Applications of Communications Theory – serie

There are many valuable and useful books on electrical communication (References 1-5 are some examples), but they have certain disadvantages for the beginner. The more advanced books present some things in a basic way, but they are very narrow for an introduction to communica­ tion. The introductory books are broader but still narrow by our stan­ dards. Further, they often pick things out of thin air rather than derive them. This book is aimed at giving the beginner a basic understanding of a wide range of topics which are essential in communication systems. These include antennas and transmission, thermal noise and its consequences, Fourier transforms, modulation and noise, sampling and pulse code modulation, autocorrelation and power spectrum, optimum filtering, gauss­ ian noise and errors in digital transmission, data transmission, limits on data rate including information theory and quantum limits, and source encoding. We have not included communications traffic, switching, and multiplexing, nor protocols for digital and computer communications. For these, Reference 6 is excellent. In general, our book does not discuss the circuits used for communication or the physics of radio propagation. We assume that these will be taught in specialized courses, but such courses are not prerequisites for this one. Chapter 1 introduces the transmission formula or antenna equation and antenna directivity. Only a very basic sophomore physics knowledge of electromagnetic theory is assumed. The radar equation is also treated.

The motivation for this book stems from an early exposure to the book Ap­ plied Mechanics by John Perry. Professor Perry strove to encourage his readers to understand the applications and use of mathematics in engineering with­ out insisting that they become immersed in pure mathematics. The following text uses this approach to the application of telecommunications switching. Readers wishing to study the derivation and proof of formulas will be able to do so using relevant references. The existence of low-cost programmable calculators frees practicing engineers from much laborious calculation, allowing more time for creative design and application of the art. The reader should not need to be able to derive formulas in order to apply them just as, to quote Professor Perry, "He should not have to be able to design a watch in order to tell time ... The material for this book has been drawn from my own experience in the field. Inevitably, however, I have used CCITT and Bell System publications for references and in some cases quotation, and I gratefully acknowledge permission for their use. I am also grateful to Stromberg Carlson Corporation for their earlier encour­ agement and support without which this book would not have been possible. Thanks are also due to Fred Hadfield for his advice and assistance in the preparation of the many figures and to my wife Ada for her support and patience as I pursued the demanding but interesting task of producing the text.

Error-correction coding is being used on an almost routine basis in most new communication systems. Not only is coding equipment being used to increase the energy efficiency of communication links, but coding ideas are also providing innovative solutions to many related communication problems. Among these are the elimination of intersymbol interference caused by filtering and multipath and the improved demodulation of certain frequency modulated signals by taking advantage of the "natural" coding provided by a continuous phase. Although several books and nu­ merous articles have been written on coding theory, there are still noticeable deficiencies. First, the practical aspects of translating a specific decoding algorithm into actual hardware have been largely ignored. The information that is available is sketchy and is widely dispersed. Second, the information required to evaluate a particular technique under situations that are en­ countered in practice is available for the most part only in private company reports. This book is aimed at correcting both of these problems. It is written for the design engineer who must build the coding and decoding equipment and for the communication system engineer who must incorporate this equipment into a system. It is also suitable as a senior-level or first-year graduate text for an introductory one-semester course in coding theory. The book U"Ses a minimum of mathematics and entirely avoids the classical theorem/proof approach that is often seen in coding texts.

This book is an outgrowth of a course given by the author for people in industry, government, and universities wishing to understand the implica­ tions of emerging optical fiber technology, and how this technology can be applied to their specific information transport and sensing system needs. The course, in turn, is an outgrowth of 15 exciting years during which the author participated in the research and development, as well as in the application, of fiber technology. The aim of this book is to provide the reader with a working knowledge of the components and subsystems which make up fiber systems and of a wide variety of implemented and proposed applications for fiber technology. The book is directed primarily at those who would be users, as opposed to developers, of the technology. The first half of this book is an overview of components and subsys­ tems including fibers, connectors, cables, sources, detectors, receivers, transmitters, and miscellaneous components. The goal is to familiarize the reader with the properties of these components and subsystems to the extent necessary to understand their potential applications and limitations.

