Wireless Digital Communications: Modulation and Spread Spectrum Applications

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Features

• explains the challenges and solutions related to adaptive power control of CDMA-spread spectrum systems and overall capacity issues.

• explores the fundamental issues and the most important criteria for increased data transmission rates and the capacity of wireless systems.

• shows the advantages and pitfalls of the major standards, as well as large- scale nonstandardized applications.

Description

Featuring the latest coverage of CDMA and TDMA systems, this is the only book in the wireless digital communications field which contains an in-depth analysis and description of practical R&D, design, and implementation sections, with an emphasis on the newest generations of modulation and spread spectrum systems. KEY TOPICS: Describes modern digital communications principles required for comprehension, analysis, design, advanced R&D, and maintenance/operation of present and future generations of digital wireless, cellular and mobile systems. Presents architectures, hardware and software designs, and solutions to common problems. Includes market data and forecasts of the world-wide growth of wireless systems. MARKET: For engineers, telecommunications managers, computer scientists, product planners, technical and market consultants, and all those interested in wireless communications.

Sample Content

Table of Contents

1. Introduction to Wireless, Cellular, Digital, PCS-Mobile Radio.

Summary. Mobile Communications: Evolution and Fundamentals. International Mobile Satellite, Low Earth Orbit, and Medium Altitude Orbit Satellite Frequency Bands. Personal Communication Systems (PCS) Universal Digital PCS. Standards: The Importance of National and International Standardization. Mobile Personal Computers (PC) and Personal Communication Systems (PCS). U.S. and World Cellular Markets.

Introduction to Digital Signal Processing (DSP) Techniques in Wireless Telephone and Broadcast Systems. Speech Coding Techniques for Audio and Voice. American and European Speech Codes.

Introduction. Fundamental Radio Propagation and System Concepts. Fundamentals of Antenna Gain. Propagation Characteristics. Models of Multipath-Faded Radio Signals. Instrumentation and Measurements for Laboratory and Field Tests. Delay-Spread Field Measurement Results. Industry Standards for Propagation Models. Problems.

Introduction. Baseband Transmission Systems. Modem Principles and Architectures. Interference. Definitions and Performance of Spectral and Power Efficiency. Performance in Complex Interference-Controlled Mobile Systems. Advantages of Coherent Demodulation over Noncoherent Systems. Advanced Modulation Methods. Adaptive Equalization for Frequency- Selective Faded and Delay-Spread Systems. Synchronization of Burst Demodulators: Carrier Recovery and Symbol Timing Recovery. Problems.

Error Control Requirements. Interleaving. Block Coding. Convolutional Coding. Price of Error Correction: Reduced Throughput? Word-Error Rate, False-Alarm Rate, and Probability of Bit Error. Repetition Transmission and Majority-Voting System: Concepts and Performance. Automatic Repeat Request.

Introduction. Fundamental Concepts of Spread-Spectrum Systems. Pseudo-noise Sequences. Performance of Direct- Sequence Spread-Spectrum Systems. Code Division Multiple Access (CDMA): Direct-Sequence (DS) and Frequency-Hopped (FH) Spread-Spectrum Systems. Frequency-Hopping Spread-Spectrum Systems. Synchronization of Spread-Spectrum Systems. Spread- Spectrum Applications in Cellular, PCS, and Mobile Communications. Problems.

Introduction. Concepts of Diversity Branch and Signal Paths. Combining and Switching Methods. Carrier-to-Noise and Carrier-to-Interference Ratio Performance Improvements. Average Pe Performance Improvement. Summary. Problems.

Introduction. Integration of GEO, LEO, and MEO Satellite and Terrestrial Mobile Systems. Personal Satellite Communications Programs.

Introduction. Access Methods: TDMA (TDD and FDMA); Spread-Spectrum Frequency-Hopping; Direct-Sequence CDMA and CSMA. Comparison of Linearly Amplified BPSK, DQPS and DQPSK and Nonlinearly Amplified (NLA) GMSK, GFSK, 4-FM, and FQPSK Radio Equipment (Coherent and Noncoherent). Radio Link Design of Digital Wireless Cellular Systems. Spectrum Utilization in Digital Wireless Mobile Systems. Capacity and Throughput (Message Delay) Study and Comparison of GMSK, GFSK, and FQPSK Modulated Wireless Systems. Time Division Multiple Access Wireless Cellular Systems. Code Division Multiple Access Spread-Spectrum Digital Cellular IS-95 System. Standards for Wireless Local Area Networks. Wireless Personal Communications. Problems.

