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1 Digital communications overview1

1.1 Electronic communications1

1.2 Sources and sinks of information4

1.3 Digital communications equipment6

1.3.1 CODECs6

1.3.2 Source,security and error control coding7

1.3.3 Multiplexers7

1.3.4 MODEMs8

1.3.5 Multiple accessing8

1.4 Radio receivers8

1.5 Signal transmission9

1.5.1 Line transmission9

1.5.2 Radio transmission13

1.6 Switching and networks14

1.7 Advantages of digital communications15

1.8 Summary16

Part One Signals and systems theory19

2 Periodic and transient signals21

2.1 Introduction21

2.2 Periodic signals22

2.2.1 Sinusoids,cisoids and phasors22

2.2.2 Fourier series27

2.2.3 Conditions for existence,convergence and Gibb's phenomenon41

2.2.4 Bandwidth,rates of change,sampling and aliasing44

2.3 Transient signals47

2.3.1 Fourier transforms47

2.3.2 Practical calculation of Fourier transforms49

2.3.3 Fourier transform pairs51

2.3.4 Fourier transform theorems and convolution56

2.4 Power and energy spectra65

2.5 Generalised orthogonal function expansions67

2.5.1 Review of vectors67

2.5.2 Vector interpretation of waveforms70

2.5.3 Orthogonal and orthonormal signals72

2.5.4 Evaluation of basis function coefficients74

2.5.5 Error energy and completeness75

2.6 Correlation functions77

2.7 Summary83

2.8 Problems84

3 Random signals and noise86

3.1 Introduction86

3.2 Probability theory86

3.2.1 Conditional probabilities,joint probabilities and Bayes's rule88

3.2.2 Statistical independence89

3.2.3 Discrete probability of errors in a data block90

3.2.4 Cumulative distributions and probability density functions92

3.2.5 Moments,percentiles and modes96

3.2.6 Joint and marginal pdfs,correlation and covariance101

3.2.7 Joint moments,correlation and covariance104

3.2.8 Joint Gaussian random variables107

3.2.9 Addition of random variables and the central limit theorem108

3.3 Random processes112

3.3.1 Stationarity and ergodicity114

3.3.2 Strict and loose sense Gaussian processes115

3.3.3 Autocorrelation and power spectral density117

3.3.4 Signal memory,decorrelation time and white noise121

3.3.5 Cross correlation of random processes122

3.4 Summary122

3.5 Problems124

4 Linear systems128

4.1 Introduction128

4.2 Linear systems128

4.2.1 Properties of linear systems129

4.2.2 Importance of linear systems130

4.3 Time domain description of linear systems133

4.3.1 Linear differential equations133

4.3.2 Discrete signals and matrix algebra134

4.3.3 Continuous signals,convolution and impulse response134

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

4.3.5 Step response138

4.4 Frequency domain description141

4.5 Causality and the Hilbert transform144

4.6 Random signals and linear systems147

4.6.1 Power spectral densities and linear systems147

4.6.2 Noise bandwidth149

4.6.3 Pdf of filtered noise149

4.6.4 Spectrum analysers151

4.7 Non-linear systems and transformation of random variables152

4.7.1 Rayleigh pdf153

4.7.2 Chi-square distributions155

4.8 Summary157

4.9 Problems157

Part Two Digital communications principles161

5 Sampling,multiplexing and PCM163

5.1 Introduction163

5.2 Pulse modulation163

5.3 Sampling165

5.3.1 Natural and flat topped sampling166

5.3.2 Baseband sampling and Nyquist's criterion167

5.3.3 Aliasing168

5.3.4 Practical sampling,reconstruction and signal to distortion ratio169

5.3.5 Bandpass sampling173

5.4 Analogue pulse multiplexing176

5.5 Quantised PAM179

5.6 Signal to quantisation noise ratio(SNqR)181

5.7 Pulse code modulation183

5.7.1 SNqR for linear PCM183

5.7.2 SNR for decoded PCM185

5.7.3 Companded PCM188

5.7.4 PCM multiplexing191

5.8 Bandwidth reduction techniques192

5.8.1 Delta PCM193

5.8.2 Differential PCM193

5.8.3 Adaptive DPCM195

5.8.4 Delta modulation196

5.8.5 Adaptive delta modulation199

5.9 Summary201

5.10 Problems202

6 Baseband transmission and line coding204

6.1 Introduction204

6.2 Baseband centre point detection204

6.2.1 Baseband binary error rates in Gaussian noise205

