Digital Transmission

Systems Third Edition

Digital Transmission

Systems Third Edition

DAVID R. SMITH George Washington University Department of Electrical Engineering and Computer Science

k4

S P R I N G E R SCIENCE+BUSINESS M E D I A , L L C

Library of Congress Cataloging-in-Publication Data

Smith, David R. (David Russell), 1945-Digital transmission systems / by David R. Smith.—3rd ed.

p. cm. Includes bibliographical references and index. ISBN 978-1-4613-4726-2 ISBN 978-1-4419-8933-8 (eBook) D O I 10.1007/978-1-4419-8933-8 1. Digital communications. I. Title. TK5103.7.S65 2003 621.382—dc22 2003058856

Copyright © 2004 by Springer Science+Business M e d i a N e w Y o r k Originally published by Kluwer Academic Publishers, N e w Y o r k in 2004 Softcover reprint of the hardcover 3rd edition 2004 A l l rights reserved. No part of this work may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, microfilming, recording, or otherwise, without written permission from the Publisher, with the exception of any material supplied specifically for the purpose of being entered and executed on a computer system, for exclusive use by the purchaser of the work.

Printed on acid-free paper.

To my wife, Carolyn, and our childrenChristy, Stacy, Allison, and Andrew

Preface

In the development of telecommunication networks throughout the world,digital transmission has now replaced analog transmission as the predom­inant choice for new transmission facilities. This trend began in the early1960s when the American Telephone and Telegraph Company first intro­duced pulse code modulation as a means of increasing capacity in their cableplant. Since that time, digital transmission applications have grown dramat­ically, notably in North America, Japan, and Europe. With the rapidity ofdigital transmission developments and implementation, however, there hasbeen a surprising lack of textbooks written on the subject.

This book grew out of my work, research, and teaching in digital trans­mission systems. My objective is to provide an overview of the subject. Toaccomplish this end, theory has been blended with practice in order to illus­trate how one applies theoretical principles to actual design and implemen­tation. The book has abundant design examples and references to actualsystems. These examples have been drawn from common carriers, manu­facturers, and my own experience. Considerable effort has been made toinclude up-to-date standards, such as those published by the ITU-T andITU-R, and to interpret their recommendations in the context of presentday digital transmission systems.

The intended audience of this book includes engineers involved in de­velopment and design, system operators involved in testing, operations, andmaintenance, managers involved in system engineering and system plan­ning, technical personnel in the IT industry, and instructors and studentsof digital communications courses. For engineers, managers, and operators,the book should prove to be a valuable reference because of its practical

Vll

VIII Preface

approach and the insight it provides into state-of-the-art digital transmissionsystems. In the classroom the book will allow the student to relate theoryand practice and to study material not covered by other textbooks. Theoret­ical treatments have been kept to a minimum by summarizing derivationsor simply stating the final result. Moreover, by consulting the extensive listof references given with each chapter the interested reader can explore thetheory behind a particular subject in greater detail. Even so, to gain from thisbook the reader should have a fundamental knowledge of communicationsystems and probability theory.

This third edition is an expanded and updated version of the second edi­tion. The tremendous growth in wireless and optical communication systemshas led to expanded treatments of these topics. Coverage of digital codingand modulation has been expanded, to include error correction, multipleaccess, and spread spectrum techniques. The development of wide area net­works is now given ample treatment. Finally, more problems and exampleshave been added to improve the book's utility as an academic textbook.The organization of this book's third edition follows a natural sequence oftopics:

• Chapter 1: Historical background and perspective on worldwide digitaltransmission systems

• Chapter 2: System design including services to be provided; parametersused to characterize performance; and means of allocatingperformance as a function of the service, media, and trans­mission equipment

• Chapter 3: Analog-to-digital-conversion techniques, starting with themost commonly used technique, pulse code modulation, andending with specialized voice and video coders

• Chapter 4: Time-division multiplexing using both asynchronous andsynchronous techniques; digital multiplex hierarchies

• Chapter 5: Baseband transmission including coding, filtering, equaliza­tion, scrambling, error correction, multiple access and spreadspectrum techniques

• Chapter 6: Digital modulation, starting with binary (two-level) formsand generalizing to M-ary and coded forms, showing compar­isons of error performance, bandwidth, and implementationcomplexity.

