.1.5 Ergodic Processes
1.6 Transmission of a Random Process Through a Linear Time-Invariant Filter
1.7 Power Spectral Density
1.8 Gaussian Process
1.9 Noise
1.10 Narrowband Noise
1.11 Representation of Narrowband Noise in Terms of In-phase and Quadrature Components
1.12 Representation of Narrowband Noise in Terms of Envelope and Phase Components
1.13 Sine Wave Plus Narrowband Noise
1.14 Computer Experiments:Flat-Fading Channel
1.15 Summary and Discussion
Notes and References
Problems

CHAPTER 2 Continuous-Wave Modulation

2.1 Introduction
2.2 Amplitude Modulation
2.3 Linear Modulation Schemes
2.4 Frequency Translation
2.5 Frequency-Division Multiplexing
2.6 Angle Modulation
2.7 Frequency Modulation
2.8 Nonlinear Effects in FM Systems
2.9 Superheterodyne Receiver
2.10 Noise in CW Modulation Systems
2.11 Noise in Linear Receivers using Coherent Detection
2.12 Noise in AM Receivers using Envelope Detection
2.13 Noise in FM Receivers
2.14 Computer Experiments:Phase-Locked Loop
2.15 Summary and Discussion
Notes and References
Problems

CHAPTER 3 Pulse Modulation

3.1 Introduction
3.2 Sampling Process
3.3 Pulse-Amplitude Modulation
3.4 Other Forms of Pulse Modulation
3.5 Bandwidth-Noise Trade-off
3.6 Quantization Process
3.7 Pulse-Code Modulation
3.8 Noise Considerations in PCM Systems
3.9 Time-Division Multiplexing
3.10 Digital Multiplexers
3.11 Virtues,Limitations,and Modifications of PCM
3.12 Delta Modulation
3.13 Linear Prediction
3.14 Differential Pulse-Code Modulation
3.15 Adaptive Differential Pulse-Code Modulation
3.16 Computer Experiment:Adaptive Delta Modulation
3.17 MPEG Audio Coding Standard
3.18 Summary and Discussion
Notes and References
Problems

CHAPTER 4 Baseband Pulse Transmission

4.1 Introduction
4.2 Matched Filter
4.3 Error Rate Due to Noise
4.4 Intersymbol Interference
4.5 Nyquist's Criterion for Distortionless Baseband Binary Transmission
4.6 Correlative-Level Coding
4.7 Baseband M-ary PAM Transmission
4.8 Digital Subscriber Lines
4.9 Optimum Linear Receiver
4.10 Adaptive Equzlization
4.11 Computer Experiments:Eye Patterns
4.12 Summary and Discussion
Notes and References
Problems

CHAPTER 5 Signal-Space Analysis

5.1 Introduction
5.2 Geometric Representation of Signals
5.3 Conversion of the Continuous AWGN Channel into a Vector Channel
5.4 Likelisood Functions
5.5 Coherent Detection of Signals in Noise:Maximum Likelihood Decoding
5.6 Correlation Receiver
5.7 Probability of Error
5.8 Summary and Discussion
Notes and References
Problems

CHAPTER 6 Passband Digital Transmission

6.1 Introduction
6.2 Passband Transmission Model
6.3 Coherent Phase-Shift Keying
6.4 Hybrid Amplitued/Phase Modulation Schemes
6.5 Coherent Frequency-Shift Keying
6.6 Detection of Signals with Unknown Phase
6.7 Noncoherent Orthogonal Modulation
6.8 Noncoherent Binary Frequency-Shift Keying
6.9 Differential Phase-Shift Keying
6.10 Comparison of Digital Modulation Schemes Using a Single Carrier
6.11 Voiceband Modems
6.12 Multichannel Modulation
6.13 Discrete Multitone
6.14 Synchronization
6.15 Computer Experiments:Carrier Recovery and Symbol Timing
6.16 Summary and Discussion
Notes and References
Problems

CHAPTER 7 Spread-Spectrum Modulation

7.1 Introduction
7.2 Pseudo-Noise Sequences
7.3 A Notion of Spread Spectrum
7.4 Direct-Sequence Spread Spectrum with Coherent Binary Phase-Shift Keying
7.5 Signal-Space Dimensionality and Processing Gain
7.6 Probability of Error
7.7 Frequency-Hop Spread Spectrum
7.8 Computer Experiments:Maximal-Length and Gold Codes
7.9 Summary and Discussion
Notes and References
Problems

