, the timeliness requirements for voice services would not apply and TDMA component could be eventually introduced. In data-only configuration, the B-VHF system could be optimised to provide support for




downlink of aircraft parameters, automated data exchanges between an aircraft and ground system and other applications with very high per-aircraft throughput, high QoS and predictable performance.

In such a case it may be sufficient to allocate single DME 1 MHz channel to the B-VHF system operating in the DME range.

Finally, with TDMA it may be even possible to assign a dedicated RL data channel to each particular aircraft within a cell.

NOTE: Dedicated Control Channel (DCCH) has been foreseen on RL within the B-VHF system design but the Synchronised RACH (sRACH) channel has been selected as a preferred RL solution in the VHF range due to the reduced resource availability with assumed overlay concept. As almost no interference has been assumed in the DME range, the resource availability would increase. It may become possible to assign a dedicated pool of RL OFDM carriers to the group of aircraft and to use TDMA within such a group to provide a dedicated RL data channel for each aircraft.

With TDMA sharing of the common RF channel, B-VHF system configuration, net initialisation and net entry procedures would have to be adapted, but otherwise no constraint could have been identified within the B-VHF design that would preclude such an approach.

Figure 7-16 shows an example of single-channel data-only B-VHF operation. Four cells with associated GSs (GS1� GS4) all share the same 1 MHz broadband channel, each operating in its dedicated Super-Frame (SF). The cumulative vertical/lateral data-only coverage for four cells is much higher than for any isolated cell. When an aircraft leaves e.g. GS4, an automated handover is executed and the GNI transfers data connection to GS3 as described in [B-VHF D7].

Airborne B-VHF transmitters would have to be restricted to transmit only in appropriate SFs. With existing B-VHF SF duration of 240 ms, this would cause additional access latency due to waiting to the appropriate SF of at most 750 ms.

Here, it was assumed that single 1 MHz channel has been assigned as a dedicated channel, but in principle the data-only concept would work under overlay conditions as well.

NOTE: The bandwidth of DME signals � that would be the main interference sources and victims � is higher than the bandwidth of the B-VHF signal. At the same time, the duration of these pulsed signals is very short. Clearly, considering overlay in the DME range requires further detailed investigations. Therefore, a conservative approach with dedicated channels has been selected as more realistic option for an initial system deployment in the DME range.

An additional TDMA component would reduce capacity of each particular cell (as each cell would be able to use shared channel for ¼ of the total time). With overlay, capacity would be further reduced, but the net capacity/throughput the B-VHF data-only system could offer on the single broadband channel would be far above aggregated requirements of all known today�s and future data link services combined with the worst-case air traffic growth hypothesis.




Figure 7-16: Single RF Channel B-VHF Operation Based on TDMA

7.3.1.10. Data-only Deployment with Multiple RF Channels (DME)

With such an approach no additional TDMA component is introduced and no modifications of the existing B-VHF concept are required. A number of dedicated 1 MHz channels in the target DME range are reserved for the B-VHF data link within a particular region of implementation. The situation depicted on Figure 7-16 applies, except that four cells GS1 � GS4 now use different B-VHF RF channels (f1/f2/f3/f4) and no TDMA is used.

In the absence of interference the offered capacity of a 1 MHz B-VHF data-only channel would be far above cumulative demands of the expected aircraft population within a cell, even with 250 kHz bandwidth of a broadband channel. With B-VHF approach for dynamic resource allocation, the entire channel capacity is managed by the GS with very few possibilities for access collisions. Moreover, the GS is able to maintain multiple simultaneous independent data link connections with multiple aircraft, providing excellent QoS in terms of access delay and potentially very high per-aircraft data throughput.

In order to reduce the required number of required 1 MHz allocations for B-VHF purposes, the B-VHF system should be preferably configured to use 500 kHz broadband channels or even 250 kHz channels (two or four such channels would fit into one 1 MHz DME allocation). This would allow for �micro frequency planning� of B-VHF channels within the umbrella of the DME frequency planning.

NOTE: �Very narrow� B-VHF channels of 250 kHz BW have not been explicitly considered in the B-VHF system design so far, but no point could be identified within the B-VHF system design that would prevent further channel bandwidth reduction below 500 kHz. The system RF bandwidth may differ between different ranges, but once selected, it should remain stable within each range.




The multi-channel approach for data-only B-VHF system deployment in the DME range can be easily combined with the TDMA enhancement that was proposed for the single-channel deployment concept (previous section).

7.3.2. Integrated B-VHF System Deployment in the Target DME Range


Within this scenario, a B-VHF system operates as an integrated system, providing both voice and data services to the equipped users.

NOTE: As indicated before, a data-only system is the preferred B-VHF deployment option within the DME range. With the �integrated� option described here, it may also be possible to dislocate some (less critical-, e.g. AOC) voice service to the DME range and retain the ATS voice service in the VHF range.


Dependent on the preferred local deployment policy, this scenario can be applied within the B-VHF supported airspace, with mixed B-VHF and NB aircraft population and voluntary airborne equipage. Alternatively, B-VHF system deployment may start within a dedicated B-VHF airspace.


Assuming an appropriate number of dedicated broadband channels is available in the target DME band (as required for the frequency planning), an integrated voice/data B-VHF system can be deployed in this band without overlay.

NOTE: An integrated deployment scenario in the DME range based on overlay may be possible, but has not been foreseen in this document due to the unknown interference mechanisms between the B-VHF system and DME/JTIDS/MIDS systems.


Airborne architecture is similar to the case of B-VHF deployment in the VHF range (Figure 7-3). Multi-mode VHF/DME radios would use a combined VHF/DME antenna. When operating in the DME range the B-VHF radio would use DME-band RF front-end, otherwise VHF front-end would be used. Moreover, such a multi-band multi-mode radio would have to support all �standard� VHF modes of operation.

All external interfaces of a VHF/DME B-VHF radio would remain the same as the interfaces of today�s VHF radios. This should allow for an easy integration within existing airborne framework and compatibility with external non-B-VHF components and systems (AMS, CMU).


B-VHF DMA physical radios (G-RX, G_TX) would have to be deployed, with appropriate antennas. Due to the shorter antenna size, beam-forming techniques may be used as a means to increase required operational coverage. The rest of the ground architecture remains unchanged compared to the VHF architecture (Figure 7-2). As ATN does not support air-air communications services, no gateways are required between the B-VHF system and narrowband data link technologies. However, within the B-VHF-supported




airspace VCS would have to act as a gateway to provide party-line between the B-VHF voice system and the DSB-AM system that is used for non-B-VHF population.

NOTE: Controller�s voice would be transmitted in parallel over both systems. Any RL voice transmission received via B-VHF sub-system would have to be re-transmitted via DSB-AM system and vice versa.


As the DME range is sufficiently separated from the VHF range, no interference is expected between the B-VHF radios operating within the DME range and the �classical� DSB-AM voice radio system operating in the VHF range. Simultaneous B-VHF/DSB-AM operation from the same aircraft (e.g. emergency channel) should be possible without significant problems. Simultaneous operation of two DME B-VHF radios in the voice mode is granted � under frequency planning constraints - due to the usage of TDD separation between FL and RL and the fact that frames of all B-VHF GSs are mutually synchronised. However, care must be taken to assure interference-free operation of the B-VHF DME radio and other airborne systems operating within � or close to the DME range.


With an integrated DME concept combined with dedicated channels required operational coverage in the DME range could be achieved even for ENR_CDOCs, therefore also for all smaller CDOCs.

NOTE: Achievable ENR_CDOC for integrated B-VHF deployment in the DME range may become comparable to the achievable corresponding CDOC in the VHF range where under overlay conditions relatively high transmitted powers and large separation distances are required for reasonable system operation. Additionally, due to higher operating frequency in the DME range it may be easier to use beam-forming techniques to increase GS coverage.


The B-VHF system would provide initial scope of voice and ATN data link services as generally applicable to the initial deployment phase.

7.4. B-VHF System Deployment in the MLS Range

[ACPF14-WP14] indicates that the MLS range (5091- 5150 MHz) may be suitable for aeronautical surface communications and short-range air-ground and air-air communications. No change is expected to the current allocation in the band 5030-5091 MHz since this band is required to satisfy the requirements of the aeronautical radio navigation service (MLS).

The B-VHF system is a candidate technology that could be deployed in the MLS range. Some B-VHF system physical layer parameters (e.g. sub-carrier spacing, guard interval) may have to be adapted to different propagation conditions in the MLS band.

No changes are expected in other parts of the B-VHF protocol stack.

A significant amount of work related to the MC-CDMA technology operating in the MLS range has been done by DLR prior to the B-VHF project ([ICNS 2003], [ETT 2002]). However, no specific investigations have been performed within the B-VHF project with




respect to the possible B-VHF system operation in the MLS range. Therefore, only a brief outlook of possible deployment scenario in that range will be given within this document.


Within this scenario, a B-VHF system operates as a data-only system, providing data services to the equipped users. Such a configuration has been assumed as it is well-aligned with the proposed long-term strategy of voice usage and requires the minimum changes of the airborne architecture. Opposite to the VHF range, data-only concept in the MLS range is perfectly feasible.


This scenario assumes B-VHF supported airspace (as a more challenging/more attractive regime) that can later on be eventually converted to B-VHF airspace.


It was assumed that a dedicated 1 MHz channel has been allocated within the MLS range to be used by the B-VHF system. Due to the relatively short range and the fact that there are no intents to deploy the MLS-range B-VHF system for TMA and ENR purposes, this single allocation could be re-used by all airports of interest.

If required by the airport topology, the same concept (TDMA extension) may be applied as proposed for the data-only deployment in the DME range with single broadband channel. This would allow for re-using single broadband channel by several mutually synchronised airport GSs.


An airborne B-VHF radio for the MLS band could be considered as a further integration stage of a VDR multi-mode radio. Multi-mode VHF/MLS B-VHF radios would use a combined VHF/MLS-band antenna. Within the B-VHF airspace or B-VHF-supported airspace the radio would use MLS-band RF front-end, otherwise it would use VHF front-end, supporting both B-VHF and �standard� VHF modes of operation.

As long as no doubled data link components are required, airborne architecture (Figure 7-3) could be reduced to just a single airborne transceiver (A_TRX3) supported by a single CMU. When doubling of data link components becomes mandated, second B-VHF radio with second multi-range antenna and second CMU may be added.


With data-only deployment concept, the ground B-VHF system architecture (Figure 7-2) becomes simplified, as all voice service would be completely decoupled from the B-VHF system, provided as an �external� DSB-AM service.

The B-VHF GNI would interface with single or multiple GSs as well as with an external ATN router.

B-VHF MLS physical radios (G-RX, G_TX) would have to be deployed, with appropriate antennas. Beam-forming techniques may be required to increase required operational coverage. The rest of the ground architecture remains unchanged compared to the VHF architecture (Figure 7-2).





As the MLS range is sufficiently separated from the VHF range, no interference is expected between the B-VHF radios operating within the MLS range and the �classical� DSB-AM voice radio system operating in the VHF range. However, care must be taken to assure interference-free operation of the B-VHF MLS radio and other airborne systems operating within � or close to the MLS range.


Propagation losses for the same LOS distance are in the MLS band (5 GHz) much higher (32.4 dB) than in the VHF range (120 MHz). As the transmitting power is limited both for an airborne and ground B-VHF TX, the system can reasonably be deployed only for short-range airport communications (corresponding to APT_CDOC = 25 nm).


Because of high propagation losses the B-VHF system deployed in the MLS range is only suitable for APT services.

7.5. B-VHF System Deployment in the VOR Range

[ACPF14-WP21] has shown that it may be possible to free in Europe � through frequency re-planning � between 1 and 2 MHz in the upper part of the ARNS VOR band (108 � 118 MHz). It has been anticipated that this spectrum (116- 118 MHz) could be used for 8.33 kHz DSB-AM system. However, if available, it could also become an option for the deployment of the new B-VHF system.


The preferred B-VHF deployment option in the target VOR range (116 � 118 MHz) is B-VHF as data-only system, with voice services provided via DSB-AM system operating in the VHF COM band (118 � 137 MHz).

NOTE: Opposite to the VHF COM range, data-only concept in the VOR range may be feasible. The VOR target band (116- 118 MHz) should be preferably organised as a sub-band, separated from the COM band by using pre-filtering within the receiver. This would remove the most of interference coming from the COM band. The remaining concern � particularly at short distances - is the radiated broadband noise floor of the B-VHF transmitter that may fall over the reception bandwidth of the VHF COM receiver. This, however, may be circumvented by using lower transmitter power than in the VHF COM range, due to the usage of dedicated broadband channel instead of overlay that is applicable to VHF COM range.


This scenario assumes B-VHF supported airspace (as a more challenging/more attractive regime) that can later on be eventually converted to B-VHF airspace.


It was assumed that a dedicated 1 MHz channel has been allocated within the VOR target range to be used by the B-VHF system. The same concept (TDMA extension combined




with sub-division into 4 B-VHF channels with 250 kHz bandwidth each) shall be applied as proposed for the data-only deployment in the DME range with a single broadband channel. This would allow for frequency planning within the deployment area and re-using single broadband channel by several mutually synchronised GSs.