• Chapter 7: Digital cable systems for twisted-pair and coaxial metalliccable, showing design and performance

Preface IX

• Chapter 8: Fiber optic transmission systems, including optical sources,detectors, fibers, system design, and optical hierarchies

• Chapter 9: Digital radio systems including fixed and mobile applica­tions, with emphasis on propagation effects, radio equipmentdesign, and link calculations

• Chapter 10: Digital network timing and synchronization, describing fun­damentals of time and frequency and means of network syn­chronization

• Chapter 11: Testing, monitoring, and control techniques used to measureand maintain system performance and manage the network

• Chapter 12: Digital transmission over telephone and cable networks, in­cluding voice-channel modems, digital subscriber lines, andcable modems

• Chapter 13: Assessment of digital transmission networks and serviceswith emphasis on personal communications, wide area net­works, optical networks, and wireless networks

The material presented in Chapters 3 through 8 has been used for graduatecourses in digital communications at both George Washington Universityand George Mason University.

David R. Smith

Acknowledgments

I am pleased to acknowledge the support of my colleagues at George Wash­ington University. The staff at the Virginia Campus library was especiallyhelpful with the publication research necessary to create this book .

My students at George Washington University and George Mason Uni­versity used early versions of chapters of this book, for all three editions, andmade many helpful contributions. Participants in numerous short coursesoffered encouragement and suggested improvements. I am indebted to allthose who have taken my courses and at the same time helped me with thewriting of this book.

In writing a book of this size, I have made considerable use of the openliterature, especially the IEEE Transactions on Communications, the IEEECommunications Magazine and proceedings of various technical confer­ences. In describing standards applicable to digital transmission systems,I have extracted from the reports and recommendations of the ITU-T andITU-R.*

Finally, I wish to thank Kluwer Academic Publishers, and especially theencouragement and guidance of Alex Greene in creating the third edition.

' The reproduction in this book of material taken from the publications of the InternationalTelecommunications Union (ITU), Place des Nations, 1211 Geneva 20, Switzerland , has beenauthorized by the ITV. Complete recommendations from which I have extracted figures andtables can be obtained from the lTV.

xi

Preface

Acknowledgments

Contents

vii

xi

1 Introduction to Digital Transmission Systems1.1 Historical Background 11.2 Present-Day Digital Transmission 61.3 Digital Transmission Standards 111.4 Advantages of Digital Transmission 151.5 A Simplified Digital Transmission System 161.6 Summary 17

1

2 Principles of System Design2.1 General Plan 212.2 Transmission Services 222.3 Hypothetical Reference Circuits2.4 Performance Objectives 38

33

21

xiii

XIV Contents

2.5 Summary 77Problems 81

3 Analog-to-DigitalConversion Techniques 843.1 Introduction 843.2 Pulse Code Modulation 853.3 Differential PCM and Delta Modulation 1123,4 Adaptive Differential Pulse Code Modulation 1233.5 Subband Coding 1313.6 Transform Coding 1343.7 Comparison of Waveform Coders 1363.8 Voice Coders (Vocoders) 1443.9 Hybrid Coders 1503.10 Voice over IP 1553.11 Video Coding 1563.11 Summary 160

Problems 167

4 Time-Division Multiplexing 1774.1 Introduction 1774.2 Synchronous Multiplexing 1804.3 Asynchronous Multiplexing 2004,4 Plesiochronous Digital Hierarchies 2144.5 Statistical Multiplexing and Speech Interpolation 2364.6 Summary 246

