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AFPReference

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Contact Information

Atoll 2.6.2 AFP Reference Guide Release AT262_ARG_E1

Copyright 1997 - 2007 by Forsk

The software described in this document is provided under a licence agreement. The software may only be used/copiedunder the terms and conditions of the licence agreement. No part of this document may be copied, reproduced ordistributed in any form without prior authorisation from Forsk.

The product or brand names mentioned in this document are trademarks or registered trademarks of their respectiveregistering parties.

About AFP Reference Guide

This document is aimed at frequency planning engineers using Atoll AFP module to perform automatic frequency planning

of their networks. This document introduces the AFP with a high level description of the frequency planning process inAtoll. Then descending lower to the practical level, this document describes in detail every aspect of frequency planningin Atoll. Main topics covered in this document include AFP pre-requisites, AFP usage, AFP minimization target and somepossible problems that may come up during training.

This document begins with a basic user guide containing a short operational introduction to the AFP process in Atoll. Thenit goes on to summarize most aspects of the practical planning process and provides detailed discussions on certaintopics. It also explains the means to evaluate a frequency plan. Furthermore, a chapter is dedicated to advanced topicsand troubleshooting in the end.

The appendices describe the technical aspects of the cost function, the BSIC allocation algorithm, the IM calculation, andthe dimensioning process.

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Table of Contents

Table of Contents

1 Overview......................................................................................... 131.1 Introduction to AFP ................................................................................................................................ 13

1.1.1 Frequency Assignment as a Cost Minimization Problem................................................................. 131.1.2 Abbreviations.................................................................................................................................... 13

1.2 Architecture............................................................................................................................................ 14

2 Basic AFP Tutorial .......................................................................... 192.1 AFP Process in Atoll .............................................................................................................................. 192.2 Loading and Validating the Network ...................................................................................................... 202.3 Definition of the AFP Scope................................................................................................................... 222.4 Preparing to Launch the AFP ................................................................................................................. 232.5 Launching the AFP and Monitoring its Progress.................................................................................... 252.6 AFP Outputs........................................................................................................................................... 27

2.6.1 Partial Commit Functionality............................................................................................................. 29

2.6.2 Automatic Constraint Violation Resolution ....................................................................................... 302.7 Visualising and Manipulating Results..................................................................................................... 312.8 Manual Frequency Allocation................................................................................................................. 31

2.8.1 Manual Frequency Allocation for SFH Case .................................................................................... 312.8.2 Manual Frequency Allocation for NH Case ...................................................................................... 31

3 Frequency Planning Prerequisites .................................................. 353.1 Atoll Data Model..................................................................................................................................... 35

3.1.1 Reliability and Propagation............................................................................................................... 353.1.2 HCS Layers ...................................................................................................................................... 353.1.3 Subcells............................................................................................................................................ 36

3.1.3.1 Key Roles of Subcells................................................................................................................. 363.1.3.2 Concentric Cells and Dual-band Cells ........................................................................................ 36

3.1.3.3 Minimum C/I................................................................................................................................ 363.1.3.3.1 Quality Targets...................................................................................................................... 36

3.1.3.4 Traffic Loads ............................................................................................................................... 363.1.3.5 Local Domain Restrictions .......................................................................................................... 36

3.1.4 TRXs ................................................................................................................................................373.1.5 Freezing Flags.................................................................................................................................. 373.1.6 AFP Weights .................................................................................................................................... 373.1.7 Spectrum Administration .................................................................................................................. 373.1.8 Redundancy and Subcell Audit ........................................................................................................ 373.1.9 Neighbour Importance...................................................................................................................... 383.1.10 SeparationConstraints Table............................................................................................................ 383.1.11 SeparationRules Table and Rule Priority ......................................................................................... 383.1.12 Adjacency Suppression.................................................................................................................... 38

3.2 AFP Performance Indicators .................................................................................................................. 383.2.1 AFP TRX Rank................................................................................................................................. 38

3.2.1.1 TRX Rank Usage........................................................................................................................ 393.2.2 Total Cost and Separation Violation Cost Component..................................................................... 39

4 Frequency Plan Optimisation.......................................................... 434.1 Step 1 (Optional): Traffic Model Usage.................................................................................................. 43

4.1.1 Creating a Traffic Map Based only on Clutter Weighting ................................................................. 434.1.2 Performing a Traffic Capture ............................................................................................................ 434.1.3 Creating IMs Based on Traffic.......................................................................................................... 44

4.2 Step 2 (Optional): Neighbour Relations and Relative Weighting ........................................................... 444.2.1 Automatic Neighbour Allocation ....................................................................................................... 444.2.2 Importing Neighbour Importance...................................................................................................... 454.2.3 Extending Existing Neighbour Relations .......................................................................................... 454.2.4 Importing Partial Sources of Neighbour Importance ........................................................................ 46

4.3 Step 3 (Optional): Using Dimensioning.................................................................................................. 474.3.1 Optimal Dimensioning of an Existing Network ................................................................................. 47

4.4 Step 4: Optimal Usage of the Atoll AFP ................................................................................................. 48


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4.4.1 Introduction to the AFP Cost Function ..............................................................................................484.4.1.1 Combination of Separation Violation and Interference Probabilities ...........................................484.4.1.2 Counting TRXs (Nodes) Instead of Relations (Edges)................................................................484.4.1.3 Each TRX Cost............................................................................................................................494.4.1.4 Separation Violation Cost............................................................................................................494.4.1.5 Interference Cost.........................................................................................................................504.4.1.6 Probabilistic Cost Combination ...................................................................................................504.4.1.7 Missing TRX Cost........................................................................................................................504.4.1.8 Corrupted TRX Cost....................................................................................................................51

4.4.1.9 Out-of-domain Frequency Assignment Cost ...............................................................................514.4.1.10 Quality Target..............................................................................................................................514.4.1.11 Modifiable and Non-Modifiable Costs..........................................................................................51

4.4.2 Most Important Cost Function Parameters and Tuning ....................................................................524.4.2.1 Interference Weight vs. Separation Weight.................................................................................524.4.2.2 Cost of Changing a TRX .............................................................................................................524.4.2.3 Quality Target and C/I Weighting ................................................................................................53

4.4.2.3.1 Quality Target........................................................................................................................534.4.2.3.2 C/I Weighting .........................................................................................................................53

4.4.2.4 Separation Weights Settings .......................................................................................................54

5 Means to Evaluate Frequency Plans...............................................575.1 Estimating Frequency Plan Quality.........................................................................................................57

5.1.1 Using Interference Studies................................................................................................................575.1.1.1 Various Interference Studies .......................................................................................................575.1.1.1.1 TRX Based Interference Study..............................................................................................575.1.1.1.2 Worst Case Interference Study..............................................................................................58

5.1.1.2 Visualising TRX Ranks with a TRX Based Interference Study....................................................585.1.1.3 Visualising C/I Distributions with a TRX Based Interference Study.............................................58

5.1.2 Using Audit........................................................................................................................................595.1.2.1 Global Separation Fitness Expression ........................................................................................59