An airborne B-VHF radio for the VOR band could be considered as a further integration stage of a VDR multi-mode radio. It would become a multi-range communications radio, with extended VHF range (116 � 137 MHz). Common RF front-end and common antenna would be used within the VOR range and VHF COM range.

As long as no doubled data link components are required, airborne architecture (Figure 7-3) could be reduced to just a single airborne transceiver (A_TRX3) supported by a single CMU. Later on, second transceiver (A-TRX2) and optionally also second CMU may be added.


With data-only deployment concept, the ground B-VHF system architecture (Figure 7-2) becomes simplified, as all voice service would be completely decoupled from the B-VHF system, provided as an �external� DSB-AM service.

The B-VHF GNI would interface with single or multiple GSs as well as with an external ATN router. Similar ground data link network architecture would apply as used today by the communications service providers (SITA and ARINC), with possible similar service provision arrangements between the SPs and air traffic service providers as today.

B-VHF VOR physical radios (G-RX, G_TX) would have to be deployed, with appropriate antennas. These radios would be similar to the radios used within the VHF COM range, with an �extended� RF front-end that allows operation below 118 MHz.

The rest of the ground architecture remains unchanged compared to the VHF COM architecture (Figure 7-2).


As the VOR range is very close to the VHF COM range, interference is expected between airborne B-VHF radios operating within the VOR range and the �classical� DSB-AM voice radio system operating in the VHF range. When used in the B-VHF data mode, the airborne receiver should preferably implement a pass-band filter over the VOR range to reduce interference coming from the DSB-AM transmitters operating within the VHF COM range. The same approach may be used with the ground B-VHF receiver operating in the data-only mode over VOR range.


Propagation losses for the same LOS distance are in the VOR band comparable to losses in the VHF COM range. As interference-free situation was assumed (dedicated channel instead of overlay), the system operation would be limited by noise rather than interference, so significantly lower transmitting powers could be used than in the VHF COM range. The system would therefore be applicable for all types of CDOCs, up to the ENR_CDOC of 200 nm.





This scenario is suitable for the provision of data link services in all airspace types (APT/TMA/ENR). The only condition is that for each GS an �empty� VOR 1 MHz channel can be found that allows for the GS deployment with desired coverage, according to B-VHF-specific planning criteria (TBD). Between such cells data link service is handed-over in a seamless manner, using B-VHF internal mechanisms [B-VHF D7].

----------- END OF SECTION -----------




8. Transition Scenarios

This chapter describes the transition from an initial, local B-VHF system deployment in selected areas of the APT/TMA/ENR airspace towards a seamless regional B-VHF coverage as currently seen by the members of the B-VHF project consortium. Initial deployment scenarios described in the previous chapter provide the baseline for such transitions:

! Integrated Deployment in the VHF COM Range (Selected APT/TMA/ENR as B-VHF-supported Airspace, ENR HIGH as B-VHF Airspace)

! Data-only/Integrated Deployment in the DME Range

! Data-only Deployment in the MLS Range

! Data-only Deployment in the VOR Range

All voice and data link services installed during the initial system deployment phase remain in use while new services are being added, dependent on the local service demands.

As it is expected that the interference situation will generally become better with time1, the system capacity also improves � an increased range of services is available with increased quality. In the transition phase more and more voice services are gradually ported from voice to data link communications. Additionally, advanced concepts become progressively installed that are oriented towards reducing the need for voice communications (trajectory-oriented ATC, initial ASAS applications). However, the role of voice communications is still very important, so the number of required voice channels only slowly decreases.

8.1. Common Aspects

For each scenario the following transition aspects have been described in the corresponding sections:

! Evolution of the spatial B-VHF system coverage

! Change of the spectrum occupancy

! Adding new services (service evolution)

! Evolution of the ground infrastructure

! Evolution of airborne equipage

8.1.1. B-VHF Operational Scenarios and Services Provided

The scope of B-VHF services inherent to the initial B-VHF system development is described in [B-VHF D7] in the chapter 8.1- Scenario for 2011-2015, while the scope of finally offered B-VHF services is described in the �2020-2025 Scenario� (chapter 8.2). This section describes an intermediate stage where all initially installed services remain in

1 Possible improvements in terms of resource availability and interference are described in sections 8.2.2 and 8.3.2.




place and additional services (as described in section 8.2.3 below) are successively added in order to reach the final deployment state.

8.2. Transition in the VHF COM Range

All options for an initial B-VHF system deployment in the VHF COM range assume an integrated voice/data system and are based on overlay. The airborne architecture considers three independent radio units and remains stable during the transition period. It has been assumed in all scenarios that the B-VHF radios cannot be simultaneously used from the same aircraft together with other VHF radios operating in the COM band (an aircraft is either B-VHF-equipped or remains a NB aircraft). Corresponding ground B-VHF infrastructure is deployed in both B-VHF airspace and B-VHF-supported airspace, whilst the airborne B-VHF equipage is only mandatory in the B-VHF airspace.

The transition scenarios in the VHF COM range assume that the B-VHF system has been initially mandated for the High ENR airspace and installed on voluntary basis in Low ENR airspace, in TMAs and at selected airports.

Mandatory equipage in the upper ENR airspace is regarded as the only realistic initial deployment option for the B-VHF airspace. Here, a similar policy may be adopted for the B-VHF system as for the 8.33 kHz system introduction.

Mandated initial B-VHF system introduction in APT, TMA and even lower ENR airspace has been perceived as not realistic due to the fact that a large airborne population (including MIL and GA) needs an access to this airspace so mandating equipage may become a very difficult task. Therefore, selected airports, TMAs and low ENR sectors have been identified as the most probable candidates to become a B-VHF-supported airspace during system introduction.

During the transition phase it is expected that the B-VHF system is introduced in further parts of the APT/TMA/ENR airspace, both within the B-VHF airspace and the B-VHF-supported airspace. In some cases this may result in an increase of the VHF channel availability, allowing deploying additional more powerful data link services within the B-VHF system.

8.2.1. B-VHF System Spatial Expansion

The major changes during the transition phase are expected from the conversion of the B-VHF-supported airspace into the B-VHF airspace. Such a conversion has generally the following impacts onto the B-VHF system:

! Local spectrum availability at airports is increased due to the withdrawal of local STRONG channels (emergency frequency 121.5 MHz remains as the sole �local� NB channel).

! B-VHF system capacity is increased as more resources � OFDM channels - are available due to the improved spectrum availability.

! The closest STRONG interferer (within adjacent NB airspace or B-VHF-supported airspace) now appears at 600 m distance in all environments (formerly, the minimum distance at airports was 210 m).

! In boundary regions both �S� and �O� constellations are allowed

! B-VHF system performance is improved due to the reduced interference.




! Interoperability between the DSB-AM and the B-VHF systems is not required any more.

8.2.1.1. Expansion of B-VHF-supported Airspace (APT/TMA/Low ENR)

During the transition phase it can be expected that the B-VHF system would be gradually introduced in additional parts of APT/TMA/Low ENR airspace based on the voluntary airborne equipage.

Expansion of the B-VHF-supported airspace provides more communications capacity for the system users but does not directly increase spectral availability for the B-VHF system itself. As both the B-VHF system and all legacy systems (NB channels) remain in operation, the number of potential interferers and the total amount of NB interference is only slightly reduced (the B-VHF aircraft do not contribute to the NB interference).

The B-VHF system would automatically react (without a need for re-configuration) to even slight improvements in the spectrum occupancy by providing gradually improved performance for existing services.

Extending B-VHF-supported airspace would play an important role in gaining users� acceptance and in achieving a �critical mass� of airborne equipage on the way to establish a possible mandate for the B-VHF carriage at some future point in time.

8.2.1.2. Expansion of B-VHF Airspace (ENR High)

Scenario for the initial B-VHF system deployment in High ENR airspace (section 7.2.5) is similar to the 8.33 kHz system introduction, starting with mandated B-VHF equipage in ENR high airspace above some defined FL (e.g. FL 245) and then reducing this FL after some time (during the transition phase). This scenario is illustrated in Figure 9-1.

As the B-VHF system becomes mandatory within the B-VHF airspace, all previously NB channels are not needed any more and are switched off. Each such �returned� channel becomes immediately �potentially available� to the B-VHF system.

It is generally expected that the mandatory B-VHF system introduction in High ENR sectors over entire Europe would occur in at most two steps � an initial system deployment above some transition FL and one additional step during the transition phase where the initial transition FL has been further reduced.

This transition scenario operates with large airspace blocks, comprising many sectors. Once the transition FL was reduced after an initial deployment, entire �clusters� of NB channels would be abandoned. The withdrawal of a particular NB channel may generate occupancy benefits both outside and within the local airspace, dependent on the position of the converted narrowband channel with respect to the locally used B-VHF channel(s).

After such a conversion it should be checked � on a regional basis � whether the B-VHF system could be re-configured (e.g. to add new services to take advantage of a recent occupancy improvement).

Once some minimum transition FL for entire Europe has been reached during the transition, the further vertical expansion of the B-VHF system may be possible (only) in selected parts of the Low ENR airspace, as well as at selected TMAs and airports.




8.2.1.3. Transition to B-VHF Airspace (Low ENR)

During the late phase of the transition period additional parts of the B-VHF-supported ENR airspace may become converted to B-VHF airspace due to increased airborne equipage.

In this particular scenario selected Low ENR sectors would be rapidly converted to the B-VHF mode of operation starting from some date and all aircraft flying through that airspace would be obliged to carry the B-VHF equipment and use it as long as they remain within the B-VHF airspace. The emergency frequency 121.5 MHz remains as a sole DSB-AM channel that may be used within that airspace.

NOTE: It is not probable that during transition phase entire European airspace could become a B-VHF-airspace. Even in the very late phase of the B-VHF system deployment some NB airspace may exist around and below the B-VHF airspace.

8.2.2. Change in the Spectrum Availability

During the B-VHF system transition phase the local spectrum occupancy may improve in two ways, directly, via expansion of the B-VHF airspace (as described in the previous section), and indirectly, via increasing sector size and reducing the number of required voice allocations in the B-VHF-supported airspace. The benefits of direct occupancy improvement are immediately visible while an indirect improvement is dependent on other activities, e.g. resizing existing ATC sectors.

In some phase of the transition new powerful data link services should become deployed [B-VHF D7], allowing for trajectory-oriented ATM and removing a lot of controller�s workload (in particular handling of a voice communications channel). Increased controller�s workload has lead to reduced sector sizes, increased number of sectors and finally an increased number of voice channels. It is expected that decreased workload would lead back to larger sectors, offering a possibility for some voice channels to be �withdrawn�. Such abandoned VHF channels may become available to the B-VHF system, further increasing system capacity.

The rate of return of VHF NB channels with that option in the mid-term is expected to be very low as mainly one channel would be returned at a time. Therefore, without successive expansion of the B-VHF airspace, the re-configuration of the B-VHF system (e.g. for adding new services) in the B-VHF-supported airspace would have to be postponed for some time until the improvement in terms of occupancy becomes clearly visible.

With the long-term concept of autonomous operations (ASAS) a number of current upper space sectors may has to be converted at once to the single large ASAS sector, with extremely large coverage requirements, but reduced voice communication demands on the associated voice channel and changed communications purpose (e.g. advisory actions instead of ATC). As future ASAS airspace can only be allocated from a part of the currently controlled airspace, consisting of many ATC sectors, a number of narrowband channels may rapidly become �free� after the ASAS equipage becomes mandated, even if the ASAS airspace itself remains a B-VHF-supported airspace.

If the number of used narrowband (NB) channels decreases, the amount of interference towards the B-VHF system would generally also decrease. The B-VHF system capacity will gradually increase due to the improved spectrum availability, while the system performance will improve due to reduced interference coming from narrowband systems.




This applies to both deployment options, in the B-VHF airspace and in the B-VHF-supported airspace.

Each such conversion may be used for re-configuring the VHF system to take advantage of recent occupancy improvements. As with the previous option, the withdrawal of some NB channel within a given airspace may generate occupancy benefits either outside or within that airspace.

8.2.3. Adding New Services

During the initial B-VHF system deployment (chapter 7) downlink of aircraft data and ADS-B/TIS-B services are expected to be provided by the Mode S technology. The B-VHF system in this phase basically provides voice party-line and broadcast services supplemented with an ATN-compatible data link.

During the transition new B-VHF services may become gradually configured and activated within the B-VHF system. The total range of services provided in each phase of the transition will depend on the local demands and local capacity of the B-VHF system that in turn heavily depends on the available spectrum for an overlay B-VHF system. It is expected that in an early transition phase new voice channels would be added to the initially installed ones, under limitations imposed by the local occupancy situation. Later on, it is expected that the following groups of new services would be gradually added to the existing ones:

! Selective voice service (B-VS) for AOC voice communications

! Additional ATN-compatible ATS data link services (e.g. DYNAV, COTRAC)

! Additional ATN-compatible AOC data link services (e.g. Graphical Weather)

! Downlink of aircraft data (CAP, SAP, PPD)

From these groups, it is expected that additional ATN services will be globally provided (by each B-VHF cell). Other two groups � selective voice and down-linked aircraft parameters - may be offered by selected cells on a local basis, dependent on the local spectrum availability and local service demands.

