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The Evolution Of Untethered Communications Committee on Evolution of Untethered Communications Computer Science and Telecommunications Board Commission on Physical Sciences, Mathematics, and Applications National Research Council NATIONAL ACADEMY PRESS Washington, D.C. 1997
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Page ii NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance. This report has been reviewed by a group other than the authors according to procedures approved by a Report Review Committee consisting of members of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The National Academy of Sciences is a private, nonprofit, self-perpetuating society of distinguished scholars engaged in scientific and engineering research, dedicated to the furtherance of science and technology and to their use for the general welfare. Upon the authority of the charter granted to it by the Congress in 1863, the Academy has a mandate that requires it to advise the federal government on scientific and technical matters. Dr. Bruce Alberts is president of the National Academy of Sciences. The National Academy of Engineering was established in 1964, under the charter of the National Academy of Sciences, as a parallel organization of outstanding engineers. It is autonomous in its administration and in the selection of its members, sharing with the National Academy of Sciences the responsibility for advising the federal government. The National Academy of Engineering also sponsors engineering programs aimed at meeting national needs, encourages education and research, and recognizes the superior achievements of engineers. Dr. William A. Wulf is president of the National Academy of Engineering. The Institute of Medicine was established in 1970 by the National Academy of Sciences to secure the services of eminent members of appropriate professions in the examination of policy matters pertaining to the health of the public. The Institute acts under the responsibility given to the National Academy of Sciences by its congressional charter to be an adviser to the federal government and, upon its own initiative, to identify issues of medical care, research, and education. Dr. Kenneth I. Shine is president of the Institute of Medicine. The National Research Council was organized by the National Academy of Sciences in 1916 to associate the broad community of science and technology with the Academy's purposes of furthering knowledge and advising the federal government. Functioning in accordance with general policies determined by the Academy, the Council has become the principal operating agency of both the National Academy of Sciences and the National Academy of Engineering in providing services to the government, the public, and the scientific and engineering communities. The Council is administered jointly by both Academies and the Institute of Medicine. Dr. Bruce Alberts and Dr. William A. Wulf are chairman and vice chairman, respectively, of the National Research Council. Support for this project was provided by the Defense Advanced Research Projects Agency. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the sponsors. Library of Congress Catalog Card Number 97-80464 International Standard Book Number 0-309-05946-1 Copyright 1997 by the National Academy of Sciences. All rights reserved. Additional copies of this report are available from: National Academy Press 2101 Constitution Ave., NW Box 285 Washington, DC 20055 800-624-6242 202-334-3313 (in the Washington metropolitan area) http://www.nap.edu Printed in the United States of America
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Page iii COMMITTEE ON EVOLUTION OF UNITHERED COMMUNICATIONS DAVID J. GOODMAN, Rutgers University, Chair NORMAN ABRAMSON, ALOHA Networks, Inc. EUGENE CACCIAMANI, Hughes Network Systems JOEL ENGEL, Ameritech MARK EPSTEIN, QUALCOMM, Inc. BRUCE FETTE, Motorola, Inc. DOUGLAS C. FIELDS, United Parcel Service BEZALEL GAVISH, Vanderbilt University ANDREA GOLDSMITH, California Institute of Technology RANDY H. KATZ, University of California at Berkeley EDWIN A. KELLEY, Hughes Aircraft Company KAVEH PAHLAVAN, Worcester Polytechnic Institute CHARLES E. PERKINS, Sun Microsystems THEODORE RAPPAPORT, Virginia Polytechnic Institute JESSE RUSSELL, AT&T Laboratories