5.1.2.1.1 Forsk Independent Separation Fitness Expression (FISFE) .................................................595.1.2.1.2 Main Separation Violation Item Summary .............................................................................59

5.2 Using Point Analysis ...............................................................................................................................605.2.1 Example 1: Combination of Interference Effects...............................................................................615.2.2 Example 2: Counting Strong Interference Only Once.......................................................................61

5.3 Uniform Frequency Usage Distribution...................................................................................................61

5.3.1 When Uniform Distribution and Quality do not Coincide...................................................................625.3.1.1 Domain Range Effect and Adjacent Constraints .........................................................................62

6 Advanced Topics and Troubleshooting ...........................................656.1 Various AFP Related Features ...............................................................................................................65

6.1.1 SFH (HSN, MAL, MAIO) ...................................................................................................................656.1.2 Definition of Atom..............................................................................................................................656.1.3 Synchronous Networks .....................................................................................................................656.1.4 Optimising Hopping Gains ................................................................................................................656.1.5 Fractional Load .................................................................................................................................656.1.6 Domain Use Ratio.............................................................................................................................666.1.7 User Defined MAL Length.................................................................................................................666.1.8 HSN Allocation..................................................................................................................................66

6.1.9 MAIO Allocation ................................................................................................................................666.1.9.1 Staggered MAIO Allocation.........................................................................................................66

6.1.10 BSIC Allocation .................................................................................................................................666.1.11 Robustness of Atoll AFP ...................................................................................................................67

6.1.11.1 Value Ranges and Limitations at Validation................................................................................676.2 Managing Consistency in Atoll and the AFP...........................................................................................68

6.2.1 Service Zone of a Subcell .................................................................................................................686.2.1.1 Specifying Correct Interference Study Coverage Criteria ...........................................................686.2.1.2 Selecting All servers or Best Server Service Zone.................................................................69

6.3 Event Viewer...........................................................................................................................................696.4 Interference Study Quality Criteria..........................................................................................................696.5 Calculation Zone Border Effect...............................................................................................................696.6 Frequency Planning Techniques ............................................................................................................70

6.6.1 Basics................................................................................................................................................706.6.2 Post-processing of Hot Spots............................................................................................................706.6.3 Learning the Network and Solving for Hot Spots ..............................................................................70

6.7 Performance and Memory Issues in Large GSM Projects......................................................................70


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7 Interference Matrices ...................................................................... 757.1 Types of Supported Interference Matrices ............................................................................................. 767.2 Interference Matrices Storage................................................................................................................ 767.3 Multiple File Import................................................................................................................................. 777.4 Maximum Likelihood Combination......................................................................................................... 77

7.4.1 Scope and Context of Interference Matrices .................................................................................... 777.4.1.1 Interference Matrix Context ........................................................................................................ 777.4.1.2 Interference Matrix Scope........................................................................................................... 797.4.1.3 Keeping the Scope and Context Up to Date............................................................................... 80

7.4.2 Interference Matrix Combination in Atoll AFP Module...................................................................... 807.5 Interference Matrix Calculation .............................................................................................................. 81

8 Appendices ..................................................................................... 858.1 Appendix 1: Description of the AFP Cost Function................................................................................ 85

8.1.1 Notations .......................................................................................................................................... 858.1.2 Cost Function ................................................................................................................................... 858.1.3 Cost Components............................................................................................................................. 87

8.1.3.1 Separation Violation Cost Component........................................................................................ 878.1.3.2 Interference Cost Component..................................................................................................... 88

8.1.4 I_DIV, F_DIV and Other Advanced Cost Parameters ...................................................................... 908.2 Appendix 2: Interferences ...................................................................................................................... 91

8.2.1 Using Interferences .......................................................................................................................... 91

8.2.2 Cumulative Density Function of C/I Levels....................................................................................... 918.2.3 Precise Definition ............................................................................................................................. 918.2.4 Precise Interference Distribution Strategy........................................................................................ 92

8.2.4.1 Direct Availability of Precise Interference Distribution to the AFP .............................................. 928.2.4.2 Efficient Calculation and Storage of Interference Distribution .................................................... 928.2.4.3 Robustness of the IM.................................................................................................................. 92

8.2.5 Traffic Load and Interference Information Discrimination................................................................. 928.3 Appendix 3: BSIC Allocation .................................................................................................................. 94

8.3.1 Definitions......................................................................................................................................... 948.3.2 Hard Criterion................................................................................................................................... 948.3.3 Soft Criterion .................................................................................................................................... 948.3.4 Behaviour ......................................................................................................................................... 94

8.4 Appendix 4: Traffic Capture and Dimensioning...................................................................................... 95

8.4.1 Introduction....................................................................................................................................... 958.4.2 Traffic Map Generation..................................................................................................................... 958.4.3 Traffic Capture Process.................................................................................................................... 95

8.4.3.1 Inputs .......................................................................................................................................... 958.4.3.2 The Engine ................................................................................................................................. 96

8.4.3.2.1 Traffic Distribution................................................................................................................. 968.4.3.2.2 Average Timeslot Capacity................................................................................................... 978.4.3.2.3 Integration............................................................................................................................. 97

8.4.3.3 Outputs ....................................................................................................................................... 988.4.4 Network Dimensioning Process ....................................................................................................... 99

8.4.4.1 Inputs .......................................................................................................................................... 998.4.4.2 Dimensioning.............................................................................................................................. 998.4.4.3 Outputs ....................................................................................................................................... 99


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List of Figures

List of Figures

Figure2.1: AFP Process in Atoll.................................................................................................................................. 19

Figure 2.2: Interaction of the AFP with Other Elements............................................................................................... 19Figure2.3: AFP Outputs .............................................................................................................................................. 20

Figure2.4: AFP Launch Wizard - AFP Session Tab.................................................................................................... 20

Figure 2.5: AFP Launch Wizard - Separations Tab..................................................................................................... 20

Figure 2.6: AFP Launch Wizard - Global Parameters Tab .......................................................................................... 21

Figure2.7: Event Viewer - Sample Messages............................................................................................................. 21

Figure2.8: Message 1................................................................................................................................................. 22

Figure2.9: Message 2................................................................................................................................................. 22

Figure2.10: AFP Launch Window................................................................................................................................. 23

Figure 2.11: Partial Interference Matrices - Report........................................................................................................ 23

Figure2.12: Complete Interference Matrices - Report................................................................................................... 24

Figure2.13: AFP Progress Window............................................................................................................................... 25

Figure2.14: Event Viewer Message - Solution Kept ..................................................................................................... 25

Figure2.15: AFP Progress Window............................................................................................................................... 26

Figure2.16: Cost Distributions on Frequencies............................................................................................................. 27

Figure2.17: Frequency Usage Distributions.................................................................................................................. 27

Figure2.18: AFP Results Window................................................................................................................................. 28

Figure2.19: Separation Constraint Violation Details Message...................................................................................... 28

Figure2.20: AFP Results Window - Partial Commit Feature......................................................................................... 29