In the cases where existing cells cannot provide the coverage required by all new services, the total system coverage will have to be increased by deploying additional B-VHF cells. Adding new cells must be accompanied by careful frequency planning. As the number of broadband B-VHF channels is limited, the preference should be adding new services to already deployed B-VHF cells.

8.2.3.1. Selective Voice

[COCR] states that selective voice service is no longer required for ATS purposes. However, it remains a possible means for future Flight Crew to Operations Centre (AOC) communications. This gives an opportunity to increase the VHF spectrum efficiency by using B-VHF internal B-VS service as a replacement for OPC voice channels that are today used in the party-line mode. The spectrum efficiency is increased due to the fact that voice duty-cycle is less than 100% and that the resources for the B-VS service are allocated only when needed.

NOTE: Where required, B-VHF party-line should remain available for AOC/OPC communications.




Assuming gradual increase in the airborne B-VHF equipage and adequate local spectrum availability, AOC selective voice services could be offered during the transition in both B-VHF airspace and B-VHF-supported airspace. In the latter case there would be no return of VHF resources as the NB aircraft would continue to use DSB-AM party-line AOC channels.

AOC selective voice service could be easily offered in the entire B-VHF airspace or B-VHF-supported airspace by allocating adequate OFDM resources for this kind of service. As a minimum, reserving a single voice channel per cell may be sufficient.

NOTE: As long as the selective voice channel is not required by any user, these �allocated� resources may be used e.g. for improving data link performance.

Within the B-VHF ground infrastructure, an adequate service access point should be available for the external AOC user.

Once installed, the new B-VS service must be announced to the users and would be invoked and handled according to the procedures described in [B-VHF D7].

8.2.3.2. Additional ATN Services

The B-VHF system has been designed to become an ATN sub-network. Like other ATN sub-networks, new ATN services can be added to the existing ones in a transparent way, without any changes of the underlying B-VHF system. Prior to any operational usage the safety analysis must be performed in order to assure that the required QoS can be preserved for the entire set of services under current air traffic and spectrum availability conditions.

NOTE: A possible strategy would be to consider some minimum amount of OFDM carriers as �reserved� for ATN data link, but to use an increased number of carriers when/where these become available.

8.2.3.3. Downlink of Aircraft Data

This type of service has been excluded from initial deployment scenarios as other method (Mode S specific protocols) has been identified to provide aircraft data at the estimated time of B-VHF initial introduction. However, due to the future increase of air traffic this external system is expected to become saturated at some point. Activating corresponding B-VHF system capability at that time could help to relieve Mode S system - a part of the entire airborne population would start to use the B-VHF system instead of Mode S.

On the airborne side, deploying this kind of service may or may not generate a need for modifying the airborne architecture (aircraft parameters may be derived directly from external systems or from the CMU). On the ground side a dedicated non-ATN system interface would have to be activated, allowing for exporting aircraft parameters towards the ground ATM automation.

8.2.4. Ground Infrastructure Evolution

The evolution of the B-VHF ground infrastructure after an initial system deployment would probably follow two ways:

! Local evolution (changes) of the ground infrastructure supporting the B-VHF airspace and B-VHF-supported airspace due to adding new voice and data services/interfaces.




! Global B-VHF infrastructure expansion due to the B-VHF system deployment in additional parts of the NB airspace.

Not all new communications services require infrastructure changes, e.g. new ATN data link services may be added to the existing ones without infrastructure changes Adding new voice services may be achieved by re-configuring an existing B-VHF system. However, some classes of services that have been excluded from an initial deployment may require activating new B-VHF system interfaces and/or deploying new/additional ground infrastructure.

Adding selective voice service for AOC purposes would require an airlines� voice access (dial-in possibility) at the B-VHF GNI that is responsible for High ENR airspace. The GNI acts as a gateway, maps airborne and ground addresses to each other and forwards the call received via the ground segment over the air-ground segment and vice versa.

NOTE: By implementing the selective voice feature an airline would get voice access to their aircraft within significantly broader area than today (where it is limited to the range of the company DSB-AM ground station). At the same time selective voice would increase communications privacy for the airlines and could return significant VHF resources that have been currently allocated for OPC party-line channels.

Adding downlinked aircraft data would require activating new system functionalities and network interfaces on the ground side. The services associated with downlink of aircraft parameters are internally mapped onto B-VHF not acknowledged B-DN internal data link service as described in [B-VHF D7].

The ground service access point may be at the GNI or GSC. The aircraft data may be transferred between the GSC and the GNI either along with other voice and data link packets or may use dedicated networks and associated protocols with a service access point placed at the GSC of the involved GSs.

8.2.5. Airborne Equipage Evolution

The evolution of the airborne equipage will be guided by two particularly important factors:

! B-VHF system acceptance by the users, leading to the increased voluntary equipage (this will happen only if the users can clearly see the benefits provided by a new system)

! Rule-making decisions of ANSPs (these would also be influenced by the general acceptance of the B-VHF system), leading to the rapid conversion of B-VHF-supported airspace to the B-VHF airspace with mandatory airborne equipage for the concerned part of airborne population

Adding new ATN services does not require any changes of the airborne B-VHF architecture (if changes of other systems should be required, they are hidden from the B-VHF system by the CMU).

Adding downlinked aircraft data may also remain hidden to the B-VHF system as long as the CMU is the only external data system that interacts with the communications sub-systems like B-VHF. However, in architectures where the CMU does not handle all data communications adding these services would require activating new system functionalities and network interfaces on the airborne side.




As there are not many opportunities for changing an airborne system after initial deployment, the evolution on the airborne side should preferably consist in just activating/configuring already existing system services and features, dependent on the regionally adopted and announced usage policy of the system.

If this is not be possible (e.g. where wiring changes are required), necessary upgrades should be performed in �packages�, during a regular aircraft maintenance cycle.

Adding the selective voice feature during the transition phase requires that at least basic mechanisms for the pilot�s selection of the called ground party and indicating an incoming ground call to the pilot would have to be installed as a part of �B-VHF basic package� from the very beginning of the system deployment. The preliminary description of the associated procedures [B-VHF D7] shows that this may probably be achieved by using existing pilot�s HMIs and existing voice system interfaces. Later on, more sophisticated HMIs can be delivered with the new aircraft as a part of an �enhanced B-VHF package�. Such �enhanced B-VHF package� may include new wiring or interconnections to additional avionics systems that have not been foreseen with the basic architecture.

8.3. Transition in the non-VHF COM Ranges

Opposite to the VHF COM range, the preferred initial deployment strategy in the DME, MLS and VOR range (sections 7.3, 0 and 0) is based on dedicated channels rather than on overlay. This aspect is not expected to change during the transition period. Otherwise, transition strategies in non-VHF COM ranges have many similarities with corresponding scenarios in the VHF COM range.

The global approach is to allow for gradual increase of airborne population based on the voluntary equipage and then impose a mandate for the B-VHF data link equipage in the non-VHF COM range. Finally, due to the long-term benefits from powerful and mandatory B-VHF data link it may be possible to reduce the number of VHF voice channels used within some area, free a part of the VHF COM spectrum and pave the way for the B-VHF system introduction within the VHF COM range.


Scenarios of initial system introduction in non-VHF COM ranges assume B-VHF-supported airspace. This type of airspace is preferred as it is less constraining than the B-VHF airspace option.

During the transition phase it is expected that the level of B-VHF airborne equipage will gradually increase. At some point it may become possible and operationally desired (or even necessary, to achieve homogenous procedures) to apply a mandate to achieve 100% B-VHF equipage in selected airspace types.

As in the VHF COM range, mandated system deployment could initially remain restricted to High ENR airspace, with an optional vertical expansion during the transition phase downwards up to some minimum transition flight level. Further mandatory B-VHF system deployment below this minimum FL in parts of Low ENR-, TMA and APT airspace would depend on the overall system acceptance. The corresponding scenario would have to take into account significant non-transport airborne population (e.g. GA, MIL).




8.3.2. Change in the Spectrum Occupancy

All scenarios of initial system introduction in non-VHF COM ranges assume that either a single or a number of dedicated broadband channels has been allocated to- and is exclusively used by the B-VHF system. This section describes possible impacts of system transition upon the availability of VHF spectrum resources.

NOTE: In scenarios where data-only B-VHF system has been initially introduced in non-VHF COM ranges the B-VHF system deployment in the VHF COM range is expected relatively late - in the final deployment phase � due to the expected slow rate of return of VHF voice channels until the concept of ATC becomes superseded by more powerful ATM concepts like trajectory-based ATM or ASAS.

As with the preferred B-VHF-supported airspace option existing VHF voice system remains in operation, introduction of new B-VHF cells in the DME range and other non-VHF COM ranges would generate only limited direct benefits in terms of the VHF COM spectrum relief.

Assuming increasing B-VHF system acceptance in non-VHF ranges (e.g. DME) due to the high-capacity/high-performance data link that can be easily provided without constraints imposed by the voice system, at some point in time the DME B-VHF system may become mandated, eventually returning a (small-) number of VDL channels in the VHF range that have previously been used in that airspace.

With this scenario a major VHF spectrum relief can only be expected on the long-term basis, due to the benefits from the powerful B-VHF data link, leading to reduced controller workload and possibly to larger blocks of airspace (greater number of sectors or larger sectors) that a single controller is able to handle during normal working conditions. This trend towards larger sectors may become further accelerated by the advent of ASAS operations and the segregated airspace for autonomous operation, with less need for voice communications.

Each such consolidation of airspace blocks may lead to the reduced number of dedicated VHF voice channels � these channels become available and could be further organised into contiguous or non-contiguous spectrum blocks, finally allowing for an introduction of an integrated B-VHF system within the VHF COM range.


The preferred B-VHF deployment option in all non-VHF COM ranges is a data-only system. Taking that option into account, following data link services would be added to the existing ones during the transition phase:

! Additional ATN-compatible ATS data link services (e.g. DYNAV, COTRAC)

! Additional ATN-compatible AOC data link services (e.g. Graphical Weather)

! Downlink of aircraft data (CAP, SAP, PPD)

NOTE: All voice services with this scenario would be provided in a traditional way in the VHF range, by using the combination of 25 kHz and 8.33 kHz DSB-AM systems.

With an integrated voice/data option for the DME range new AOC voice service would become activated during the transition:

! Selective voice service (B-VS) for AOC voice communications




NOTE: With that option, a number of VHF AOC DSB-AM party-line voice channels may be converted to the B-VHF selective voice, providing an improved service to the airlines without known coverage constraints existing in the VHF COM range.


With the DME B-VHF system, an increased number of GSs would be required to provide the same ENR coverage in the DME range as with the current VHF systems. Taking the number and density of currently used ENR VHF GSs (section 7.1.10.1) into account, there should be no problem with ENR coverage over continental areas.

The major problems are expected with off-shore coverage. Due to higher propagation losses in the DME range ground antennas should be used with antenna gain above that of a typical VHF ground antenna (2,15 dBi). Specifics of such antennas were not investigated within the B-VHF project, but such high-gain antennas should be feasible in the DME range because of the same reason that caused a demand for them � an increased operating frequency.

Similar considerations apply to the ground data link system (and an integrated AOC voice/data link system in the DME range) as already described in section 8.2.4 for the VHF transition scenario. Again, the final goal is to convert an entire block of airspace to the B-VHF mode of operation in the non-VHF COM range and return the corresponding VHF resources to be used (from some point on in the future) by the B-VHF system operating in the VHF COM range.


As long as the similar airborne architecture can be assumed in all deployment ranges, similar considerations apply to the airborne data link system (and an integrated AOC voice/data link system in the DME range) as already described in section 8.2.5 for the case of VHF transition.

Data-only scenarios in non-VHF COM ranges require only one dedicated data B-VHF radio to be installed (the remaining two COM radio units are operated in the DSB-AM mode within the VHF COM range). No mutual interference is expected due to large frequency separation between two systems.

The DME and MLS radios have been considered to be stand-alone transceiver units. In the DME/MLS range, 18/33 dB more transmitting power, respectively, is required for the same distance than in the VHF range due to the higher operating frequency (chapter 5). This restricts the B-VHF system usage in the MLS range to APT environments only.

Combined DME/VHF airborne antennas are already available and are expected to become widespread in the future, e.g. due to the UAT system deployment in the USA.

A B-VHF system operating in the MLS range would require a multi-range MLS/VHF-capable antenna.

----------- END OF SECTION -----------




9. Final B-VHF System Deployment Scenarios

By the end of the transition phase the significant part of narrowband spectrum resources formerly used by NB systems within the selected region has been abandoned � these resources are now used by the B-VHF system.

Now the system operates at almost full capacity. The interference picture has significantly improved as in large airspace blocks only few NB channels remained (e.g. emergency frequency, SAR frequency).

As in this time-frame the demand for data link services prevails and voice channels are successively abandoned due to the powerful data link concepts (e.g. 4D trajectory management, ASAS), the B-VHF system is being steadily re-configured in order to benefit from increased availability. Therefore, increased spectrum availability reflects itself mainly in increased availability of B-VHF data link services.