CHAPTER 8 Multiuser Radio Communications

8.1 Introduction
8.2 Multiple-Access Techniques
8.3 Satellite Communications
8.4 Radio Link Analysis
8.5 Wireless Communications
8.6 Statistical Characterization of Multipath Channels
8.7 Binary Signaling over a Rayleigh Fading Channel
8.8 TDMA and CDMA Wireless Communication Systems
8.9 Source Coding of Speech for Wireless Communications
8.10 Adaptive Antenna Arrays for Wireless Communications
8.11 Summary and Discussion
Notes and References
Problems

CHAPTER 9 Fundamental Limits in Information Theory

9.1 Introduction
9.2 Uncertainty,Information,and Entropy
9.3 Source-Coding Theorem
9.4 Data Compaction
9.5 Discrete Memoryless Channels
9.6 Mutual Information
9.7 Channel Capacity
9.8 Channel-Coding Theorem
9.9 Differential Entropy and Mutual Information for Continuous Ensembles
9.10 Information Capacity Theorem
9.11 Implications of the Information Capacity Theorem
9.12 Information Capacity of Colored Noise Channel
9.13 Rate Distortion Theory
9.14 Data Compression
9.15 Summary and Discussion
Notes and References
Problems

CHAPTER 10 Error-Control Coding

10.1 Introduction
10.2 Discrete-Memoryless Channels
10.3 Linear Block Codes
10.4 Cyclic Codes
10.5 Convolutional Codes
10.6 Maximum Likelihood Decoding of Convolutional Codes
10.7 Trellis-Coded Modulation
10.8 Turbo Codes
10.9 Computer Experiment:Trubo Decoding
10.10 Low-Density Parity-Check Codes
10.11 Irregular Codes
10.12 Summary and Discussion
Notes and References
Problems

APPENDIX 1 Probability Theory
APPENDIX 2 Representation of Signals and Systems
APPENDIX 3 Bessel Functions
APPENDIX 4 Confluent Hypergeometric Functions
APPENDIX 5 Cryptography
APPENDIX 6 Tables

