1 INTRODUCTION 1
1.1 Historical Review 1
1.2 Elements of an Electrical Communication System 5
1.2.1 Digital Communication System, 7
1.2.2 Early Work in Digital Communications, 10
1.3 Communication Channels and Their Characteristics 12
1.4 Mathematical Models for Communication Channels 19
1.5 Further Reading 22
2 SIGNALS AND LINEAR SYSTEMS 23
2.1 Basic Concepts 23
2.1.1 Basic Operations on Signals, 24
2.1.2 Classification of Signals, 25
2.1.3 Some Important Signals and Their Properties, 33
2.1.4 Classification of Systems, 40
2.1.5 Analysis of LTI Systems in the Time Domain, 44
2.2 Fourier Series 46
2.2.1 Fourier Series and Its Properties, 46
2.2.2 Response of LTI Systems to Periodic Signals, 56
2.2.3 Parseval’s Relation, 59
2.3 Fourier Transform 61
2.3.1 From Fourier Series to Fourier Transforms, 61
2.3.2 Basic Properties of the Fourier Transform, 67
2.3.3 Fourier Transform for Periodic Signals, 81
2.3.4 Transmission over LTI Systems, 84
2.4 Filter Design 88
2.5 Power and Energy 92
2.5.1 Energy-Type Signals, 93
2.5.2 Power-Type Signals, 96
2.6 Hilbert Transform and Its Properties 99
2.7 Lowpass and Bandpass Signals 102
2.8 Further Reading 105
Problems 105
3 AMPLITUDE MODULATION 124
3.1 Introduction to Modulation 125
3.2 Amplitude Modulation （AM） 126
3.2.1 Double-Sideband Suppressed-Carrier AM, 126
3.2.2 Conventional Amplitude Modulation, 134
3.2.3 Single-Sideband AM, 139
3.3 Implementation of AM Modulators and Demodulators 144
3.4 Signal Multiplexing 151
3.4.1 Frequency-Division Multiplexing, 152
3.4.2 Quadrature-Carrier Multiplexing, 153
3.5 AM-Radio Broadcasting 154
Appendix 3A: Derivation of the Expression for SSB-AM Signals 156
Problems 158
4 ANGLE MODULATION 169
4.1 Representation of FM and PM Signals 170
4.2 Spectral Characteristics of Angle-Modulated Signals 174
4.2.1 Angle Modulation by a Sinusoidal Signal, 174
4.2.2 Angle Modulation by an Arbitrary Message Signal, 179
4.3 Implementation of Angle Modulators and Demodulators 180
4.4 FM-Radio and Television Broadcasting 188
4.4.1 FM-Radio Broadcasting, 188
4.4.2 Television Broadcasting, 190
4.5 Mobile Wireless Telephone Systems 200
4.6 Further Reading 202
Problems 202
5 PROBABILITY AND RANDOM PROCESSES 210
5.1 Review of Probability and Random Variables 210
5.1.1 Sample Space, Events, and Probability, 210
5.1.2 Conditional Probability, 211
5.1.3 Random Variables, 214
5.1.4 Functions of a Random Variable, 221
5.1.5 Multiple Random Variables, 224
5.1.6 Sums of Random Variables, 229
5.2 Random Processes: Basic Concepts 229
5.2.1 Statistical Averages, 233
5.2.2 Wide-Sense Stationaty Processes, 235
5.2.3 Multiple Random Processes, 236
5.2.4 Random Processes and Linear Systems, 237
5.2.5 Power Spectral Density of Stationary Processes, 240
5.2.6 Power Spectral Density of a Sum Process, 244
5.3 Gaussian and White Processes 245
5.3.1 Gaussian Processes, 245
5.3.2 White Processes, 247
5.3.3 Filtered Noise Processes, 249
5.4 Further Reading 254
Problems 255
6 EFFECT OF NOISE ON ANALOG COMMUNICATION SYSTEMS 273
6.1 Effect of Noise on Amplitude-Modulation Systems 273
6.1.1 Effect of Noise on a Baseband System, 274