Statistical Communication Theory: Terms, Definitions, and Concepts. Software Package of CREATE-1 (Disk Enclosed). Dr. Feher Associates Patented Filter, Digital Signal Processing, and Correlated Modulation/RF Amplification Means: GMSK, GFSK, FBPSK and FQPSK Implementations of Digcom, Inc. Licensed Technologies. Abbreviations and Acronyms.

Preface

You may be a self-motivated and ambitious engineer. Perhaps you are a student or professor. Regardless of your position or occupation, we have one goal in common: the desire or the need to be at the forefront of the fascinating field of wireless digital communications. Are you reading this preface to find out why you should read this book or what you will learn from it? How is this book unique? Should you use it as a reference text in your courses? Is it necessary to read complete sections, or is it effective to us e the book as a reference text? Should you use the CREATE-1 software diskette contained in this book? Please continue to read this preface and allow me to respond to the preceding questions.

My goal is to cooperate with you in the learning process. I wish to share my product and system design experience and enthusiasm in order to improve our joint understanding of wireless communications systems. The following quotation summarizes one vision of the importance and tremendous potential of wireless computer and phone systems as:

A new era of human communications where wireless technologies become information skyways, a new avenue to send ideas and masses of information to remote locations in ways most of us would never have imagined. Wireless hand-held computers and phones will deliver the world to our fingertips wherever we may be, with speed and flexibility.

William Clinton
President of the United States of America

Users opinions, understanding, and learning of wireless communications applications, particularly those of future communications customers, are of utmost importance to all of us. The following quotation illustrates the opinion and understanding of a 12-year-old:

Wireless Communications: Communications in our world is very important. We could not have as many things going on around this world as we do now. Police, for example, would have a much tougher job. They could not tell each other what is going on where and no dispatcher could tell them if there is a call. Communications makes it easier to build big buildings. They need to have it because then they could tell each other to do this or that. This world would be quite chaotic.

There are two types of communications. Wired communications and wireless communications. Wireless communications includes examples such as hand held CB radio, or a hand held cellular phone. Wired communications are like house phones, or faxes. Today I am going to be talking about Wireless Communications
Antoine-Kamilo Feher, Sixth-Grade Student, 1994
Pioneer Elementary School Report
Davis, California

The size of the annual cellular communications business in the United States has grown from $100 million to more than $30 billion in less than 10 years. Cellular, wireless-cable, and other telecommunications and broadcasting corporations are increasi ng the voice (telephony) capacity of their networks and are adding new data features so that customers with wireless modulation-demodulation devices (modems) in portable personal computers and workstations can access electronic mail and facsimile, wr itten, graphic, audio, and video messages. For the cellular industry, selection of the most appropriate access method is a challenging task. This task is focused on the choice between time division multiple access (TDMA) and spread-spectrum code divi sion multiple access (CDMA) architectures. Both of these access methods have the capability to increase the capacity of analog cellular systems by approximately 10 to 40 times. Already in 1995, more than five million cellular subscribers are using se cond-generation TDMA digital technology. Spread-spectrum systems have the promise of further increasing the capacity of TDMA-based cellular and wireless systems. Both of these architectures will be extensively used during the next decade.

The ultimate wireless information-communication advances will have to achieve truly unlimited capabilities and services. New satellite communications projects, such as the multibillion dollar IRIDIUM project of Motorola, which uses 66 satellites, cou ld guarantee the "anytime, anywhere" promise; however, whether it could reach a broad consumer market at a reasonable price is questionable.

The business fields affected by the wireless computer information and communications revolution are broad and challenging. To meet this challenge, managers, engineers, students, and professors will have to become very familiar with the technologies a nd system architectures described in this book. I do not know of another book of comparable scope and depth in the wireless digital communications field. Most modern digital communications techniques required for the comprehension, analysis, design, and maintenance of digital wireless systems are described in this book. An introductory overview of basic material is included. After the description of principles of operation and concepts we proceed with the study of modern techniques, architecture s, products, and standards. In-depth material on some of the most advanced digital modulation, spread-spectrum, and wireless radio engineering research, business developments, and worldwide applications is also included.

