Table Of ContentPERFORMANCE ENHANCEMENTS IN A FREQUENCY HOPPING
GSM NETWORK
Performance Enhancements in a
Frequency Hopping GSM Network
by
ThomasToftegaard Nielsen
Aalborg University, CPK
ERICSSON Telebit
and
JeroenWigard
Aalborg University, CPK
NOKIA Networks
KLUWER ACADEMIC PUBLISHERS
NEW YORK, BOSTON, DORDRECHT, LONDON, MOSCOW
eBookISBN: 0-306-47313-5
Print ISBN: 0-792-37819-9
©2002 Kluwer Academic Publishers
New York, Boston, Dordrecht, London, Moscow
All rights reserved
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Contents
PREFACE xi
ACKNOWLEDGEMENTS xiii
1 INTRODUCTION 1
1. Evolution of Digital Systems 1
2.Performance of a Mobile Network 3
3.The aim of the book 5
2 PERFORMANCEENHANCING STRATEGIES AND EVALUATION
METHODS 7
1. RadioPerformanceEnhancements 7
1.1Engineering of the Network Infrastructure 8
1.2Radio Interface Channel Allocation Techniques 10
1.3Techniques to Limit the Influence of Interference 13
1.4Data Services for GSM 15
1.5Closing Comments on Performance Enhancements 16
2. Computer Aided GSM network Design 16
2.1The Simulation Tool 17
3. C lassic Traffic Theory 18
v
vi Performance Enhancements in a Frequency Hopping GSM Network
4.Network Field Trials 18
3.A BRIEF INTRODUCTION TO THE GSM SYSTEM 19
1.GSM System Structure 19
2.Multiple Access Scheme in GSM 20
3.Channel Types in GSM 21
4.Mapping Logical to Physical Channels 23
5.Modulation Scheme in GSM 24
6.Typical Cell Architecture 25
7.Measurement Reporting in GSM 26
8.Frequency Hopping in GSM 27
9.Discontinuous Transmission in gsm 29
10. The Dropped Call Algorithm 30
4. LINK MODELLING AND LINK PERFORMANCE 31
1. TheGSMLink 31
1.1TheChannelCoding 33
1.2Interleaving 34
2.The GSM Link Simulator 35
2.1 Structure of the Link Simulator 35
2.2Output Parameters from the Link Simulator 36
3. Influence of Frequency Hopping on the Link Performance 37
3.1Aim of Frequency Hopping 37
3.2Link Simulation Reference Conditions 39
3.3Link Simulation Results 39
3.4Performance Comparison to Existing GSM Mobiles 43
4. Predicting the BER/FERwith FH 43
4.1The FER/BER Prediction Method 44
4.2Accuracy of the BER/FER Prediction Method 50
Preface vii
5.Summary and Conclusions 51
5. COMPUTER AIDEDNETWORKDESIGN 53
1.Introduction to Computer Aided Network Design 53
2.Network Modelling by CAPACITY 54
2.1 The General Program Structure 54
3.Available Output Parameters 61
4.Dropped Call Algorithm comparison 62
5.Accuracy of simulation results 64
6.Default simulation Parameters 65
6.INFLUENCE OF FH ON A GSM SYSTEM 67
1. Capacity Limits of a FH GSM Network 67
1.1Defining Coverage 69
1.2Determining the Hard Blocking 69
1.3Determining the Soft Blocking 71
2.Network Simulation Results 75
2.1 Introduction to the Network Simulations 75
2.2The CAPACITY Network Simulation Results 75
2.3Alternative Network Topologies 80
3.Interaction between Network Quality Parameters 84
3.1 Simulations on Dropped Calls versus RXQUAL 84
3.2Live Network Measurements on Dropped Calls versus RXQUAL 85
3.3FER on the SACCH versus FER on the TCH 86
4. Using Frequency Hopping in Band Limited One Layer Networks 88
4.1The Basic Problem 88
4.2The MAIO-Management Concept 89
4.3Soft Capacity versus MAIO-Management 92
4.4Network Simulation Results using CAPACITY 93
4.5Concluding Remarks on MAIO-Management 94
5. Exploiting Frequency Hopping in a LIVE Network 95
5.1 Introduction 96
5.2Frequency Hopping Trial Results 97
viii Performance Enhancements in a Frequency Hopping GSM Network
5.3Summary on Live Frequency Hopping Trial 101
6.Summary and Conclusions 102
7. POWER CONTROL AND DTX IN A FH GSM SYSTEM 103
1.An introduction to power control 104
1.1Previous Work Concerning Power Control 105
1.2The Potential Gain from Power Control 106
2.A Brief Introduction to Discontinuous Transmission 109
3. The GSM Power Control Algorithm 110
3.1Introduction 110
3.2The Simplified Power Control Algorithm 113
3.3Performance of the Simplified PC Algorithm 115
3.4NetworkSimulations of the GSM PC Algorithm 121
3.5Trial Results of Downlink PowerControl and DTX
in a FH Network 133
4. DiscontinuousTransmissioninGSM 137
4.1The Basic Functionality of DTX in GSM 137
4.2RXQUAL Estimation Accuracy with DTX 138
4.3The Gain From DTX in a FH GSM Network 146
5. Conclusion on Power Control and DTX in a FH GSM network 146
8. HANDOVER ALGORITHMS IN A GSM SYSTEM 149
1.Introduction 149
1.1Handover Basics 149
1.2Literature Study 151
1.3Chapter Outline 155
2.The Simulation Model 155
2.1Modelling and Implementation in CAPACITY 155
2.2Simulation Results 160
2.3Live Network Measurements 164
2.4Frequency Hopping in Relation to Handovers 166
3. Theoretical Handover Modelling 168
3.1 Simple theoretical analysis of handover probability 168
3.2Birth Dead Model 172
Preface ix
3.3Multiple cells scenario 174