It may be assumed that the airborne equipage is now mandated in extended airspace blocks, but some parts of the airspace within or around such B-VHF airspace blocks may still be operating in the B-VHF-supported mode. Close to that boundary the impact of narrowband �in-band� channels would still be significant, leading to an overlay situation. The interference impact will generally decrease with increasing B-VHF airspace size, but may still be visible in peripheral areas even with very large-size B-VHF airspace.

9.1. Common Aspects

For each of the following final deployment scenarios the following aspects have been described:

! Evolution of the spatial B-VHF system coverage

! Change of the spectrum occupancy

! Adding new services (service evolution)

! Evolution of the ground infrastructure

! Evolution of airborne equipage

9.1.1. B-VHF Operational Scenarios and Functional Scope

The scope of finally offered B-VHF services is described in [B-VHF D7] in the �2020-2025 Scenario� (Ch. 8.2). Detailed overview of operational applications and data link services applicable to that scenario is given in Table 7-1 (column �2020�) of the same document.

Initially, only ATN-compatible data link services, broadcast and party-line voice services have been installed, as described in chapter 7. During the transition phase selective voice service has been added for AOC purposes and the capability of the data link sub-system has been significantly increased. It may be expected that when approaching the final deployment phase the B-VHF system would already support even the most demanding ATN data link services and provide aircraft data to the ground systems.

In the final deployment phase basically the following new data link capabilities will become available:

! Broadcast surveillance data link (ADS-B, TIS-B)




! FIS service provision in broadcast mode (D-ORIS, D-OTIS, D-RVR, D-SIGMET, D-FLUP, in addition/exclusive to the ATN on-demand provision)

! Air-air data link services

These services use non-ATN broadcast capability (B-DB) or not acknowledged addressed capability (B-DN) as described in [B-VHF D7]. These services have not been installed earlier as they may have significant capacity demands that, combined with high performance expectations, cannot be fulfilled in earlier deployment phases due to spectrum availability constraints. During initial and transition phases of the B-VHF system deployment the broadcast services have been provided by the 1090ES technology. As even in that phase not full ASAS capabilities are exploited, there was no demand for addressed air-air data link communications.

At the time of the full B-VHF system deployment, Mode S enhanced surveillance data link and 1090 ES broadcast data link are expected to become saturated. At the same time broadcast data link demands will be increased due to an increased use of ASAS with increased number of airborne users and increased �per-user� traffic volumes. An air-air data link may become required in support of ASAS concepts.

The B-VHF system is configured to supplement other broadcast links by providing additional capacity, assuming B-VHF airspace with mandatory B-VHF equipage it may even be used as a sole surveillance data link, providing ADS-B services for ground surveillance and TIS-B services to flying aircraft.

All previously installed services, capabilities and interfaces remain in use.

9.2. Final B-VHF System Deployment in the VHF COM Range


At the time of the final B-VHF system deployment in the COM range it may be expected that the European High ENR airspace and parts of the Low ENR airspace have been converted to the B-VHF airspace and that significant part of remaining airspace is already operated as B-VHF-supported airspace. In the final deployment phase the process of conversion continues and is primarily oriented towards selected parts of TMA and APT airspace.

9.2.1.1. Transition to B-VHF Airspace (TMA, APT)

In this particular scenario selected TMAs or APTs would be rapidly converted to the B-VHF mode of operation starting from some date and all aircraft population visiting that airspace would be required to carry and use B-VHF equipment as long as it remains within the B-VHF airspace. This transition is shown in Figure 9-1.

NOTE: Such a scenario may become applicable in the very late phase of the system deployment by applying the mandate for the B-VHF equipage in the affected airspace after a significant percentage of all aircraft has become B-VHF capable due to the voluntary equipage. EUROCONTROL is considering [SES_AG] a similar policy to eventually mandate 8.33 kHz equipage below FL195, in TMA and APT airspace, however this decision is made dependent on the outcome of ongoing studies, including feedback from GA and military users. If such a mandate could be created for 8.33 kHz equipage in TMA and APT airspace, the similar reasoning may be applied to the B-VHF deployment.




When selecting the �local� broadband B-VHF channel for a particular airport or TMA it is still important to minimise the number of �S� interferers (within the surrounding NB airspace or B-VHF-supported airspace) that affect that channel.

If a large airport like Heathrow could be converted to become B-VHF airspace and all existing AOC voice channels were converted to the B-VHF selective voice service, the local APT broadband RF channel would have to be re-configured during conversion as well. Looking at Figure 7-10, the best candidate for the local B-VHF channel at Heathrow - after conversion to the B-VHF airspace - would be the channel 131-132 MHz that was formerly occupied by the AOC voice channels.

NOTE: If Heathrow were operated as a B-VHF-supported airspace (section 7.2.2), this particular 1 MHz channel was to be strictly avoided.

In this particular case, at least 22 NB channels (more than 50% of the total RF channel bandwidth) would become immediately available to the Heathrow APT B-VHF system solely due to the change of the broadband RF channel.

Figure 9-1: B-VHF Airspace Expansion

NOTE: Even in the very late phase of the B-VHF system deployment there will always remain a NB airspace around the B-VHF airspace and some TMAs and APTs below �B-VHF ENR airspace� may remain configured as �NB airspace� (Figure 9-1).




9.2.1.2. Transition to B-VHF Airspace (all Europe)

With this scenario all European TMAs and APTs would be rapidly converted to the B-VHF mode of operation starting from some date and all aircraft population visiting European airspace would be required to carry and use B-VHF equipment.

NOTE: Such a scenario could eventually become applicable after a significant percentage of all aircraft flying over Europe has become B-VHF capable due to the voluntary equipage. As European airspace is currently visited by very heterogeneous aircraft population, it is not very probable that this goal could easily be achieved. The scenario has been listed here as a similar policy was planned for the VDL Mode 3 system in the USA.

As all European airspace now became B-VHF airspace, the overlay constraints would apply only in the �boundary� regions, while the full B-VHF system capacity and performance could be exploited in the Core Europe (where it is required at most).


Due to the spatial expansion of the B-VHF system some of broadband B-VHF channels would become almost completely free of NB channels and would start to operate in the noise-limited instead of interference-limited mode. This would allow either to further reduce per-carrier B-VHF TX power (via configuration) or to increase system performance (as without interference the system would operate at very high SNR values, therefore with very good BER values).

At the same time, the system capacity would be increased due to an increase in the number of available OFDM carriers per cell.


In the final deployment phase it is expected that the voice communications are used only as a supplementary communications means, with the corresponding reduction in the number of required voice channels. Therefore, excess B-VHF system capacity that would become available in that phase would be used to increase the quality/performance of existing and introduction of new data link services.

The performance enhancement for existing services becomes visible as the GS would allocate more and more FL resources to data link due to the reduction in the number of required voice channels. At the same time, each aircraft would be assigned more and more powerful RL data link and an increased number of aircraft would be simultaneously supported by the GS on RL.

It is expected that in this deployment phase following groups of data link services would be gradually added to the existing ones:

! Broadcast data link services (ADS-B, TIS-B)

! Air-air data link services

The ASAS concept foresees a gradual introduction of ASAS-related services by initially using non-B-VHF technologies (1090ES, UAT, VDL4). Initially, only a sub-set of all ASAS services should be used, later on more advanced services should be installed. At some point the existing technologies (in particular 1090ES) may become saturated. From this point on an alternative technology like B-VHF will be needed to relieve congestion.




Full aircraft autonomy represents the last phase of ASAS deployment and would probably be the most challenging scenario due to the expected high number of participating users, requiring very high system capacity, high operational performance and some supporting features that do not exist today, including addressed air-air data link.

Because of these operational reasons these two service groups � broadcast data link and air-air data link - have been tied together and are proposed to be deployed relatively late during the B-VHF deployment cycle. Another reason is that broadcast surveillance services (ADS-B, TIS-B) may require significant bandwidth that would be difficult to allocate during the B-VHF transition phase due to the lack of spectral resources.

9.2.3.1. Broadcast Data Link Services

Broadcast surveillance data link (ADS-B, TIS-B) would be re-built within the B-VHF system by using internal non-ATN system data link mechanisms. Participating aircraft would direct their position reports towards the B-VHF GS, the GCS would forward them towards GNI. As the GNI defines regional configuration for wide-area services like ADS-B, it would forward received RL ADS-B reports to all configured GSs to be re-transmitted towards flying aircraft.

At the same time the TIS-B service would have to be provided in the B-VHF-supported airspace to allow the B-VHF aircraft to �see� non-ADS-B capable aircraft and NB aircraft that is not transmitting ADS-B reports via B-VHF system, but is using some other technology (1090ES, UAT). In order to achieve operational interoperability, the ground surveillance system (TIS-B server) would have to convert ADS-B reports received over 1090ES sub-network to the B-VHF-specific format and vice versa. The TIS-B server would then forward the TIS-B information to all involved sub-networks. The B-VHF GS would transmit the received TIS-B message in the broadcast mode.

The B-VHF broadcast mode would be optionally used � where and when required - for FIS service provision (D-ORIS, D-OTIS, D-RVR, D-SIGMET, D-FLUP), in addition to the on-demand provision of these services via ATN.

9.2.3.2. Air-air Data Link Services

Air-air data link aims to support ASAS concepts and applications. The corresponding communications services are not yet mature, but it is expected that they would be used e.g. for co-ordination purposes (resolving possible mid-term conflicts) between airborne users. B-VHF internal acknowledged data link service (B-DA) described in [B-VHF D7] should be used for that purpose.

NOTE: As indicated in [B-VHF D7], such services would need an adequate method � including the HMI - for the pilot to select the peer aircraft. These aspects lie outside scope of the B-VHF project. One possibility would be to replicate in each aircraft the information about local IDs of other aircraft that exist at the B-VHF GS and within the GNI.


ADS-B and TIS-B services would require activating new system functionalities and network interfaces on the ground side. These services are mapped onto not acknowledged FL and RL B-VHF internal services. The corresponding messages may be transferred either along with other voice and data link packets between the GSC and the GNI (ground access point is at the GNI) or may use dedicated surveillance networks and associated protocols with direct service access at the GSC of each involved GS.




Air-air addressed data link uses acknowledged B-VHF internal mechanisms. Associated B-VHF internal functionalities would have to be activated at the time of the intended service introduction. As for other system functionalities that may be added during the transition phase, the preferable mechanism would be just upgrading the existing software of involved B-VHF entities (GSC, GNI, eventually TX and RX).

All involved B-VHF cells would have to implement all required data services (B-DA, B-DB, B-DN, supporting ATN as well as non-ATN broadcast and point-to-point data link services) � this would make the best usage of B-VHF system, with the fewest number of unnecessary handoffs between cells and simplest handover procedures.

As some advanced ATN data link services (e.g. PPD, COTRAC or DYNAV) cannot be efficiently deployed by using voice, it can be expected that in the final B-VHF deployment phase almost all aircraft would be equipped with an ATN data link.

As no voice backup is possible and operational circumstances may require high availability of data link communications, doubled ground data link equipment or another method of increasing the availability of the ground data link sub-system may become mandated in that time-frame.

NOTE: ATN data link services shall be available at each B-VHF cell. As the cells overlap, the overall service availability will be increased.


It is expected that air-air services will be handled from pilot�s HMIs that are yet TBD. Moreover, the entire set of air-air applications must be yet developed, together with the associated concept of operation and detailed operational procedures. These issues are clearly outside the scope of the B-VHF project.

The preferred concept for integrating broadcast and air-air services within the B-VHF system would be to provide a communications support through the CMU � this would reduce interfacing problems and probably easy certification of involved sub-systems. The proposed airborne B-VHF architecture concept [B-VHF D7] where a dedicated airborne B-VHF radio unit handles all kinds of data link exchanges is aligned with that preferred approach.

However, in architectures where CMU does not handle all data communications adding non-ATN services such an approach may not be feasible (e.g. wiring changes may be required). The proposed architecture alternatively allows for direct radio interfacing with external items other than CMU. In such a case necessary upgrades should be performed in �packages�, during a regular aircraft maintenance cycle.

During the aircraft maintenance procedure not only new services could be added, but some existing may be improved, by adding e.g. improved pilot�s HMIs for handling selective voice services and air-air data link services.

As some data link services cannot be efficiently deployed by using voice and operational circumstances may require high availability of communications, mandatory doubled airborne data link equipage may be expected in that time-frame. This would probably include two B-VHF airborne radio units and/or doubled CMU installation. This option is also included in [B-VHF D7]. One B-VHF radio remains dedicated to data links, another radio unit provides both voice services and the data link backup in case of failure of the data radio.




NOTE: Airborne B-VHF radio units are independent, separately addressable and capable to handle their own internal states. It is not yet clear how the maintenance of data link state machines for higher protocol layers would be handled by involved CMU(s).

Assuming sufficiently large B-VHF airspace, the mandatory number of airborne B-VHF radio units could be reduced from three to two, but this would only be applicable to aircraft that never leaves B-VHF airspace. Outside that airspace, the mandatory carriage of three radio units (two voice radios/one data radio) would still be required.