I assume that, to understand this book, you have a reasonable background in the foundations of basic communications engineering and technology. Selected chapters from this book have been taught at the University of California, Davis, in undergraduate and graduate courses. Sections of this text have also been presented at numerous professional short courses around the world to practicing engineers, managers, and system operators. The enthusiastic feedback received from hundreds of participants of these courses and from readers of my previously published books motivated me to formalize my notes and write this text. I believe that university professors will find educational and intellectually challenging material for senior undergraduate and graduate level courses.

If you are a practicing engineer and already have a generally broad knowledge of some of the topics covered in this volume, I hope that reading this text will motivate you to read the more advanced subjects. Even if you do not have the time, energy, or interest to study all of the derivations and mathematical and theoretical concepts, you could benefit from the more than 300 figures, graphs, tables, photographs, and original measurement results. Numerous comparisons of system specifications and standards of the 1990s should be of considerable value to the system architect and design engineer.

Thus this volume could be used for your in-depth studies or as a professional reference. It is my intent to motivate you to be inventive in this fas cinating field. In my courses I devote considerable time and effort to help students develop inventive, cost- efficient solutions. In some cases in this text I felt that I needed to become provocative in order to really challenge you and to uncover and encourage your inventive mind. Although the principal objective of this text is to provide general knowledge transfer and technology transfer to you, I believe that the general educational material should be complemented by research achieveme nts. Research, particularly research and development from my university and industry- based teams, is reported extensively in this book.

In several sections, combined modulation and nonlinearly amplified, power-efficient and spectrally efficient radio developments, implementations, and technology transfer and licensing activities for a broad family of patented GMSK, GFSK, FQPSK, FBPSK , and FQAM (Dr. Feher, Engineering Associates-Digcom, Inc., El Macero, California) wireless systems are described. These systems have a spectral efficiency advantage of more than 200% as compared with internationally standardized (GMSK) and Gaussian frequency shift keying (GFSK) systems, are compatible with GMSK systems, and have a radio frequency (or infrared) power efficiency advantage of more than 300% as compared with standardized /4-DQPSK and other conventional QPSK systems.

Unique features of this book include its pragmatic, down-to-earth treatment of some of the most complex and advanced digital wireless communications concepts. Physical layer (PHY) wireless system designs, advanced baseband processing, filtering, mo dulation, radio frequency amplification, efficient radio architecture, demodulation, and synchronization subsystems are given a comprehensive treatment for the first time in a book. Most important, critical interaction among these subsystems and essential joint system and hardware design, optimization, implementation, and testing of components is thoroughly discussed. In-depth mathematical and analytical treatment of radio propagation, cellular interference, digital modem, error-control, spread-spectrum, and diversity wireless systems is presented for the advanced reader; however, the busy professional could skip the derivations and use the final performance charts and tables.

For computer-aided analysis and design, our software package CREATE-1 is appended to the back cover. The software adds to the uniqueness and value of this book. It is a software package that you could install on your personal computer and meaningfully use with a minimal investment of time. This package enables you to design standard modulation, linear and nonlinear wireless systems and to create and analyze your own waveforms and modulated systems in a relatively complex linearly or nonlinearly amplified environment.

Chapter 1 is an introduction to cellular, digital personal communications systems and to the wireless mobile radio environment. Brief sections on the evolution of mobile communications and mobile communication fundamentals are followed by descriptions of the cellular concept and first, second, third, and subsequent generations of digital cellular and wireless systems. The importance of national and international standards and standardization efforts is highlighted. Tremendous market opportunities, demands, and forecasts are presented.

In Chapter 2, digital signal processing techniques for wireless telephone and broadcast systems are highlighted. We progress from the basics of pulse code modulation (PCM) toward the description of advanced vocoders and linear predictive coding conce pts and devices. The performance of reduced data rate (4.8 kb/s range) and of conventional 64 kb/s PCM systems is compared. Standardized American, European, and international speech coders and decoders (codecs) are highlighted.

