Spread Spectrum and CDMA

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1 Spread Spectrum and CDMA Principles and Applications Valery P. Ipatov University of Turku, Finland and St. Petersburg Electrotechnical University LETI, Russia

3 Spread Spectrum and CDMA

5 Spread Spectrum and CDMA Principles and Applications Valery P. Ipatov University of Turku, Finland and St. Petersburg Electrotechnical University LETI, Russia

6 Copyright Ó 2005 John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex PO19 8SQ, England Telephone (þ44) (for orders and customer service enquiries): Visit our Home Page on All Rights Reserved. No part of this publication may be reproduced, stored in a retrieval system or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, scanning or otherwise, except under the terms of the Copyright, Designs and Patents Act 1988 or under the terms of a licence issued by the Copyright Licensing Agency Ltd, 90 Tottenham Court Road, London W1T 4LP, UK, without the permission in writing of the Publisher. Requests to the Publisher should be addressed to the Permissions Department, John Wiley & Sons Ltd, The Atrium, Southern Gate, Chichester, West Sussex PO19 8SQ, England, or ed to permreq@wiley.co.uk, or faxed to (þ44) Designations used by companies to distinguish their products are often claimed as trademarks. All brand names and product names used in this book are trade names, service marks, trademarks or registered trademarks of their respective owners. The Publisher is not associated with any product or vendor mentioned in this book. This publication is designed to provide accurate and authoritative information in regard to the subject matter covered. It is sold on the understanding that the Publisher is not engaged in rendering professional services. If professional advice or other expert assistance is required, the services of a competent professional should be sought. Other Wiley Editorial Offices John Wiley & Sons Inc., 111 River Street, Hoboken, NJ 07030, USA Jossey-Bass, 989 Market Street, San Francisco, CA , USA Wiley-VCH Verlag GmbH, Boschstr. 12, D Weinheim, Germany John Wiley & Sons Australia Ltd, 33 Park Road, Milton, Queensland 4064, Australia John Wiley & Sons (Asia) Pte Ltd, 2 Clementi Loop #02-01, Jin Xing Distripark, Singapore John Wiley & Sons Canada Ltd, 22 Worcester Road, Etobicoke, Ontario, Canada M9W 1L1 Wiley also publishes its books in a variety of electronic formats. Some content that appears in print may not be available in electronic books. British Library Cataloguing in Publication Data A catalogue record for this book is available from the British Library ISBN (HB) Typeset in 10/12pt Times by Integra Software Services Pvt. Ltd, Pondicherry, India. Printed and bound in Great Britain by Antony Rowe Ltd, Chippenham, Wiltshire. This book is printed on acid-free paper responsibly manufactured from sustainable forestry in which at least two trees are planted for each one used for paper production.

7 Contents Preface xi 1 Spread spectrum signals and systems Basic definition Historical sketch 5 2 Classical reception problems and signal design Gaussian channel, general reception problem and optimal decision rules Binary data transmission (deterministic signals) M-ary data transmission: deterministic signals Complex envelope of a bandpass signal M-ary data transmission: noncoherent signals Trade-off between orthogonal-coding gain and bandwidth Examples of orthogonal signal sets Time-shift coding Frequency-shift coding Spread spectrum orthogonal coding Signal parameter estimation Problem statement and estimation rule Estimation accuracy Amplitude estimation Phase estimation Autocorrelation function and matched filter response Estimation of the bandpass signal time delay Estimation algorithm Estimation accuracy Estimation of carrier frequency Simultaneous estimation of time delay and frequency Signal resolution Summary 61 Problems 62 Matlab-based problems 68 3 Merits of spread spectrum Jamming immunity Narrowband jammer Barrage jammer 80

8 vi Contents 3.2 Low probability of detection Signal structure secrecy Electromagnetic compatibility Propagation effects in wireless systems Free-space propagation Shadowing Multipath fading Performance analysis Diversity Combining modes Arranging diversity branches Multipath diversity and RAKE receiver 102 Problems 106 Matlab-based problems Multiuser environment: code division multiple access Multiuser systems and the multiple access problem Frequency division multiple access Time division multiple access Synchronous code division multiple access Asynchronous CDMA Asynchronous CDMA in the cellular networks The resource reuse problem and cellular systems Number of users per cell in asynchronous CDMA 125 Problems 129 Matlab-based problems Discrete spread spectrum signals Spread spectrum modulation General model and categorization of discrete signals Correlation functions of APSK signals Calculating correlation functions of code sequences Correlation functions of FSK signals Processing gain of discrete signals 145 Problems 145 Matlab-based problems Spread spectrum signals for time measurement, synchronization and time-resolution Demands on ACF: revisited Signals with continuous frequency modulation Criterion of good aperiodic ACF of APSK signals Optimization of aperiodic PSK signals Perfect periodic ACF: minimax binary sequences Initial knowledge on finite fields and linear sequences Definition of a finite field Linear sequences over finite fields m-sequences Periodic ACF of m-sequences More about finite fields 170