Problems 250

5 Baseband Transmission 2585.1 Introduction 2595.2 Types of Binary Coding 2615.3 Power Spectral Density of Binary Codes 2695,4 Error Performance of Binary Codes 2755.5 Block Line Codes 2805.6 Pulse Shaping and Intersymbol Interference 2855.7 Multilevel Baseband Transmission 2895.8 Partial Response Coding 2915.9 Eye Patterns 3015.10 Equalization 3015.11 Data Scrambling Techniques 3095.12 Spread Spectrum 3165.13 Access Techniques 3235.14 Error Detection and Correction Coding 327

Contents xv

5.15 Summary 342Problems 346

6 Digital ModulationTechniques 3636.1 Introduction 3636.2 Binary Amplitude-Shift Keying (ASK) 3706.3 Binary Frequency-Shift Keying (FSK) 3746.4 Binary Phase-Shift Keying (BPSK) 3776.5 Comparison of Binary Modulation Systems 3806.6 M-ary FSK 3816.7 M-ary PSK 3866.8 Quadrature Amplitude Modulation (QAM) 3946.9 Offset QPSK, n/4 QPSK, and Minimum-Shift

Keying 3996.10 Quadrature Partial Response (QPR) 4086.11 Orthogonal Frequency Division

Multiplexing (OFDM) 4126.12 Trellis Coded Modulation 4156.13 Summary 424

Problems 429

7 Digital Cable Systems 4377.1 Introduction 4377.2 Cable Characteristics 4387.3 Regenerative Repeaters 4447.4 Clock Recovery and Jitter 4457.5 Crosstalk 4517.6 Performance of Digital Subscriber Lines 4547.7 Error Performance Tandem Repeaters 4557.8 Repeater Spacing in Multipair Cable Systems 4567.9 Repeater Spacing in Coaxial Cable Systems 4647.10 Implementation Considerations 4667.11 Summary 468

Problems 470

8 Fiber Optic Transmission Systems8.1 Introduction 4728.2 Fiber Optic Cable 4748.3 Optical Sources 4848.4 Optical Detectors 4898.5 Optical Amplifiers 4963.6 Wavelength-Division Multiplexing 501

472

XVI Contents

8.7 Fiber Optic Link Design 5088.8 SONET 5208.9 Synchronous Digital Hierarchy 5348.10 Summary 537

Problems 541

9 Digital RadioSystems 5479.1 Introduction 5479.2 Propagation 5489.3 Fading 5669.4 Diversity 5799.5 Antennas 5859.6 Frequency Allocations and Interference Effects 5909.7 Radio Link Calculations 5929.8 Summary 597

Problems 600

10 Network Timingand Synchronization 61210.1 Introduction 61210.2 Time Standards 61410.3 Frequency Sources and Clocks 61610.4 Network Synchronization Techniques 62910.5 Time and Frequency Dissemination Systems 64210.6 Examples of Network Synchronization Schemes 65210.7 Summary 656

Problems 660

11 Transmission SystemTesting, Monitoring, and Control 66211.1 Introduction 66211.2 Testing Techniques 66311.3 Performance Monitoring Techniques 67411.4 Fault Isolation 68111.5 Monitoring and Control Systems 68511.6 Digital Cross-Connect Systems 69311.7 Summary 669

Problems 702

12 DigitalTransmission Over Analog Networks 70512.1 Introduction 70512.2 Transmission Parameters 70612.3 Conditioning 71112.4 Voice-Band Modems 713

12.5 V.90 Modems 72012.6 Digital Subscriber Lines 72212.7 Cable Modems 73212.7 Summary 739

Problems 742

13 Digital Transmission Networks13.1 Introduction 74513.2 Private Networks 74613.3 Personal Communication Networks13.4 Wide Area Networks 76113.5 Optical Networks 77613.6 Summary 793

Problems 795

Index

751

Contents xvii

745

799