Understanding Information Transmission

Preface vii

1. Introduction: First Ideas and Some History 1

1.1 What is communication? 2

1.2 Why digital communication? 6

1.3 Some history 8

1.4 A few remarks on intellectual history 27

1.5 Conclusions 28

References 29

2. Mathematical Methods of Information Transmission: Why Sinusoids? 30

2.1 Linear, time-invariant (LTI) systems 31

2.2 On the importance of being sinusoidal 43

2.3 The Fourier transform 48

2.4 What is bandwidth? 58

2.5 Discrete-time systems 66

2.6 Conclusions 69

References 70

Problems 70

3. Information Sources: What is Out There to be Sent? 77

3.1 What is text? 78

3.2 What is speech? 81

3.3 What is music? 88

3.4 What is an image? 94

3.5 What is video? 98

3.6 Conclusion 102

References 102

Problems 103

4. Transmission Methods: How is Information Sent? 105

4.1 Communication channels 105

4.2 Analog modulation 117

4.3 Digital modulation 127

4.4 FM stereo, television and a little about electronics 139

4.5 Conclusions 146

References 147

Problems 147

5. Information Theory and Coding: What did Shannon Promise? 150

5.1 Information theory—a primer 152

5.2 Methods of source coding 179

5.3 Methods of channel coding 189

5.4 Trellis coded modulation 199

5.5 Conclusions 205

References 206

Problems 207

6. Cryptology: FUBSWRORJB?? 211

6.1 Fundamentals of cryptosystems 211

6.2 Caesar and Vigenere ciphers 215

6.3 The Vernam cipher and perfect secrecy 219

6.4 Stream ciphers 220

6.5 Block ciphers 223

6.6 Cryptomachines during World War II 224

6.7 Two-key cryptography 228

6.8 Conclusions 239

References 239

Problems 239

7. Communication Networks: Let's Get Connected 241

7.1 An overview of information networks 241

7.2 Circuit switching: The telephone net 252

7.3 Mobile telephony 260

7.4 The Internet 265

References 275

Appendix A: Complex Numbers 276

Appendix B: Sinusoids and Circuit Theory 281

Appendix C: Probability Theory: A Primer 297

Index 306

About the Authors