Current Status of LDACS Development first meeting...Current Status of LDACS Development Michael Schnell German Aerospace Center (DLR) • Chart 1 ICAO Communications Panel 1-5 December

Current Status of LDACS Development

Michael Schnell German Aerospace Center (DLR)

www.DLR.de • Chart 1

ICAO Communications Panel 1-5 December 2014 Presentation of IP01

Motivation The Future Communications Infrastructure (FCI)


Motivation Air/Ground Communications


From Voice to Data …

DSB-AM: Analog Voice

VDL2: Kind of SMS

… to Internet and SWIM

LDACS: Connectivity

Outline


Achievements and Current Status of LDACS LDACS1 Extension Towards Navigation Conclusions Open Issues

Achievements and Current Status of LDACS Brief Review of LDACS - L-band Digital Aeronautical Communications System (LDACS) is the

future ground-based communications link within the FCI

- Two proposals: LDACS1 and LDACS2

- Deployment in L-band (960-1164 MHz)

- L-band already heavily used by - Aeronautical navigation services - Aeronautical military communications systems

- Different deployment options - Use only lower part of L-band, 960-978 MHz (LDACS2) - Use lower and upper part of L-band, 960-978 MHz / 1150-1157 MHz - Slight rearrangement of L-band assignments for radar navigation - Inlay scenario (preferred approach for LDACS1)


Achievements and Current Status of LDACS Brief Comparison Between LDACS1 and LDACS2 - LDACS1 can utilize more spectrum in L-band due to inlay approach; no

reorganization of spectrum assignments required

- LDACS1 is the broadband LDACS proposal (fivefold bandwidth) making available considerably more capacity

- LDACS1 applies modern communications concepts (OFDM)

- LDACS1 considerably more mature than LDACS2 - Continuous development since 2007 - Detailed evaluations of PHY and MAC layer - Receiver concept with strong robustness against interference - Numerous publications (> 30 since 2007) - Several demonstrators/prototypes available

- Europe: DLR, Frequentis AG, Rohde & Schwarz - Japan: ENRI, GNU radio implementation - China: BUAA, hardware implementation, flight testing


Achievements and Current Status of LDACS Potentials of LDACS1


- LDACS1 enables high-capacity aeronautical communications - Min. net data rate (FL+RL=overall): 291+270 = 561 kbit/s - Max. net data rate (FL+RL=overall): 1.32+1.27 = 2.59 Mbit/s - Well suited to serve modern ATM application and future needs

- Comparison with LDACS2 (overall): 70-115 kbit/s

- LDACS1 is highly flexible and scalable, enables long-term evolution - OFDM based physical layer - Scalability towards higher data rates

- LDACS1 foresees quality-of-service - Fast access to resources and low delays for application - Different priorities for different applications

- LDACS1 enables integration of navigation functionality

Achievements and Current Status of LDACS LDACS1 Work in Europe


SESAR JU Project P15.2.4 ATM Research

in Europe

LDACS1 Demonstrator Developed by FRQ

Compatibility Testing at DFS labs

SESAR 2020? Mature Technology, Update Specification

Achievements and Current Status of LDACS LDACS1 Work in Germany


DLR Internal Projects

Receiver Optimization Interference Mitigation

Receiver Concept

Demonstrator Complete Transmitter

Software Receiver

Achievements and Current Status of LDACS LDACS1 Work in Germany


ICONAV German National

Project with R&S as Industry Lead LDACS-COM

Hardware Implementation Including Security

LDACS-NAV DLR Internal Project

MICONAV Follow-on Project

Achievements and Current Status of LDACS LDACS1 Work Outside Europe


Japan ENRI (Electronic Navigation Research Institute)

LDACS1 Demonstrator Based on GNU Radio Hardware Implementation

China Beihang University (aka BUAA)

National Key Laboratory of CNS/ATM Theoretical Studies and Simulation on LDACS1

Demonstrator Implementation Preliminary Flight Tests in (May 2014)

LDACS1 Extension Towards Navigation Navigation Functionality for APNT - What is APNT? Alternative Positioning Navigation and Timing - Why APNT? For the GNSS failure case!


GNSS becomes primary navigation means

Navigation services require high performance

for all phases of flight Large distance

SAT-aircraft, GPS easily jammed

Newark Liberty Int’l Airport

“GPS Jammer” Personal Privacy

Device

LDACS1 Extension Towards Navigation LDACS1 as Pseudolite System


Continuously transmitting LDACS1 ground stations

act as pseudolites: “GPS on Ground”

Aircraft performs pseudo-range measurements towards LDACS1 ground station

LDACS1 Extension Towards Navigation Performance Bounds on Ranging With LDACS1


0 5 10 15 20 25

100

101

102

103

104

Carrier to Noise Ratio [dB]

Mea

n R

ange

Erro

r [m

]

Schmidl-Cox SynchronizationFreq. Domain: Synchronization SymbolsTime Domain: Synchronization SymbolsCRLB: Synchronization Symbols

~4.1 m

~4.1 m

~230 m

Theory: • Cramer Rao Lower Bound (CRLB) • Mean range error several meters

Simulations: • Slight adjustments to sync. • Theoretical bound achievable

@ reasonable C/N

Reality: • Performance in real environment? • Flight measurement campaign!

LDACS1 Extension Towards Navigation Flight Measurement Campaign


f/MHz 960 970

GSM

975 965 962

TAC

AN

LDAC

S A

LDAC

S B

LDAC

S C

LDAC

S D

Three flight levels: • FL100 • FL280 • FL380

LDACS – L-band Digital Aeronautical Communications System > Michael Schnell > October 2014

30 km

LDACS1 Extension Towards Navigation Range Estimation Results – Whole Flight


-60 -40 -20 0 20 40 600

0.02

0.04

0.06

0.08µ = 6.7 mRMSE = 15.2 m

Estimation Error [m]

Pro

babi

lity

µ = 6.7 m RMSE = 15.2 m

Raw range estimates,

averaged over 1 s time intervals

LDACS1 Extension Towards Navigation Range Estimation Results – Whole Flight


-60 -40 -20 0 20 40 600

0.02

0.04

0.06

0.08µ = 6.7 mRMSE = 15.2 m

Estimation Error [m]

Pro

babi

lity

µ = 6.7 m RMSE = 15.2 m

Main error source: Multipath propagation

Main error source: Troposphere

Second campaign for channel sounding

Ranging algorithms: Maximum Likelihood Doppler Smoothing

Particle Filtering

Channel modeling

Tropospheric models available

Significant reduction of bias possible

Conclusions

- LDACS1 is well-suited to serve modern ATM applications - High-capacity data link - Highly flexible and scalable

- LDACS1 has been considerably matured within the last years

- First compatibility investigations (LDACS1 DME) have been

performed

- LDACS1 offers an excellent opportunity for extension towards navigation - APNT service on top of communications infrastructure - Theoretical ranging performance in the order of meters - Measurement campaign validates navigation performance for APNT


Open Issues

- Further L-band compatibility evaluations for LDACS1 - DME/TACAN, UAT, SSR Mode S - Military communications systems (JTIDS)

- Development of deployment concept for LDACS1

- Development of a migration strategy from VDL2 to LDACS1

- Development of final LDACS1 specification including technology

amendments as required and initiation of standardization

- Development of fully functional LDACS1 prototype and flight testing



Thank You! More about LDACS1

www.ldacs.com

Documents

Current Status of LDACS Development first meeting...Current Status of LDACS Development Michael Schnell German Aerospace Center (DLR) • Chart 1 ICAO Communications Panel 1-5 December