In Chapter 3 you learn the most significant cellular engineering concepts and practical characteristics of radio propagation. After a basic treatment of radio propagation, including envelope fading, Doppler spread, time delay spread, shadowing, and path loss, antenna directional and omnidirectional fundamentals and radiation patterns are described. Propagation characteristics for free-space line-of- sight (LOS) and non-line-of-sight (NLOS) wireless systems are discussed. Frequently used empirical formulas and numerous path loss charts are presented. I provide a study of the mathematical model of multipath faded radio signals and include a simple theoretical delay spread bound. This delay spread bound is useful for a simple, effective predict ion of the maximal delay spread to be anticipated in a new system design, without the requirements for extensive and time- consuming field measurements. Conventional and original instrumentation and measurement setups, including the design and constru ction of low-cost delay spread field measurement apparatus, are described for the first time in a book. Extensive field measurement results of personal communications systems (PCS), cellular, and land-based mobile radio applications are presented in numerous charts. Industry standards for propagation models are also described. These standards highlight the differences for various bit- rate mobile applications.

Chapter 4 places a strong emphasis on the treatment of modem and combined modulation and radio engineering design techniques for wireless applications. This chapter presents original, in-depth coverage of modulation topics. Comprehensive study of pro pagation- interference and synchronization of modem and combined modem-radio equipment is provided, as these have a critical importance in the overall wireless radio and PHY architecture and performance. The wide range of modulation choices is beneficial, since it allows us to select and design the best new and emerging systems. The challenge we face is that we have to take a fair amount of time to study these choices in order to standardize these systems and to design compatible systems that can interact with previously standardized systems. After the study of essential principles of baseband premodulation, techniques of spectral density, eye diagrams, and Nyquist transmission theorems, we describe modem principles and architectures. These include coherent and noncoherent conventional bi nary phase shift keying (BPSK), quadrature phase shift keying (QPSK), and /4-DQPSK modems and radio systems that have been adopted as some of the major U.S. and Japanese standards. You will find it interesting and thought- provoking that I dare to qu estion the wisdom of standardizing /4- DQPSK and of GFSK modulated wireless systems in the United States and internationally. Some of the standardized modulated systems have substantially inferior performance as compared with existing alternatives. In hindsight, it is easy for me to criticize some of the specifications of U.S. and international standards in the cellular and wireless local area network fields, such as the Institute of Electrical and Electronic Engineers (IEEE) 802.11 standard. In this book you learn the strengths and pitfalls of the specifications of standardized systems, and you will be in a position to design better systems and standards and to create improved-performance systems that are compatible with previously standar dized systems. Detailed study of Chapter 4 in regard to QPSK, GMSK, FQPSK, and GFSK wireless systems operated in an interference environment is expected to lead to more efficient future system designs. Complex cellular interference environment, including in-band carrier and adjacent channel interference and their relation to the newest, most powerful modulated system performance, is described for the first time in a book. Fundamental and practical definitions of spectral and power efficiency, as well as specifications, are presented. A thorough study of advantages of coherent demodulation over noncoherent systems is also included in this chapter.

In Chapter 5, error correction and detection methods and techniques are highlighted. By adding redundancy to the information (customer or source) bits, errors induced by a noisy or interference-limited wireless system can be detected and corrected. B lock coding concepts and definitions, repetition codes, Hamming distance and codes, BCH, and Golay, Reed-Solomon, and convolutional coding methods are briefly described. In addition to bit-error-rate performance, also known as probability of error (P e), word-error-rate, false-alarm-rate, and throughput of wireless systems are studied. Performance studies of repetition codes and of majority voting systems, as well as automatic repeat request or query (ARQ), are reviewed.

In Chapter 6 you learn spread-spectrum system fundamentals and applications. These systems have been used in government and military systems for at least 50 years. Large-scale commercial applications, promoted by many industry and academic engineerin g leaders, were triggered by the far-sighted and innovative approach of the Federal Communications Commission (FCC) of the U.S. government, which authorized wireless applications in the popularly known ÒFCC-15Ó 900 MHz, 2.4 GHz, and 5.7 GHz bands. Th ese bands, also known as instrumentation scientific and medical (ISM) bands, initiated completely new business applications and engineering research and development. The FCC stipulated that as much as 1 watt of power can be transmitted in these bands if spread-spectrum techniques, frequency hopping, or direct sequencing is employed. In addition to the regulatory leadership of the FCC, Qualcomm, Inc., of San Diego, California, pioneered the introduction of CDMA spread-spectrum cellular and wirele ss systems. The founders of Qualcomm, including Drs. Viterbi and Jacobs, used extraordinary knowledge of communication theory, practical engineering and technology, and business entrepreneurship skills to demonstrate America's leadership in advanced CDMA communications technology. Industry leaders such as Air Touch (formerly PacTel), led by its vice-president and chief engineer, Dr. William Lee, embraced the CDMA concept and with the cooperation of an increasing number of corporations contribute d to the successful implementation and use of CDMA techniques, systems, and standards. Fundamental concepts of spread-spectrum systems, including direct- sequence spread-spectrum and frequency-hopped spread-spectrum systems, are described. Important pseudonoise (PN) sequences are reviewed. Performance of direct-sequence CDMA and frequen cy-hopped systems is analyzed in a complex interference environment. A comparison of frequency-hopped and direct-sequence CDMA spread-spectrum systems is presented, and some of their applications are illustrated.

