数字通信 英文版PDF电子书下载

1 Digital communications overview 1

1.1 Electronic communications 1

1.2 Sources and sinks of information 4

1.3 Digital communications equipment 6

1.3.1 CODECs 6

1.3.2 Source,security and error control coding 7

1.3.3 Multiplexers 7

1.3.4 MODEMs 8

1.3.5 Multiple accessing 8

1.4 Radio receivers 8

1.5 Signal transmission 9

1.5.1 Line transmission 9

1.5.2 Radio transmission 13

1.6 Switching and networks 14

1.7 Advantages of digital communications 15

1.8 Summary 16

Part One Signals and systems theory 19

2 Periodic and transient signals 21

2.1 Introduction 21

2.2 Periodic signals 22

2.2.1 Sinusoids,cisoids and phasors 22

2.2.2 Fourier series 27

2.2.3 Conditions for existence,convergence and Gibb's phenomenon 41

2.2.4 Bandwidth,rates of change,sampling and aliasing 44

2.3 Transient signals 47

2.3.1 Fourier transforms 47

2.3.2 Practical calculation of Fourier transforms 49

2.3.3 Fourier transform pairs 51

2.3.4 Fourier transform theorems and convolution 56

2.4 Power and energy spectra 65

2.5 Generalised orthogonal function expansions 67

2.5.1 Review of vectors 67

2.5.2 Vector interpretation of waveforms 70

2.5.3 Orthogonal and orthonormal signals 72

2.5.4 Evaluation of basis function coefficients 74

2.5.5 Error energy and completeness 75

2.6 Correlation functions 77

2.7 Summary 83

2.8 Problems 84

3 Random signals and noise 86

3.1 Introduction 86

3.2 Probability theory 86

3.2.1 Conditional probabilities,joint probabilities and Bayes's rule 88

3.2.2 Statistical independence 89

3.2.3 Discrete probability of errors in a data block 90

3.2.4 Cumulative distributions and probability density functions 92

3.2.5 Moments,percentiles and modes 96

3.2.6 Joint and marginal pdfs,correlation and covariance 101

3.2.7 Joint moments,correlation and covariance 104

3.2.8 Joint Gaussian random variables 107

3.2.9 Addition of random variables and the central limit theorem 108

3.3 Random processes 112

3.3.1 Stationarity and ergodicity 114

3.3.2 Strict and loose sense Gaussian processes 115

3.3.3 Autocorrelation and power spectral density 117

3.3.4 Signal memory,decorrelation time and white noise 121

3.3.5 Cross correlation of random processes 122

3.4 Summary 122

3.5 Problems 124

4 Linear systems 128

4.1 Introduction 128

4.2 Linear systems 128

4.2.1 Properties of linear systems 129

4.2.2 Importance of linear systems 130

4.3 Time domain description of linear systems 133

4.3.1 Linear differential equations 133

4.3.2 Discrete signals and matrix algebra 134

4.3.3 Continuous signals,convolution and impulse response 134

4.3.4 Physical interpretation of y(t)=h(t)＊x(t) 136

4.3.5 Step response 138

4.4 Frequency domain description 141

4.5 Causality and the Hilbert transform 144

4.6 Random signals and linear systems 147

4.6.1 Power spectral densities and linear systems 147

4.6.2 Noise bandwidth 149

4.6.3 Pdf of filtered noise 149

4.6.4 Spectrum analysers 151

4.7 Non-linear systems and transformation of random variables 152

4.7.1 Rayleigh pdf 153

4.7.2 Chi-square distributions 155

4.8 Summary 157

4.9 Problems 157

Part Two Digital communications principles 161

5 Sampling,multiplexing and PCM 163

5.1 Introduction 163

5.2 Pulse modulation 163

5.3 Sampling 165

5.3.1 Natural and flat topped sampling 166

5.3.2 Baseband sampling and Nyquist's criterion 167

5.3.3 Aliasing 168

5.3.4 Practical sampling,reconstruction and signal to distortion ratio 169

