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//INTEGRAS/KCG/PAGINATION/WILEY/SSPA/FINALS_17-02-05/PRELIMS.3D 3 [112/12] 18.2.2005 5:15PM

Spread Spectrum andCDMAPrinciples and Applications

Valery P. Ipatov

University of Turku, Finland

and

St. Petersburg Electrotechnical University LETI, Russia

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Spread Spectrum and CDMA


Spread Spectrum andCDMAPrinciples and Applications

Valery P. Ipatov

University of Turku, Finland

and

St. Petersburg Electrotechnical University LETI, Russia


Copyright 2005 John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester,West Sussex PO19 8SQ, England

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Contents

Preface xi

1 Spread spectrum signals and systems 1

1.1 Basic definition 1

1.2 Historical sketch 5

2 Classical reception problems and signal design 7

2.1 Gaussian channel, general reception problem and optimal decision rules 7

2.2 Binary data transmission (deterministic signals) 11

2.3 M-ary data transmission: deterministic signals 17

2.4 Complex envelope of a bandpass signal 23

2.5 M-ary data transmission: noncoherent signals 26

2.6 Trade-off between orthogonal-coding gain and bandwidth 28

2.7 Examples of orthogonal signal sets 31

2.7.1 Time-shift coding 31

2.7.2 Frequency-shift coding 33

2.7.3 Spread spectrum orthogonal coding 33

2.8 Signal parameter estimation 37

2.8.1 Problem statement and estimation rule 37

2.8.2 Estimation accuracy 39

2.9 Amplitude estimation 41

2.10 Phase estimation 43

2.11 Autocorrelation function and matched filter response 43

2.12 Estimation of the bandpass signal time delay 46

2.12.1 Estimation algorithm 46

2.12.2 Estimation accuracy 48

2.13 Estimation of carrier frequency 53

2.14 Simultaneous estimation of time delay and frequency 55

2.15 Signal resolution 58

2.16 Summary 61

Problems 62

Matlab-based problems 68

3 Merits of spread spectrum 77

3.1 Jamming immunity 77

3.1.1 Narrowband jammer 78

3.1.2 Barrage jammer 80


3.2 Low probability of detection 82

3.3 Signal structure secrecy 87

3.4 Electromagnetic compatibility 88

3.5 Propagation effects in wireless systems 89

3.5.1 Free-space propagation 90

3.5.2 Shadowing 90

3.5.3 Multipath fading 91

3.5.4 Performance analysis 95

3.6 Diversity 98

3.6.1 Combining modes 98

3.6.2 Arranging diversity branches 100

3.7 Multipath diversity and RAKE receiver 102

Problems 106


4 Multiuser environment: code division multiple access 115

4.1 Multiuser systems and the multiple access problem 115

4.2 Frequency division multiple access 117

4.3 Time division multiple access 118

4.4 Synchronous code division multiple access 119

4.5 Asynchronous CDMA 121

4.6 Asynchronous CDMA in the cellular networks 124

4.6.1 The resource reuse problem and cellular systems 124

4.6.2 Number of users per cell in asynchronous CDMA 125

Problems 129


5 Discrete spread spectrum signals 135

5.1 Spread spectrum modulation 135

5.2 General model and categorization of discrete signals 136

5.3 Correlation functions of APSK signals 137

5.4 Calculating correlation functions of code sequences 139

5.5 Correlation functions of FSK signals 142

5.6 Processing gain of discrete signals 145

Problems 145


6 Spread spectrum signals for time measurement, synchronization

and time-resolution 149

6.1 Demands on ACF: revisited 149

6.2 Signals with continuous frequency modulation 151

6.3 Criterion of good aperiodic ACF of APSK signals 154

6.4 Optimization of aperiodic PSK signals 155

6.5 Perfect periodic ACF: minimax binary sequences 159

6.6 Initial knowledge on finite fields and linear sequences 161

6.6.1 Definition of a finite field 161

6.6.2 Linear sequences over finite fields 163

6.6.3 m-sequences 165

6.7 Periodic ACF of m-sequences 167

6.8 More about finite fields 170

vi Contents


6.9 Legendre sequences 172

6.10 Binary codes with good aperiodic ACF: revisited 174

6.11 Sequences with perfect periodic ACF 176

6.11.1 Binary non-antipodal sequences 177

6.11.2 Polyphase codes 179

6.11.3 Ternary sequences 181