9.3. B-VHF System Deployment in the non-VHF COM Ranges

The target ranges for the B-VHF system deployment outside VHF COM range comprise DME, MLS and VOR ranges where the preferred deployment strategy is based on dedicated channels rather than on overlay. Initial and transitional deployment scenarios in that range focus onto data-only B-VHF system where voice services continue to be provided by the DSB-AM system operating in the VHF COM range.


The deployment of the B-VHF system in the MLS range has from the very beginning been restricted to selected airports � there will be no further expansion of the MLS B-VHF system outside an airport environment.

During the transition phase the data-only B-VHF system has been installed in the DME and/or VOR range in entire European High ENR airspace and in parts of Low ENR airspace. In the final phase the vertical expansion of DME and VOR B-VHF systems continues toward selected TMAs and APTs.

The deployment below some minimum FL is considered to be a local decision, so the B-VHF system may become deployed in some TMAs and APTs while NB VHF communications systems may remain in operation in other TMAs and APTs (with an optional B-VHF support for the equipped part of aircraft population).


A major VHF spectrum relief can be expected on the long-term basis, in the final system deployment phase, due to the benefits from the powerful B-VHF data link provided in the non-VHF COM ranges. This will lead to reduced controller workload and larger blocks of airspace that a single controller is able to handle under normal working conditions..

This trend will be further accelerated by the ASAS operations within a segregated airspace, with reduced need for voice communications. As a number of ATC sectors is today used to control operations in that airspace, it can be expected that with introduction of �full ASAS� a number of voice channels will be abandoned.

NOTE: With ASAS, the classical ATC does not exist any more � the controller is not responsible for aircraft separation. This means that the requirements upon the QoS of voice services in the ASAS context may be significantly lower than today. If required, remaining party-line voice channels can be converted to more efficient on-demand addressed voice channels. This would again increase voice efficiency and return further VHF resources.




Each such consolidation of airspace blocks would lead to the reduced number of required dedicated VHF voice channels � these channels could be organised into contiguous or non-contiguous VHF spectrum blocks, finally allowing for an introduction of an integrated or data-only B-VHF system within the VHF COM range.

NOTE: This scenario is very similar to the one proposed for an initial B-VHF system introduction in the VOR range. Due to the airborne co-location constraints it is difficult to assume that even in that phase a data-only B-VHF system could be deployed in the VHF COM range under overlay conditions while retaining DSB-AM voice operation from the same aircraft. However, assuming that a number of dedicated broadband RF channels could be allocated without overlay in the lower VHF COM range, data-only B-VHF operation may become feasible.


It is expected that in this deployment phase broadcast data link services (ADS-B, TIS-B) and air-air data link services would be added to the existing data link services (ATN ATS and AOC data link, downlink of aircraft parameters).

When adding such services, basically the same scenarios would apply as described for the VHF COM range in section 9.2.3.


In the non-VHF COM ranges basically the same description would apply to the ground infrastructure evolution as for the final system deployment in the VHF COM range (0).


Data-only scenarios in non-VHF COM ranges in the transitional phase require only one dedicated data link B-VHF radio to be installed (remaining two COM radio units are operated in the DSB-AM mode within the VHF COM range).

As some advanced data link services cannot be efficiently deployed by using voice and operational circumstances may require high availability of data link communications, mandatory doubled airborne data link equipage may be expected in that time-frame. This would probably include two B-VHF airborne radio units and/or doubled CMU installation. One B-VHF radio is used by default as a data radio. The second data radio could be configured to work in parallel with the first one, or remain inactive, providing backup only in case of a failure of the first data radio.

As with initial and transitional scenarios, the B-VHF system usage in the MLS range is restricted to just an APT environment because of high required transmitter power.

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10. Non-B-VHF Aeronautical Communications Systems

10.1. Introduction

The B-VHF system has been designed for a variety of different aeronautical communications applications. However, when the system operates in an overlay mode, its capacity is typically significantly reduced when compared to the full deployment scenarios where more VHF resources are available.

As an overlay scenario is the preferred selection for the system deployment in the VHF range, it is necessary to consider other VHF aeronautical communications systems as well as systems operating in other radio frequency bands as a possible supplement of the B-VHF system. In other words, the total aeronautical communications requirements may in this phase be easier met by a combination of different systems rather than by the B-VHF system alone.

Such an approach is also reflected in [B-VHF D7] where some service classes (e.g. selective voice services, broadcast data link) have been excluded from initial deployment scenarios due to the fact that other technologies (e.g. 1090 ES, Mode S) will be in place, providing the same services. During the transition phase, the functional scope of the B-VHF system is expected to be gradually expanded, finally all service classes are expected to be covered by the B-VHF system itself.

It is important to emphasize that B-VHF system introduction neither imposes constraints upon the use nor requires decommissioning of �alternative� technologies like Mode S, 1090 ES or VDL2 in B-VHF-supported and NB airspace. Similarly, as B-VHF is a terrestrial system without pretension to be used for oceanic and remote areas, its introduction and usage is completely decoupled from the introduction and usage of satellite systems like HFDL or SDLS.

This chapter describes current and future VHF and non-VHF communications systems that are already deployed or may be deployed along with the B-VHF system. Moreover, it describes their ability to support known communication applications and classes of service, including AOC voice and data communications. Finally, a possible distribution of voice/data services between B-VHF and other systems is described.

10.2. Current and Future VHF Communication Systems

It is highly probable that other VHF systems will be used at the time of initial B-VHF system deployment and would remain in use during relatively long transition phase. While it is improbable that other VHF systems could be used by the same aircraft that carries and uses B-VHF communications services, there may be other aircraft in the vicinity (in the B-VHF-supported airspace or NB airspace) that would continue to use narrowband VHF systems.

10.2.1. Current VHF Communication Systems

[RDMAP_DL] identifies the following VHF communication systems which are currently used or for which significant deployment decisions have been taken. Systems that do not operate in VHF frequency band will be explained in the next sections. The following systems currently operate on the VHF spectrum




! DSB-AM 25 kHz and 8.33 kHz voice systems

! ACARS VHF sub-networks

! VDL Mode 2

10.2.1.1. DSB-AM 25 kHz and 8.33 kHz

Currently used analogue voice system exists in two different forms: 25 kHz and 8.33 kHz (25 kHz channel sub-divided into three narrow channels), both using the Double Side Band Amplitude Modulation (DSB-AM). This type of analogue modulation occupies about 7/5 kHz of RF spectrum with 25/8.33 kHz channel assignments, respectively.

The total number of 25 kHz channels in the VHF band (118 � 137 MHz) is 760 and could be increased to 2280 channels if all the voice channels were converted to 8.33 kHz mode of operation. However, this conversion is not possible in all airspace types as some aircraft still carry old 25 kHz equipment and cannot be easily forced to re-equip and CLIMAX wide-area coverage feature of the 25 kHz system is not compatible with 8.33 kHz mode of operation. Therefore, the 8.33 kHz system is implemented only in the European upper space (above FL 245, with possible extension to lower airspace above FL 195).

In the future 8.33 kHz DSB-AM will in Europe play an increasingly important role and may become an option for the USA and other regions facing voice capacity problems.

10.2.1.2. ACARS

The Aircraft Communications Addressing and Reporting System (ACARS) was the first airline data-link, able to use different sub-networks. The VHF sub-network uses voice-grade radios, providing 2400 bps raw data transfer rate with in-band MSK modulation. Such mode of operation is called �Plain Old ACARS� (POA) and is progressively replaced by the more capable �ACARS over AVLC� (AoA) mode.

AoA mode uses a lower part of the VDL Mode 2 protocol stack specified by ICAO. Opposite to the �full� VDL Mode 2 that is essentially an ATN sub-network, AoA concept uses ACARS network protocols and can be easily integrated within the ACARS system as a �fast ACARS�.

The raw throughput on the single VHF 25 kHz channel is increased to 31.5 kbps. Moreover, the same physical channel can be shared between the AoA and VDL Mode 2 airborne population.

10.2.1.3. VDL Mode 2

VDL Mode 2 (VDL2) provides an air/ground bit-oriented point-to-point VHF data link which is compatible with the ATN and can support both AOC and ATS applications. VDL2 is also intensively used for AOC services outside ATN framework. The associated concept is called �ACARS over AVLC� (AoA).

VDL2 has been designed to improve the existing ACARS system. The best known improvement is the increase in channel data rate from the ACARS 2.4 kbps rate to 31.5 kbps rate. The improved channel data rate is expected to yield user data rates 10 to 15 times above the values obtained with current VHF ACARS sub-network. During the implementation of VDL2 the ground station networks for VDL2 and ACARS will co-exist for some time, a part of aircraft population will use VDL2 while remaining aircraft will continue to use ACARS.




VDL2 uses a point-to-point service topology and only supports data link without support for voice communication. European LINK 2000+ program aims to use VDL2 to provide support for initial ATS data link services.

In the USA, VDL2 standard has been further modified (regional solution, outside ICAO standardisation) to provide broadcast data link services to the General Aviation. However, no similar intentions are known for Europe.

It is highly probable that at the time of the B-VHF system initial introduction a large part of transportation aircraft operating in the upper European airspace will be ATN/VDL Mode 2-capable.

10.2.2. Future VHF Communication Systems

There are two mature VHF technologies, VDL Mode 3 and VDL Mode 4, for which development, standardization and validation have already been carried out, but the technologies are not yet widely used.

10.2.2.1. VDL Mode 3

The VHF Digital Link Mode 3 (VDL3) system provides up to four digital voice/data circuits on a single 25 kHz channel assignment. The VDL3 system uses the same physical layer as VDL2 (D8PSK modulation) and uses a 4.8 kbps vocoder for voice operation.

VDL3 employs Time Division Multiple Access (TDMA). The system divides a radio transmission into four 30-millisecond segments (slots) which equates to a 120-millisecond frame. Each of these slots can be assigned to a different voice user group to achieve a theoretical four-fold increase in a number of voice channels. It is possible and recommended to use VDL3 to provide voice and data link services on the same 25 kHz channel. Several fixed configurations exist, e.g. 2V2D (two dedicated voice/two dedicated data channels), 3V1D (three dedicated voice/one shared dedicated data channel) etc. The system uses a point-to-point communication architecture. Pilot�s voice is broadcasted and can be directly heard by the controller, but also other pilots.

NOTE: VDL Mode 3 has been included for information only. The system was standardised as a global solution, but has not gained wide acceptance outside USA. As it is incompatible with the ongoing European 8.33 kHz deployment and even the corresponding USA deployment program (NEXCOM) has been put on hold, its deployment in Europe is considered to be unrealistic and not compatible with the deployment of the B-VHF system so VDL3 is not further discussed in this document.

10.2.2.2. VDL Mode 4

The VHF Digital Link Mode 4 (VDL4) is a digital data link designed to operate in the VHF frequency band using one or more standard 25 kHz VHF communication channels. It provides both point-to-point and broadcast data services. Furthermore, VDL4 can operate in an ATN compliant mode and is deployable in Europe, but the firm deployment programmes only exist for Scandinavian countries and in Russia. The system is not well accepted in the USA.

The self-organising concept allows VDL4 to operate efficiently without a centralised co-ordinating station, thus without the need for a ground infrastructure. Ground stations may however play an important role providing supplementary services that enhance autonomous VDL4 operations. VDL4 is foreseen to operate on (two) specific channels,




called Global Signalling Channels (GSCs), which should eventually be allocated worldwide. In high traffic density airspace, the GSCs can be supplemented by Regional Signalling Channels (RSCs), or by Local Signalling Channels (LSCs). The GSC channels are used to acquire new aircraft. These channels must be supported by all participating ground stations, and are used to broadcast Directory of Services (DoS) information about the services available on the GSC channels, regional or local channels.

Frequencies for VDL4 in Europe have been proposed by EUROCONTROL at the top of the COM band. The plan has been approved by the ICAO Frequency Management Group in Europe. VDL4 may alternatively operate on 25 kHz frequency channels in the NAV frequency band.

NOTE: At the time of B-VHF system introduction, VDL4 may be regionally used in Scandinavia and other isolated European regions. It is improbable that the VDL4 system could be used from the same aircraft that uses B-VHF services.

10.3. Current and Future non-VHF Systems

10.3.1. Current non-VHF Systems

This section does briefly describe non-VHF communication systems which are currently in use or for which significant deployment decisions have been taken. Non-VHF systems are those systems which do not operate in the VHF spectrum.

[RDMAP_DL] identifies the following communication systems:

! ACARS supported by HFDL

! ACARS supported by AMSS

! Mode S (Elementary Surveillance)

! Mode S (Enhanced Surveillance)

! 1090 Extended Squitter

As already described in 6.2.1 the airlines AOC data link is currently implemented by Aircraft Communications Addressing and Reporting System ACARS which can be supported by VHF data links (PoA, AoA), High Frequency Data Link (HFDL) and Aeronautical Mobile Satellite Service (AMSS).

10.3.1.1. HFDL

HFDL is a global end-to-end packet data communication system operating in the part of the 3 � 30 MHz frequency band assigned for aeronautical applications. It is designed as an Aeronautical Telecommunications Network (ATN) data link sub-network, using point-to-point topology and providing a world-wide coverage with only around 10 HFDL ground stations. Because of the extremely wide coverage of each ground station (5000 km radius) it is used for transmission of information data in oceanic and remote areas.