Figure2.21: AFP Results Window - Partial Commit Feature......................................................................................... 30

Figure2.22: Constraint Violation Resolution Tool.......................................................................................................... 31

Figure2.23: Scanning for Frequencies.......................................................................................................................... 32

Figure2.24: Scanning for Frequencies.......................................................................................................................... 32

Figure3.1: Model Standard Deviation - Default Value................................................................................................. 35

Figure4.1: Automatic Neighbour Allocation................................................................................................................. 45

Figure4.2: Automatic Neighbour Allocation Results.................................................................................................... 46Figure4.3: Neighbours Table...................................................................................................................................... 46

Figure 4.4: Dimensioning Process............................................................................................................................... 47

Figure4.5: Atoll AFP Module Properties - Separation Weights Tab............................................................................ 49

Figure 4.6: Atoll AFP Module Properties - Cost Tab.................................................................................................... 52

Figure4.7: C/I Weighting............................................................................................................................................. 53

Figure4.8: Atoll AFP Module Properties - Separation Weights Tab............................................................................ 54

Figure5.1: Interference Study Report.......................................................................................................................... 57

Figure5.2: TRX Based Interference Studies ............................................................................................................... 58

Figure5.3: TRX Based Interference Study - C/I Distributions ..................................................................................... 59

Figure5.4: Event Viewer Messages............................................................................................................................ 60

Figure5.5: Event Viewer Message 1........................................................................................................................... 60

Figure5.6: Event Viewer Message 2........................................................................................................................... 60

Figure5.7: Combinatin of Interference Effects ............................................................................................................ 61

Figure5.8: Counting Strong Interference Only Once................................................................................................... 61

Figure6.1: Hopping Sequence Numbers..................................................................................................................... 66

Figure7.1: Interference Matrix Properties Dialog - General Tab................................................................................. 78

Figure7.2: Interference Matrix Properties Dialog - Advanced Tab.............................................................................. 78

Figure7.3: Interference Matrix Scope.......................................................................................................................... 79

Figure7.4: AFP Interference Matrices Parameters ..................................................................................................... 81

Figure 8.1: Atoll AFP Module Properties - Advanced Tab........................................................................................... 90

Figure8.2: The cumulative density of C/I levels between [TX1, BCCH] and [TX2, BCCH]......................................... 91

Figure 8.3: Traffic Maps Overlay.................................................................................................................................. 96

Figure 8.4: Traffiic Overflow......................................................................................................................................... 97

Figure8.5: Intra-Layer Distribution .............................................................................................................................. 97

Figure8.6: Traffic Distribution in Atoll.......................................................................................................................... 98Figure8.7: Network Dimensioning Process................................................................................................................. 99


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Chapter 1Overview



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AFP Reference Guide


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Chapter 1: Overview

Forsk 2007 AT262_ARG_E1 13

1 Overview

This document describes every aspect of frequency planning in Atoll, from high level description of the frequency planningprocess to the practical level detail. Main topics covered in this document include AFP prerequisites, AFP usage, AFP mini-misation target and some possible problems that may come up during training.

This document begins with a basic user guide, a short operational introduction to the AFP process in Atoll, and goes onto summarize most aspects of the practical planning process with detailed discussions on certain topics. It also explainsthe means to evaluate a frequency plan available in Atoll. A chapter is dedicated to advanced topics and troubleshooting

in the end.

Four appendices contain in-depth information on technical aspects of the cost function, the BSIC allocation algorithm, theIM calculation and the dimensioning process respectively. All in all, this document is almost self sufficient with respect tothe use of Atoll AFP.

1.1 Introduction to AFPThe main role of an Automatic Frequency Planner (AFP) is to assign frequencies (channels) to the network such that theoverall network quality is optimised. With the evolution of GSM over the years to integrate many improvements, additionalrequirements have emerged in the process of radio network planning. The implementation of baseband and synthesisedfrequency hopping, discontinous transmission and network synchronisation, for example, has led to higher sophisticationin the process of frequency planning. These enhancements require that an AFP also be intelligent and advanced enoughto help the frequency planner through out his tedious task.

The Atoll AFP considers a large number of constraints and directives; for example, ARFCN separation requirementsbetween transmitters, interference relations, HSN assignment methods, frequency domain constraints, a certain fractionalload to maintain etc. Hence, the AFP depends on a variety of input data, such as the interference matrix, neighbourhoodrelations, traffic information and so on.

This document not only explains how to use the Atoll AFP, by describing the AFP GUI, but also includes detailed descrip-tions of the various constraints, directives, and data sources. The primary target of this document is to explain the technicalbackground of the AFP.

1.1.1 Frequency Assignment as a Cost Minimization Problem

From the technical point of view, the Frequency Assignment Problem (FAP) is considered as a minimization problem. Thismeans that the AFP will generate a set of Frequency Plans (FPs), and propose the one that has the lowest cost as theBest Solution. Therefore, the AFP cost is the equivalent of AFP quality estimation: the lower the cost, the better should

be the quality from the AFP point of view.

The approach of cost minimization is not only the most common approach to the FAP but probably also the easiest tounderstand and control. It provides the user with means of guiding the AFP in its task. For example, by setting the cost ofinterference violation low, the AFP will concentrate its efforts on resolving the separation violations.

There are AFP tools in which certain types of objectives are presented as hard constraints. If a hard constraint is notsatisfied, the AFP does not offer any solution or offers a partial solution (with fewer frequencies and satisfying hardconstraints). The philosophy of hard constraints vs. soft constraints has nothing to do with the quality of an AFP engine, itis merely a behaviour convention. In Atoll, we prefer always offering a solution to offering partial assignments or violatingdomain limitations. This ensures that you will always get a result when you launch the Atoll AFP. This result will very welldepict the difficulty of the FAP. The cost of this solution will clearly indicate if unacceptable violations have occurred or ifthis plan has improved the current frequency plan.

The cost function definition permits you to place as much emphasis as required on certain elements of the cost function.This manipulation will make the AFP behave as if it were guided by hard constraints, from the optimisation viewpoint, while

retaining its property of being a quality monitor and a hardness-of-assignment monitor both.

1.1.2 Abbreviations

Some abbreviations and terminologies used in the document are listed below:

GSM Global System for Mobile Communications (Groupe Speciale Mobile)

GPRS General Packet Radio Service

EDGE Enhanced Data rates for GSM (or Global) Evolution

EGPRS EDGE based GPRS

TSL Timeslot

TX Transmitter or sector

TRX Transceiver

BCCHBroadcast Control CHannel. A term usually employed in Atoll to refer to the TRX carrying thischannel.


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1.2 ArchitectureThe Atoll Automatic Frequency Planning (AFP) module is an optional module that enables you to generate frequency plans

for GSM and TDMA networks automatically. The Atoll AFP module can allocate the following parameters: Frequencies Frequency hopping groups (MAL) HSN, MAIO BSIC (TSC planning)

TCHTraffic CHannel. A term usually employed in Atoll to refer to a TRX carrying traffic with usually thesame coverage area as the BCCH.