5.3.5 Bandpass sampling 173

5.4 Analogue pulse multiplexing 176

5.5 Quantised PAM 179

5.6 Signal to quantisation noise ratio(SNqR) 181

5.7 Pulse code modulation 183

5.7.1 SNqR for linear PCM 183

5.7.2 SNR for decoded PCM 185

5.7.3 Companded PCM 188

5.7.4 PCM multiplexing 191

5.8 Bandwidth reduction techniques 192

5.8.1 Delta PCM 193

5.8.2 Differential PCM 193

5.8.3 Adaptive DPCM 195

5.8.4 Delta modulation 196

5.8.5 Adaptive delta modulation 199

5.9 Summary 201

5.10 Problems 202

6 Baseband transmission and line coding 204

6.1 Introduction 204

6.2 Baseband centre point detection 204

6.2.1 Baseband binary error rates in Gaussian noise 205

6.2.2 Multilevel baseband signalling 209

6.3 Error accumulation over multiple hops 211

6.4 Line coding 214

6.4.1 Unipolar signalling 217

6.4.2 Polar signalling 219

6.4.3 Dipolar signalling 219

6.4.4 Bipolar alternate mark inversion signalling 219

6.4.5 Pulse synchronisation and HDBn coding 220

6.4.6 Coded mark inversion(CMI) 220

6.4.7 nBmT coding 220

6.5 Multiplex telephony 221

6.6 Digital signal regeneration 222

6.6.1 PCM line codes 223

6.6.2 Equalisation 224

6.6.3 Eye diagrams 226

6.6.4 Crosstalk 228

6.7 Symbol timing recovery(STR) 230

6.8 Repeater design 232

6.9 Digital transmission in local loop 232

6.10 Summary 236

6.11 Problems 236

7 Decision theory 238

7.1 Introduction 238

7.2 A priori,conditional and a posteriori probabilities 239

7.3 Symbol transition matrix 240

7.3.1 Binary symmetric channel 240

7.4 Bayes's decision criterion 243

7.4.1 Decision costs 243

7.4.2 Expected conditional decision costs 243

7.4.3 Optimum decision rule 244

7.4.4 Optimum decision threshold voltage 245

7.4.5 Average unconditional decision cost 246

7.5 Neyman-Pearson decision criterion 249

7.6 Summary 250

7.7 Problems 251

8 Optimum filtering for transmission and reception 253

8.1 Introduction 253

8.2 Pulse shaping for optimum transmissions 253

8.2.1 Intersymbol interference(ISI) 254

8.2.2 Bandlimiting of rectangular pulses 254

8.2.3 ISI-free signals 255

8.2.4 Nyquist's vestigial symmetry theorem 259

8.2.5 Raised cosine filtering 260

8.2.6 Nyquist filtering for rectangular pulses 263

8.2.7 Duobinary signalling 263

8.2.8 Partial response signalling 270

8.3 Pulse filtering for optimum reception 271

8.3.1 Matched filtering 272

8.3.2 Correlation detection 276

8.3.3 Decision instant SNR 281

8.3.4 BER performance of optimum receivers 284

8.3.5 Comparison of baseband matched filtering and centre point detection 286

8.3.6 Differences between matched filtering and correlation 287

8.4 Root raised cosine filtering 288

8.5 Equalisation 289

8.6 Summary 292

8.7 Problems 293

9 Information theory,source coding and encryption 295

9.1 Introduction 295

9.2 Information and entropy 296

9.2.1 The information measure 296

9.2.2 Multisymbol alphabets 297

9.2.3 Commonly confused entities 298

9.2.4 Entropy of a binary source 298

9.3 Conditional entropy and redundancy 299

9.4 Information loss due to noise 302

9.5 Source coding 305

9.5.1 Code efficiency 305

9.5.2 Decoding variable length codewords 306

9.6 Variable length coding 308

9.6.1 Huffman coding 308

9.7 Source coding examples 310

9.7.1 Source coding for speech signals 311

9.7.2 High quality speech coders 314

9.7.3 Audio coders 315

9.7.4 String coding 318

9.8 Data encryption 319

9.8.1 The locked box analogy 319

9.8.2 Secrecy 320

9.8.3 Substitution and permutation 321