The last ten years have seen a great flowering of the theory of digital data modulation. This book is a treatise on digital modulation theory, with an emphasis on these more recent innovations. It has its origins in a collabor­ ation among the authors that began in 1977. At that time it seemed odd to us that the subjects of error-correcting codes and data modulation were so separated; it seemed also that not enough understanding underlay the mostly ad hoc approaches to data transmission. A great many others were intrigued, too, and the result was a large body of new work that makes up most of this book. Now the older disciplines of detection theory and coding theory have been generalized and applied to the point where it is hard to tell where these end and the theories of signal design and modulation begin. Despite our emphasis on the events of the last ten years, we have included all the traditional topics of digital phase modulation. Signal space concepts are developed, as are simple phase-shift-keyed and pulse-shaped modulations; receiver structures are discussed, from the simple linear receiver to the Viterbi algorithm; the effects of channel filtering and of hardlimiting are described. The volume thus serves well as a pedagogical book for research engineers in industry and second-year graduate students in communications engineering. The production of a manageable book required that many topics be left out.

When we were first approached by Dr. Lucky to write this book we were very enthusiastic about the prospect, since we had contemplated a similar project for quite some time. The difficulty lay in how best to digest the vast amount of data on optical propagation, reduce it to a book of manageable size, and simultaneously form the transition from the physics of propagation to the engineering of optical channels. This is the intent of Optical Channels. In accomplishing our goal it was necessary to condense the material on optical propagation and, in so doing, we have left a large amount to be handled via references. We have tried to make these decisions in a consistent manner so that the book will be uniform in its treatment of this topic. We identify four channels for consideration: the free-space channel, which: is characteristic of a tranquil atmosphere or a space-to-space link; the turbulent channel, which is characteristic of the atmospheric channel; the scatter channel in two forms, clouds and water; and the fiber optic channel. For each of these channels we have tried to reduce the applicable propagation theory to a level that can be used for engineering design. This has been done by example, but here again decisions had to be made on which examples to present. We have not tried to present any material on optical components and consequently other references on engineering would be necessary to supplement this book.

Since the publication of the first edition of Fundamentals of Digital Switching in 1983, there has been substantial improvement in digital switching technology and in digital networks. Packet switching has advanced from a low-speed data-oriented switching approach into a robust broadband technology which supports services ranging from low-speed data to video. This technology has eclipsed the flexibility of circuit switching. Fiber optic cable has advanced since the first edition and has substantially changed the technology of transmission. to research in optical devices to find a still better means of This success has led switching. Digital switching systems continue to benefit from the 100-fold improvement in the capabilities of semiconductor devices which has occurred during the past decade. The chip industry forecasts a similar escalation in complexity during the next 10 years. Networks of switching systems have changed due to regulatory policy reform in many nations, including the breakup of the Bell System in the United States, the introduction of new types of carriers in Japan, competition in the United Kingdom, and a reexamination of public policy in virtually all nations. Standards bodies have been productive in specifying new capabilities for future networks involving interactive and distributive services through STM and A TM technologies.

This unique text, for both the first year graduate student and the newcomer to the field, provides in-depth coverage of the basic principles of data communications and covers material which is not treated in other texts, including phase and timing recovery and echo cancellation. Throughout the book, exercises and applications illustrate the material while up-to-date references round out the work.

In response to the increasing interest in developing photonic switching fabrics, this book gives an overview of the many technologies from a systems designer's perspective. Optically transparent devices, optical logic devices, and optical hardware are all discussed in detail and set into a systems context. Comprehensive, up-to-date, and profusely illustrated, the work will provide a foundation for the field, especially as broadband services are more fully developed.