TCH_INNERInner Traffic CHannel. A term usually employed in Atoll to refer to a TRX carrying traffic but usuallyhaving a coverage area less than that of a TCH.

HR/FR Half Rate/Full Rate

CS Circuit-switched

PS Packet-switched

HCS Hierarchical Cell Structure

Subcell An entity defined by the pair [TX, TRX Type]

HO Handover

kbps Kilobits per second

GoS Grade of Service

QoS Quality of Service

KPI Key Performance Indicators

TL Traffic Load

P Probability

C Carrier power (Signal strength)

C/I Carrier to Interference ratio

AFP Automatic Frequency Planner/Planning

DTX Discontinuous transmission

GUI Graphical User Interface

FP Frequency Plan

BBH Baseband Hopping

SFH Synthesized Hopping

NH No Hopping

MALMobile Allocation List. In the context of SFH, MAL is the group of frequencies used by thefrequency hopping TRX.

AMR Adaptive Multi-Rate

CC Concentric Cells

Transmitter Atoll synonym for cell or sector in conventional GSM jargon

FER Frame Erasure Rate

FH Frequency Hopping

DLPC Down Link Power Control

RRM Radio Resource Management

Synchronised

transmittersTransmitters that are synchronised and can, therefore, share the same HSN.

Data ModelA project can be saved in a filename.ATL file or as a database. In both cases, most of the projectsinformation is saved in database tables. We refer to these tables as the data model.

IM, IMco, IMadj Interference Matrix, Co-channel / Adjacent-channel Interference MatrixFN Frame Number

CDF Cumulative Density Function

TSC Training Sequence Code

FAP Frequency Assignment Problem

# Number of


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Chapter 1: Overview


TRX rank (can be used to prioritise the use of good frequencies) Performance Indicators at Site/Cell/TRX levels

Atoll works with an open AFP interface. Any AFP built using this interface can be able to allocate the following additionalparameters. Future versions of the Atoll AFP module are planned to assign the following parameters as well:

Group ID (better administration of the frequency resources) TN offsets FN offsets

Atoll AFP implements simulated annealing, taboo search, graph heuristics and machine learning. It manages its timeresources to match the users time directive. If allowed enough time, the AFP will employ a major part of this time in learn-

ing the network. During the learning phase, the AFP tunes up its internal parameters. Towards the end of the user-definedtime, the AFP switches to a randomised combinatorial search phase.

Network learning is performed by executing numerous fast and deterministic instances of the AFP. The one that obtainsthe best performance is memorized in the document and is, therefore, the most suitable for the specific network. The nexttime an AFP is executed it will start where the learning process ended and it will use the parameter profile of the best solu-tion stored in the document.

The Atoll AFP is built based on a specified COM interface designed as a part of Atolls open platform strategy. The interfaceis designed in such a way that puts aside elements that are not inherent to the AFP process. At the same time, throughthe modelling capabilities of the planning tool, the AFP can support complete list of features expected from an AFP.

Remark:The role of this learning phase is extremely important in order to get good results. You should often let the AFP run over

a night or a weekend by specifying corresponding target time. If you never run the AFP specifying a long time period, it

will never be able to calibrate itself and will always perform from 10 to 70 solutions and stop.

Note:

The following scenario will demonstrate the usefulness of AFP learning capabilities:

- Create a GSM GPRS EGPRS project and import its network elements and maps.

- Create a copy of Atoll AFP module and name it Atoll AFP module 2.

- If the network has X transmitters, run Atoll AFP module 2 for X / 10 minutes to obtain acost Y. (Short execution)

- Now run Atoll AFP module 2 for a longer time (for example, X / 5 hours).

- Another cost, Z, is obtained, which is better than Y (i.e. Z < Y). The network dependentinformation is memorized in the Atoll AFP module 2 instance whereas the Atoll AFPmodule instance remains unchanged.

- Now if you perform a short execution with Atoll AFP module 2, you can get the improvedresult (Z) right away. While a short execution of the Atoll AFP module instance will givethe initial cost (Y).

- If X / 5 hours is too long, you can perform the learning on a small (representative) part of

the network.


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Basic AFP Tutorial

Chapter 2



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Chapter 2: Basic AFP Tutorial


2 Basic AFP Tutorial

Atoll AFP framework complies with its global open architecture strategy. Any AFP module, Atoll AFP or 3rdparty AFP, canbe interfaced and made available to RF planning engineers through Atoll. Furthermore, different AFP modules are acti-vated, accept their main inputs and generate their main outputs in the same manner. This section teaches the basics ofactivating an AFP in Atoll.

2.1 AFP Process in AtollThe AFP process is a cycle in which the AFP is only one of its many steps:

The figure below gives a better view of interaction of the AFP with other elements in Atoll:

The following figure depicts the outputs of the AFP:

Figure 2.1: AFP Process in Atoll

Figure 2.2: Interaction of the AFP with Other Elements


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2.2 Loading and Validating the NetworkTo launch the AFP, choose theAu tomat ic Al locat ion command from the Frequency Plan menu of the Transmitters

folder context menu. This initiates a series of dialogs called theAFP w izard.

Figure 2.3: AFP Outputs

Figure 2.4: AFP Launch Wizard - AFP Session Tab

Figure 2.5: AFP Launch Wizard - Separations Tab


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Here you can,

Specify the AFP module you would like to use and set its parameters, Choose the network parameters and AFP performance indicators you want the AFP to allocate, Specify the networks default separation requirements, Consult the networks Exceptional Pairs and define other separation constraints for them, and Indicate whether interferences are to be included in calculations or not.

For explanations of AFP performance indicators, refer to section 3.2 "AFP Performance Indicators". The last wizard dialogcontains some global parameters that often vary from one AFP instance to another:

The most important option here is the one proposing the two sources of the traffic load information. Traffic load can beread directly from the subcells table, which could have been filled manually, by the dimensioning process or by a KPI calcu-lation. You can also specify that the traffic load should be read from the default traffic capture (explained later).

ClickingValidate will start the data verification and storage optimisation aimed at providing fast access to data needed bythe AFP . This stage may generate many warnings for real-life networks (for example, values out of range). These aredisplayed in the Event viewer. It is recommended to revise the network data according to these messages and continueonce all the data are clean and coherent. If a certain message is not clear or self evident, you can always contact Forskstechnical support. The figure below depicts the Event viewer with some sample messages:

Let us look at two of these messages:

Figure 2.6: AFP Launch Wizard - Global Parameters Tab

Notes:

In case the traffic load is taken from the Subcells table, committed after a KPI calculation,you must be aware of a certain difference: in the KPI calculation, Atoll divides the captured

traffic by the timeslot capacity of the existing number of TRXs, while the AFP requires it tobe divided by the timeslot capacity of the required number of TRXs.

The traffic load is artificially increased to 0.1, if it is too low (less than 0.1), in order tomaintain the AFP robust against partial data conditions. Hence, the AFP cannot completelyignore the existence of a frequency in a TRX.