6.2.2 Multilevel baseband signalling209

6.3 Error accumulation over multiple hops211

6.4 Line coding214

6.4.1 Unipolar signalling217

6.4.2 Polar signalling219

6.4.3 Dipolar signalling219

6.4.4 Bipolar alternate mark inversion signalling219

6.4.5 Pulse synchronisation and HDBn coding220

6.4.6 Coded mark inversion(CMI)220

6.4.7 nBmT coding220

6.5 Multiplex telephony221

6.6 Digital signal regeneration222

6.6.1 PCM line codes223

6.6.2 Equalisation224

6.6.3 Eye diagrams226

6.6.4 Crosstalk228

6.7 Symbol timing recovery(STR)230

6.8 Repeater design232

6.9 Digital transmission in local loop232

6.10 Summary236

6.11 Problems236

7 Decision theory238

7.1 Introduction238

7.2 A priori,conditional and a posteriori probabilities239

7.3 Symbol transition matrix240

7.3.1 Binary symmetric channel240

7.4 Bayes's decision criterion243

7.4.1 Decision costs243

7.4.2 Expected conditional decision costs243

7.4.3 Optimum decision rule244

7.4.4 Optimum decision threshold voltage245

7.4.5 Average unconditional decision cost246

7.5 Neyman-Pearson decision criterion249

7.6 Summary250

7.7 Problems251

8 Optimum filtering for transmission and reception253

8.1 Introduction253

8.2 Pulse shaping for optimum transmissions253

8.2.1 Intersymbol interference(ISI)254

8.2.2 Bandlimiting of rectangular pulses254

8.2.3 ISI-free signals255

8.2.4 Nyquist's vestigial symmetry theorem259

8.2.5 Raised cosine filtering260

8.2.6 Nyquist filtering for rectangular pulses263

8.2.7 Duobinary signalling263

8.2.8 Partial response signalling270

8.3 Pulse filtering for optimum reception271

8.3.1 Matched filtering272

8.3.2 Correlation detection276

8.3.3 Decision instant SNR281

8.3.4 BER performance of optimum receivers284

8.3.5 Comparison of baseband matched filtering and centre point detection286

8.3.6 Differences between matched filtering and correlation287

8.4 Root raised cosine filtering288

8.5 Equalisation289

8.6 Summary292

8.7 Problems293

9 Information theory,source coding and encryption295

9.1 Introduction295

9.2 Information and entropy296

9.2.1 The information measure296

9.2.2 Multisymbol alphabets297

9.2.3 Commonly confused entities298

9.2.4 Entropy of a binary source298

9.3 Conditional entropy and redundancy299

9.4 Information loss due to noise302

9.5 Source coding305

9.5.1 Code efficiency305

9.5.2 Decoding variable length codewords306

9.6 Variable length coding308

9.6.1 Huffman coding308

9.7 Source coding examples310

9.7.1 Source coding for speech signals311

9.7.2 High quality speech coders314

9.7.3 Audio coders315

9.7.4 String coding318

9.8 Data encryption319

9.8.1 The locked box analogy319

9.8.2 Secrecy320

9.8.3 Substitution and permutation321

9.8.4 Confusion,diffusion and the unicity distance322

9.8.5 Block ciphers and stream ciphers324

9.8.6 Product ciphers325

9.8.7 Data encryption standard326

9.8.8 Public key encryption334

9.8.9 Hash functions and OAEP339

9.8.10 Hybrid public key/private key encryption and PGP339

9.9 Authentication341

9.10 Integrity342

9.11 Digital signatures342

9.12 Summary342

9.13 Problems344

10 Error control coding347

10.1 Introduction347

10.1.1 Error rate control concepts349

10.1.2 Threshold phenomenon350

10.1.3 Applications for error control351

10.2 Hamming distance and codeword weight351

10.3 (n,k)block codes352

10.3.1 Single parity check code352

10.4 Probability of error in n-digit codewords356

10.5 Linear group codes356

10.5.1 Members of the group code family357

10.5.2 Performance prediction357

10.5.3 Error detection and correction capability358

10.6 Nearest neighbour decoding of block codes359

10.6.1 Hamming bound359

10.7 Syndrome decoding360

10.7.1 The generator matrix360

10.7.2 Syndrome table for error correction361

10.8 Cyclic codes364

10.8.1 Polynomal codeword generation365

10.8.2 Interleaving368

10.9 Encoding of convolutional codes369

10.9.1 Tree diagram representation370

10.9.2 Trellis diagram371

10.9.3 State transition diagram371