Basic Concepts in Information Theory and Coding is an outgrowth of a one­ semester introductory course that has been taught at the University of Southern California since the mid-1960s. Lecture notes from that course have evolved in response to student reaction, new technological and theoretical develop­ ments, and the insights of faculty members who have taught the course (in­ cluding the three of us). In presenting this material, we have made it accessible to a broad audience by limiting prerequisites to basic calculus and the ele­ mentary concepts of discrete probability theory. To keep the material suitable for a one-semester course, we have limited its scope to discrete information theory and a general discussion of coding theory without detailed treatment of algorithms for encoding and decoding for various specific code classes. Readers will find that this book offers an unusually thorough treatment of noiseless self-synchronizing codes, as well as the advantage of problem sections that have been honed by reactions and interactions of several gen­ erations of bright students, while Agent 00111 provides a context for the discussion of abstract concepts.

This is an elementary textbook on an advanced topic: broadband telecommunica­ tion networks. I must declare at the outset that this book is not primarily intended for an audience of telecommunication specialists who are weIl versed in the concepts, system architectures, and underlying technologies of high-speed, multi­ media, bandwidth-on-demand, packet-switching networks, although the techni­ caIly sophisticated telecommunication practitioner may wish to use it as a refer­ ence. Nor is this book intended to be an advanced textbook on the subject of broadband networks. Rather, this book is primarily intended for those eager to leam more about this exciting fron tier in the field of telecommunications, an audience that includes systems designers, hardware and software engineers, en­ gineering students, R&D managers, and market planners who seek an understand­ ing of local-, metropolitan-, and wide-area broadband networks for integrating voice, data, image, and video. Its primary audience also includes researchers and engineers from other disciplines or other branches of telecommunications who anticipate a future involvement in, or who would simply like to leam more about, the field of broadband networks, along with scientific researchers and corporate telecommunication and data communication managers whose increasingly sophis­ ticated applications would benefit from (and drive the need for) broadband net­ works. Advanced topics are certainly not ignored (in fact, a plausible argument could be mounted that aIl of the material is advanced, given the infancy of the topic).

The Second Edition details the established international standards for digital imagery. Chapters discuss standards for the digitalization of bilevel images, color pictures, video conferencing, and television.

Designed for senior electrical engineering students, this textbook explores the theoretical concepts of digital signal processing and communication systems by presenting laboratory experiments using real-time DSP hardware. Each experiment begins with a presentation of the required theory and concludes with instructions for performing them. Engineering students gain experience in working with equipment commonly used in industry. This text features DSP-based algorithms for transmitter and receiver functions.

Synchronization is a critical function in digital communications; its failures may have catastrophic effects on the transmission system performance. Furthermore, synchronization circuits comprehend such a large part of the receiver hardware that their implementation has a substantial impact on the overall costs. For these reasons design engineers are particularly concerned with the development of new and more efficient synchronization structures. Unfortunately, the advent of digital VLSI technology has radically affected modem design rules, to a point that most analog techniques employed so far have become totally obsolete. Although digital synchronization methods are well established by now in the literature, they only appear in the form of technical papers, often concentrating on specific performance or implementation issues. As a consequence they are hardly useful to give a unified view of an otherwise seemingly heterogeneous field. It is widely recognized that a fundamental understanding of digital synchronization can only be reached by providing the designer with a solid theoretical framework, or else he will not know where to adjust his methods when he attempts to apply them to new situations. The task of the present book is just to develop such a framework.

Basic Concepts in Information Theory and Coding is an outgrowth of a one­ semester introductory course that has been taught at the University of Southern California since the mid-1960s. Lecture notes from that course have evolved in response to student reaction, new technological and theoretical develop­ ments, and the insights of faculty members who have taught the course (in­ cluding the three of us). In presenting this material, we have made it accessible to a broad audience by limiting prerequisites to basic calculus and the ele­ mentary concepts of discrete probability theory. To keep the material suitable for a one-semester course, we have limited its scope to discrete information theory and a general discussion of coding theory without detailed treatment of algorithms for encoding and decoding for various specific code classes. Readers will find that this book offers an unusually thorough treatment of noiseless self-synchronizing codes, as well as the advantage of problem sections that have been honed by reactions and interactions of several gen­ erations of bright students, while Agent 00111 provides a context for the discussion of abstract concepts.

