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Digital communications: Principles and Systems aims to provide post graduate students and practising engineers with a thorough understanding in the core principles and design issues of digital communications to meet the industry demand for in-depth expertise in digital transmission techniques.

A worldwide digital and wireless communication revolution has taken place in the last 20 years which has created a high demand in industry for graduates with in-depth expertise in digital transmission techniques and a sound and complete understanding of their core principles.

Although digital communications is developing at a fast pace, this book recognises that the core principles remain the same. Many existing works on emerging digital transmission techniques are largely confined to academic research papers; therefore this book will give postgraduate students and practicing engineers a sound mastery of the subject.

This textbook concentrates on giving a solid foundation of core principles and design issues of digital communications. Engineering concepts and underlying physical considerations are described as well as a clear appreciation of the parameters involved, offering a good feel for the interplay of these parameters. Extensive coaching in the solution of practical problems are also drawn from various application areas.

Digital communications: Principles and Systems is an ideal textbook for those who wish to;

gain a thorough understanding of the core principles
undertake digital communication systems analysis
design and computer simulations
deal with specialised applications
keep up to date with advances in the technology
Topics covered include:

overview of digital communication
linear channels and systems
nonlinear systems
sampling of baseband and bandpass signals
quantisation and PCM
source coding and lossless data compression
line codes
transmission through bandlimited AWGN channels
transmitted digital signals
noise impact in digital transmission
error control coding
digital transmission link analysis and design



Book contents
1 Overview of digital communication 1
1.1 Introduction 1
1.2 Building blocks of a digital communication system 2
1.2.1 Transmitter and receiver 2
1.2.2 Analogue and digital communication systems 3
1.2.3 Information source 7
1.2.4 Information sink 10
1.2.5 Channel 12
1.3 Signal processing tasks 15
1.3.1 Source coding 17
1.3.2 Multiplexing 18
1.3.3 Channel coding 22
1.3.4 Line coding 24
1.3.5 Carrier modulation 27
1.3.6 Spread spectrum 30
1.3.7 Synchronisation 31
1.3.8 Filtering operations 33
1.4 Why digital communication? 36
1.4.1 The digital revolution 36
1.4.2 Advantages of digital over analogue communication 37
1.4.3 Disadvantages of digital communication 39
1.5 Summary 39

2 Linear channels and systems 41
2.1 Introduction 41
2.2 Linearity and system classifications 42
2.3 Time-domain characterisation of LTI systems 45
2.4 Frequency-domain characterisation of LTI systems 50
2.5 Output spectral density of LTI systems 57
2.6 LTI system bandwidth 59
2.6.1 3-dB and null-bandwidths 60
2.6.2 Noise-equivalent bandwidth 61
2.7 Distortionless transmission 65
2.8 Multipath distortion 68
2.9 Terrestrial mobile radio channel 76
2.10 Summary 77
2.11 References 78

3 Non-linear systems 79
3.1 Introduction 79
3.2 Memoryless non-linear systems 80
3.3 Non-linear systems with memory 84
3.4 Simulation of non-linear systems 86
3.5 Intermodulation distortion 88
3.6 Summary 101
3.7 Reference 101

4 Sampling of base band and band pass signals 103
4.1 Introduction 103
4.2 The sampling concept and theorem 104
4.3 Sampling a sinusoidal signal 106
4.4 Base band signal sampling and alias distortion 109
4.5 Band pass signal sampling 118
4.6 Mathematical basis of sampling 129
4.7 Non-instantaneous sampling and aperture effect 138
4.8 Anti-alias filter 144
4.9 Summary 147
4.10 Reference 147

5 Quantisation and PCM 149
5.1 Introduction 149
5.2 Concept and classes of quantisation 150
5.3 Uniform quantisation 152
5.3.1 Quantisation design parameters and trade-offs 154
5.3.2 Shortcomings of uniform quantisation 155
5.4 Non-uniform quantisation 158
5.4.1 Ideal log-companding 159
5.4.2 A-law companding 162
5.4.3 m-Law companding 163
5.4.4 Specification of companding 164
5.4.5 Companding gain and penalty 167
5.5 PCM 171
5.5.1 A-law and m-law PCM 172
5.5.2 SQNR of A-law and m-law PCM 178
5.6 Lossy compression 181
5.6.1 Waveform coders 182
5.6.2 Vocoder 188
5.6.3 Hybrid coder 190
5.7 Summary 190
5.8 References 191

6 Source coding and lossless data compression 193
6.1 Introduction 193
6.2 Classes and features of data compression 194
6.3 Information content and entropy 194
6.4 Prefix and non-prefix variable-length codes 198
6.4.1 Source coding theorem and code efficiency 201
6.4.2 The code space concept 202
6.5 Huffman coding 206
6.5.1 Encoding process 206
6.5.2 Decoding process 212
6.5.3 Weaknesses of Huffman coding 213
6.6 Lempel-Ziv coding 215
6.6.1 Run-length encoding (RLE) 215
6.6.2 Lempel-Ziv encoding process 216
6.6.3 Lempel-Ziv decoding process 219
6.6.4 Strengths and drawbacks of Lempel-Ziv 220
6.7 Arithmetic coding 220
6.7.1 Arithmetic encoding process 221
6.7.2 Arithmetic decoding 227
6.7.3 Arithmetic precision issue 228
6.7.4 Adaptive model 229
6.7.5 Weaknesses of arithmetic coding 229
6.8 Summary 230
6.9 References 232

7 Line codes 233
7.1 Introduction 233
7.2 Classes and efficiency of line codes 234
7.3 Power spectral density of line codes 235
7.3.1 Autocorrelation and spectral density 235
7.3.2 PSD of random binary waveforms 237
7.3.3 PSD of general line code waveforms 239
7.4 Basic line codes 246
7.4.1 Nonreturn to zero (NRZ) line codes 246
7.4.2 Return to zero (RZ) line codes 250
7.4.3 Biphase line codes 253
7.5 Advanced codes 255
7.5.1 Run length limited (RLL) line codes 255
7.5.2 Block line codes 259
7.6 Summary 262
7.7 Reference 263

8 Transmission through band limited AWGN channels 265
8.1 Introduction 265
8.2 ISI and bandwidth constraint on symbol rate 269
8.2.1 Nyquist filtering 270
8.2.2 Raised cosine filtering 272
8.2.3 Square root raised cosine filtering 274
8.2.4 Duobinary signalling 277
8.3 Noise constraint on bit rate 283
8.3.1 Characterisation of a discrete memoryless channel 283
8.3.2 Mutual information and channel capacity 285
8.3.3 Channel coding theorem and information capacity law 290
8.4 The matched filter 295
8.4.1 Heuristic approach 295
8.4.2 Mathematical basis 298
8.4.3 Matched filter as a correlator 299
8.5 Eye diagram 300
8.6 Summary 303
8.7 References 304

9 Transmitted digital signals 305
9.1 Introduction 305
9.2 Geometric representation of signals 306
9.2.1 Orthogonality of signals 306
9.2.2 Signal space 312
9.3 Symbols in digital transmission systems 319
9.3.1 Base band systems 319
9.3.2 Modulated systems 320
9.4 Complex representation of signals 328