3.4Mobility Dependency 177
4. Handover Improvements 179
4.1Channel Reservation for Handover Traffic 179
4.2Channel Reservation Combined with Queuing 184
4.3Traffic Reason Handover 189
4.4 Dynamic HO Margin 197
5. Summary on handover algorithms in a gsm network 201
9.COMBINING REUSE PARTITIONING AND FREQUENCYHOPPING
IN A GSM NETWORK 203
1.Introduction to Frequency Reuse Partitioning 204
1.1Reuse Partitioning in a Cellular Communication System like GSM 205
1.2Previous Frequency Reuse Partitioning Studies 206
1.3Idealised Frequency Reuse Partitioning Considerations 207
1.4Practical Considerations Concerning ReusePartitioning 212
2.The Intelligent Underlay-Overlay Algorithm 212
2.1Estimating C/I in GSM 214
2.2Practical Frequency Planning Difficulties of IUO 216
2.3Estimating the Hard Blocking Limit of an IUO Cell 217
2.4 Remarks on the IUO Algorithm 226
3.The Capacity Enhancement Proposal 227
4. Preliminary Simulation Studies of IUO withFrequency Hopping 230
4.1Problems Discovered with the Original IUO Algorithm and FH 230
4.2Improvements to Enhance the IUO Algorithm 230
5.The Improved IUO Algorithm 231
5.1 Improved Handover Characteristics with IUO 232
5.2 Hard Blocking Traffic Model of the Improved IUO 233
6.Implementation of IUO in CAPACITY 239
6.1The IUO Input Parameter List 240
6.2Implementation of the Handover Algorithm 240
7. Outline for CAPACITY Simulations Concerning IUO 243
7.1 IUO Parameter Settings 244
7.2Network Parameter Settings 244
x Performance Enhancements in a Frequency Hopping GSM Network
8. CAPACITY Simulation Results 246
8.1 Simulations of the Functionality of IUO and FH 247
8.2CAPACITY Simulations of IUO and Baseband FH 254
9. Live Network Trials Related to the combination of IUO and FH 261
10. Concluding Comments on the Combination of IUO and FH for GSM 262
10.1 Analytical Calculations and Network Simulations 262
10.2 Ideas for Future Improvements of IFH 265
10. FREQUENCY PLANNING OF FREQUENCY HOPPING NETWORKS 267
1.Introduction 267
1.1The Frequency Planning Problem 268
1.2Existing Techniques 271
1.3Chapter Outline 274
2.The Frequency Allocation Principle 274
2.1Propagation Prediction Input 275
2.2Frequency Planning in FH Networks 275
2.3Broadcast Channels versus Traffic Channels 277
2.4The Frequency Planning Method 279
3. Performance of theFHPlanningTool 297
3.1Performance of the Search Algorithm 297
3.2Evaluation Method for a Frequency Plan with Frequency Hopping 303
3.3Results from Live Network 307
4. Other Parameters to be planned 308
4.1Frequency Hopping Parameters 308
4.2Training Sequences 309
5.Conclusions and Improvements 312
5.1 Summary 312
5.2Future Improvements 314
REFERENCES 317
INDEX 331
Preface
Mobile communications has during the last couple of years undergone an
explosive progress in terms of number of subscribers as well in the effort put into
related research. The subscriber increase has lead to requirements concerning better
network quality and highernetworkcapacity in order for the operators to be able to
handle the requests. During the last 5 years a substantial amount of resources has
therefore been put into enhancement to existing mobileradio systems like GSM.
This book provides a detailed description on how to enhance the BSS part of a
GSM network using frequency hopping. The intention is to present a newly
developed method for modelling a frequency hopping GSM network as well as to
show the performance gains of different capacity enhancements. Everything is done
within the scope of enhancing the performance of a frequency hopping GSM
network.
One of the main issues in this book is to describe a new way of designing radio
system performance enhancement features by using detailed computer network
modelling. It has been done by combining link level and system level simulations to
be able to achieve a high resolution in time. The link simulator developed and
exploited provides a link performance model of the slow associated control channel
(SACCH) as well as the full rate traffic channel (TCH/FS) in GSM. The network
simulator, able to model the BSS part of the GSM network, is described and used
extensively. Effects like cell structure, handover and power control algorithms,
discontinuous transmission, traffic distribution, radio propagation and other network
functionality’s are modelled. In the book a model of the gain from frequency
hopping is described and used for link as well as for system level calculations.
Correspondingly the book treats the issue of measuring network quality in a
frequency hopping network using simulations as well as real data. Alternative ways
of exploiting frequency hopping using MAIO-management are also proposed.
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