Figure 2.7: Event Viewer - Sample Messages


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AFP Reference Guide

This means that the value entered in the AFP weight column of the Transmitters table for the transmitter 19941 is invalid.

In the database, this fields name is COST_FACTOR. A value of 2 for the cost factor implies that the AFP should gener-ate the worst assignment possible for the transmitter. It would be interesting to investigate the origin of this erroneous valueas it may avoid possible errors in the future. Atoll automatically resets this value to 1 in order to avoid such calculationerrors.

This message informs that 3678 subcells were loaded successfully. The next section explains the significance of the termeffectively selected and why 3678 subcells were loaded and only 6 selected for the AFP process.

2.3 Definition of the AFP ScopeIn the example above, the 6 subcells effectively selected for the AFP process had many potential interferers, neighbours,neighbours of neighbours, and/or transmitters with exceptional separation constraints with them. No AFP can perform agood allocation for these 6 subcells without dragging in a large part of the network. The AFP considers the part that isdragged in to be frozen. On the other hand, there are many other ways to freeze network elements in Atoll. Someprecise definitions are provided in order to avoid misconceptions.

Let us define 4 groups of transmitters (ALL, NET, SEL, RING):

ALL =All the transmitters in the project. NET =Active transmitters that pass the filters on the main Transmitters folder and on the main Sites folder. SEL =Transmitters belonging to the (sub)folder for which the AFP was launched and that are located inside the

focus zone. RING =Transmitters belonging to NET, not belonging to SEL and having some relationship with the transmitters

in SEL:- If interferences are to be taken into account (see the dialog above), all transmitters whose calculation radii

intersect the calculation radius of any transmitter in SEL will be included in RING. For large calculation radii(20 km for example), a single site can have a very large RING loaded.

- Neighbours are always included in RING.- If one transmitter of an Exceptional Pair is included in SEL and the other is not, then the other will be included

in RING as well.- If BSIC assignment is required, then all the second order neighbours (neighbours of a neighbour) will be

included in RING as well.

Both the RING and the SEL parts of the network are loaded. It is important to know which subcells are loaded as the costis calculated for all loaded subcells. The RING part is frozen for all assignments (BSIC, HSN, MAL, MAIO and channels).

The SEL part may be assigned some parameters but only the ones specified in the dialog above. For example, if the userdid not select BSIC, it will not be assigned.

In addition to the generic freezing options above, there are some finer freezing options available in the data structure:

1. Individual transmitters can be frozen for channel (and MAL), HSN and/or BSIC assignment.2. Individual TRXs can be frozen for channel (and MAL) assignment.

In an Atoll project, it is strongly recommended to avoid TRXs without channels. For this reason, never create transmittersautomatically if there are no channels to assign to them. Therefore, if the user does not ask for MAL/MAIO assignment, allSFH subcells are considered frozen and no TRX will be created for them. The same occurs when only a MAL/MAIOassignment is requested. In this case, all NH and BBH subcells will be considered frozen and no TRXs will be created.

Figure 2.8: Message 1

Figure 2.9: Message 2

Note:

See Developer Reference Guide for details on the TO_ASSIGN and FROZEN assignmentstates available in the AFP API.


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2.4 Preparing to Launch the AFPOnce the network is loaded and all warnings resolved, the AFP launch dialog will appear. This dialog contains a shortsummary of the state of the loaded network, SEL +RING.

Interference matrices can be managed through the Interference Matrices folder. You can have more than one interferencematrices in your document. The top most active interference matrices set is used by the AFP. You can either embed theinterference matrices in the document or store them in external files. Atoll compresses the interference matrices if storedin the .atl document itself. It is not necessary to load IMs or look for them each time AFP is launched. You can view thereports on different interference matrices available in the Interference Matrices folder. This report has a summary sectionwhich indicates the current state of the IMs.

Figure 2.10: AFP Launch Window

Example 1: When partial IM info exists, we can see that 9 transmitters out of 24 do not have anyinterferers.

Figure 2.11: Partial Interference Matrices - Report


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The AFP launch dialog also lets you define a generator initilialisation number. This number serves as a directive ofrandomness for the AFP process being launched. If the generator initialisation is set to 0, the AFP will be fully random. Aninteger other than 0 will define a given deterministic sequence for the AFP process. Each generator initialisation number(other than 0) corresponds to a deterministic sequence. Therefore, each AFP instance launched with the same generatorinitialisation number will yeild the same results.

You can use this option if you want to have the same set of solutions every time you launch the AFP for the same part of

the same network.The Atoll AFP has a single algorithm with a number of steps. The AFP ignores some of these steps if the alloted targetcalculation time is too short. One of these steps is deterministic, i.e. independent of the generator initialisation number,while the other steps are initialized by this number.

Generator Initialisation =0 (default value) signifies that this intialisation number will be calculated randomly.

Generator Initialisation 0 means that the number will be the one set by the user. Every time you define the same

number, the AFP algorithm will be initialised in the same way, and hence the set of solutions will be the same.

It is advised to set Generator Initialisation =0, and let the AFP reach the end of the Target Computation Time defined.

However, you must keep in mind that all the AFP computations are deterministic in the start, independent of the generatorinitialisation. The AFP must be allowed to compute during the target time to observe the effects of randomness.

Example 2: When complete IM info exists, observe that the IM topology is more or less normal.

Figure 2.12: Complete Interference Matrices - Report

Notes:

Since the method chosen by the AFP depends on the target time provided, you might not

get the same results using the same generator initialisation number if the defined targettimes are different. Therefore, to actually get the exact same results from the AFP process,you must define a certain target time and a certain generator initialisation.

The AFP may be perfectly deterministic during a portion of the target computation time (5 -15%). During this period, the randomness seed will have no effect on the solutions. If youwant to see the effect of randomness, let the AFP calculate until the end of the target time,or set a shorter target time.


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2.5 Launching the AFP and Monitoring its ProgressProvide a time quota and a generator initialisation number in the above dialog and launch the AFP by clicking Run. It isimportant to set a long time quota from time to time to allow the AFP to calibrate itself. If not stopped, the AFP will usuallycontinue for a while before stopping by itself.

The window below opens when the AFP is started, and displays information about the AFP process:

The Progress section of this window in the top left displays the target time allocated to the AFP, the time elapsed and thenumber of AFP solutions that have been evaluated so far.

The general information and interference matrices report section in the top right gives some general information about thecurrent solution in real time. This display depends on the selected AFP module. This section lists the status of the currentsolution, the initial cost, the cost of the current best solution, the cost of the previous solution and whether the previoussolution was kept or rejected. You can use the >>button to switch to the report on the currently used interference matrices.

The Event viewer has been made accessible through the AFP progress dialog in order to help the user keep track of allthe important warnings and messages generated before and during the AFP process. This also enables you to export

these messages as an AFP log file.If a solution is kept, a corresponding message appears in the Event viewer. Double-clicking the message in the Eventviewer will open a dialog with the full details of this message, which will look something like the following figure.