[RDMAP_DL] mentions that the existing HFDL is the only current system capable of covering north polar routes. It is retained in the roadmap as an existing system, but has a poor quality and should in the long term be replaced by future satellite communication systems.




10.3.1.2. AMSS

AMSS is a mobile satellite communication system which can be used for voice and data communication services to and from the aircraft. Applications for the AMSS communications services include airline passenger communications (APC), airline operations communications (AOC) and air traffic control (ATC) services.

The system has a point-to-point service topology, operates on Ka and L-band and provides an ATN compliant data link sub-network. AMSS can also be used as a non-ATN ACARS subnetwork.

AMSS has moderate throughput, communication service costs are high and QoS is not suitable for continental area CPDLC services.

10.3.1.3. Mode S

SSR Mode S is the intended replacement [RDMAP_DL] for the existing Monopulse SSR Mode aircraft systems and may be used in selected European areas to support:

! Mode S Elementary Surveillance

! Mode S Enhanced Surveillance

Mode S Elementary Surveillance enables the use of the unique 24 bit aircraft address for selective interrogation and allows the Aircraft Identity to be acquired from the aircraft. It also enables to read out the flight level in 25 foot vertical resolution. Mode S Elementary Surveillance therefore constitutes a significant improvement of the Air Traffic Surveillance system in dense traffic areas.

Mode S Enhanced Surveillance consists of Elementary Surveillance supplemented by the extraction of airborne parameters known as Downlink Airborne Parameters (DAPs) to be used in the ground Air Traffic Management systems. Some parameters are for display to controllers, known as Controller Access Parameters (CAPs), and some are for (ATM) system function enhancements, known as System Access Parameters (SAPs).

10.3.2. Future non-VHF Systems

[RDMAP_DL] proposes the following non-VHF communications technologies which could probably be used in the future:

! Universal Access Transceiver (UAT)

! Gatelink

! Next Generation Satellite Service (NGSS)

! Satellite Data Link Service (SDLS)

! 3G/UMTS (Wideband CDMA)

10.3.2.1. UAT

The Universal Access Transceiver (UAT) system is [AATT_2015] intended for distribution of surveillance and weather data. The system is only intended to support broadcast applications. It uses a unique hybrid access method combining TDMA and random access. The TDMA portion is used to transmit the traffic and weather information while the random access portion is used by an aircraft to transmit its autonomously determined position in conformance with the RTCA DO-242 broadcast approach. The system is experimental and currently operates on a UHF frequency of 966 MHz. Moreover,




[RDMAP_DL] states that in addition to ADS-B, UAT is intended to support uplink broadcast data from ground stations. This could include TIS-B and/or FIS-B data.

10.3.2.2. Gatelink

Gatelink is [RDMAP_DL] a high bandwidth communication system for aircraft which are at or near the gate. There are three main Wireless LAN technologies which could be used for Gatelink:

! Systems operating at 2.4 GHz conforming to IEEE 802.11b standards:

" 2.4 GHz FHSS / DHSS

" 2.4 GHz DSSS HDR

! High Performance Radio Local Area Network (HiperLAN) according to ETSI HiperLAN standards:

" 5.2 and 5.8 GHz HiperLAN/1 and HiperLAN/2

" 17.1 GHz HiperLAN

! Systems conforming to Digital European Cordless Telecommunications (DECT) standards.

Gatelink uses up � and downlink point-to-point service topology. It is not ATN-compliant, instead it is based on TCP/IP. Gatelink offers a potential for Airline Operational Communications (AOC), Airline Administrative Communications (AAC) and Air Passenger Correspondence (APC). The system applicability for air traffic control hay not yet been proven.

10.3.2.3. NGSS

NGSS and SDLS are satellite systems.

New Generation Satellite System (NGSS) is a generic term that refers to the potential aeronautical use of emerging satellite systems like Iridium, ICO and Globalstar.

The Iridium system consists of 66 satellites in low earth orbit (780 km) connected by inter-satellite links, is supported by a network of gateway earth stations. It uses point-to-point service topology, data and voice reaches any destination on earth. Because of its relatively short relay distance the voice delay is low and voice transmission quality is good. [RDMAP_DL] also mentions that this system currently offers an aeronautical voice and data communications service, however without ICAO standardisation.

The ICO constellation consists of 10 satellites in medium earth orbit. It offers integrated mobile satellite communications with terrestrial cellular networks through dual mode handsets. [RDMAP_DL] states that there are currently no plans to offer an aeronautical service.

The Globalstar system offers global, digital real time voice, data and fax service via a constellation of 48 mini-satellites in low earth orbits. The system is not available above 72° North or below 72° South. [RDMAP_DL] states that there are currently no plans to offer an aeronautical service.

SDLS

SDLS system being developed by ESA could also become a potential NGSS. The idea is to use existing satellite and communications infrastructure as far as possible. Moreover, the




concept aims to provide improved satellite communications and surveillance services including [RDMAP_DL]:

! Circuit Mode Voice for AOC

! ATS Specific Voice Service � replication of party-line with quasi-instant access by allocating dedicated forward and return voice channels to each ATC sector.

" All tuned receivers will constantly monitor traffic on the channel.

" The party-line capability can be emulated by re-broadcasting the voice transmissions from aircraft via the forward channel.

! Point-to-Point ATN Compliant data link sub-network.

! Polling Service � allows the transfer of repetitive data between aircraft and ground and is similar to automated downlink of aircraft parameters. It can be used to send:

" Basic information � Position (latitude, longitude, altitude); Time, Figure of Merit; Flight ID.

" Extended information � Ground Vector; Weather information; Projected profile; Short term intent; Intermediate intent.

10.3.2.4. 3G

The Third Generation Mobile Communications concept (3G) has been developed by the telecommunications industry and uses Universal Mobile Telecommunications System (UMTS) protocols, Code Division Multiple Access (CDMA) and point-to-point service topology. It supports broadband personal mobile communications and can be made an ATN compliant sub-network. EUROCONTROL is actively developing a 3G terrestrial system for aviation use. The goal is to provide high-throughput data, voice, and video communication link over continental airspace, supporting a wide range of ATS, AOC, AAC and APC services. The protocol suite will be compatible with the future satellite services, so that a seamless 3G service over continental and oceanic airspace will be possible. The 3G technology is already developed, standardised and widely available for commercial purposes. Therefore rapid standardization for aeronautical purposes is expected, with low component costs.

NOTE: 3G system can operate on three different frequency bands: 5 GHz (C-band), 2 GHz and even on VHF aeronautical band.

10.3.3. Applicability of Communication Systems for CoS Classes

Table 10-1 shows the ability of different aeronautical communication systems to support classes of service (CoS) defined in [B-VHF-D5] and [MACONDO] where Dx represents a data service class and Vy a voice service class, respectively. The systems that have not been developed or standardised for safety services (e.g. Gatelink, Iridium) and the systems that would be deployed exclusive with the B-VHF system (VDL Mode 3, 3G) have been excluded.

Table 10-1 shows that, opposite to the B-VHF system, no other aeronautical communication system is capable of supporting all (voice/data) classes.

However, some of remaining systems are able to support a sub-set of all services (there are several choices for voice services as well as for broadcast and point-to-point data link




services). These systems could support/relieve the B-VHF system during its initial deployment by providing support for some service classes.

NOTE: Service classes for which the applicability is not clear (e.g. VDL2 for CAP/SAP services) are marked as �?� Systems where deployment in European airspace has not yet been confirmed or only regional deployment is anticipated around 2015 are marked yellow.

CoS Data/Voice Service Classes B-VHF 25 kHz 8.33 kHz ACARS VDLM2 VDLM4 Mode S 1090 ES UAT SDLS

D1 Controller-pilot Data Dialogue X X X X XD2 Pilot-pilot Data Dialogue XD3 Flight Information Exchanges X X X X XD4 ATM Exchanges X X X X XD5 Downlink of Aircraft Data X ? X

D6-1 Ground-air (SUR) Broadcast X X X X XD6-2 Air (SUR) Broadcast x X X X

D-AOC AOC Data Link X X X X XV1 Controller-pilot Party-line X X X XV2 Controller-pilot Selective Voice X ?V3 Pilot-pilot Voice X X X ?V4 Broadcast Voice X X X ?V5 Interactive Voice X ?

V-AOC AOC Voice X X X X

Table 10-1: Mapping of Services onto Communication Systems

10.4. Distribution of Services between B-VHF and Other Systems

The B-VHF system would not be able to support all classes of service right from the start of its deployment as with preferred overlay approach there would be not enough VHF spectral resources available at that time.

At the same time, some other communication systems will be widely deployed and used for voice and data link communications, driven by the Single European Sky (SES) incentives and the SESAR programme, while some other systems may be available on the regional basis, according to Table 10-1. These systems are expected to supplement the B-VHF system in such a way that all required (voice/data) classes of service would be available at any time for entire aircraft population.

By the year 2015 analogue 25 kHz DSB-AM voice system will still be used on the lower airspace, while the 8.33 kHz DSB-AM system will be increasingly used above FL 195, providing voice service classes V1 (Controller-pilot Party-line), V3 (Pilot-pilot Voice), V4 (Broadcast Voice) and V-AOC (Airline Operational Voice).

NOTE: Controller-pilot Selective Voice (V2) and Interactive Voice (V5) classes will not be required at the time.

The �Plain old ACARS� VHF data link is expected to be progressively replaced by the AoA VHF data link, but ACARS is expected to be still widely used at the time of B-VHF system introduction by a significant part of the aircraft population for D-AOC (AOC Data Link) communications and some selected initial data link services from the classes D1 (Controller-pilot Data Dialogue) and D3 (Flight Information Exchange).

At the same time, due to the LINK2000+ programme relatively large ATN//VDL2 aircraft population will operate in Europe, using ATS data link services with adequate ground support. This technology will be used for providing data link service classes D1




(Controller-pilot Data Dialogue), D3 (Flight Information Exchange), D4 (ATM Exchanges) and D-AOC (AOC Data Link) to the equipped aircraft.

Downlink of Aircraft Data (D5) for enhanced surveillance and broadcast services (D6) defined in [B-VHF D5] are expected to be deployed in the course of Mode S & ACAS and CASCADE programmes and handled by a combination of Mode S and 1090 ES technologies. Broadcast services (D6) may be regionally also deployed by using UAT and VDL4 technologies.

NOTE: Pilot-pilot data dialogue (D2) class will not be required at the time.

The introduction strategies for operational services are for safety reasons based on careful matching of the QoS required by the service and the QoS offered by the carrier communications technology. This means that although nearly all service classes will be offered by 2015 the initial scope of offered operational services will be reduced to the services with moderate QoS and capacity requirements. Increasing aircraft population is expected to be primarily handled by increasing communications bandwidth � after initial deployment on the single channel, additional VHF channels are planned for ATN/VDL2 data link � or by adding new communications systems like B-VHF.

The B-VHF operational scenario for the year 2015 described in [B-VHF D7] is related to the system initial introduction and assumes that the system would be first introduced in an overlay mode within limited geographical area, either voluntarily in a B-VHF�supported airspace or mandated in a limited B-VHF airspace. The B-VHF system would initially relieve existing systems (DSB-AM voice system, VDL2) by offering equivalent services with improved QoS and capacity without a need for additional spectrum.

Assuming increasing B-VHF population and taking into account that B-VHF system has been designed to provide support for all communications classes, during the transition phase B-VHF deployment may become mandated in parts of European airspace. Legacy DSB-AM and VDL2 systems would be gradually decommissioned in that airspace, returning more and more VHF channels to be converted to the B-VHF operation. With more bandwidth available, the scope of services offered by the B-VHF system in the B-VHF airspace could be expanded by including service classes D5 and D6 that were initially exclusively handled by Mode S/1090 ES systems. At the same time selective voice service (V5) may be introduced at large airports, allowing for significant amount of VHF dedicated channels previously used for AOC voice communications to be converted to the B-VHF operation.

Finally, after the transition to the B-VHF system was nearly completed (almost all airspace became B-VHF airspace), the system would operate at its theoretical capacity limits and would be able to offer additional services like Pilot-pilot data dialogue (D2) and (if still required) Controller-pilot Selective Voice (V2).

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11. B-VHF Standardisation Concept

11.1. Introduction

The ongoing B-VHF project carries out a bottom-up research on broadband multi-carrier (MC) technology for aeronautical communications. The past experiences with other communications systems indicated that physical layer capabilities and peculiarities cannot be overestimated within an end-to-end communications concept. Therefore, the significant efforts of the B-VHF project were put onto the OFDM physical layer and its capability to operate under overlay conditions over a broadband channel in the VHF range. At the same time, the suite of protocols and functions above physical layer (data link layer and higher layers) has been developed or adapted as required for specific aeronautical communications purposes.

The important work of protocol selection and optimisation is being done by using computer modelling and simulations. By the end of the project a simple low-power demonstrator of the physical layer will be built, but it cannot be regarded to be a true validation platform or even �representative B-VHF hardware�.