10.10 Viterbi decoding of convolutional codes372

10.10.1 Decoding window375

10.10.2 Sequential decoding376

10.11 Practical coders377

10.12 Concatenated coding and turbo codes378

10.12.1 Serially concatenated codes379

10.12.2 Parallel-concatenated recursive systematic convolutional codes380

10.12.3 Turbo decoding382

10.12.4 Turbo code performance385

10.12.5 Other applications of the turbo principle and LDPC codes386

10.13 Summary387

10.14 Problems388

11 Bandpass modulation of a carrier signal390

11.1 Introduction390

11.2 Spectral and power efficiency391

11.3 Binary IF modulation391

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 keying399

11.3.4 BFSK symbol correlation and Sunde's FSK402

11.3.5 Comparison of binary shift keying techniques405

11.3.6 Carrier recovery,phase ambiguity and DPSK408

11.4 Modulation techniques with increased spectral efficiency410

11.4.1 Channel capacity411

11.4.2 M-symbol phase shift keying412

11.4.3 Amplitude/phase keying and quadrature amplitude modulation416

11.4.4 Quadrature phase shift keying(QPSK)and offset QPSK421

11.4.5 Minimum shift keying428

11.4.6 Gaussian MSK431

11.4.7 Trellis coded modulation431

11.5 Power efficient modulation techniques437

11.5.1 Multidimensional signalling and MFSK437

11.5.2 Orthogonal frequency division multiplex(OFDM)442

11.5.3 Optimum constellation point packing445

11.5.4 Optimum constellation point boundaries446

11.6 Data modems447

11.7 Summary448

11.8 Problems449

12 System noise and communications link budgets452

12.1 Introduction452

12.2 Physical aspects of noise452

12.2.1 Thermal noise453

12.2.2 Non-thermal noise457

12.2.3 Combining white noise sources460

12.3 System noise calculations463

12.3.1 Noise temperature463

12.3.2 Noise temperature of cascaded subsystems465

12.3.3 Noise factor and noise figure468

12.4 Radio communication link budgets471

12.4.1 Antenna gain,effective area and efficiency471

12.4.2 Free space and plane earth signal budgets476

12.4.3 Antenna temperature and radio noise budgets482

12.4.4 Receiver equivalent input CNR485

12.4.5 Multipath fading and diversity reception486

12.5 Fibre optic transmission links488

12.5.1 Fibre types489

12.5.2 Fibre transmission systems491

12.5.3 Optical sources492

12.5.4 Optical detectors492

12.5.5 Optical amplifiers492

12.5.6 Optical repeater and link budgets494

12.5.7 Optical FDM496

12.5.8 Optical signal routers496

12.6 Summary496

12.7 Problems497

13 Communication systems simulation500

13.1 Introduction500

13.2 Equivalent complex baseband representations502

13.2.1 Equivalent baseband signals502

13.2.2 Equivalent baseband systems503

13.2.3 Equivalent baseband system output505

13.2.4 Equivalent baseband noise509

13.3 Sampling and quantisation512

13.3.1 Sampling equivalent baseband signals512

13.3.2 Quantisation514

13.4 Modelling of signals,noise and systems514

13.4.1 Random numbers514

13.4.2 Random digital symbol streams516

13.4.3 Noise and interference520

13.4.4 Time invariant linear systems521

13.4.5 Non-linear and time varying systems522

13.5 Transformation between time and frequency domains523

13.5.1 DFT524

13.5.2 DFS526

13.5.3 DFS spectrum and rearrangement of spectral lines526

13.5.4 Conservation of information527

13.5.5 Phasor interpretation of DFS527

13.5.6 Inverse DFS and DFT528

13.5.7 DFT accuracy529

13.6 Discrete and cyclical convolution535

13.7 Estimation of BER538

13.7.1 Monte Carlo simulation538

13.7.2 Quasi-analytic simulation540

13.8 Summary546

Part Three Applications549

14 Fixed-point microwave communications551

14.1 Introduction551

14.2 Terrestrial microwave links551

14.2.1 Analogue systems553

14.2.2 Digital systems554

14.2.3 LOS link design556

14.2.4 Other propagation considerations for terrestrial links565

14.3 Fixed-point satellite communications572

14.3.1 Satellite frequency bands and orbital spacing574

14.3.2 Earth station look angles and satellite range575

14.3.3 Satellite link budgets577

14.3.4 Slant path propagation considerations583