After the AFP is allowed to compute solutions and try to optimise the network for a while, the AFP progress dialog wouldlook somewhat like this:

Important:

If only a short time is specified, the full optimisation potential of the AFP will not be utilised.

Figure 2.13: AFP Progress Window

Figure 2.14: Event Viewer Message - Solution Kept


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The Best Frequency Plan Costs section displays the current values of modifiable and total costs, and their respective sepa-ration components. This section also displays the total weighted Erlangs of the network concerned in the AFP process,i.e. the total cost of a 100% interfered frequency plan). It gives a general idea of how good the cost of a certain frequencyplan is. The cost of any solution remains between 0 and the Network Weighted Erlangs. The cost is as better as it is closerto 0.

Apart from the above information, this section also contains a table listing the initial frequency plan and all the AFP solu-

tions kept so far sorted in ascending order of cost. This table can display:

Modifiable costs Total costs Frozen costs Summed components Main components (separation violation cost component, interference component and modified TRX component) Additional taxes (corrupted, missing or out of domain TRXs)

For detailed description of modifiable and non-modifiable parts of the total cost, please refer to section4.4.1.11 "Modifiableand Non-Modifiable Costs".

Using the buttons available in the Plan comparison section in the bottom right, it is possible to visually compare the initialfrequency plan and the current best solution (with the Best Plan column in the AFP cost details table checked). Clickingthese buttons opens dialogs containing graphs corresponding to Cost Distribution on Frequencies and Usage Distribu-tion on Frequencies.

The cost of a frequency f is given as:

Where, FL(i) is the fractional load of frequency f in the MAL of i, and cost(i) is the AFP cost of TRX i in Erlangs.

Figure 2.15: AFP Progress Window

Cost f ( ) FL i( ) Cost i( )

i TRXs using f =


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You can pause or stop the AFP process any time to check the current best solution, and resume optimising the networkafter you have checked it. Pausing the AFP process opens the AFP results window with the current best solution resultslisted.

2.6 AFP Outputs

When calculations stop (completed or paused to view the current situation), Atoll displays the frequency plan proposed bythe AFP. All results/violations are listed in a dialog window. This window contains a table listing all the assignedresources.These resources and related items (transmitters, subcells) are coloured differently to indicate different reasons:

Arctic blue: frozen resource Red: resource modified compared to the previous allocation but with separation violation Green: resource modified compared to the previous allocation respecting the separation constraints Black: resource not modified Blue: resource assigned with no separation violation Purple: resource assigned but with separation violation Grey: items and resources involved in computation but not available for allocation

Positioning the cursor over a resource in the table displays the reason for its colour in a tool tip.

The AFP result dialog is a non-blocking dialog. It enables the user to access other Atoll windows while the AFP is still pend-ing. Thus, it is possible to view other data or warning/error messages in the Event viewer (for example, the history of AFPsolutions). From this stage, it is possible to commit, to resume or to quit the AFP. It is good practice to keep a report through

the export option before resuming the AFP. The user can also partially commit some of the results as explained in the nextsection.

The results window displays all the results of the AFP session. It is possible to only display some of the results by checking/un-checking the relevant choices in the Display options menu. You can choose to display the results related to:

Cells (BSICs) Subcells (HSNs) TRXs (Channels/MAL, MAIO) and related separation violations

Selected AFP performance indicators (AFP TRX ranks, and total and separation costs at TRX, subcell, transmitter andsite levels) will also be available in the results window. These AFP performance indicators are also available to export.You can choose whether to display the AFP indicators in the results as separate columns. The Show AFP Indicatorscommand in the Display options menu controls the display of AFP TRX ranks, and total costs and separation cost compo-nents at TRX, subcell, transmitter, and site levels.

Figure 2.16: Cost Distributions on Frequencies

Figure 2.17: Frequency Usage Distributions


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As the network had been loaded according to both the items to assign and the ones they relate to, it is possible to displaythe frequency plan of either:

Items belonging to the selected transmitters (see the definition of SEL), or Items belonging to the loaded transmitters (see the definition of SEL +RING). In the preceding example, there

were no transmitters in the RING set, so the option is not available.

It is also possible to display detailed information about separation constraint violations, i.e. the co-channel and adjacentchannel collision probabilities for relevant TRXs. You can choose to display these separation constraint violations throughthe Display options menu.

The Separation violations column lists each each type of separation constraint violation realted to a given TRX, i.e. excep-tional pair, co-transmitter, co-site, or neighbour. Another column titled With the TRX contains a button for each type ofseparation constraint violation. This caption of this button shows the TRX with which the separation constraint violationoccurs. Clicking this button takes you to the corresponding TRX row in the table. Right-clicking a row with a separationconstraint violation opens a Separation Constraint Violations context menu, which opens a dialog mentioning the reason

of violation when clicked. For example:

Use the Commit button to assign the allocated resources and AFP performance indicators. The resume button permitsresuming the AFP optimisation from where it stopped the last time.

Figure 2.18: AFP Results Window

Figure 2.19: Separation Constraint Violation Details Message

Note:

At the bottom of the AFP results window, messages related to the last solution aredisplayed, which may list problems as well.


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2.6.1 Partial Commit Functionality

It is often required to commit only a part of the automatically generated frequency plan rather than committing it entirely.The purpose is to avoid committing TRXs that violate separation constraints (sometimes referred to as not closing thefrequency plan). Future Atoll versions will incorporate advanced automatic filters for partial commit.

The dialog examples below depict a case where removing a TRX eliminates a separation constraint violation on neigh-bours. Once a TRX is manually removed from the resulting plan, separation violations are recalculated (may take a fewseconds). If the TCH TRX of transmitter Site36_3, causing neighbour separation constraint violations, is removed from thesample frequency plan below, the resulting frequency plan has no neighbour separation constraint violations on the TCH

TRX of transmitter Site36_1.

It is possible to specify the action to be taken with each TRX individually, or globally delete all TRXs with separation viola-tions. It is also possible to mix the old plan and the new plan. Though this is not recommended, since it can cause inter-ferences of which the user might be unaware. The dialog examples below depict how this operation can be carried out.

TheDelete the TRX option implies that the resulting frequency plan will not respect the number of required TRXs. In theabove example, note than the neighbour separation constraint violations at transmitter Site36_1 vanished once the TCHTRX at Site36_31 was deleted.

Figure 2.20: AFP Results Window - Partial Commit Feature


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2.6.2 Automatic Constraint Violation Resolution

Different types of constraint violations, i.e. co-transmitter, co-site, neighbour, and exceptional pair, can automatically beeliminated from the propsed frequency plan using the Automatic Constraint Violation Resolution tool. This tool is accessi-ble from the Actions button menu.

The aim of this tool is to find the TRXs in the currently proposed frequency plan that cause constraint violations of any ofthe four following types:

1. Co-transmitter2. Co-site3. Neighbour4. Exceptional pair

Once it finds the TRXs that satisfy the criteria, it sets their corresponding values to Delete the TRX in the Channel Assign-ment column of the AFP results window.