9.8.4 Confusion,diffusion and the unicity distance 322

9.8.5 Block ciphers and stream ciphers 324

9.8.6 Product ciphers 325

9.8.7 Data encryption standard 326

9.8.8 Public key encryption 334

9.8.9 Hash functions and OAEP 339

9.8.10 Hybrid public key/private key encryption and PGP 339

9.9 Authentication 341

9.10 Integrity 342

9.11 Digital signatures 342

9.12 Summary 342

9.13 Problems 344

10 Error control coding 347

10.1 Introduction 347

10.1.1 Error rate control concepts 349

10.1.2 Threshold phenomenon 350

10.1.3 Applications for error control 351

10.2 Hamming distance and codeword weight 351

10.3 (n,k)block codes 352

10.3.1 Single parity check code 352

10.4 Probability of error in n-digit codewords 356

10.5 Linear group codes 356

10.5.1 Members of the group code family 357

10.5.2 Performance prediction 357

10.5.3 Error detection and correction capability 358

10.6 Nearest neighbour decoding of block codes 359

10.6.1 Hamming bound 359

10.7 Syndrome decoding 360

10.7.1 The generator matrix 360

10.7.2 Syndrome table for error correction 361

10.8 Cyclic codes 364

10.8.1 Polynomal codeword generation 365

10.8.2 Interleaving 368

10.9 Encoding of convolutional codes 369

10.9.1 Tree diagram representation 370

10.9.2 Trellis diagram 371

10.9.3 State transition diagram 371

10.10 Viterbi decoding of convolutional codes 372

10.10.1 Decoding window 375

10.10.2 Sequential decoding 376

10.11 Practical coders 377

10.12 Concatenated coding and turbo codes 378

10.12.1 Serially concatenated codes 379

10.12.2 Parallel-concatenated recursive systematic convolutional codes 380

10.12.3 Turbo decoding 382

10.12.4 Turbo code performance 385

10.12.5 Other applications of the turbo principle and LDPC codes 386

10.13 Summary 387

10.14 Problems 388

11 Bandpass modulation of a carrier signal 390

11.1 Introduction 390

11.2 Spectral and power efficiency 391

11.3 Binary IF modulation 391

11.3.1 Binary amplitude shift keying(and on-off keying) 391

11.3.2 Binary phase shift keying(and phase reversal keying) 395

11.3.3 Binary frequency shift keying 399

11.3.4 BFSK symbol correlation and Sunde's FSK 402

11.3.5 Comparison of binary shift keying techniques 405

11.3.6 Carrier recovery,phase ambiguity and DPSK 408

11.4 Modulation techniques with increased spectral efficiency 410

11.4.1 Channel capacity 411

11.4.2 M-symbol phase shift keying 412

11.4.3 Amplitude/phase keying and quadrature amplitude modulation 416

11.4.4 Quadrature phase shift keying(QPSK)and offset QPSK 421

11.4.5 Minimum shift keying 428

11.4.6 Gaussian MSK 431

11.4.7 Trellis coded modulation 431

11.5 Power efficient modulation techniques 437

11.5.1 Multidimensional signalling and MFSK 437

11.5.2 Orthogonal frequency division multiplex(OFDM) 442

11.5.3 Optimum constellation point packing 445

11.5.4 Optimum constellation point boundaries 446

11.6 Data modems 447

11.7 Summary 448

11.8 Problems 449

12 System noise and communications link budgets 452

12.1 Introduction 452

12.2 Physical aspects of noise 452

12.2.1 Thermal noise 453

12.2.2 Non-thermal noise 457

12.2.3 Combining white noise sources 460

12.3 System noise calculations 463

12.3.1 Noise temperature 463

12.3.2 Noise temperature of cascaded subsystems 465

12.3.3 Noise factor and noise figure 468

12.4 Radio communication link budgets 471

12.4.1 Antenna gain,effective area and efficiency 471

12.4.2 Free space and plane earth signal budgets 476