14.3.5 Analogue FDM/FM/FDMA trunk systems589

14.3.6 Digital TDM/PSK/TDMA trunk systems593

14.3.7 DA-TDMA,DSI and random access systems598

14.3.8 Economics of satellite communications599

14.3.9 VSAT systems599

14.3.10 Satellite switched TDMA and onboard signal processing599

14.4 Summary601

14.5 Problems602

15 Mobile and cellular radio605

15.1 Introduction605

15.1.1 Private mobile radio605

15.1.2 Radio paging systems607

15.2 Mobile radio link budget and channel characteristics607

15.2.1 Prediction of median signal strength608

15.2.2 Slow and fast fading610

15.2.3 Dispersion,frequency selective fading and coherence bandwidth611

15.2.4 Multipath modelling and simulation612

15.3 Nationwide cellular radio communications614

15.3.1 Introduction614

15.3.2 Personal cordless communications615

15.3.3 Analogue cellular radio communication616

15.3.4 Cell sizes616

15.3.5 System configuration619

15.4 Digital TDMA terrestrial cellular systems620

15.4.1 TDMA systems620

15.4.2 TDMA data format and modulation621

15.4.3 Speech and channel coding622

15.4.4 Other operational constraints623

15.4.5 Trunked radio for paramilitary use624

15.5 Code division multiple access(CDMA)624

15.5.1 The CDMA concept624

15.5.2 CDMA receiver design626

15.5.3 Spreading sequence design629

15.5.4 Data modulation633

15.5.5 CDMA multipath processing633

15.5.6 The cdmaOne system634

15.5.7 Frequency hopped transmission638

15.6 Mobile satellite based systems640

15.7 Third generation mobile cellular standards642

15.7.1 Mobile data transmission642

15.7.2 3G systems643

15.7.3 4G or 3G evolution645

15.8 Summary645

15.9 Problems646

16 Video transmission and storage647

16.1 Introduction647

16.2 Colour representation648

16.3 Conventional TV transmission systems650

16.3.1 PAL encoding650

16.3.2 PAL television receiver652

16.3.3 Other encoding schemes653

16.4 High definition TV653

16.4.1 What is HDTV?653

16.4.2 Transmissions654

16.5 Digital video655

16.6 Video data compression656

16.6.1 Run length coding657

16.6.2 Conditional replenishment658

16.6.3 Transform coding658

16.7 Compression standards659

16.7.1 COST 211659

16.7.2 JPEG660

16.7.3 MPEG-1 and MPEG-2662

16.7.4 MPEG-4 and MPEG-7664

16.7.5 H.261,H.263 and H.264665

16.7.6 Model based coding666

16.8 Digital video broadcast668

16.9 Packet video669

16.10 Other multimedia services670

16.11 Summary670

16.12 Problems672

Part Four Networks673

17 Network applications,topologies and architecture675

17.1 Introduction675

17.2 Network applications676

17.3 Network function678

17.4 Network classification678

17.5 Switched network topologies and representation680

17.5.1 Star or hub681

17.5.2 Tree682

17.5.3 Mesh682

17.5.4 Matrix representation683

17.6 Generic network switching philosophies684

17.6.1 Circuit switching684

17.6.2 Message switching685

17.6.3 Packet switching685

17.7 Broadcast network topologies688

17.7.1 Bus or multidrop688

17.7.2 Passive ring689

17.7.3 Active ring690

17.8 Transmission media691

17.9 Interconnected networks691

17.10 User and provider network views693

17.11 Connection-oriented and connectionless services696

17.12 Layered network architectures696

17.12.1 ISO OSI protocol reference model697

17.12.2 Network layers in use700

17.13 Summary702

17.14 Problems702

18 Network protocols704

18.1 Introduction704

18.2 Physical layer704

18.2.1 A physical layer protocol-X.21705

18.3 Data-link layer709

18.3.1 Synchronisation710

18.3.2 Error control713

18.3.3 Flow control727

18.3.4 A data-link protocol-HDLC730

18.4 Network layer733

18.4.1 Routing734

18.4.2 Congestion control740

18.4.3 Error control741

18.4.4 Quality of service741

18.4.5 A connection-oriented network level protocol-X.25 PLP741

18.4.6 A connectionless network level protocol(CLNP)745

18.4.7 Use of primitives750

18.5 Transport layer752

18.5.1 Message segmentation and reassembly753

18.5.2 Multiplexing and parallel virtual circuit transmission753

18.5.3 End-to-end error and flow control754