9 Contents vii 6.9 Legendre sequences Binary codes with good aperiodic ACF: revisited Sequences with perfect periodic ACF Binary non-antipodal sequences Polyphase codes Ternary sequences Suppression of sidelobes along the delay axis Sidelobe suppression filter SNR loss calculation FSK signals with optimal aperiodic ACF 192 Problems 194 Matlab-based problems Spread spectrum signature ensembles for CDMA applications Data transmission via spread spectrum Direct sequence spreading: BPSK data modulation and binary signatures DS spreading: general case Frequency hopping spreading Designing signature ensembles for synchronous DS CDMA Problem formulation Optimizing signature sets in minimum distance Welch-bound sequences Approaches to designing signature ensembles for asynchronous DS CDMA Time-offset signatures for asynchronous CDMA Examples of minimax signature ensembles Frequency-offset binary m-sequences Gold sets Kasami sets and their extensions Kamaletdinov ensembles 241 Problems 243 Matlab-based problems DS spread spectrum signal acquisition and tracking Acquisition and tracking procedures Serial search Algorithm model Probability of correct acquisition and average number of steps Minimizing average acquisition time Acquisition acceleration techniques Problem statement Sequential cell examining Serial-parallel search Rapid acquisition sequences Code tracking Delay estimation by tracking Early late DLL discriminators DLL noise performance 270 Problems 273 Matlab-based problems 274

10 viii Contents 9 Channel coding in spread spectrum systems Preliminary notes and terminology Error-detecting block codes Binary block codes and detection capability Linear codes and their polynomial representation Syndrome calculation and error detection Choice of generator polynomials for CRC Convolutional codes Convolutional encoder Trellis diagram, free distance and asymptotic coding gain The Viterbi decoding algorithm Applications Turbo codes Turbo encoders Iterative decoding Performance Applications Channel interleaving 302 Problems 302 Matlab-based problems Some advancements in spread spectrum systems development Multiuser reception and suppressing MAI Optimal (ML) multiuser rule for synchronous CDMA Decorrelating algorithm Minimum mean-square error detection Blind MMSE detector Interference cancellation Asynchronous multiuser detectors Multicarrier modulation and OFDM Multicarrier DS CDMA Conventional MC transmission and OFDM Multicarrier CDMA Applications Transmit diversity and space time coding in CDMA systems Transmit diversity and the space time coding problem Efficiency of transmit diversity Time-switched space time code Alamouti space time code Transmit diversity in spread spectrum applications 333 Problems 334 Matlab-based problems Examples of operational wireless spread spectrum systems Preliminary remarks Global positioning system General system principles and architecture GPS ranging signals Signal processing 343

11 Contents ix Accuracy GLONASS and GNSS Applications Air interfaces cdmaone (IS-95) and cdma Introductory remarks Spreading codes of IS Forward link channels of IS Pilot channel Synchronization channel Paging channels Traffic channels Forward link modulation MS processing of forward link signal Reverse link of IS Reverse link traffic channel Access channel Reverse link modulation Evolution of air interface cdmaone to cdma Air interface UMTS Preliminaries Types of UMTS channels Dedicated physical uplink channels Common physical uplink channels Uplink channelization codes Uplink scrambling Mapping downlink transport channels to physical channels Downlink physical channels format Downlink channelization codes Downlink scrambling codes Synchronization channel General structure Primary synchronization code Secondary synchronization code 367 References 369 Index 375

13 Preface Spread spectrum and CDMA (code division multiple access) are up-to-date technologies widely used in operational radar, navigation and telecommunication systems and playing a dominant role in the philosophy of the forthcoming generations of systems and networks. The amount of interest and effort invested in this encouraging area by research institutions and industry is gigantic and constantly growing, especially after the prominent commercial success of CDMA mobile telephone IS-95 and the use of CDMA as the basic platform of 3G (and beyond) mobile radio. No wonder that the fundamentals of spread spectrum theory have assumed a solid place in the basic university disciplines, while the detailed issues form the contents of numerous advanced courses. 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 of researchers. It is based on the experience and knowledge gained by the author during more 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 Petersburg Electrotechnical University LETI and has since been continually developed and modernized, absorbing many state-of-the-art achievements and being presented to audiences from Russia, the UK, Australia, China, Finland and other countries. The intention of the author in preparing this book was to present the key ideas of spread spectrum in the most general form equally applicable to both systems of collecting and recovering information (such as radar and navigation) and telecommunication systems or networks. The author s second concern was to link the material as tightly as possible to classical signal and communication theory, which gives Chapter 2 a special role. The goal pursued everywhere was harmony between mathematical rigour and physical transparency of some or other issue under discussion and the reader s deep understanding of the reasons underlying the preference for spread spectrum and CDMA. The main question the author tried to answer in considering this or that problem 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. Many popular books, although deservedly reputable, do not go into this problem beyond presenting a brief survey of m-sequences and Gold codes. A reader may thereby get a false idea that nothing valuable exists outside this narrow range of attractive signal families. In Chapters 6 and 7 we try to show that the designer s freedom and the

