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