The electrical engineering handbook SN07

The electrical engineering handbook

Shaw, L “Section VII – Communications”

The Electrical Engineering Handbook

Ed Richard C Dorf

Boca Raton: CRC Press LLC, 2000

The IRIDIUM system is a satellite-based, wireless personal communications network designed to permit any type of telephone transmission—voice, data, fax, or paging—to reach its destination anywhere on earth The IRIDIUM constellation will consist of 66 interconnected satellites like the one shown above

Each IRIDIUM satellite, weighing approximately 689 kg (1,500 lb), will orbit above the earth at an altitude

of 420 nautical miles and communicate directly with subscriber equipment Each of the satellites will function like extremely tall cellular towers and will project tightly focused beams over the ground The low-earth orbit

of IRIDIUM satellites as well as recent advances in microelectronics make it possible to communicate with a handheld phone

The IRIDIUM system was conceived in 1987 by engineers at Motorola’s Satellite Communications Division

It is being financed by a private international consortium of telecommunications and industrial companies and

is expected to begin operation in 1998 (Photo courtesy of Motorola.)

© 2000 by CRC Press LLC

Communications

M.S Roden, S Salek, A.H Clegg

Modulation and Demodulation • Radio • Television Systems • High-Definition Television • Digital Audio Broadcasting

Error Control Coding • Equalization • Spread Spectrum Communications

Lightwave Technology for Video Transmission • Long Distance Fiber Optic Communications • Photonic Networks

B-ISDN • Computer Communication Networks • Local-Area Networks • The Intelligent Network

T.M Cover

Signal Detection • Noise • Stochastic Processes • The Sampling Theorem • Channel Capacity • Data Compression

Satellite Applications • Satellite Functions • Satellite Orbits and Pointing Angles • Communications Link • System Noise Temperature and G/T • Digital Links • Interference • Some Particular Orbits • Access and Modulation • Frequency Allocations • Satellite Subsystems • Trends

Mobile Radio and Cellular Communications • Facsimile • Wireless Local-Area Networks for the 1990s • Wireless PCS

Loop Filter • Noise • PLL Design Procedures • Components • Applications

Introduction to Telemetry • Measuring and Transmitting • Applications of Telemetry • Limitations of Telemetry • Transmitters and Batteries • Receivers and Discriminators • Antennas and Total System Operation • Calibration • Telemetry Frequency Allocations • Telemetry Antennas • Measuring and Transmitting • Modulating and Multiplexing • Passive Telemeters • The Receiving Station

K.L Kosbar

The Role of Simulation • Motivation for the Use of Simulation • Limitations of Simulation • Simulation Structure • The Interdisciplinary Nature of Simulation • Model Design • Low-Pass Models • Pseudorandom Signal and Noise Generators • Transmitter, Channel, and Receiver Modeling • Symbol Error Rate Estimation • Validation of Simulation Results • A Simple Example Illustrating Simulation Products

Leonard Shaw

Polytechnic University, New York

LECTRICAL TECHNOLOGY has been involved in aiding communication between a sender and a receiver of information since the advent of the electrical telegraph The evolution of electrical commu-nications technology has been influenced by both advances in devices for processing and transmitting electrical signals, as well as the growth and variety of communications applications that have become essential

to modern society A large fraction of electrical engineers are involved with some aspect of communications,

as evidenced by the size of the IEEE Communications Society, which is second only to the Computer Society

In fact, communication between computers makes up a large part of communication system traffic, and communication technology is playing an increasing role within computers as they employ multiple processors and processors that are geographically distributed

This section presents an overview of a variety of communication systems that have been developed to overcome the constraints of physical communication channels by exploiting the capabilities of the electronic and optoelectronic devices that are described elsewhere in this handbook As a reflection of the dual influences

of electrotechnology and user applications, some of the following chapters have application themes (broad-casting, satellite and aerospace, personal and office, and telemetry), while the rest have themes related to systems techniques (digital, optical, network, information theory, phase-locked loop, and computer-aided design) The conventional radio station is a prototype of a broadcasting system in which a single transmitter sends the same message to multiple receivers Chapter 69 reviews the basic notions of modulation needed to match the transmitted signal to the propagation and noise characteristics of the transmission medium and outlines recent developments in systems for high-definition television (HDTV) and digital audio broadcasting (DAB) The chapter on digital techniques emphasizes the coding techniques used to detect and correct transmission errors (which are inevitable even if systems can be designed to reduce their frequency of occurrence) Since the rate of pulse transmission over a channel can be maximized by having an accurate model for the channel, such systems are improved by continually readjusting the channel model as the characteristics change with time This chapter also discusses adaptive equalizers that match electrical pulse shapes to changing channels The development of fiber-optic cables and efficient solid-state lasers has revolutionized telephone commu-nications Chapter 71 describes some of the related developments in signal design and transmission for optical systems that carry voice, video, and computer data messages

Traditional telephone switching has evolved into a huge field of telecommunication networks, with the advent

of new media such as fiber-optic cables and satellites and the rapidly growing digital traffic such as that between computers, and supporting e-mail and the World Wide Web Chapter 72 describes switching and transmission protocols and other standards that are being developed to coordinate the design of equipment that sends and receives messages over the networks

The chapter on information theory uses that term in a broad sense to describe mathematical models and techniques for describing and simplifying both deterministic and random signals These techniques can be used for efficient communication by removing inessential information and by showing how a receiver can distinguish useful information from noise disturbances

Satellite and aerospace applications, described in Chapter 74, provide dramatic examples of challenging communication environments where, due to equipment weight limitations and great distances, signals are weak compared to the associated noise, and propagation characteristics are nonlinear

Personal and office innovations related to communication systems are as dramatic to the ordinary citizen as those in entertainment applications such as HDTV and digital audio Chapter 75 describes how facsimile systems, which are especially useful for rapid transmission of graphical information, exploit standardized techniques for compressing black-and-white images Also presented are new developments in modulation techniques and propagation modeling that have been stimulated by mobile telephone and wireless network applications

Phase-locked loops are presented in Chapter 76 as good examples of electronic systems that are able to detect

E

Telemetry systems are dedicated to collection and transmission of data from many sensors, often in hostile

or distant environments Chapter 77 describes how constraints on equipment size, weight and power often lead

to novel methods for data multiplexing and transmission

This section concludes with a chapter on computer-aided design methods that are being exploited to design communication systems more rapidly and effectively Many of the problems, such as best location of a large number of nodes in a network where the construction costs and performance measures are a complex function

of design parameters, are best solved by a designer who works interactively with computer algorithms

Nomenclature

Aeff effective area of antenna m2

CIR carrier-to-interference ratio

CNR carrier-to-noise ratio

E electric field intensity V/m

F noise figure

g(t) complex envelope

h quantum efficiency

m(t) modulating signal

M bit rate delay product

M detector gain

m rms modulation index

n effective input current noise

density

N number of equalizer coefficients

NF noise ratio

P probability of error

PE preemphasis factor

q interference reduction factor

r correlation coefficient

s(t) modulated signal

SNR signal-to-noise ratio

s2 variance of noise samples

Z fs impedance of free space 120p W