The B-VHF project will provide a solid basis for the following standardisation activities, but cannot produce the full scope of the required standardisation material. Moreover, it is possible and even probable that some further modifications/optimisations of selected B-VHF protocols and functions (�lessons learnt�) will be required after the initial simulation work that cannot be accommodated within the scope of the ongoing B-VHF project.

Apparently, much additional work will be needed after an initial feasibility study performed within the B-VHF project to establish B-VHF as a fully validated, mature technology that can be deployed and operationally used for safety-related aeronautical communications. This chapter outlines the most important actors and actions on the roadmap towards such a system.

11.2. General Approach for Certification of Airborne Systems

Due to the international nature of air transport, the need for world-wide interoperability of airborne systems has resulted in the evolution of an international standardization process. The chain runs from ICAO (SARPS) through JAA/EASA/FAA (JARS/FARS/TSO) and EUROCAE/RTCA (MASPS/MOPS) to ARINC (Equipment Characteristics). This process supports the safe introduction of new products and operational capabilities across national borders and within international airspace.

For classical technologies, ICAO has standards in order to ensure worldwide interoperability between any aircraft and any ATS provider under the responsibility of the contracting States. The use of data communications between ATS providers and aircraft increases system complexity. Because of this increased complexity, ATS supported by data communications require a high degree of coordination among the stakeholders and approval authorities to ensure compatibility between operator use and ATS provision.

As interoperability is required at all levels, the standardisation covers both operational services that are using some particular communications technology as well as the technology (e.g. B-VHF) itself.

The validation of the newly developed technology standard must be performed as a supplementary activity to the ICAO standardisation. The validation normally comprises




both laboratory tests and flight tests. The feedback from the validation activities is typically used for the refinement of SARPs after the initial publication.

11.2.1. ICAO

The main objective of the International Civil Aviation Organization (ICAO) is to ensure safe, regular, efficient, and economical air transport. Its main tool towards this goal is a comprehensive series of international rules - �Standards and Recommended Practices (SARPs)� - which member states agree to follow.

A new system like B-VHF would naturally be subject to ICAO standardisation. According to the past experience with other technologies, this procedure may last several years.

The formulation of new or revised SARPs begins with a proposal for action from ICAO itself or from its Contracting States. Proposals may also be submitted by international organizations (e.g. EUROCONTROL).

For technical SARPs, proposals are analysed first by the Air Navigation Commission (ANC). Depending on the nature of the proposal, the ANC may assign its review to a specialized working group. Working groups meetings are the main vehicle for drafting and finalising the SARPs work and reaching the necessary consensus.

The original recommendations for core SARPs along with any alternative proposals developed by the ANC are submitted to Contracting States and selected international organizations for comment. Finally, the amendments to Annexes recommended by the ANC are presented to the ICAO Council for adoption.

Adopted SARPs are periodically reviewed and revised, as necessary, to keep abreast with technological and other developments affecting the aviation industry.

The current ICAO approach is to keep the SARPs relatively short and delegate detailed information to the dedicated �Manuals on Technical Specifications� for the corresponding system.

Taking VDL as an example, ICAO Annex 10 now comprises basic definitions and VDL system capabilities as well as short SARPs for VDL modes 2, 3 and 4, describing system characteristics of the ground and airborne installation (transmitting power, adjacent channel and spurious emissions, receiving functions), physical layer protocols and services. Basic information about the VDL Mobile SNDCFs applicable to different VDL modes is also included, as well as the description of the Voice Unit for VDL Mode 3.

Details of VDL mode-specific link layer and subnetwork layer protocols and services have been delegated to the corresponding �Manuals of VDL Technical Specifications�. As a specific example, ICAO Doc 9816-AN/448 - Manual on VHF Digital Link (VDL) Mode 4 - comprises Part I (Implementation Manual) and Part II (Technical Manual).

Implementation Manual (Part I) comprises an overview of the VDL Mode 4 services in support of CNS/ATM, key functions and applications supported by the system, technical description of VDL Mode 4 and its operating principles, architecture and implementation options for airborne, ground, airport and surface vehicle installations, methods for channel management and channel switching and possible future applications of VDL Mode 4.

Technical Specifications (Part II) describes in detail VDL Mode 4 link layer protocols and services and VDL Mode 4 SNDCF, providing additional detailed material for ADS-B application and definitions for Compact Position Reporting.




The development of ICAO SARPs is an inevitable step for any safety-related mobile aeronautical communications technology, therefore SARPs would be required for the B-VHF system as well. Once available, B-VHF SARPs would provide the necessary input for other standardisation bodies (e.g. EUROCAE/RTCA, ARINC) to develop their standards.

For the B-VHF system, similar structure of the ICAO standards can be anticipated as for VDL, comprising B-VHF SARPs to be included in Annex 10 as well as separated detailed �Manual on B-VHF Technical Implementation�. Moreover, similar basic contents would be applicable to both documents as in the VDL case.

The existing B-VHF deliverables � in particular B-VHF Functional Principles and Architecture [B-VHF D6], B-VHF Operational Concept [B-VHF D7], reports on detailed design of the B-VHF physical layer, DLL and upper layers � provide an initial basis for producing such standards.

NOTE: The next necessary step is to motivate the EUROCONTROL, FAA or an ICAO member State to place an official proposal for action to ICAO with respect to the B-VHF standardisation. Such hypothetic future action would be clearly conditioned by the overall success of the B-VHF project.

11.2.2. EUROCAE/RTCA

The primary task of EUROCAE and RTCA (Radio Technical Commission for Aeronautics) working groups is to prepare performance specifications and similar documents, which may be referenced by Aviation Authorities in Technical Standard Orders (TSO).

[RTCA DO-264] identifies a set of different standards that apply to a given communications system:

! Operational Services and Environment Definition (OSED)

! Operational, Safety and Performance Requirements (SPR)

! Interoperability Requirements (INTEROP)

! Minimum Operational Performance Standards (MOPS) / Minimum Aviation System Performance Standards (MASPS)

These standards are developed by EUROCAE/RTCA, but some may be delegated to other bodies and groups.

The OSED is used as the basis for assessing and establishing operational, safety, performance, and interoperability requirements for the related CNS/ATM system. The OSED identifies the operational Air Traffic Services (ATS) supported by data communications and their intended operational environments and includes the operational performance expectations, functions, and selected technologies of the related CNS/ATM system. The OSED captures requirements that have been derived and/or validated as being necessary for a particular operational service.

An SPR standard is used to coordinate the operational, safety, and performance objectives and allocate requirements for the different approval types:

! ATS provider operational approval

! Aircraft type design approval

! Operator operational approval




SPR is developed using an Operational Safety Assessment (OSA) and an Operational Performance Assessment (OPA) of the functions, performance expectations, and characteristics of operational environments needed to support the ATS identified in the OSED.

An INTEROP standard is used to provide sufficient information to enable different stakeholders to develop system elements that are compatible for an operational implementation. It is developed using an interoperability assessment (IA) of selected functions and technologies needed to support the ATS identified in the OSED. An INTEROP standard identifies the technical, interface, and related functional requirements for a specific technology or a mix of technologies. The INTEROP provides traceability from each requirement to the functions it supports, the services, and the operating environments in the OSED. Similar to an SPR standard, an INTEROP standard can be tailored to meet the needs of a particular operational implementation.

In most cases, Minimum Operational Performance Standards (MOPS) and Minimum Aviation System Performance Standards (MASPS) published by EUROCAE and RTCA provide performance requirements tailored to characteristics of a specific technology. These standards can be used to assess the feasibility of a specific technology to meet the minimum operational, safety, and performance requirements defined in an SPR. These standards normally do not provide an operational performance basis.

For the B-VHF system the B-VHF MOPS would have to be developed and referenced in the OSED, SPR and INTEROP documents.

In order to preserve required safety and performance levels, prior to any practical operational usage a careful analysis and mapping of applications onto �carrier technologies� must be done. The B-VHF technology has been developed by taking requirements for known operational services into account, however, the detailed mapping and investigation must be done separately for each B-VHF service that is intended to be deployed.

11.2.3. JAA/EASA/FAA

The mission of these bodies is to develop, maintain, and promote safety standards in the field of design and production of aeronautical products. In 2003 the European Community and the other entities involved in the sector have established the European Aviation Safety Agency (EASA) to give Europe a single aviation safety authority, like the Federal Aviation Administration (FAA) of the United States. With the start of EASA operations, the Central Joint Aviation Authorities (JAA) Certification Division is providing support to EASA in its certification related activities for

! certification of aeronautical products, parts and appliances

! approval of organisations/personnel engaged in the maintenance of these products;

! approval of air operations;

! licensing of air crew etc.

Communication equipment must meet a Technical Standard Order (TSO), which is a form of certification for a particular piece of equipment. A TSO is a minimum performance standard issued by the Administrator for specified materials, processes, and appliances used on civil aircraft.




The installation of airborne avionics systems generally requires airworthiness certification, which is part of its Type certificate (TC) for new aircraft or Supplemental Type Certificate (STC) for aircraft already in service.

11.2.4. ARINC

The intent of an ARINC Characteristic is to provide design guidance for the development and installation of the airborne equipment. As such, this guidance covers the operational capabilities of the system and the standards necessary to achieve interchangeability of the hardware produced by various manufactures. Heart of all ARINC Characteristics is the standardized interwiring including e.g. specific form factor, mounting provisions, input/output interfaces, and power supply characteristics.

Due to the target concept of the B-VHF airborne system architecture (packaging within two existing units) the implementation of the B-VHF technology would affect two existing avionics standards:

! ARINC 750 - VHF Data Radio (VDR)

! ARINC 758 - Communications Management Unit (CMU)

The B-VHF airborne transceiver should be preferably deployed as an upgrade of the VDR radio. This would allow the VDR to be used with existing wiring in �traditional� modes (DSB-AM, VDL Mode 2) in the NB airspace, and in the B-VHF mode � including digitised voice - in the B-VHF- or B-VHF-supported airspace.

The CMU should be upgraded to implement necessary B-VHF-specific data link functions that are not suitable to be implemented within the physical transceiver.

11.2.5. ETSI

ETSI is involved in producing European standards for VDL Mode 4 ground installations and would probably be tasked with developing similar standards for other types of the aeronautical ground equipment, including the B-VHF ground station.

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12. Conclusions

This document � �B-VHF Deployment Scenario� � describes different scenarios for the deployment of the B-VHF system in both the VHF COM range as well as in other spectrum ranges anticipated to be potentially used by new communications systems.

Chapter 4 identifies some requirements that should be considered in the future work. Developing representative mature radio hardware was clearly no a goal of the B-VHF project. Hence, the RF front-end performance had to be assumed, as it may be critical for the system deployment.

Chapter 5 provides an initial estimate of parameters of the B-VHF system that are relevant for frequency planning and co-existence with other systems in the VHF COM range, and therefore directly influence the system deployment. These parameters are based on the results of different simulations and laboratory measurements performed under different constraints. Developing frequency planning criteria for the B-VHF system is a challenging task. The procedure normally starts, as for other VHF systems, with laboratory measurements using representative B-VHF and narrowband equipment. The current results of the laboratory measurements � in particular those related to the spectrum of the B-VHF signal-in-space cannot be considered as representative for the mature B-VHF system. For that reason, in Chapter 6 of this document just an outline of the frequency planning approach is provided, together with some explanatory material about basic interactions between DSB-AM and B-VHF systems.

The clear focus of this deliverable is put on the development of possible deployment scenarios for an initial B-VHF system deployment, as well as for the system transition towards �full� deployment. In all scenarios it is assumed that an aircraft is either fully equipped with B-VHF radios (�B-VHF aircraft�) or it continues to carry narrowband equipment (�NB aircraft�). In addition to the current situation where the entire airspace is �narrowband-one� (NB airspace), in the B-VHF scenarios two other options have been identified: one where B-VHF equipage is mandatory for all aircraft (�B-VHF airspace�) and another one (�B-VHF-supported airspace�) where B-VHF equipage is voluntary and mixed B-VHF/NB aircraft population may exist.

The initial deployment is outlined in Chapter 7 both for the VHF- and non-VHF ranges (DME, MLS and VOR). These scenarios and associated airborne and ground B-VHF system architectures are well aligned with the B-VHF operational concept [B-VHF D7].

All VHF scenarios are based on overlay, as it has been assumed that this is the only feasible option in the densely populated VHF spectrum. On the contrary, all non-VHF scenarios are based on the usage of dedicated channels that are not used by other systems.

Additionally, in all VHF scenarios an integrated voice/data B-VHF system is assumed. Airborne co-location of B-VHF and other narrowband DSB-AM systems in the VHF range, that would be the consequence of a data-only B-VHF concept, is considered to be very difficult or impossible to realize.

The preferred options for initial B-VHF system deployment in the VHF range under overlay conditions are:

! Introduction in the B-VHF-supported airspace (APT/TMA/ENR_Low)

! Introduction in the B-VHF airspace (ENR_High)

While other combinations are not precluded, the above scenarios are the preferred combination because it may become very difficult or impossible to mandate B-VHF




equipage for small aircraft in APT/TMA/ENR_Low airspace from the very beginning of the B-VHF system deployment.