12.4.3 Antenna temperature and radio noise budgets 482

12.4.4 Receiver equivalent input CNR 485

12.4.5 Multipath fading and diversity reception 486

12.5 Fibre optic transmission links 488

12.5.1 Fibre types 489

12.5.2 Fibre transmission systems 491

12.5.3 Optical sources 492

12.5.4 Optical detectors 492

12.5.5 Optical amplifiers 492

12.5.6 Optical repeater and link budgets 494

12.5.7 Optical FDM 496

12.5.8 Optical signal routers 496

12.6 Summary 496

12.7 Problems 497

13 Communication systems simulation 500

13.1 Introduction 500

13.2 Equivalent complex baseband representations 502

13.2.1 Equivalent baseband signals 502

13.2.2 Equivalent baseband systems 503

13.2.3 Equivalent baseband system output 505

13.2.4 Equivalent baseband noise 509

13.3 Sampling and quantisation 512

13.3.1 Sampling equivalent baseband signals 512

13.3.2 Quantisation 514

13.4 Modelling of signals,noise and systems 514

13.4.1 Random numbers 514

13.4.2 Random digital symbol streams 516

13.4.3 Noise and interference 520

13.4.4 Time invariant linear systems 521

13.4.5 Non-linear and time varying systems 522

13.5 Transformation between time and frequency domains 523

13.5.1 DFT 524

13.5.2 DFS 526

13.5.3 DFS spectrum and rearrangement of spectral lines 526

13.5.4 Conservation of information 527

13.5.5 Phasor interpretation of DFS 527

13.5.6 Inverse DFS and DFT 528

13.5.7 DFT accuracy 529

13.6 Discrete and cyclical convolution 535

13.7 Estimation of BER 538

13.7.1 Monte Carlo simulation 538

13.7.2 Quasi-analytic simulation 540

13.8 Summary 546

Part Three Applications 549

14 Fixed-point microwave communications 551

14.1 Introduction 551

14.2 Terrestrial microwave links 551

14.2.1 Analogue systems 553

14.2.2 Digital systems 554

14.2.3 LOS link design 556

14.2.4 Other propagation considerations for terrestrial links 565

14.3 Fixed-point satellite communications 572

14.3.1 Satellite frequency bands and orbital spacing 574

14.3.2 Earth station look angles and satellite range 575

14.3.3 Satellite link budgets 577

14.3.4 Slant path propagation considerations 583

14.3.5 Analogue FDM/FM/FDMA trunk systems 589

14.3.6 Digital TDM/PSK/TDMA trunk systems 593

14.3.7 DA-TDMA,DSI and random access systems 598

14.3.8 Economics of satellite communications 599

14.3.9 VSAT systems 599

14.3.10 Satellite switched TDMA and onboard signal processing 599

14.4 Summary 601

14.5 Problems 602

15 Mobile and cellular radio 605

15.1 Introduction 605

15.1.1 Private mobile radio 605

15.1.2 Radio paging systems 607

15.2 Mobile radio link budget and channel characteristics 607

15.2.1 Prediction of median signal strength 608

15.2.2 Slow and fast fading 610

15.2.3 Dispersion,frequency selective fading and coherence bandwidth 611

15.2.4 Multipath modelling and simulation 612

15.3 Nationwide cellular radio communications 614

15.3.1 Introduction 614

15.3.2 Personal cordless communications 615

15.3.3 Analogue cellular radio communication 616

15.3.4 Cell sizes 616

15.3.5 System configuration 619

15.4 Digital TDMA terrestrial cellular systems 620

15.4.1 TDMA systems 620

15.4.2 TDMA data format and modulation 621

15.4.3 Speech and channel coding 622

15.4.4 Other operational constraints 623

15.4.5 Trunked radio for paramilitary use 624

15.5 Code division multiple access(CDMA) 624

15.5.1 The CDMA concept 624

15.5.2 CDMA receiver design 626

15.5.3 Spreading sequence design 629

15.5.4 Data modulation 633

