Table Of ContentData
Transportation
and Protection
Applications of Communications Theory
Series Editor: R. W. Lucky,
AT & T Bell Laboratories
COMPUTER NETWORK ARCHITECTURES AND PROTOCOLS
Edited by Paul E. Green, Jr.
DATA TRANSPORTATION AND PROTECTION
John E. Hershey and R. K. Rao Yarlagadda
DEEP SPACE TELECOMMUNICATIONS SYSTEMS ENGINEERING
Edited by Joseph H. Yuen
DIGITAL PHASE MODULATION
John B. Anderson, Tor Aulin, and Carl-Erik Sundberg
ERROR-CORRECTION CODING FOR DIGITAL COMMUNICATIONS
George C. Clark, Jr., and J. Bibb Cain
FIBER OPTICS: Technology and Applications
Stewart D. Personick
FUNDAMENTALS OF DIGITAL SWITCHING
Edited by John C. McDonald
INTRODUCTION TO COMMUNICATION SCIENCE AND SYSTEMS
John R. Pierce and Edward C. Posner
MODELING AND ANALYSIS OF COMPUTER
COMMUNICATIONS NETWORKS
Jeremiah F. Hayes
MODERN TELECOMMUNICATION
E. Bryan Carne
OPTICAL FIBER TRANSMISSION SYSTEMS
Stewart D. Personick
PRACTICAL COMPUTER DATA COMMUNICATIONS
William J. Barksdale
TELECOMMUNICATIONS SWITCHING
J. Gordon Pearce
A Continuation Order Plan is available for this series. A continuation order will bring delivery of
each new volume immediately upon publication. Volumes are billed only upon actual shipment.
For further information please contact the publisher.
Data
Transportation
and Protection
John E. Hershey
The BDM Corporation
Boulder, Colorado
and
R. K. Rao Yarlagadda
Oklahoma State University
Stillwater, Oklahoma
Plenum Press • New York and London
Library of Congress Cataloging in Publication Data
Hershey, J. E. (John E.)
Data transportation and protection.
(Applications of communications theory)
Bibliography: p.
Includes index.
1. Data transmission systems. 2. Data transmission systems-Security measures. I.
Yarlagadda, R. K. Rao. II. Title. III. Series.
TK5105.H47 1986 005.7 86-15065
ISBN-13: 978-1-4612-9290-6 e-ISBN-13: 978-1-4613-2195-8
DOl: 10.1007/978-1-4613-2195-8
© 1986 Plenum Press, New York
Softcover reprint of the. hardcover 15t edition 1986
A Division of Plenum Publishing Corporation
233 Spring Street, New York, N.Y. 10013
All rights reserved
No part of this book 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
TO MY WIFE ANNA TO MY WIFE MARCElL
AND AND
OUR CHILDREN OUR CHILDREN
DAVID TAMMY
JOHN RYAN
JIMMY TRAVIS
(JOHN E. HERSHEy) (R. K. RAO YARLAGADDA)
Preface
A new breed of engineer is developing in our contemporary society. These
engineers are concerned with communications and computers, economics
and regulation. These new engineers apply themselves to data-to its pack
aging, transmission, and protection. They are data engineers.
Formal curricula do not yet exist for their dedicated development.
Rather they learn most of their tools "on the job" and their roots are in
computer engineering, communications engineering, and applied mathe
matics. There is a need to draw relevant material together and present it so
that those who wish to become data engineers can do so, for the betterment
of themselves, their employer, their country, and, ultimately, the world-for
we share the belief that the most effective tool for world peace and stability
is neither politics nor armaments, but rather the open and timely exchange
of information. This book has been written with that goal in mind.
Today numerous signs encourage us to expect broader information
exchange in the years to come. The movement toward a true Integrated
Services Digital Network (ISDN) is perhaps the clearest of these. Also, the
development offormal protocol layers reflects both a great deal of brilliance
and compromise and also the desire for a common language among data
engineers.
The first eight chapters of this book deal with some very basic mathe
matical "tools." The reader has undoubtedly been exposed to many of
them, but it is our experience that many engineers are deficient in at least
some of them. This is perhaps because many of the topics, when taught,
are not properly motivated or integrated into the larger picture. There is
also a wide assortment of useful tools that simply do not fit into any of the
extant curricula for electrical or computer engineering. We have therefore
assembled what, at first, may seem to be an unusual assortment of topics.
These topics were not chosen haphazardly but rather as a collection of
those concepts that have been of the greatest use to us as practicing data
vii
viii Preface
engineers. We do not treat the topics with rigor. Rather, what we hope to
impart is a "visceral feel" for the material. We hope to inculcate in the
reader a belief that real problems can be analyzed and solved by the
application of very powerful, "user-friendly" tools that are already out
there, just waiting to be used.
Chapter 1 deals with the issues of representing and manipulating data.
Uniradix and mixed-radix number systems are reviewed. The specific topics
chosen were selected to stimulate thought, to serve as the foundation for
later chapters, or both. The latter part of the chapter touches on the vast
and rich field of boolean functions. Most students never come to know and
appreciate the beauty of the mathematics that intertwines with the boolean
algebras-and it's a pity! But also of concern is the hazard that powerful
results may remain locked in the literature, unsprung and unapplied to real
problems.
Chapter 2 recounts some of the very powerful and straightforward
tools of combinatorics, the mathematics of counting and choice. These
topics themselves are preparatory for the chapter's latter half, which is a
modest refresher on discrete probability theory. Only a few concepts and
distributions are covered, but the sad fact remains that it is in probability
issues where engineers stumble most often and fall the hardest. The topics
were chosen so that the reader will be aware of some of the important
issues, learn a few very useful procedures, and be able to discern where it
is appropriate to apply the rudiments so learned.