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Page iv COMPUTER SCIENCE AND TELECOMMUNICATIONS BOARD DAVID D. CLARK, Massachusetts Institute of Technology, Chair FRANCES E. ALLEN, IBM T.J. Watson Research Center JAMES CHIDDIX, Time Warner Cable JEFF DOZIER, University of California at Santa Barbara A.G. FRASER, AT&T Corporation SUSAN L. GRAHAM, University of California at Berkeley JAMES GRAY, Microsoft Corporation BARBARA J. GROSZ, Harvard University PATRICK M. HANRAHAN, Stanford University JUDITH HEMPEL, University of California at San Francisco DEBORAH A. JOSEPH, University of Wisconsin BUTLER W. LAMPSON, Microsoft Corporation EDWARD D. LAZOWSKA, University of Washington MICHAEL LESK, Bellcore DAVID LIDDLE, Interval Research BARBARA H. LISKOV, Massachusetts Institute of Technology JOHN MAJOR, QUALCOMM, Inc. DAVID G. MESSERSCHMITT, University of California at Berkeley DONALD NORMAN, Hewlett-Packard Company RAYMOND OZZIE, Rhythmix Corporation DONALD SIMBORG, KnowMed Systems LESLIE L. VADASZ, Intel Corporation MAJORY S. BLUMENTHAL, Director HERBERT S. LIN, Senior Staff Officer JERRY R. SHEEHAN, Program Officer ALAN S. INOUYE, Program Officer JON EISENBERG, Program Officer MARK E. BALKOVICH, Research Associate JANET BRISCOE, Administrative Associate LISA L. SHUM, Project Assistant SYNOD P. BOYD, Project Assistant
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Page v COMMISSION ON PHYSICAL SCIENCES, MATHEMATICS, AND APPLICATIONS ROBERT J. HERMANN, United Technologies Corporation, Co-chair W. CARL LINEBERGER, University of Colorado, Co-chair PETER M. BANKS, Environmental Research Institute of Michigan WILLIAM BROWDER, Princeton University LAWRENCE D. BROWN, University of Pennsylvania RONALD G. DOUGLAS, Texas A&M University JOHN E. ESTES, University of California at Santa Barbara MARTHA P. HAYNES, Cornell University L. LOUIS HEGEDUS, Elf Atochem North America, Inc. JOHN E. HOPCROFT, Cornell University CAROL M. JANTZEN, Westinghouse Savannah River Company PAUL G. KAMINSKI, Technovation, Inc. KENNETH H. KELLER, University of Minnesota KENNETH I. KELLERMANN, National Radio Astronomy Observatory MARGARET G. KIVELSON, University of California at Los Angeles DANIEL KLEPPNER, Massachusetts Institute of Technology JOHN KREICK, Sanders, a Lockheed Martin Company MARSHA I. LESTER, University of Pennsylvania NICHOLAS P. SAMIOS, Brookhaven National Laboratory CHANG-LIN TIEN, University of California at Berkeley NORMAN METZGER, Executive Director
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Page vii Preface In 1994, the Defense Advanced Research Projects Agency (DARPA) initiated the Global Mobile Information Systems (GloMo) program to apply advances in high-speed computation, signal processing, and miniaturization to mobile, wireless, multimedia information systems. The GloMo program is intended to develop the technologies that will enable military forces to carry out communication and computing tasks free of tethersthat is, cables to power sources or telecommunications networks. The concept of "untethered" communications unites mobile and wireless operations. In response to a request from DARPA, the Computer Science and Telecommunications Board (CSTB) of the National Research Council initiated a one-year study on untethered communications in July 1996. To carry out the study, the CSTB appointed a committee of 15 wireless-technology experts, including researchers, program managers, technology developers, and users working in industry and academia. The Committee on the Evolution of Untethered Communications was charged with advising DARPA on where to invest in information technology for mobile wireless systems. In particular, DARPA posed the following questions: • What will industry do on its own? When? • What are the military requirements and needs in mobile wireless information technology? • To what extent will commercial technology development support military needs?