A set of scenarios based on the data-only B-VHF system usage has been proposed for the DME and MLS range. In that case voice services remain in the VHF range, sufficiently isolated from the data-only B-VHF system operating in non-VHF ranges.

With a data-only approach the airborne B-VHF avionics reduces to just a single B-VHF radio with usual ATN-compatible external interface. The ground B-VHF system architecture also becomes simplified, as all voice-relevant functions and components may be omitted.

Scenarios for an initial B-VHF system deployment have been used as a starting point for further discussion in the Chapter 8 where transitional aspects are discussed. During the transition the initial system �grows� � more and more airspace is converted to either B-VHF airspace or B-VHF-supported airspace. At the same time new services are successively added to the system (e.g. selective voice for AOC usage, downlink of aircraft data, powerful ATS services for trajectory-based ATM). The impact of spatial system expansion upon spectrum availability in the VHF range has been discussed for the case of initial B-VHF system deployment within- and outside the VHF range.

In the final deployment phase, described in Chapter 9, the functional scope of the B-VHF system will further improve as the change in the spectrum occupancy would now allow the air-air data link and broadcast surveillance services to be deployed (ADS-B, TIS-B), as well as possibly other broadcast services (e.g. FIS-B). Even in that phase some parts of the European airspace still will be operated as narrowband (NB) airspace, so there will be always some boundary to other �NB regions� outside Europe.

As not all services can be immediately offered by the B-VHF system, it is important to know which other systems would be available during the initial B-VHF system deployment, because such systems could relieve the B-VHF system by taking-over some services foreseen in the operational scenarios. Such systems are described in Chapter 10, comprising DSB-AM and VDL systems in the VHF range. Existing and emerging non-VHF systems like Mode S, AMSS or SDLS have significant potential to relieve B-VHF system in the sensitive phase of its initial deployment.

Apparently, additional work will be needed after this initial feasibility study to establish B-VHF system as a fully validated, mature technology that can be deployed and operationally used for safety-related aeronautical communications. It is expected that this remaining work will be done in the course of system standardisation. One chapter of this document (Chapter 11) is dedicated to the standardisation activities, identifying the most important actors and actions on the roadmap towards a mature B-VHF system.

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13. References

Reference ID Reference

[B-VHF D5] B-VHF D-05 � Report on Applications Communications Requirements, Issue 1.2, 28.06.2004

[B-VHF D6] B-VHF D-06 � B-VHF Functional Principles and Architecture, Issue 1.0, 05.04.2005

[B-VHF D8] B-VHF D-08 � B-VHF Reference Environment, Issue 1.0, 22.04.2005

[B-VHF D7] B-VHF D-07 � B-VHF Operational Concept, Issue 1.0, 10.10.2005

[B-VHF D9] B-VHF D-09 - Interference on the B-VHF Overlay System, Issue 1.1, 04.10.2005

[B-VHF D11] B-VHF D-11 - Operational Issues Related to System Co-existence in the VHF Band, Issue 1.0, 02.06.2005

[B-VHF D12] B-VHF D12 � Report on VHF Channel Occupancy Measurements, Issue 1.0, 01.02.2005

[B-VHF D18] B-VHF D-18 � Physical Layer Design for the Forward and Reverse Link, Issue 1.0, 12.05.2006

[B-VHF D23] B-VHF D-23 - Performance Evaluation of the Physical Layer, Issue 1.0, 25.09.2006

[B-VHF D34] B-VHF D-34 � B-VHF Testbed Evaluation, Issue 1.0

[ACPF14-WP5] ACP-WG�F14/WP5 - FREQUENCY ASSIGNMENT PLANNING CRITERIA FOR VDL MODES 2, 3 AND 4 (TB included in ICAO Handbook), Malmö, Sweden, 22-26 August 2005

[EUROCAE WG47]

EUROCAE WG47 to RTCA SC-172 Liaison Paper, 1998, Proposal for ACP requirements, July 24, 1998.

[NEXCOM MDR] FAA-E-2938, July 23, 2001, V4.0 � Subsystem Specification � Multimode Digital Radio (MDR)

[ETSI-DAB] ETS -300 401 - Digital Audio Broadcasting (DAB) to mobile, portable and fixed receivers, May 1997, Figure 106

[VDL2 COSITE] EUROCONTROL - Assessment of VDL Mode-2 airborne co-site interference in Link2000+ framework, V2.02, Nov. 2004

[ACPF14-WP12] ACP-WGF-14/WP12 - Interference Susceptibilities of Systems Operating in the 960-1215 MHz Band - Application to the Compatibility Analysis of the Future Communication System, Malmö, Sweden, 22-26 August 2005

[ICAO EUR 011] ICAO EUR Doc 011 � EUR Frequency Management Manual, Ed. 2003.

[UAT SARPs] DRAFT SARPs for UAT, Rev. 4.2, March 2005

[ACPF14-WP14] ACP-WGF14/WP14 � ITU WRC-07, Agenda Item 1.6 � Allocations to the AeronauticaMobile (R) Service, Malmö, Sweden, 22-26 August 2005

[ACPF14-WP21] ACP-WGF14/WP21 � ITU WRC-07, Agenda Item 1.6 � Feasibility of VOR/DME Re-planning in Europe to Free the Sub-band 116-118 MHz for AM(R)S Usage , Malmö, Sweden, 22-26 August 2005

[RTCA DO-282] RTCA DO-282, Minimum Operational Performance Standards for Universal Access Transceiver (UAT) Automatic Dependent Surveillance � Broadcast (ADS-B), August 2002




Reference ID Reference

[COCR] EUROCONTROL/FAA Future Communications Study Operational Concepts and Requirements Team, Communications Operating Concept and Requirements for the Future Radio System (COCR), Version 1.0, 03.03.2006

[AATT_2015] NASA AATT project, �Communications System Architecture Development For Air Traffic Management & Aviation Weather Information Dissemination�.

[RDMAP_DL] Roadmap for the implementation of data link services in European ATM - Technology Assessment.

[RTCA DO-264] RTCA/DO-264, GUIDELINES FOR APPROVAL OF THE PROVISION AND USE OF AIR TRAFFIC SERVICES SUPPORTED BY DATA COMMUNICATIONS, December 14, 2000

[ARINC 716] ARINC Characteristics 716-10, Jan. 15, 1998

[ICNS 2006] bvhf_2006_04_UniSBG_input_for_ICNS_paper_v0.doc

[EUROC_VHF] EUROCONTROL Data base of European VHF Frequency Allocations, BP17_COM2DB.mdb

[UK_AIP] www.ais.org.uk

[SES_AG] EUROCONTROL - SINGLE EUROPEAN SKY (SES) REGULATION - REGULATORY APPROACH FOR THE AIR-GROUND VOICE CHANNEL SPACING, December 2005 Released Edition 1.0

[ICNS 2003] M. Schnell, E. Haas, �Advanced Airport Data Link � Concept and Demonstrator Implementation for a Modern Airport Data Link,� Proceedings of Third Integrated Communications, Navigation and Surveillance Technologies Workshop (ICNS 2003), Annapolis, Maryland, USA, May 2003, pp. 83-92.

[ETT 2002] E. Haas, H. Lang, M. Schnell, �Development and Implementation of an Advanced Airport Data Link Based on Multi-Carrier Communications,� European Transactions on Communications (ETT), Vol. 13, No. 5, September/October 2002, pp.447-454.

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14. Abbreviations

1090ES 1090 MHz Extended Squitter

A_TRX Aircraft Transceiver

AAC Aeronautical Administrative Communications

ACARS Aircraft Communications Addressing and Reporting System

ACC Area Control Centre

ACMS Aircraft Condition and Monitoring System

AMC ATC Microphone Check

AMS Audio Management System

AMSS Aeronautical Mobile Satellite Services

ANSP Air Navigation Services Provider

AoA ACARS over AVLC

AOC Airline Operations Centre

AOC Airline Operational Communications

APC Aeronautical Passenger Communications

APT Airport

ARINC Aeronautical Radio INCorporated

ARNS Aeronautical Radio Navigation Services

ASAS Airborne Separation Assurance System

ATC Air Traffic Control

ATCO Air Traffic Controller

D-ATIS Data Link Automatic Terminal Information Service

D-FLUP Data Link Flight Updates Service

D-ORIS Data Link Operational En-route Information Service

D-RVR Data Link Runway Visual Range

D-SIGMET Data Link Significant Meteorological Information

ATM Air Traffic Management

ATN Aeronautical Telecommunications Network

ATS Air Traffic Services

ATSP Air Traffic Service Provider

AVLC Aviation VHF Link Control

BER Bit Error Rate

BIS Boundary Intermediate System

CAP Controller Access Parameters (service)

CDMA Code Division Multiple Access

CDOC Cell Designed Operational Coverage




CMU Communications Management Unit

CoS Class of Service

COTRAC Common Trajectory Coordination (service)

CPDLC Controller Pilot Data Link Communication

CW Continuous Wave

D8PSK Differentially encoded 8-Phase Shift Keying

DAP Downlink of Aircraft Parameters

DCCH Dedicated Control Channel

dCL Departure CLearance

DLS Data Link Services (DLL sub-layer)

DLS Data Link System

DME Distance Measuring Equipment

DOC Designated Operational Coverage

DoS Directory of Services

DSB Dual Side Band

DSB-AM Dual Side Band Amplitude Modulation

DYNAV Dynamic Route Availability (service)

EASA European Aviation Safety Authority

EIRP Equivalent Isotropically Radiated Power

ETSI European Telecommunications Standard(isation) Institute

ENR En-route

EUROCAE EURopean Organisation for Civil Aviation Equipment

EUROCONTROL European Organisation for the Safety of Air Navigation

FAA Federal Aviation Administration

FCS Future Communications System

FDM Frequency Division Multiplex

FDMA Frequency Division Multiple Access

FEC Forward Error Coding

FIR Flight Information Region

FIS-B Flight Information Service - Broadcast

FL Flight Level

FL Forward Link

FLIPCY Flight Plan Consistency 8service)

FLIPINT Extension of FLIPCY service

G_RX Ground Receiver

G_TX Ground Transmitter




GND Ground

GNI Ground Network Interface

GNSS Global Navigation Satellite System

GS Ground Station

GSC Ground Station Controller

GSC Global Signalling Channel

HFDL High Frequency Data Link

HZ Homogenous Zone

IA Interoperability Assessment

ICAO International Civil Aviation Organisation

INR Interference to Noise Ratio

INTEROP Interoperability Requirements

IP3 3rd order intercept point

JAA Joint Aviation Authority

JTIDS Joint Tactical Information Distribution System

LME Link Management Entity

LSC Local Signalling Channel

MASPs Minimum Aviation System Performance Standards

MC Multi-Carrier

MC-CDMA Multi-Carrier Code Division Multiple Access

MDS Minimum Detectable Signal

MIDS Multi-Function Information Distribution System

MOPS Minimum Operational Performance Standards

MSK Minimum Shift Keying

mds Minimum Detectable Signal (single carrier)

NAV Navigation

NAVSIM ATM/ATC & CNS simulation tool

NGSS Next Generation Satellite Service

OFDM Orthogonal Frequency Division Multiplexing

OPA Operational Performance Assessment

OPC Operational Control Communications

OSA Operational Safety Assessment

OSED Operational Services and Environment Definition

PHY Physical Layer (OSI model)

PoA Plain old ACARS

PPD Pilot Preferences Downlink (service)




QoS Quality of Service

QPSK Quadrature Phase-shift Keying

RACH Random Access Channel

RF Radio Frequency

RL Reverse Link

RSC Regional Signalling Channel

RTCA Radio Technical Commission for Aeronautics

RWY Runway

RX Receiver

SAP System Access Parameters (service)

SARPS Specification And Recommended Practices

SDLS Satellite Data Link Service

SF Super-Frame

SITA Societe Internationale de Telecommunications Aeronautiques

SNDCF Subnetwork Dependent Convergence Facility

SNR Signal to Noise Ratio

SP Service Provider

SPR Operational, Safety and Performance Requirements

SSR Secondary Surveillance Radar

STC Supplemental Type Certificate

sRACH Synchronised Random Access Channel

TACAN UHF Tactical Air Navigatoion aid

TBC To be confirmed

TC Terminal Control

TC Type Certificate

TCAS Traffic Alert and Collision-Avoidance System

TDD Time Division Duplex

TDMA Time Division Multiple Access

TIS-B Traffic Information Service - Broadcast

TMA Terminal Manoeuvring Area

TSO Technical Standard Orders

TWR ToWeR

TX Transmitter

UAT Universal Access Transceiver

UIR Upper Flight Information Region

UMTS Universal Mobile Telecommunications System




UNL Unlimited

URCO Urgent Contact Service

VDL VHF Digital Link

VDL2 VHF Digital Link Mode 2



VDR VHF Data link Radio

VHF Very High Frequency

VOLMET Meteorological Information for Aircraft in Flight

VOR VHF Omnidirectional Range

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Documents

REPORT D-27 B-VHF Deployment Scenario · Project co-funded by the European Community within the 6th Framework Programme (2002-2006) REPORT D-27 B-VHF Deployment Scenario