Chapter 3 is an introduction to number theory. Number theory is "the
queen of mathematics" and a topic not usually introduced to engineers.
Recently, however, number theory has become an essential mathematical
tool for understanding and applying contemporary ideas and techniques in
signal processing and cryptography, and, once again, one need not be
thoroughly immersed in the topic to avail oneself of much of its power. In
this chapter, as in others, we have attempted to organize a useful subset of
the collective knowledge and still preserve some of the "spice" that has
proved to be so highly addictive to countless mathematicians throughout
the centuries, consuming their lives and their talents.
The next four chapters (4-7) are intended to compose a unit on matrices.
Almost a monograph in itself, the four chapters take the reader through
this vast and powerful field. Matrix representations and matrix operations
are probably the most valuable tools in the data engineering arts, yet, sadly,
most students seem to have little working knowledge in these disciplines.
These four chapters are designed to remedy this problem and not only
prepare the student for the latter chapters of the book but also lay the
groundwork for a variety of other courses of study.
Chapter 8, the final chapter on mathematical tools, is devoted to random
and pseudorandom sequences, the study of which is traditionally extremely
Preface ix
difficult for most engineers. And rightly SO! For it has only been recently
that theories have been unified and many of the related questions solved
or even properly posed. The subject needs study because, time and time
again, the same questions are asked, particularly in synchronization prob
lems. The Markov chain is introduced and reviewed because of its lawful
universality: It is easily and naturally employed quite often when all else
fails. The chapter concludes with a rather lengthy review of m-sequences
cast, for the most part, in a matrix formalism. The section is offered with
no apology or further motivation save for the observation that the m
sequence is one of the most prevalent, persistent, and, indeed, useful of
all of the semiarcane topics in communications theory. The reader
will not learn much high-powered math, but will be able to understand
and employ the m-sequence-or, if appropriate, reject a suggestion to
use it.
The final six chapters deal with selected techniques of data engineering
that rest on the tools which preceded them. It was very difficult to pick
topics out of the many that could have been chosen. Rather than attempting
to cover everything, we focused on six particular topics that have enjoyed
much publicity in the past decade.
The first of these chapters, Chapter 9, is devoted to source encoding.
As consumer sensitivity to the communications time-bandwidth product
continues to increase, it is more and more common to find attention paid
to source encoding. Certainly it is a logical place to start and, as we often
tell our students, "Your very first priority in data engineering is to understand
your source." The topics we picked for the chapter are traditional and
extremely powerful. The student should be able to employ them directly or
use them as a springboard for researching and devising more sophisticated
schema.
Chapter 10 is an introduction to cryptography, which has become one
of the most vital topics of the present decade. We divided the chapter into
three parts. The first deals with classical cryptography, specifically the Data
Encryption Standard (DES) promulgated by the National Bureau of Stan
dards in 1977. The DES is undergoing integration into many different data
architectures as public awareness and acceptance of a credible threat to
privacy grows. The second part of the chapter is concerned with so-called
two-key or public key cryptography (PKC). The study of PKC systems is
hampered by the technique's relative newness and the lack of any widely
accepted standards. It is important for the data engineer to be aware of
PKC systems, however, and we have also striven to create an awareness of
the importance of the interplay between cryptosystem and protocol-an
interplay which can have a tremendous, but often difficult to recognize,
impact on total system security. The final part of the chapter is devoted to
the important new technique of secret sharing systems or "shadow" systems,
x Preface
as they are sometimes called. All of these topics are prime candidates as
tools for computer security.
Chapter 11 is on synchronization, an extremely important part of data
communications. The techniques and concepts presented in this chapter
are probably most useful and immediately applicable to data links that use
the RF spectrum.
Chapter 12 introduces the data frame or packet concept. This concept
arose naturally as a response to the requirement to send data over a two-way
channel that was not error-free but yet not plagued with errors to the same
degree as, for example, a battlefield communications channel operating in
the presence of electronic warfare jamming.
Chapter 13 is an introduction to space division switching or connecting
networks. These networks are seeing great utilization not only in data
communications but also in signal processing and parallel and data flow
computing architectures. We believe that space division switching will
continue to grow in importance as the division between communications
and computation becomes increasingly blurred.
The final chapter provides a brief introduction to network architectures,
which must be designed to enhance network reliability or survivability.
These topics are of extreme interest to many national programs and commer
cial data services as well.
In writing these chapters, we continually asked ourselves two questions:
"What do I, as a practicing data engineer, need to know about this particular
topic?" and "What particular methods, algorithms, ways oflooking at issues,
and tricks have been most useful to me in my professional career?" We
were guided by the answers. The book that resulted is intended to be suitable
as a text for motivated upper-level undergraduate students and first-year
graduate students, and as a reference work.
John E. Hershey
R. K. Rao Yadagadda
Boulder and Stillwater
Acknowledgments
I express my thanks to the BDM Corporation and its farsighted management
team for providing me with a working atmosphere conducive to professional
development. I also thank my colleagues who, through the years, have
shared their wisdom and insights with me and helped me to grow profession
ally. Explicit thanks go to W. J. Pomper, H. P. Kagey, C.-L. Wu, H. M.
Gates, A. D. Spaulding, M. Nesenbergs, L. W. Pederson, M. Marcus, G.
Simmons, R. Kubichek, W. Hartman, and P. McManamon.
J.E.H.
I express my thanks to the Oklahoma State University and to the students
I have worked with. It has been a pleasure.
R.K.R.Y
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