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Page viii • Where can DARPA have the greatest impact in technology development or acceleration of technology development to support the military? This report presents the results of the CSTB study. In addition to answering DARPA's questions, the report provides a wealth of information of interest to a broader audience, suggesting that this is an era of unprecedented change, growth, and promise in untethered communications for both civilian and military users. The report explores the evolution of wireless technology, the often-fruitful synergy between commercial and military research and development efforts, and the technical challenges still to be overcome. Many examples of past ingenuity and future opportunities in wireless systems are noted. Although much of the information can be obtained piecemeal from other sources, it is rarely collected and analyzed in the manner found here. This is the CSTB's first report on wireless communications. The committee met four times during the one-year study time frame. The report is based on the committee's discussions with representatives of military organizations and commercial developers, background information from the literature, the expertise and judgment of individual committee members, and the deliberations of the committee as a group. The committee appreciates DARPA's sponsorship of this project and in particular acknowledges the participation of four individuals. Howard Frank, former director of the Information Technology Office, provided valuable advice to the CSTB prior to the initiation of the study. Barry Leiner, the original driving force behind the GloMo program, had the vision to appreciate how a comprehensive technology assessment could complement the specific research projects already under way. Kevin Mills, who later assumed leadership of the GloMo program, addressed the committee at the beginning of its study. Rob Ruth, who succeeded Mills, shared his insights into operational military needs and encouraged the committee and CSTB staff to support DARPA's needs to advance and refine GloMo planning. All of these individuals provided regular reminders of DARPA's strong interest in this study and helped motivate the committee's efforts to develop a comprehensive analysis that takes into account the context of military decision making. The committee also benefited enormously from the assistance of a number of anonymous reviewers. Reviewer comments and constructive criticisms helped the committee transform a voluminous early draft into a tighter, well-organized final report, calibrate the emphasis placed on a variety of topics, and clarify the analysis of specific issues. Finally, the committee appreciates the effort and energy devoted to this project by former CSTB staff member Paul Semenza, who organized the study and guided the writing and revision of this report, and former
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Page ix CSTB project assistant Gail Pritchard, who provided administrative and logistical support. It also is grateful for the yeoman efforts of Laura Ost, the writer-editor who worked with the committee during the summer of 1997 to improve the organization and written presentation of its ideas. David Goodman, Chair Committee on Evolution of Untethered Communications
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Page xi Contents EXECUTIVE SUMMARY 1 1 PAST, PRESENT, AND FUTURE 10 1.1 Overview 11 1.2 Historical Perspective 13 1.2.1 Communications Before the Industrial Age 13 1.2.2 Telegraphy 15 1.2.3 Early Wireless 15 1.2.4 Telephony 16 1.2.5 Communications Satellites 17 1.2.6 Mobile Radio and the Origins of Cellular Telephony 18 1.2.7 The Internet and Packet Radio 19 1.3 Military Wireless Systems and Research 21 1.3.1 Terrestrial Systems 21 1.3.2 Satellite Systems 24 1.3.3 Research Initiatives in Untethered Communications 25 126.96.36.199 Global Mobile Information Systems Program 26 188.8.131.52 Software-Defined Radio Research 28 184.108.40.206 Communications Systems Research 29 220.127.116.11 Radio Component Research 29 18.104.22.168 Small Unit Operations 30 22.214.171.124 Modeling and Simulation 30