18.5.4 Use of well known and ephemeral ports754

18.5.5 A transport level protocol-TP4754

18.6 Session layer759

18.6.1 Session connection,maintenance and release759

18.6.2 Dialogue supervision760

18.6.3 Recovery760

18.6.4 A session level protocol-ISO-SP760

18.7 Presentation layer764

18.7.1 Translation between local and transfer syntaxes764

18.2 Abstract syntax notation 1 (ASN.1)765

18.7.3 A presentation level protocol-ISO-PP766

18.8 Application layer766

18.9 Non-OSI protocol stacks766

18.10 Summary767

18.11 Problems769

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

19.1 Introduction771

19.1.1 The arrival process772

19.1.2 Queueing systems775

19.2 The M/M/1 queue776

19.2.1 The equilibrium probabilities776

19.2.2 Performance measures778

19.3 The M/M/1/N queue780

19.3.1 General Markovian queueing equations782

19.3.2 The M/M/N/N queue786

19.3.3 The M/M/N/N/K queue788

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

19.3.5 Distribution of waiting times792

19.4 M/M/N/K/K queue:queueing behaviour in a mobile communication system793

19.4.1 Speech source model794

19.4.2 Equilibrium probability794

19.5 Summary796

19.6 Problems797

20 Switched networks and WANs799

20.1 Introduction799

20.2 WAN characteristics and classification800

20.3 Application of graph theory to core networks802

20.3.1 Topology,cost and capacity matrices802

20.3.2 Network capacity803

20.3.3 Network connectivity808

20.4 The UK public network811

20.4.1 The traditional analogue network812

20.4.2 The modern digital network813

20.5 Multiplexing816

20.5.1 The plesiochronous digital hierarchy816

20.5.2 SDH and SONET824

20.6 Circuit switching836

20.6.1 Space switching836

20.6.2 Time switching836

20.6.3 Time-space-time and space-time-space switching838

20.6.4 Multi-stage space switches839

20.6.5 Switch connectivity845

20.6.6 Concentration and expansion845

20.6.7 Switch design846

20.6.8 Probability of blocking849

20.6.9 Circuit switched data over the PSTN851

20.7 Packet switching855

20.7.1 Packet switched data over the PDN856

20.7.2 Frame relay861

20.8 Integrated services digital network(ISDN)862

20.8.1 ISDN structure862

20.8.2 Basic and primary rate access863

20.8.3 ISDN services865

20.9 Signalling866

20.9.1 In-channel and common channel signalling867

20.9.2 Signalling system No.7868

20.10 Asynchronous transfer mode and the broadband ISDN870

20.10.1 Transport mechanism871

20.10.2 Service classes873

20.10.3 Connection admission control874

20.10.4 Access protocols875

20.10.5 Synchronous versus asynchronous transfer modes875

20.10.6 Transition from ATM to IP876

20.11 Access technologies877

20.11.1 Digital subscriber line877

20.11.2 Fibre881

20.11.3 Cable884

20.11.4 Broadband fixed wireless access(IEEE 802.16)890

20.11.5 Comparison of access network technologies903

20.11.6 Convergence of access network services903

20.12 Summary906

20.13 Problems908

21 Broadcast networks and LANs911

21.1 Introduction911

21.2 LAN topologies912

21.3 LAN protocol stack912

21.3.1 Fixed access multiplexing913

21.3.2 Polling913

21.3.3 Token passing913

21.3.4 Contention914

21.4 Popular wired LAN standards915

21.4.1 Ethernet(IEEE 802.3)916

21.4.2 Token ring(IEEE 802.5)923

21.5 Wireless LANs933

21.5.1 WLAN(IEEE 802.11)934

21.5.2 MIMO techniques942

21.5.3 HIP ERLAN947

21.6 Metropolitan area networks951

21.6.1 Fibre distributed data interface951

21.6.2 Distributed queue dual bus955

21.6.3 ATM MANs/LANs958

21.7 Wireless personal area networks960

21.7.1 Bluetooth(IEEE 802.15.1)960

27.2 Other IEEE 802.15 PAN technologies969

21.8 Home networking technologies974

21.8.1 Wired home networks975

21.8.2 Wireless home networks976

21.9 Residential gateways978

21.10 Summary979

21.11 Problems981

Appendix A.Tabulated values of the error function982

Appensix B.Summations of common series985

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

Appendix D.LAN/MAN examples987

Standards989

WWW addresses993

Bibliography995

Index1011