This is a book about the bricks and mortar from which are built those edifices that will permeate the emerging information society of the future-computer networks. For many years such computer networks have played an indirect role in our daily lives as the hidden servants of banks, airlines, and stores. Now they are becoming more visible as they enter our offices and homes and directly become part of our work, entertainment, and daily living. The study of how computer networks function is a combined study of communication theory and computer science, two disciplines appearing to have very little in common. The modern communication scientist wishing to work in this area soon finds that solving the traditional problems of transmission, modulation, noise immunity, and error bounds in getting the signal from one point to another is just the beginning of the challenge. The communication must be in the right form to be routed properly, to be handled without congestion, and to be understood at various points in the network. As for the computer scientist, he finds that his discipline has also changed. The fraction of computers that belong to networks is increasing all the time. And for a typical single computer, the fraction of its execution load, storage occupancy, and system management problems that are in­ volved with being part of a network is also growing.

Computer communications is one of the most rapidly developing technologies and it is a subject with which everyone in the computer systems profession should be familiar. Computer communications and networks is an introduction to communications technology and system design for practising and aspiring computer professionals. The subject is described from the computer system designer's point of view rather than from the communications engineer's viewpoint. The presentation is suitable for introductory reading as well as for reference. The emphasis is on practical, rather than theoretical, aspects and on technology which will become more important in the future. The majority of the subject matter applies to civil and military communications but some aspects which are unique to military applications have been included where considered signifi­ cant. Computer communications is a rapidly changing and highly complex subject. Sufficient practical knowledge of the subject is not usually gained at university or college but is generally developed over a period of several years by trial and error, attending courses, reading reference books and journals; this book attempts to simplify and speed up the process by bringing together a body of information which is otherwise distributed throughout many books and journals. The information is presented in a framework which makes a wider understanding of the subject possible. Basic knowledge of communications is assumed, a general famil­ iarity with computer systems is anticipated in later chapters, and, where relevant, theory is explained.

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.

This unique text, for both the first year graduate student and the newcomer to the field, provides in-depth coverage of the basic principles of data communications and covers material which is not treated in other texts, including phase and timing recovery and echo cancellation. Throughout the book, exercises and applications illustrate the material while up-to-date references round out the work.

This is a book about the bricks and mortar out of which are built those edifices that so well characterize late twentieth century industrial society­ networks of computers and terminals. Such computer networks are playing an increasing role in our daily lives, somewhat indirectly up to now as the hidden servants of banks, retail credit bureaus, airline reservation offices, and so forth, but soon they will become more visible as they enter our offices and homes and directly become part of our work, entertainment, and daily living. The study of how computer networks work is a combined study of communication theory and computer science, two disciplines appearing to have very little in common. The modern communication scientist wishing to work in this area finds himself in suddenly unfamiliar territory. It is no longer sufficient for him to think of transmission, modulation, noise immun­ ity, error bounds, and other abstractions of a single communication link; he is dealing now with a topologically complex interconnection of such links. And what is more striking, solving the problems of getting the signal from one point to another is just the beginning of the communication process. The communication must be in the right form to be routed properly, to be handled without congestion, and to be understood at the right points in the network. The communication scientist suddenly finds himself charged with responsibility for such things as code and format conversions, addressing, flow control, and other abstractions of a new and challenging kind.