6.12 Suppression of sidelobes along the delay axis 185

6.12.1 Sidelobe suppression filter 186

6.12.2 SNR loss calculation 187

6.13 FSK signals with optimal aperiodic ACF 192

Problems 194


7 Spread spectrum signature ensembles for CDMA applications 203

7.1 Data transmission via spread spectrum 203

7.1.1 Direct sequence spreading: BPSK data modulation and

binary signatures 203

7.1.2 DS spreading: general case 207

7.1.3 Frequency hopping spreading 212

7.2 Designing signature ensembles for synchronous DS CDMA 214

7.2.1 Problem formulation 214

7.2.2 Optimizing signature sets in minimum distance 215

7.2.3 Welch-bound sequences 223

7.3 Approaches to designing signature ensembles for asynchronous

DS CDMA 227

7.4 Time-offset signatures for asynchronous CDMA 232

7.5 Examples of minimax signature ensembles 235

7.5.1 Frequency-offset binary m-sequences 235

7.5.2 Gold sets 236

7.5.3 Kasami sets and their extensions 239

7.5.4 Kamaletdinov ensembles 241

Problems 243


8 DS spread spectrum signal acquisition and tracking 251

8.1 Acquisition and tracking procedures 251

8.2 Serial search 253

8.2.1 Algorithm model 253

8.2.2 Probability of correct acquisition and average number of steps 254

8.2.3 Minimizing average acquisition time 258

8.3 Acquisition acceleration techniques 261

8.3.1 Problem statement 261

8.3.2 Sequential cell examining 262

8.3.3 Serial-parallel search 263

8.3.4 Rapid acquisition sequences 264

8.4 Code tracking 265

8.4.1 Delay estimation by tracking 265

8.4.2 Earlylate DLL discriminators 267

8.4.3 DLL noise performance 270

Problems 273


Contents vii


9 Channel coding in spread spectrum systems 277

9.1 Preliminary notes and terminology 277

9.2 Error-detecting block codes 279

9.2.1 Binary block codes and detection capability 279

9.2.2 Linear codes and their polynomial representation 281

9.2.3 Syndrome calculation and error detection 284

9.2.4 Choice of generator polynomials for CRC 285

9.3 Convolutional codes 286

9.3.1 Convolutional encoder 286

9.3.2 Trellis diagram, free distance and asymptotic

coding gain 289

9.3.3 The Viterbi decoding algorithm 292

9.3.4 Applications 296

9.4 Turbo codes 296

9.4.1 Turbo encoders 296

9.4.2 Iterative decoding 299

9.4.3 Performance 300


9.5 Channel interleaving 302

Problems 302


10 Some advancements in spread spectrum systems development 307

10.1 Multiuser reception and suppressing MAI 307

10.1.1 Optimal (ML) multiuser rule for synchronous CDMA 307

10.1.2 Decorrelating algorithm 309

10.1.3 Minimum mean-square error detection 311

10.1.4 Blind MMSE detector 314

10.1.5 Interference cancellation 315

10.1.6 Asynchronous multiuser detectors 316

10.2 Multicarrier modulation and OFDM 316

10.2.1 Multicarrier DS CDMA 317

10.2.2 Conventional MC transmission and OFDM 318

10.2.3 Multicarrier CDMA 322


10.3 Transmit diversity and spacetime coding in CDMA systems 326

10.3.1 Transmit diversity and the spacetime coding problem 326

10.3.2 Efficiency of transmit diversity 327

10.3.3 Time-switched spacetime code 329

10.3.4 Alamouti spacetime code 331

10.3.5 Transmit diversity in spread spectrum applications 333

Problems 334


11 Examples of operational wireless spread spectrum systems 339

11.1 Preliminary remarks 339

11.2 Global positioning system 339

11.2.1 General system principles and architecture 340

11.2.2 GPS ranging signals 341

11.2.3 Signal processing 343

viii Contents


11.2.4 Accuracy 344

11.2.5 GLONASS and GNSS 344


11.3 Air interfaces cdmaOne (IS-95) and cdma2000 345

11.3.1 Introductory remarks 345

11.3.2 Spreading codes of IS-95 346

11.3.3 Forward link channels of IS-95 347

11.3.3.1 Pilot channel 347

11.3.3.2 Synchronization channel 347

11.3.3.3 Paging channels 348

11.3.3.4 Traffic channels 349

11.3.3.5 Forward link modulation 351

11.3.3.6 MS processing of forward link signal 352

11.3.4 Reverse link of IS-95 353

11.3.4.1 Reverse link traffic channel 353

11.3.4.2 Access channel 355

11.3.4.3 Reverse link modulation 355

11.3.5 Evolution of air interface cdmaOne to cdma2000 356