GLOSSARY
BIBLIOGRAPHY
INDEX

. Phase modulation
Frequency modulation
The time-domain and spectral characteristics of these modulated waves. methods for their generation and detection, and the effects of channel noise on their Performances are discussed.
Chapter 3 covers pulse modulation and discusses the processes of sampling. quantization, and coding that are fundamental to the digital transmission of analog signals. This chapter may be viewed as the transition from analog to digital communications. Specifically, the following types of pulse modulation are discussed:
(i) Analog pulse modulation, where only time is represented in discrete form: it
embodies the following special forms:
Pulse amplitude modulation
Pulse width (duration) modulation
Pule position modulation
The charaaeristics of pulse amplitude modulation are discussed in detail. as it is basic to all forms of pulse moduladon, be they of the analog or digital type.
(ii) Digital pulse modulation, in which both time and signal amplitude are represented in discrete form; it embodies the following special forms:
Pulse-code modulation
Delta modulation
Differential pulse-code modulation
In delta modulation, the sampling rate is increased far in excess of that used in oulsecode modulation so as to simplify implementation of the system. In contrast. in differential Pulse-code modulation, the sampling rate is reduced through the use of a predictor that exploits the correlation propenies of the information-bearing signal.
(iii) MPEG/audio coding standard, which includes a psychoacoustic model as a key element in the design of the encoder.
Chapter 4 covers baseband pulse transmission, whick deals with the transmission of pulse-amplitude modulated signals in their baseband form. Two important issues are discussed: the effects of channel noise and limited channel bandwidth on the performance of a digital communication system. Assaming that the channel noise is additive and white, this effect is minimized by using a matched filter,with is basic to the design of communication receivers. As for limited channel bandwidth. it manifests itself in the form of a phenomenon known as intersymbol interference. To combat the degrading effects of this signal-dependent interference, we may use either a pulseshaping filter or correlative encoder/decoder; both of these approaches are discussed.
The chapter includes a discussion of digital subscriber lines for direct communication
between a subscriber and an Internet service provider. This is followed by a derivation of the optimum linear receiver for combatting the combined effects of channel noise and intersymbol ioterference, which, in turn, leads to an introductorv treatment of adaptiue equalization.
Chapter 5 discusses signal-space analysis for an additive white Ganssian noise channel. In particular, the foundations for the geometric representation of signals with finite energy are established. The correlation receiver is derived, and its equivalence with the matched filter receiver is demonstrated. The chapter finishes with a discussion of the probability of error and its approximate calculation.
Chapter 6 discusses passband data transmission, where a sinusoidal carrier wave is employed to facilitate the transmission of the digitally modulated wave over a band pass channel. This ckapter builds on the geometric interpretation of signals presented in Chapter 5. In particular, the effect of channel noise on the performance of digital commonication systems is evaluated, using the following modulation techniques:
(i) Phase-shift keying, which is the digital counterpart to phase modulation with the phase of the carrier wave taking on one of a prescribed set of discrete values.
(ii) Hybrid amplitode/phase modulation schemes inclading quadrature-amplitude
modulation (QAM), and camierless amplitude/phase modulation (CAP).
(iii) Frequency-shift krying, which is the digital counterpart of frequency modulation with the frequency of the carrier wave taking on one of a prescribed set of discrete values.
(iv) Generic multichannel modulation, followed by discrete multitone, the use of which has been standardized in asymmetric digital subscriber lines.
In a digital commnnication system, timing is everytking, which means that the receiver must be synchronized to the uansmiRer. In this eontext, we speak of the receiver being coherent or noncoherent. In a cokHent receiuer, provisions are made for the recovery of both the carrier phase and symbol timing. In a noncoherent receiver the carrier phase is ignored and provision is only made for svmbol timine. spch a strategy is dictated by the faa that the carrier phase may be random, makinvg phase recovery a costly proposition. Synchronization techniques are discussed in the laner part of the chapter, with particular emphasis on discrete-time signal processing.
Chapter 7 inuodaces spread-spectrum modulation. Unlike uaditional forms of modulation discussed in earlier chapters, channel bandwidth is purposely sacrificed in spread-spectrnm modulation for the sake of security or proteHion against interfering signals. The direct-sequence and frequency-hop forms of spread-spectrum modulavtion are discussed.
Chapter 8 deals with multiuser radio commnunications, where a multitude of users have access to a common radio channel. This type of communication channel is well represented in satellite and wireless communication systems, both of which are discusssed. The chapter includes a presentation of link budget analysisx empkasizing the related antenna and propagation concepts, and noise calculations.
Chapter 9 develops the fundamental limits in information theory. wkick are embodied in Shannon's theorems for data compaction, data compression, and data transmission. These theorems provide upper bounds on the performance of inlormation sources and communication channels. Two concepts, basic to forntulation of the theorems, are (1) the entropy of a source (whose definition is analogous to that of entropy in thermodynamics), and (2) channel capacity.
Chapter 10 deals with error-control coding, which encompasses techniques for the encoding and decoding of digital data streams for their reliable transmission over noisy channels. Four types of error-control coding are discussed:
(i) Linear block codes, which are completely described by sets of linearly independent code words, each of which consists of message bits and parity-check bits.
The parity-check bits are included for the purpose of error control.
(ii) Cyclic codes, which form a subclass of linear block codes.
(iii) Conuolutional codes, which involve operating on the message sequence continuously in a serial manner.
{iv) Turbo codess which provide a novel method of consuucting good codes that approach Shannon's chanoel capacity in a physically realizable manner.
Methods for the generation of these codes and their decoding are discussed.
The book also includes supplementary material in the form of six appendices as
follows:
Appendix 1 reviews probability theory.
Appendix 2, on the representation of signals and systems, reviews the Fomier transform and its propeHies, the various definitions of bandwidth, the HilbeR transform, and the low-pass equivalents of narrowband signals and systems.
Appendix 3 presents an introductory treatment of the Bessel function and its modified form. Bessel functions arise in the study of frequency modulation, noncoherent deteHion of signals in noise, and symbol timing synchronization.
Appendix 4 introduces the confluent hypergeometric functioa, the need for which arises in the envelope detection of amplitude-modulated signals in noise.
Appendix 5 provides an introduHion to cryptography, which is basic to secure communications.
Appendix 6 includes 12 useful tables of various kinds.
As mentioned previonsly, the primary purpose of this book is to provide a modern treatment of communication systems suitable for use in a one- or two-semester undergraduate conrse at the senior level. The make-up of the material for the course is naturally determined by the background of the students and the interests of the teachers involved. The material covered in the book is both broad and deep enough to satisfy a variety of backgrounds and interests, thereby providing considerable aexibility in the choice of course material. As an aid to the teacher of the course, a detailed solutions manual for all the problems in the book is available from the publisher.