14 xii Preface multitude of alternatives are much broader and comprise many solutions potentially competitive or clearly superior to those mentioned above. In no way is this book intended to be looked upon as a manual introducing concrete operational or projected systems and standards. However, some such systems give a rich soil to illustrate the theory and for this reason are frequently mentioned in the text as examples of practical realization of spread spectrum principles. Another aid for better adoption of the contents is offered by the problems at the end of every theoretical chapter. Especially recommended are the Matlab-based problems, since their running involves and develops investigatory skills and allows execution of an extensive experimental study. The book is supported by the companion website on which instructors and lecturers can 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 list of abbreviations etc. Please go to ftp://ftp.wiley.co.uk/pub/books/ipatov. If you have any comments regarding the book please feel free to contact the author directly at valery.ipatov@utu.fi. The author is sceptical enough to realize that no book including this one can be totally free of shortcomings. In our case the difficulties were greatly intensified by the necessity of writing in a non-mother tongue. Nevertheless, the author is entirely responsible for all of the statements as well as the drawbacks of the book and is ready to accept any constructive remarks or criticism. I would like to express my sincere gratitude to the Department of Information Technology of the University of Turku for the friendly and creative atmosphere during my work in Finland. I address my special appreciation to Professor Jouni Isoaho and Dr Esa Tjukanoff for their daily support and cooperation. Many thanks to my colleagues Dr Nastooh Avessta and Dr Igor Samoilov, who kindly and carefully read the manuscript and, by way of innumerable discussions, helped in my endeavour to streamline it. The assistance of Jarkko Paavola and Alexey Dudkov in rectifying and debugging the manuscript can hardly be overestimated, too. This is a good opportunity to emphasize my deepest gratitude to my dear teachers Professor Yu. A. Kolomensky, Professor Yu. M. Kazarinov and Professor Yu. 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 Saint Petersburg 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 my special thanks to the Nokia Foundation for the grant awarded to me at the final stage of preparing the manuscript. And finally I cannot help mentioning my wife s patience and care during the year of my working on this book. Valery P. Ipatov

15 1 Spread spectrum signals and systems 1.1 Basic definition The term spread spectrum is today one of the most popular in the radio engineering and communication community. At the same time, it may appear difficult to formulate an unequivocal and precise definition distinctively separating the spread spectrum philosophy from a non-spread spectrum one. Certainly, every expert in system design and every experienced researcher has an intuitive understanding of the core of the issue, but unlike a newcomer such a person does not need to think about definitions in order to respond successfully to his or her professional challenges. From the point of view of the target audience of the book it seems worthwhile to dedicate some space to elaborating an appropriate explanation of what is implied in the following text under the spread spectrum concept. Let us start with a reminder of the basics of spectral analysis. Every signal s(t) of finite energy can be synthesized as a sum of an uncountable number of harmonics whose amplitudes and phases within the infinitesimal frequency range [f, f þ df ] are determined by a spectral density or spectrum ~s(f ). It is the pair of inverse and direct Fourier transforms that expresses this fact mathematically: Z 1 sðtþ ¼ ~sðf Þ expðj2ftþ df 1 Z 1 ~sðf Þ¼ sðtþ expð j2ftþ dt 1 ð1:1þ Due to the one-to-one correspondence between the signal representation in the time domain s(t) and in the frequency domain ~s(f ), we are able to switch arbitrarily between these two tools, selecting the more convenient one for any specific task. To characterize the size of the zones occupied by signal energy in the time and frequency domains we use the notions of signal duration T and bandwidth W, respectively. A signal whose energy Spread Spectrum and CDMA: Principles and Applications Ó 2005 John Wiley & Sons, Ltd Valery P. Ipatov

Wideband TDD. WCDMA for the Unpaired Spectrum. Prabhakar Chitrapu. InterDigital Communications Corporation, USA. With a Foreword by Alain Briancon

Wideband TDD. WCDMA for the Unpaired Spectrum. Prabhakar Chitrapu. InterDigital Communications Corporation, USA. With a Foreword by Alain Briancon Wideband TDD WCDMA for the Unpaired Spectrum Prabhakar Chitrapu InterDigital Communications Corporation, USA With a Foreword by Alain Briancon Wideband TDD Wideband TDD WCDMA for the Unpaired Spectrum