15.5.5 CDMA multipath processing 633

15.5.6 The cdmaOne system 634

15.5.7 Frequency hopped transmission 638

15.6 Mobile satellite based systems 640

15.7 Third generation mobile cellular standards 642

15.7.1 Mobile data transmission 642

15.7.2 3G systems 643

15.7.3 4G or 3G evolution 645

15.8 Summary 645

15.9 Problems 646

16 Video transmission and storage 647

16.1 Introduction 647

16.2 Colour representation 648

16.3 Conventional TV transmission systems 650

16.3.1 PAL encoding 650

16.3.2 PAL television receiver 652

16.3.3 Other encoding schemes 653

16.4 High definition TV 653

16.4.1 What is HDTV? 653

16.4.2 Transmissions 654

16.5 Digital video 655

16.6 Video data compression 656

16.6.1 Run length coding 657

16.6.2 Conditional replenishment 658

16.6.3 Transform coding 658

16.7 Compression standards 659

16.7.1 COST 211 659

16.7.2 JPEG 660

16.7.3 MPEG-1 and MPEG-2 662

16.7.4 MPEG-4 and MPEG-7 664

16.7.5 H.261,H.263 and H.264 665

16.7.6 Model based coding 666

16.8 Digital video broadcast 668

16.9 Packet video 669

16.10 Other multimedia services 670

16.11 Summary 670

16.12 Problems 672

Part Four Networks 673

17 Network applications,topologies and architecture 675

17.1 Introduction 675

17.2 Network applications 676

17.3 Network function 678

17.4 Network classification 678

17.5 Switched network topologies and representation 680

17.5.1 Star or hub 681

17.5.2 Tree 682

17.5.3 Mesh 682

17.5.4 Matrix representation 683

17.6 Generic network switching philosophies 684

17.6.1 Circuit switching 684

17.6.2 Message switching 685

17.6.3 Packet switching 685

17.7 Broadcast network topologies 688

17.7.1 Bus or multidrop 688

17.7.2 Passive ring 689

17.7.3 Active ring 690

17.8 Transmission media 691

17.9 Interconnected networks 691

17.10 User and provider network views 693

17.11 Connection-oriented and connectionless services 696

17.12 Layered network architectures 696

17.12.1 ISO OSI protocol reference model 697

17.12.2 Network layers in use 700

17.13 Summary 702

17.14 Problems 702

18 Network protocols 704

18.1 Introduction 704

18.2 Physical layer 704

18.2.1 A physical layer protocol-X.21 705

18.3 Data-link layer 709

18.3.1 Synchronisation 710

18.3.2 Error control 713

18.3.3 Flow control 727

18.3.4 A data-link protocol-HDLC 730

18.4 Network layer 733

18.4.1 Routing 734

18.4.2 Congestion control 740

18.4.3 Error control 741

18.4.4 Quality of service 741

18.4.5 A connection-oriented network level protocol-X.25 PLP 741

18.4.6 A connectionless network level protocol(CLNP) 745

18.4.7 Use of primitives 750

18.5 Transport layer 752

18.5.1 Message segmentation and reassembly 753

18.5.2 Multiplexing and parallel virtual circuit transmission 753

18.5.3 End-to-end error and flow control 754

18.5.4 Use of well known and ephemeral ports 754

18.5.5 A transport level protocol-TP4 754

18.6 Session layer 759

18.6.1 Session connection,maintenance and release 759

18.6.2 Dialogue supervision 760

18.6.3 Recovery 760

18.6.4 A session level protocol-ISO-SP 760

18.7 Presentation layer 764

18.7.1 Translation between local and transfer syntaxes 764

18.2 Abstract syntax notation 1 (ASN.1) 765

18.7.3 A presentation level protocol-ISO-PP 766

18.8 Application layer 766

18.9 Non-OSI protocol stacks 766

18.10 Summary 767

18.11 Problems 769

19 Network performance using queueing theory(M.E.Woodward) 771

19.1 Introduction 771

19.1.1 The arrival process 772