11.4 Air interface UMTS 357

11.4.1 Preliminaries 357

11.4.2 Types of UMTS channels 358

11.4.3 Dedicated physical uplink channels 359

11.4.4 Common physical uplink channels 360

11.4.5 Uplink channelization codes 361

11.4.6 Uplink scrambling 362

11.4.7 Mapping downlink transport channels to physical channels 363

11.4.8 Downlink physical channels format 364

11.4.9 Downlink channelization codes 365

11.4.10 Downlink scrambling codes 365

11.4.11 Synchronization channel 366

11.4.11.1 General structure 366

11.4.11.2 Primary synchronization code 366

11.4.11.3 Secondary synchronization code 367

References 369

Index 375

Contents ix


Preface

Spread spectrum and CDMA (code division multiple access) are up-to-date technologieswidely used in operational radar, navigation and telecommunication systems and play-ing a dominant role in the philosophy of the forthcoming generations of systems andnetworks. The amount of interest and effort invested in this encouraging area byresearch institutions and industry is gigantic and constantly growing, especially afterthe prominent commercial success of CDMA mobile telephone IS-95 and the use ofCDMA as the basic platform of 3G (and beyond) mobile radio. No wonder that thefundamentals of spread spectrum theory have assumed a solid place in the basicuniversity disciplines, while the detailed issues form the contents of numerous advancedcourses.

This book was conceived as a textbook for postgraduate and undergraduate students,and is also expected to be useful in training industry personnel and in the daily work ofresearchers. It is based on the experience and knowledge gained by the author duringmore than three decades of research activity in the area, as well as on his lecture courses.The original version of such a course started in the late 1970s at the Saint PetersburgElectrotechnical University LETI and has since been continually developed and mod-ernized, absorbing many state-of-the-art achievements and being presented to audiencesfrom Russia, the UK, Australia, China, Finland and other countries.

The intention of the author in preparing this book was to present the key ideas ofspread spectrum in the most general form equally applicable to both systems of collect-ing and recovering information (such as radar and navigation) and telecommunicationsystems or networks. The authors second concern was to link the material as tightly aspossible to classical signal and communication theory, which gives Chapter 2 a specialrole. The goal pursued everywhere was harmony between mathematical rigour andphysical transparency of some or other issue under discussion and the readers deepunderstanding of the reasons underlying the preference for spread spectrum andCDMA. The main question the author tried to answer in considering this or thatproblem was Why?i.e. why a designer may or should prefer one solution over others.

A particular emphasis of the book is designing spread spectrum signals. Manypopular books, although deservedly reputable, do not go into this problem beyondpresenting a brief survey of m-sequences and Gold codes. A reader may thereby geta false idea that nothing valuable exists outside this narrow range of attractive signalfamilies. In Chapters 6 and 7 we try to show that the designers freedom and the


multitude of alternatives are much broader and comprise many solutions potentiallycompetitive or clearly superior to those mentioned above.

In no way is this book intended to be looked upon as a manual introducing concreteoperational or projected systems and standards. However, some such systems give a richsoil to illustrate the theory and for this reason are frequently mentioned in the text asexamples of practical realization of spread spectrum principles. Another aid for betteradoption of the contents is offered by the problems at the end of every theoreticalchapter. Especially recommended are the Matlab-based problems, since their runninginvolves and develops investigatory skills and allows execution of an extensive experi-mental study.