6.1.2 Effect of Noise on DSB-SCAM, 274
6.1.3 Effect of Noise on SSB AM, 276
6.1.4 Effect of Noise on Conventional AM, 278
6.2 Effect of Noise on Angle Modulation 282
6.2.1 Threshold Effect in Angle Modulation, 291
6.2.2 Preemphasis and Deemphasis Filtering, 294
6.3 Comparison of Analog-Modulation Systems 297
6.4 Carrier-Phase Estimation with a Phase-Locked Loop （PLL） 299
6.4.1 Effect of Additive Noise on Phase Estimation, 303
6.5 Effects of Transmission Losses and Noise in Analog Communication Systems 308
6.5.1 Characterization of Thermal Noise Sources, 309
6.5.2 Effective Noise Temperature and Noise Figure, 310
6.5.3 Transmission Losses, 313
6.5.4 Repeaters for Signal Transmission, 315
6.6 Further Reading 318
Problems 318
7 ANALOG-TO-DIGITAL CONVERSION 328
7.1 Sampling of Signals and Signal Reconstruction from Samples 329
7.1.1 The Sampling Theorem, 329
7.2 Quantization 334
7.2.1 Scalar Quantization, 334
7.2.2 Vector Quantization, 342
7.3 Encoding 344
7.4 Waveform Coding 345
7.4.1 Pulse Code Modulation （PCM）, 346
7.4.2 Differential Pulse Code Modulation （DPCM）, 350
7.4.3 Delta Modulation （DM）, 352
7.5 Analysis-Synthesis Techniques 355
7.6 Digital Audio Transmission and Digital Audio Recording 358
7.6.1 Digital Audio in Telephone Transmission Systems, 359
7.6.2 Digital Audio Recording, 361
7.7 The JPEG Image-Coding Standard 365
7.8 Further Reading 369
Problems 369
8 DIGITAL MODULATION IN AN ADDITIVE WHITE GAUSSIAN NOISE BASEBAND CHANNEL 379
8.1 Geometric Representation of Signal Waveforms 380
8.2 Binary Pulse Modulation 384
8.2.1 Binary Pulse Amplitude Modulation, 384
8.2.2 Binary Pulse Position Modulation, 386
8.3 Optimum Receiver for Binary Modulated Signals in Additive White Gaussian Noise 389
8.3.1 Correlation-Type Demodulator, 391
8.3.2 Matched-Filter-Type Demodulator, 397
8.3.3 The Performance of the Optimum Detector for Binary Signals, 405
8.4 M-ary Pulse Modulation 407
8.4.1 M-ary Pulse Amplitude Modulation, 409
8.4.2 M-ary Orthogonal Signals, 411
8.4.3 Biorthogonal Signals, 413
8.4.4 Simplex Signal Waveforms, 416
8.4.5 Binary-Coded Signal Waveforms, 417
8.4.6 The Optimum Receiver for M-ary Signals in AWGN, 420
8.5 Probability of Error for M-ary Pulse Modulation 431
8.5.1 Probability of Error for M-ary Pulse Amplitude Modulation, 431
8.5.2 Probability of Error for M-ary Orthogonal Signals, 435
8.5.3 A Union Bound on the Probability of Error, 437
8.5.4 Probability of Error for M-ary Biorthogonal Signals, 441
8.5.5 Probability of Error for M-ary Simplex Signals, 442
8.5.6 Probability of Error for Binary-Coded Signals, 444
8.5.7 Comparison of Digital Pulse Modulation Methods, 444
8.6 Symbol Synchronization 445
8.6.1 Early-Late Gate Synchronizers, 446
8.6.2 Minimum Mean-Square-Error Method, 448
8.6.3 Maximum-Likelihood Method, 450
8.6.4 Spectral-Line Method, 451
8.7 Further Reading 454
Problems 454
9 DIGITAL TRANSMISSION THROUGH BANDLIMITED AWGN CHANNELS 475
9.1 Digital Transmission through Bandlimited Channels 475
9.1.1 Digital PAM Transmission through Bandlimited Baseband Channels, 480
9.2 Signal Design for Bandlimited Channels 482