In Chapter 9, additional spread-spect rum applications, developments, and standards are presented.

In Chapter 7, diversity techniques, particularly antenna diversity systems that are used extensively in wireless radio systems, are described. You learn that in a multipath Rayleigh fading environment various combining and switching diversity methods improve the probability of error versus carrier-to-noise performance by orders of magnitude. Advanced mathematical concepts and performance derivations are given. The theoretical part of the chapter is of particular benefit to the advanced research engineer and graduate student, whereas the numerous performance graphs and results are intended as an easily read reference for the practical-minded applications engineer.

Chapter 8 highlights satellite mobile communications and broadcasting systems. These systems have the unique capability of providing both multipoint-to-point, that is, multiple access, and point-to- multipoint, that is, broadcast, modes of transmittin g voice, high- quality audio, image, broadcast-quality television (TV), and other data simultaneously. This capability can be turned into a universal, global mobile network system application and service. The traditional geosynchronous (GEO) satellite systems have a two-hop radio propagation delay of approximately 500 ms. This amount of delay is considered excessive for several voice and data applications of toll- grade quality. The emergence of low earth orbit (LEO) and medium earth orbit (MEO) s atellite systems in the mid-1990s mitigated the impact of large-delay GEO satellites. Emerging personal wireless satellite communication programs such as the National Aeronautics and Space Administration (NASA) Advanced Communications Technology Sate llite (ACTS), the Canadian Advanced Satellite Program, Advanced Intelsat, TRW's Odyssey, and Motorola's IRIDIUM program are briefly described in Chapter 8, as are integrated satellite and terrestrial mobile systems and services.

Chapter 9 presents some of the most important principles and applications of integrated cellular and wireless systems. A brief review is made of access methods, including TDMA time division duplex (TDD) and frequency division duplex (FDD) methods, fr equency division multiple access (FDMA) methods, and spread-spectrum systems. A performance comparison of frequently used GMSK, GFSK, FQPSK, and /4- DQPSK systems is followed by radio link design of wireless cellular systems. Spectrum utilization of cellular systems, including geographical cochannel reuse and capacity/throughput of various systems, is studied. Mature standards, as well as emerging standards for cellular, mobile, and personal networks and wireless local area networks (WLANs), are presented.

Problems are listed at the end of several chapters, and worked-out examples are contained within the text. These, combined with the CREATE-1 software, provide educational and practical experience to motivate the reader to further explore this challen ging field. This book contains basic tutorial and advanced material. The copyright of my four previous Prentice Hall books has reverted to me, and I have permission of Prentice Hall to use material previously published in these books. The tutorial ma terial contained in Chapter 5 has been extracted predominantly from Dr. Tranter's chapter in Digital Communications Satellite Earth Station Engineering. I used extensively the results originally published by Dr. Hirade in Advanced Digital Communicati ons. I had to rely on the contributions and publications of hundreds of engineers who are active in this field, and I have quoted the reference source wherever possible and practical. In Chapters 4, 9, and Appendix 3 my filter, DSP, GMSK, GFSK, FBPSK, and FQPSK patents and inventions are also described. It is a real challenge to produce a "high-tech" book within a reasonable time limit in a very rapidly evolving field. Within my constraint of time, I did my best to write an authoritative and comprehensive book. I hope that you will be motivated and challenged and that you may even "fall in love" with this fascinating field as I have throughout the last years. For myself, the largest professional gratification I can receive is to see this book contribute to engineering knowledge and achievements and to be able to foster worldwide development of digital wireless communications.

Dr. Kamilo Feher, Fellow, IEEE Kamilo Feher
Professor, Electrical and Computer Engineering Lake Tahoe, California
University of California, Davis March, 1995
Davis, CA 95616
President, Dr. Feher Associates-Digcom, Inc.
FQPSK Consortium & Consulting, El Macero, CA 95618

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