19.1.2 Queueing systems 775

19.2 The M/M/1 queue 776

19.2.1 The equilibrium probabilities 776

19.2.2 Performance measures 778

19.3 The M/M/1/N queue 780

19.3.1 General Markovian queueing equations 782

19.3.2 The M/M/N/N queue 786

19.3.3 The M/M/N/N/K queue 788

19.3.4 M/M/N/N+j queue(Erlang-C equation) 789

19.3.5 Distribution of waiting times 792

19.4 M/M/N/K/K queue:queueing behaviour in a mobile communication system 793

19.4.1 Speech source model 794

19.4.2 Equilibrium probability 794

19.5 Summary 796

19.6 Problems 797

20 Switched networks and WANs 799

20.1 Introduction 799

20.2 WAN characteristics and classification 800

20.3 Application of graph theory to core networks 802

20.3.1 Topology,cost and capacity matrices 802

20.3.2 Network capacity 803

20.3.3 Network connectivity 808

20.4 The UK public network 811

20.4.1 The traditional analogue network 812

20.4.2 The modern digital network 813

20.5 Multiplexing 816

20.5.1 The plesiochronous digital hierarchy 816

20.5.2 SDH and SONET 824

20.6 Circuit switching 836

20.6.1 Space switching 836

20.6.2 Time switching 836

20.6.3 Time-space-time and space-time-space switching 838

20.6.4 Multi-stage space switches 839

20.6.5 Switch connectivity 845

20.6.6 Concentration and expansion 845

20.6.7 Switch design 846

20.6.8 Probability of blocking 849

20.6.9 Circuit switched data over the PSTN 851

20.7 Packet switching 855

20.7.1 Packet switched data over the PDN 856

20.7.2 Frame relay 861

20.8 Integrated services digital network(ISDN) 862

20.8.1 ISDN structure 862

20.8.2 Basic and primary rate access 863

20.8.3 ISDN services 865

20.9 Signalling 866

20.9.1 In-channel and common channel signalling 867

20.9.2 Signalling system No.7 868

20.10 Asynchronous transfer mode and the broadband ISDN 870

20.10.1 Transport mechanism 871

20.10.2 Service classes 873

20.10.3 Connection admission control 874

20.10.4 Access protocols 875

20.10.5 Synchronous versus asynchronous transfer modes 875

20.10.6 Transition from ATM to IP 876

20.11 Access technologies 877

20.11.1 Digital subscriber line 877

20.11.2 Fibre 881

20.11.3 Cable 884

20.11.4 Broadband fixed wireless access(IEEE 802.16) 890

20.11.5 Comparison of access network technologies 903

20.11.6 Convergence of access network services 903

20.12 Summary 906

20.13 Problems 908

21 Broadcast networks and LANs 911

21.1 Introduction 911

21.2 LAN topologies 912

21.3 LAN protocol stack 912

21.3.1 Fixed access multiplexing 913

21.3.2 Polling 913

21.3.3 Token passing 913

21.3.4 Contention 914

21.4 Popular wired LAN standards 915

21.4.1 Ethernet(IEEE 802.3) 916

21.4.2 Token ring(IEEE 802.5) 923

21.5 Wireless LANs 933

21.5.1 WLAN(IEEE 802.11) 934

21.5.2 MIMO techniques 942

21.5.3 HIP ERLAN 947

21.6 Metropolitan area networks 951

21.6.1 Fibre distributed data interface 951

21.6.2 Distributed queue dual bus 955

21.6.3 ATM MANs/LANs 958

21.7 Wireless personal area networks 960

21.7.1 Bluetooth(IEEE 802.15.1) 960

27.2 Other IEEE 802.15 PAN technologies 969

21.8 Home networking technologies 974

21.8.1 Wired home networks 975

21.8.2 Wireless home networks 976

21.9 Residential gateways 978

21.10 Summary 979

21.11 Problems 981

Appendix A.Tabulated values of the error function 982

Appensix B.Summations of common series 985

Appendix C.International Alphabet No.5(ASCII code set) 986

Appendix D.LAN/MAN examples 987

Standards 989

WWW addresses 993

Bibliography 995

Index 1011