9.2.1 Design of Bandlimited Signals for Zero ISI—The Nyquist Criterion, 484
9.2.2 Design of Bandlimited Signals with Controlled ISI—Partial Response Signals, 490
9.3 Probability of Error for Detection of Digital PAM 493
9.3.1 Probability of Error for Detection of Digital PAM with Zero ISI, 493
9.3.2 Symbol-by-Symbol Detection of Data with Controlled ISI, 494
9.3.3 Probability of Error for Symbol-by-Symbol Detection of Partial Response Signals, 498
9.3.4 Maximum-Likelihood Sequence Detection of Partial Response Signals, 501
9.4 System Designin the Presence of Channel Distortion 503
9.4.1 Design of Transmitting and Receiving Filters for a Known Channel, 505
9.4.2 Channel Equalization, 507
9.5 Further Reading 525
Problems 526
10 TRANSMISSION OF DIGITAL INFORMATION VIA CARRIER MODULATION 541
10.1 Amplitude-Modulated Digital Signals 541
10.1.1 Demodulation and Detection of Amplitude-Modulated Signals, 545
10.2 Phase-Modulated Digital Signals 548
10.2.1 Demodulation and Detection of Phase-Modulated Signals, 553
10.2.2 Differential-Phase Modulation and Demodulation, 558
10.2.3 Probability of Error for Phase-Coherent PSK Modulation, 560
10.2.4 Probability of Error for DPSK, 565
10.3 Quadrature Amplitude-Modulated Digital Signals 567
10.3.1 Demodulation and Detection of Quadrature-Amplitude Modulated Signals, 571
10.3.2 Probability of Error for QAM, 574
10.4 Frequency-Modulated Digital Signals 579
10.4.1 Demodulation and Detection of Frequency-Modulated Signals, 581
10.4.2 Probability of Error for Noncoherent Detection of FSK, 588
10.4.3 Continuous-Phase FSK （CPFSK）, 591
10.5 Comparison of Modulation Methods 602
10.6 Symbol Synchronization for Carrier-Modulated Signals 606
10.7 Further Reading 606
Problems 607
11 SELECTED TOPICS IN DIGITAL COMMUNICATIONS 623
11.1 Digital Transmission in Fading Multipath Channels 623
11.1.1 Channel Models for Time-Variant Multipath Channels, 624
11.1.2 Performance of Binary Modulation in Frequency Nonselective Rayleigh Fading Channels, 629
11.1.3 Performance Improvement through Signal Diversity, 631
11.1.4 Frequency Selective Channels and the RAKE Demodulator, 635
11.2 Multicarrier Modulation and OFDM 639
11.2.1 Modulation and Demodulation in an OFDM System, 641
11.2.2 An OFDM System Implemented via the FFT Algorithm, 643
11.2.3 Spectral Characteristics of OFDM Signals, 646
11.2.4 Peak-to-Average Power Ratio in OFDM Systems, 647
11.2.5 Applications of OFDM, 649
11.3 Spread-Spectrum Communication Systems 652
11.3.1 Model of a Spread-Spectrum Digital Communication System, 653
11.3.2 Direct Sequence Spread-Spectrum Systems, 654
11.3.3 Some Applications of DS Spread-Spectrum Signals, 663
11.3.4 Generation of PN Sequences, 667
11.3.5 Frequency-Hopped Spread Spectrum, 670
11.4 Digital Cellular Communication Systems 673
11.4.1 The GSM System, 673
11.4.2 CDMA System Based on IS-95, 677
11.4.3 Third Generation Cellular Communication Systems, 681
11.5 Performance Analysis for Wireline and Radio Communication Channels 682
11.5.1 Regenerative Repeaters, 683
11.5.2 Link Budget Analysis for Radio Channels, 684
11.6 Further Reading 688
Problems 689
REFERENCES 702
INDEX 712