For thousands of years mankind has been creating pictures which attempt to portray real or imagined scenes as perceived by human vision. Cave drawings, paintings and photographs are able to stimulate the visual system and conjure up thoughts of faraway places, imagined situations or pleasant sensations. The art of motion picture creation has advanced to the point where viewers often undergo intense emotional experiences. On-the­ spot news coverage gives the impression of actually witnessing events as they unfold. Relatively recently, other forms of visual information have been invented which do not, in themselves, stimulate the eye. For example, vol­ tage variations in an electrical signal, as in television, can represent in analogous fashion the brightness variations in a picture. In this form the visual information can be stored on magnetic tape or transmitted over long distances, and, at least for engineering purposes, it is often much more use­ ful than other forms which do stimulate human vision. With the evolution of digital techniques for information processing, storage, and transmission, the need arises for digital representation of visual information, that is, the representation of images by a sequence of integer numbers (usually binary). In this form, computer processing and digital circuit techniques can be utilized which were undreamed of only a short time ago. Machine manipulation and interpretation of visual infor­ mation becomes possible. Sophisticated techniques can be employed for efficient storage of images. And processing methods can be used to significantly reduce the costs of picture transmission.

In large measure the traditional concern of communications engineers has been the conveyance of voice signals. The most prominent example is the telephone network, in which the techniques used for transmission multiplex­ ing and switching have been designed for voice signals. However, one of the many effects of computers has been the growing volume of the sort of traffic that flows in networks composed of user terminals, processors, and peripherals. The characteristics of this data traffic and the associated perfor­ mance requirements are quite different from those of voice traffic. These differences, coupled with burgeoning digital technology, have engendered a whole new set of approaches to multiplexing and switching this traffic. The new techniques are the province of what has been loosely called computer communications networks. The subject of this book is the mathematical modeling and analysis of computer communications networks, that is to say, the multiplexing and switching techniques that have been developed for data traffic. The basis for many of the models that we shall consider is queueing theory, although a number of other disciplines are drawn on as well. The level at which this material is covered is that of a first-year graduate course. It is assumed that at the outset the student has had a good undergraduate course in probability and random processes of the sort that are more and more common among electrical engineering and computer science departments.

Organized society depends on communication of all kinds, including the ability to communicate at a distance, instantaneously. With the development of solid­ state electronics and its application to digital processing, telecommunication has become extremely important to large segments of American business. The in­ troduction of competition to serve these voice, data, and video needs has ex­ panded the number of service options available, and some of them are finding their way into the residential sector. From a relatively stable, mature industry, telecommunication has rapidly become a technology-driven marketplace in which a host of companies are competing for customer attention with new services and equipment. Heretofore, books on telecommunications have addressed facilities and how they work. In this book, I am seeking to provide a much broader perspective which includes information on the motives driving the business itself, on new media and services, and on advancing technologies, as well as on digital facilities and their integration into the environment of future businesses and households. Covering so wide a set of topics presents many problems, not the least of which is that the character of the information is different in each chapter, and the material will be read by persons skilled in disparate fields. It is possible to read each chapter by itself-although a reading of all of them is needed to understand the new dimensions being introduced into the telecommunication experience.

Several years ago when I began consulting full time, I quickly discovered that despite three advanced academic degrees my practical industrial experience had some significant gaps. It thus was necessary initially to spend considerable (nonbillable) time collecting and organizing a great deal of essential information on the various aspects of modern data communica­ tions. The task was made more difficult by the highly interdisciplinary nature of the field, with the required information scattered throughout the vast international literature of telecommunications, computers, electrical engineering, military systems, mathematics, operations research, optimiza­ tion, speech processing, and the murky world oflegal and regulatory policy. Although there were a number of fine books and periodicals in each of these specialized disciplines, I was unable to find a single comprehensive text that covered the entire field at even a modestly attractive technical and mathematical level. After going to the trouble of organizing all this diverse material for my clients and students, it seemed rather natural to put it into book form and thus share it with those professionals working with computer data communi­ cations who need a comprehensive coverage of the subject at a level immediately applicable to their work and yet easily accessible for self-study. The project was facilitated by an agreeable publisher and an incredibly understanding and cooperative family, and Practical Computer Data Com­ munications is the result.