This tool lets you resolve any type of constraint violations for different types of TRXs, control or traffic. You can also define

a threshold of co-channel and adjacent channel collision probabilities. This restriction will only set those TRXs to Deletethe TRX, which have a co-channel or adjacent channel collision probability higher than the threshold you defined.

Figure 2.21: AFP Results Window - Partial Commit Feature


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2.7 Visualising and Manipulating ResultsThe Commit button copies the frequency plan to the data structure. It is not necessary to save the document or committhe changes to the database right away as the AFP cycle has not yet ended. At this stage, various generic and specifictools are available in Atoll, and can be used to inspect the candidate frequency plan. Interference and C/I prediction studiesand various consistency checks are described in the following chapters of document. In addition to these, a useful tool isalso available in Atoll, called the Search tool. Its function is to facilitate visualising co-channel and adjacent-channel trans-mitters. This tool is explained in detail in the User Manual. Other means of inspection include the common grouping, filter-ing, advanced filtering, display and tool tip management features.

2.8 Manual Frequency AllocationThis section describes quick and useful techniques for performing manual frequency allocations in Atoll.

2.8.1 Manual Frequency Allocation for SFH Case

It is possible to perform frequency allocations for irrgular pattern networks, i.e. patten allocation of type 1/N. The followingset of operations will results in a frequency allocation even if the network is not a 100% regular pattern network.

1. Run the AFP so that it creates the required number of TRXs.2. Group the transmitters by azimuth and manually assign the MALs to the most important azimuth groups.3. Filter out these azimuth groups and delete the TRXs of all transmitters that were not assigned a MAL manually.4. Run the AFP again selecting MAIO assignment only. This will assign proper MAIOs to the TRXs to which MAL

was manually assigned.5. Remove the filter and freeze the existing TRXs. Now use the AFP to complete the assignment (assigning all

resources).

2.8.2 Manual Frequency Allocation for NH Case

To carry out manual frequency assignment:

1. Create a Best Server map and display it,2. Display neighbours of the transmitter for which you want to find a frequency manually,3. Open the Search tool,4. By scanning the spectrum a good frequency can easily be found and can be allocated to the transmitter.

Figure 2.22: Constraint Violation Resolution Tool


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In this example, frequency 11 is not a good choice since it is used as a neighbour co channel. Frequencies 10 and 12present similar characteristics.

On the other hand, frequency 14 is a good one and can be possibly allocated. None of the frequencies {13, 14, 15}areallocated at the selected transmitter of at its neighbours.

Figure 2.23: Scanning for Frequencies

Figure 2.24: Scanning for Frequencies


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Chapter 3



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3 Frequency Planning Prerequisites

The principal difference between AFP and other planning activities is that the impacts of poor frequency planning are morewidespread in a network. For example, poor planning of a site or a cell will have somewhat local influences, while imple-menting a poor frequency plan will affect a much larger part of the network. Moreover, creating a poor frequency plan israther relatively easy, the presence of a single faulty parameter in the process can be sufficient for the damage the entireplan.

Therefore, it is mandatory that the AFP user acquires a minimum level of knowledge regarding Atoll data model. This chap-

ter familiarises the user with the essentials of the data model and depicts their relations with the AFP.

3.1 Atoll Data Model

3.1.1 Reliability and PropagationOften the user senses that the AFP does not have enough constraints:

The unfrozen part of the AFP cost is 0 and the AFP stops due to this fact. There appear to be close frequency reuses in the resulting frequency plan.

This means that the problem is too easy for the AFP and the user would like to create a more difficult IM in order for theAFP to have a more difficult problem to solve.

The best method to accomplish this is to increase the cell edge reliability and recalculate the IMs. When the reliabilityrequirement is elevated, a larger part of the standard deviation is reduced from C when calculating the C/I for each IMentry.

The user should also verify that the standard deviation is properly defined in all clutter classes and its default value. Thisverification is more important in the case of Atoll documents converted from older versions or connected to a database.

3.1.2 HCS Layers

HCS layers have several roles in Atoll. Their most important role is related to the way Atoll manages traffic maps. Differentlayers have different priorities and mobility limitations. There is also the possibility to manage traffic overflow from one layerto another. The objective of all these options is to model the behaviour of a real network, where two potential servers thatdo not belong to the same layer usually do not compete for best server.

When calculating an IM, or when generating an interference study, HCS layers are used in generating service zone maps,the basis of these calculations. If two transmitters belong to different layers, they can both serve the same pixel even ifreceived signal from one is much stronger than the others. For equal HO margins, more HSC layers mean higher over-lapping levels in the network. As the overlapping level increases, the constraint level in the IM and the amount of interfer-ence in an interference study also increase.

Figure 3.1: Model Standard Deviation - Default Value

Note:

Be sure to study the priority mechanism in your network, both in the re-selection processand in the handover process. Define the corresponding HCS layers once you know itsworking. When using a traffic model, make sure that there are a few levels of mobility in

order to model high speed / low speed mobility behaviours.


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3.1.3 Subcells

Subcells are defined as a group of TRXs in the same transmitter. Two subcells of the same transmitter can requestfrequencies from different domains, require different C/I qualities, have different downlink power offsets and even havedifferent Radio Resource Managements (RRM). Different RRMs can lead to different service zones under the same cell.Subcells are crucial for modelling concentric and dual band transmitters. In these cases, the TRXs belonging to the innersubcell serve traffic within a limited zone.

3.1.3.1 Key Roles of Subcells Associating TRX groups with required quality definitions Associating TRX groups with weak / strong constraints (interference , separation) Associating TRX groups with different domain limitations Visualising and filtering by TRX Type The following additional parameters are also defined in the Subcells table:

- HSN (since the inner zone HSN may be different from the outer zone HSN)- Power offset- Reception threshold (can limit the zone of the inner subcell)- Hopping mode- Assignment mode (in SFH, group constrained mode limits the choice of MAL to one of the groups in the

domain)

- Support of DTX- Traffic load and supplementary AFP weight- Some other parameters influencing the AFP indirectly (for example, the overflow rate)

3.1.3.2 Concentric Cells and Dual-band Cells

Concentric cells were created in order to exploit downlink power control (DLPC) and radio resource management (RRM)in frequency planning. This is accomplished by associating channels with subcells. Subcells may have different servicezones with respect to the transmitters geographic coverage. For example, a subcell TCH_INNER covers a zone requiringminimum reception level of 75 dBm and TCH_OUTER covers a zone with minimum reception level of 94 dBm. In thiscase, the inner zone has a higher resistance to increasing interference. The AFP has the possibility ot assign a relativelyinterfered frequency to the TCH_INNER zone to give more choice to the outer zone.

The other important property of concentric cells is the fact that a downlink power offset is associated with each subcell.The inner subcells can have higher DLPC implying that the frequencies assigned to the inner zones will interfere less with

other transmitters. Concentric cells permit a higher reuse pattern between inner zones, providing up to 40% increase incapacity.