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Page xii 1.4 Commercial Terrestrial Mobile Telephone Systems and Services 30 1.4.1 First-Generation Systems 31 1.4.2 Second-Generation Systems 33 1.4.3 Third-Generation Systems 38 1.5 Commercial Satellite Systems 41 1.6 Mobile Data Services 44 1.7 Wireless Local Area Networks 47 1.8 Comparison of International Research, Development, and Deployment Strategies 47 1.9 Summary and Report Organization 52 Notes 54 2 TECHNOLOGY LIMITS, TRADE-OFFS, AND CHALLENGES 56 2.1 Communication Link Design 58 2.1.1 Characteristics of the Wireless Channel 60 126.96.36.199 Path Loss 60 188.8.131.52 Shadow Fading 61 184.108.40.206 Small-Scale (Multipath) Fading 62 220.127.116.11 Interference 63 18.104.22.168 Satellite Channels 64 2.1.2 Capacity Limits of Wireless Channels 64 2.1.3 Modulation 65 2.1.4 Channel Coding and Link-Layer Retransmission 65 2.1.5 Countermeasures for Fading 67 22.214.171.124 Flat-Fading Countermeasures 67 126.96.36.199 Countermeasures for Frequency-Selective Fading 69 2.1.6 Channel Access 72 188.8.131.52 Fixed-Allocation Multiple Access 72 184.108.40.206 Demand-Assigned Multiple Access 73 220.127.116.11 Random Access 74 2.2 Network Issues 75 2.2.1 Architecture 75 18.104.22.168 Cellular System Design 76 22.214.171.124 Packet Radio System Design 78 2.2.2 Physical Resource Allocation 79 2.2.3 Interoperability 80 2.2.4 Routing and Mobility Management 81 126.96.36.199 Multihop Routing 81 188.8.131.52 Terminal Mobility 82 184.108.40.206 Wireless Overlay Networks 84
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Page xiii 2.2.5 Resource Discovery 85 2.2.6 Network Simulation and Modeling Tools 85 2.3 End-to-End System Design Issues 86 2.3.1 Application-Level Adaptation 86 2.3.2 Quality of Service 87 220.127.116.11 Approaches to Quality of Service 87 18.104.22.168 Transport-Layer Issues 91 2.3.3 Security 92 2.4 Hardware Issues 94 2.4.1 Antennas 95 2.4.2 Other Radio Components 97 22.214.171.124 Analog-to-Digital Converters 98 126.96.36.199 Digital Signal Processors 99 188.8.131.52 Filters 100 184.108.40.206 Radio Frequency Amplifiers 100 2.4.3 Portable Terminal Design 101 220.127.116.11 Displays, User Interfaces, and Input Devices 101 18.104.22.168 Processors 102 22.214.171.124 Batteries 102 126.96.36.199 Storage 103 2.5 Summary 103 Notes 104 3 COMMERCIAL-DEFENSE SYNERGY IN WIRELESS COMMUNICATIONS 108 3.1 Overview 109 3.2 Motivations for Commercial-Defense Synergy 111 3.2.1 Design Reuse 113 3.2.2 Production Learning Curve 114 3.2.3 Maintenance and Logistics Support 116 3.2.4 Training 117 3.2.5 Cycle Time 117 3.3 Barriers to Commercial-Defense Synergy 119 3.3.1 Risks of Dependence on Commercial Technologies 120 3.3.2 Trade-offs Between Cost and Complexity 121 188.8.131.52 Performance Issues 121 184.108.40.206 Quality and Testing 122 3.3.3 Infrastructure Differences 124 3.4 Designing Wireless Systems for Military Applications 125 3.4.1 Network Architecture 125 220.127.116.11 Network Design Issues 125 18.104.22.168 Bandwidth Requirements 129
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Page xiv 22.214.171.124 Source Coding 131 126.96.36.199 Highly Adaptive Systems 133 3.4.2 Security 134 188.8.131.52 Availability of Service 135 184.108.40.206 Confidentiality and Integrity 135 3.4.3 Multimode, Multiband Communications 137 220.127.116.11 Software-Defined Radios 138 18.104.22.168 Co-Site Interference 139 3.5 Defense Technology Policy Issues 141 3.5.1 Implications of Changes in Military Tactics 141 3.5.2 Rapid Infrastructure Deployment 142 3.5.3 Logistics 142 3.5.4 Preparing for Unsophisticated Adversaries 143 3.5.5 Preparing for Sophisticated Adversaries 144 3.6 Summary 144 Notes 145 4 CONCLUSIONS AND RECOMMENDATIONS 149 4.1 History and Challenges of Wireless Communications 149 4.2 Standards Development 152 4.3 Demonstration and Testing Rather Than Development 154 4.4 Procurement 155 4.5 Modeling and Simulation 156 4.6 Network Architecture 158 4.7 Network Security 159 4.8 High-Density Communications Platforms 160 4.9 Software Radios 162 4.10 Smart Antennas 162 4.11 Smart Waveforms 163 4.12 Filter Technology 164 4.13 Novel Components 165 BIBLIOGRAPHY 167 APPENDIXES A Biographies of Committee Members 175 B Briefers to the Committee 180 C Glossary 182