Since the publication of the first edition of Fundamentals of Digital Switching in 1983, there has been substantial improvement in digital switching technology and in digital networks. Packet switching has advanced from a low-speed data-oriented switching approach into a robust broadband technology which supports services ranging from low-speed data to video. This technology has eclipsed the flexibility of circuit switching. Fiber optic cable has advanced since the first edition and has substantially changed the technology of transmission. to research in optical devices to find a still better means of This success has led switching. Digital switching systems continue to benefit from the 100-fold improvement in the capabilities of semiconductor devices which has occurred during the past decade. The chip industry forecasts a similar escalation in complexity during the next 10 years. Networks of switching systems have changed due to regulatory policy reform in many nations, including the breakup of the Bell System in the United States, the introduction of new types of carriers in Japan, competition in the United Kingdom, and a reexamination of public policy in virtually all nations. Standards bodies have been productive in specifying new capabilities for future networks involving interactive and distributive services through STM and A TM technologies.

The challenge of communication in planetary exploration has been unusual. The guidance and control of spacecraft depend on reliable communication. Scientific data returned to earth are irreplaceable, or replaceable only at the cost of another mission. In deep space, communications propagation is good, relative to terrestrial communications, and there is an opportunity to press toward the mathematical limit of microwave communication. Yet the limits must be approached warily, with reliability as well as channel capacity in mind. Further, the effects of small changes in the earth's atmosphere and the interplanetary plasma have small but important effects on propagation time and hence on the measurement of distance. Advances are almost incredible. Communication capability measured in 18 bits per second at a given range rose by a factor of 10 in the 19 years from Explorer I of 1958 to Voyager of 1977. This improvement was attained through ingenious design based on the sort of penetrating analysis set forth in this book by engineers who took part in a highly detailed and amazingly successful pro­ gram. Careful observation and analysis have told us much about limitations on the accurate measurement of distance. It is not easy to get busy people to tell others clearly and in detail how they have solved important problems. Joseph H. Yuen and the other contribu­ tors to this book are to be commended for the time and care they have devoted to explicating one vital aspect of a great adventure of mankind.

This is an elementary textbook on an advanced topic: broadband telecommunica­ tion networks. I must declare at the outset that this book is not primarily intended for an audience of telecommunication specialists who are weIl versed in the concepts, system architectures, and underlying technologies of high-speed, multi­ media, bandwidth-on-demand, packet-switching networks, although the techni­ caIly sophisticated telecommunication practitioner may wish to use it as a refer­ ence. Nor is this book intended to be an advanced textbook on the subject of broadband networks. Rather, this book is primarily intended for those eager to leam more about this exciting fron tier in the field of telecommunications, an audience that includes systems designers, hardware and software engineers, en­ gineering students, R&D managers, and market planners who seek an understand­ ing of local-, metropolitan-, and wide-area broadband networks for integrating voice, data, image, and video. Its primary audience also includes researchers and engineers from other disciplines or other branches of telecommunications who anticipate a future involvement in, or who would simply like to leam more about, the field of broadband networks, along with scientific researchers and corporate telecommunication and data communication managers whose increasingly sophis­ ticated applications would benefit from (and drive the need for) broadband net­ works. Advanced topics are certainly not ignored (in fact, a plausible argument could be mounted that aIl of the material is advanced, given the infancy of the topic).

In response to the increasing interest in developing photonic switching fabrics, this book gives an overview of the many technologies from a systems designer's perspective. Optically transparent devices, optical logic devices, and optical hardware are all discussed in detail and set into a systems context. Comprehensive, up-to-date, and profusely illustrated, the work will provide a foundation for the field, especially as broadband services are more fully developed.