Atoll can fully exploit this increase in capacity since it calculates interferences between subcells. It uses the power offsetand the C/I threshold that defines the subcell boundaries. Furthermore, it is also possible to define separation constraintsat subcell level.

3.1.3.3 Minimum C/I

The required quality thresholds for BCCH and TCH are usually 12 and 9 dB respectively. But, since the GSM standardtests this behaviour under the comfortable reception conditions of 20 dB above thermal noise, it does not reflect the behav-iour for, for example, received signals being only 15 dB above thermal noise.

Atoll provides the possibility to define these thresholds at subcell level allowing maximum flexibility and possibility tosupport a mixture of old and new equipment. Moreover, the safety margins corresponding to these values can be definedin the AFP cost definition. Refer to section 4.4.2.3 "Quality Target and C/I Weighting" for more information.

3.1.3.3.1 Quality Targets

Various quality targets can be set in Atoll by defining a C/I threshold value min C/I, with a probability threshold % maxinterference. These two values combined together define a quality target which implies that in order to have acceptablequality, the probability of having C/I lower than the min C/I value must be less than % max interference.

This method enables Atoll to exploit the fact that a larger number of TCH channels can be assigned with quality require-ments lower than the BCCH quality. This results in less constraining interferences and an easier and faster assignment.Refer to section 4.4.2.3 "Quality Target and C/I Weighting" for more information.

3.1.3.4 Traffic Loads

Traffic loads of all the subcells are used as input to the AFP. These traffic loads can be calculated by Atoll or read fromthe Subcells table. Traffic loads are discussed in detail afterwards.

3.1.3.5 Local Domain RestrictionsLow level domain restrictions can be introduced at subcell level through the excluded channels column in the Subcellstable.

Note:

All TRXs in a subcell share the same TRX type.


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3.1.4 TRXs

Atolls TRX table enables the following:

Support of an external ID space of the TRXs of a transmitter (important for import and export utilities). MAL / channel at TRX level. MAIO at TRX level. Fine freezing: The user can freeze specific TRXs in an unfrozen transmitter.

The TRX table does not contain an active field. Therefore, all TRXs in it should contain a valid frequency or MAL and areall considered to be on air. It is better to remove an entire TRX record than removing only the frequency or MAL from itschannels list.

3.1.5 Freezing Flags

A multilevel freezing mechanism enables freezing resources at TRX level as well as at transmitter level. This, in turn,enables the user to use an existing plan while assigning only newly added demand for channels. These options are inaddition to the working zone limitations.

3.1.6 AFP WeightsThe AFP weight field in the Transmitters table enables the user to assign high or low weightings to certain transmitters. Itcan be used to improve quality at a problematic location or to boost quality in a particular covered region of the network.An additional AFP weight field exists at the subcell level. It enables the user to assign weighting to subcells. A conventionalidea could be to assign a higher weight to the BCCH. The AFP uses the multiplicative product of transmitter level AFPweight and subcell level AFP weight.

3.1.7 Spectrum Administration

Many levels of administration exist relative to frequency planning. In order to avoid confusion, here is a comprehensive list:

ARFCNs

ARFCN is the method employed by the GSM/DCS standards to enumerate 200 kHz frequency carriers.

Frequency Bands

Frequency Bands are subgroups of ARFCNs. Different equipment may be limited to different frequency bands(BTS, MS, ). In addition, propagation models use the central frequency of the band for calculating propagation.

Frequency Domains

Domains are used for managing the usage of the Frequency Bands. For example, an operator may use frequen-cies 1 to 50 while the other uses 52 to 100. Splitting the band on channel usage basis is of great importance aswell (BCCH frequencies, TCH frequencies, Hopping layer).

Domain Groups

Domain groups are used for further managing the use of the frequencies in a domain. For example, f1 and f2 canbe assigned at the same transmitter if and only if they belong to the same group. Another frequent use for groupsis in the MAL assignment.

In Atoll, a domain is defined as a union of groups. It points to a frequency band and must be included therein. The AFPrespects domain limitations at subcell level.

3.1.8 Redundancy and Subcell Audit

Atoll incorporates some deliberate redundancies between the subcells and TRX levels, and the Transmitters table:

The channel list in the Transmitters table is the intersection of all channels appearing in the TRXs of a transmitter. The hopping mode of a transmitter is the hopping mode of its default traffic carrier (the TCH TRX Type) The frequency band of the transmitter (the one used by the propagation model to deduce the central frequency),

is read from the domain of the BCCH subcell of the transmitter.

Atoll considers the low level to be the accurate source of information. For example:

Atoll will automatically update the TRX table if the channel list of a transmitter in the transmitter table is changed. The frequency band of a transmitter cannot be edited.

These redundancies provide some additional features (for example, grouping transmitters according to the frequency

bands).

On the other hand, there is a chance of mistakes and bugs which may damage a redundancy in the ATL file. Therefore, itis recommended that the audit tool be used from time to time in order to fix these problems (right click the Transmittersfolder, choose Audit from the Subcells menu).

Note:

When freezing channels, keep in mind that the MAIOs are not frozen.


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3.1.9 Neighbour Importance

Neighbour importance field exists in the neighbour relation tables. It is also available in the AFP and can assist in resolvingcongestion situations. This is discussed in detail in subsequent chapters.

3.1.10 SeparationConstraints Table

It is a separation exceptional-pair table containing pairs of subcells with associated separation requirements. Special sepa-rations have a higher priority with respect to all other separations and can be used to relax separation constraints as well.

3.1.11 SeparationRules Table and Rule Priority

The SeparationRules table is simple to understand once the order of priority that exists between various separation rulesis kept in mind:

1. Highest priority: exceptional pairs

2. Second higher: co-transmitter

3. Third priority: co-site

4. Last priority: Neighbour.

For example, if two subcells are neighbours and at the same site, their associated separation requirement will be accordingto the co-site separation rules. And, if this separation requirement is not fulfilled, their separation violation costs will be

weighted by the co-site weight.Separation rules depend on equipment, and refer to the non-hopping configuration. Separation rules are "administrationrules" that are set once according to the equipment and are not meant to be modified during routine operations. Separationrules do not depend on whether SFH is available in the network or not. Atoll and the AFP consider SFH independent ofthe separation rules. If you relax the separation constraints, and have SFH TRXs, this means that you are asking the AFPand Atoll to take into account the effect of SFH twice.

3.1.12 Adjacency Suppression

Adjacency suppression is defined as the difference between the required C/I and the required C/A (C/A being the Carrierto Adjacent Intensity ratio). By default this is set to 18 dB following the standard. It is available in the Predictions folderproperties dialog window under the name Adjacent channel protection level.

The GSM standard requires this desired behaviour but does not specify any amplification level. It is recommended to be

sure that the physical equipment in the network support this value. The value of this parameter is used in the AFP whenextracting the interference caused by an adjacent channel, and in Atoll in interference and C/I studies.

It might be a good idea to use a safety margin for this parameter and set it to 16 dB, for example.

3.2 AFP Performance IndicatorsThe AFP can be used to generate differe

Documents

106090698 AFP Reference Guide E1