The book is supported by the companion website on which instructors and lecturerscan find a solutions manual for the problems and matlab programming within the book,electronic versions of some of the figures and other useful resources such as a listof abbreviations etc. Please go to ftp://ftp.wiley.co.uk/pub/books/ipatov. If you haveany comments regarding the book please feel free to contact the author directly [email protected].

The author is sceptical enough to realize that no bookincluding this onecan betotally free of shortcomings. In our case the difficulties were greatly intensified by thenecessity of writing in a non-mother tongue. Nevertheless, the author is entirely respon-sible for all of the statements as well as the drawbacks of the book and is ready to acceptany constructive remarks or criticism.

I would like to express my sincere gratitude to the Department of InformationTechnology of the University of Turku for the friendly and creative atmosphere duringmy work in Finland. I address my special appreciation to Professor Jouni Isoaho andDr Esa Tjukanoff for their daily support and cooperation.

Many thanks to my colleagues Dr Nastooh Avessta and Dr Igor Samoilov, whokindly and carefully read the manuscript and, by way of innumerable discussions,helped in my endeavour to streamline it. The assistance of Jarkko Paavola and AlexeyDudkov in rectifying and debugging the manuscript can hardly be overestimated, too.

This is a good opportunity to emphasize my deepest gratitude to my dear teachersProfessor Yu. A. Kolomensky, Professor Yu. M. Kazarinov and ProfessorYu. D. Ulianitsky, who introduced me to the fascinating world of signals and noise,and were for decades my advisors in many professional as well as personal matters.

Warmest thanks to all my colleagues at the Department of Radio Systems of SaintPetersburg State Electrotechnical University LETI for a long-standing collaboration.

I bring my gratitude also to Sarah Hinton and her colleagues at John Wiley &Sons, Ltd for initiating this project and inspiring me in the course of writing, and myspecial thanks to the Nokia Foundation for the grant awarded to me at the final stage ofpreparing the manuscript.

And finally I cannot help mentioning my wifes patience and care during the year ofmy working on this book.

Valery P. Ipatov

xii Preface

//INTEGRAS/KCG/PAGINATION/WILEY/SSPA/FINALS_17-02-05/C01.3D 1 [16/6] 18.2.2005 5:15PM

1

Spread spectrum signals andsystems

1.1 Basic definition

The term spread spectrum is today one of the most popular in the radio engineeringand communication community. At the same time, it may appear difficult to formulatean unequivocal and precise definition distinctively separating the spread spectrumphilosophy from a non-spread spectrum one. Certainly, every expert in system designand every experienced researcher has an intuitive understanding of the core of the issue,butunlike a newcomersuch a person does not need to think about definitions inorder to respond successfully to his or her professional challenges. From the point ofview of the target audience of the book it seems worthwhile to dedicate some space toelaborating an appropriate explanation of what is implied in the following text under thespread spectrum concept.

Let us start with a reminder of the basics of spectral analysis. Every signal s(t) of finiteenergy can be synthesized as a sum of an uncountable number of harmonics whoseamplitudes and phases within the infinitesimal frequency range [f , f df ] aredetermined by a spectral density or spectrum ~ss(f ). It is the pair of inverse and directFourier transforms that expresses this fact mathematically:

st Z11

~ssf expj2ft df ~ssf Z11

st expj2ft dt 1:1

Due to the one-to-one correspondence between the signal representation in the timedomain s(t) and in the frequency domain ~ss(f ), we are able to switch arbitrarily betweenthese two tools, selecting the more convenient one for any specific task. To characterizethe size of the zones occupied by signal energy in the time and frequency domains we usethe notions of signal duration T and bandwidth W, respectively. A signal whose energy

Spread Spectrum and CDMA: Principles and Applications Valery P. Ipatov

2005 John Wiley & Sons, Ltd

spread spectrum and cdma - buch.de - bücher ...€¦ · spread spectrum and cdma ... 8 ds spread...

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