Introduction to Communication Systems Simulation DISCLAIMER OF WARRANTY The technical descriptions, procedures, and computer programs in this book have beendevelopedwiththegreatestofcareandtheyhavebeenusefultotheauthorina broadrangeofapplications;however,theyareprovidedasis,withoutwarrantyof anykind.ArtechHouse,Inc.andtheauthorandeditorsofthebooktitledIntroduc- tion to Communication Systems Simulation make no warranties, expressed or implied,thattheequations,programs,andproceduresinthisbookoritsassociated software are free of error, or are consistent with any particular standard of mer- chantability, or will meet your requirements for any particular application. They should not be relied upon for solving a problem whose incorrect solution could result in injury to a person or loss of property. 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Contents Preface xiii CHAPTER 1 Elements of a Communication System 1 1.1 The Transmitter 1 1.1.1 The Data Source 1 1.1.2 Source Encoding 1 1.1.3 Forward Error Correction 6 1.1.4 Interleaving 7 1.1.5 Baseband Filtering 8 1.1.6 Modulation 8 1.2 The Transmission Channel 8 1.2.1 Additive White Gaussian Noise 9 1.2.2 Interference 9 1.2.3 Fading 9 1.3 Receiver 10 1.3.1 Frequency Offset 10 1.3.2 Phase Offset 10 1.3.3 Timing Offset 11 1.3.4 Data Recovery 11 1.4 Conclusion 11 Selected Bibliography 11 CHAPTER 2 Linear Time Invariant Systems 13 2.1 LTI Systems 13 2.2 Fourier Transform (FT) Theory 15 2.3 The Digital Fourier Transform 17 2.4 DFT Windows 21 2.5 The Fast Fourier Transform 25 2.6 Conclusion 27 Selected Bibliography 27 CHAPTER 3 Sampling 29 3.1 The Sampling Operation 29 3.2 The Nyquist Sampling Theorem 33 vii viii Contents 3.3 Recovering the Signal from Its Samples 38 3.4 Band-Pass Sampling 41 3.5 Conclusion 44 Selected Bibliography 45 CHAPTER 4 Filters 47 4.1 General Considerations 47 4.2 The Laplace Transform 50 4.3 Poles, Zeros, and Stability 51 4.4 The Two Worlds of a Filter 53 4.4.1 Infinite Impulse Response filters 53 4.4.2 Finite Impulse Response Filters 54 4.5 The z Transform 54 4.6 From s to z 55 4.7 Frequency Warping 58 4.8 The IIR Filter 59 4.9 General Implementation of a Filter of Form N(z)/D(z) 61 4.10 Practical Consideration in IIR Filter Simulation 62 4.11 Conclusion 63 Selected Bibliography 63 CHAPTER 5 Digital Detection 65 5.1 The Vector Channel 65 5.2 The Waveform Channel 68 5.3 The Matched Filter Receiver 69 5.4 From Signals to Vectors 73 5.5 The I, Q Vector Space 76 5.6 Conclusion 77 Selected Bibliography 77 CHAPTER 6 Modulation 79 6.1 Amplitude Modulation (MASK) 79 6.2 Frequency Modulation (MFSK) 79 6.3 Phase Modulation (MPSK) 83 6.4 π/4 DQPSK Modulation 86 6.5 Offset QPSK Modulation 86 6.6 QAM Modulation 86 6.7 MSK Modulation 88 6.8 OFDM Modulation 89 6.9 Pulse Position Modulation 92 6.10 Pulse Width Modulation 93 6.11 GSM EDGE Modulation 93 6.12 Spread Spectrum Modulation 94 6.12.1 Frequency Hopping 96 Contents ix 6.12.2 Direct Sequence Pseudo Noise 96 6.13 Conclusion 102 Selected Bibliography 102 CHAPTER 7 Demodulation 103 7.1 In-Phase (I) and Quadrature (Q) Down Conversion Process 103 7.2 Low-Pass Filtering 104 7.2.1 CIC Filter 105 7.2.2 Polyphase Filter 105 7.2.3 Half Band Filter 106 7.3 Offset Parameter Recovery 107 7.3.1 Frequency Offset 107 7.3.2 Data Timing 110 7.4 Phase/Frequency Recovery 112 7.4.1 BPSK 113 7.4.2 QPSK 114 7.4.3 Decision Feedback 115 7.5 Conclusion 115 Selected Bibliography 117 CHAPTER 8 Baseband Pulse Shaping 119 8.1 Baseband Pulse Analyses 119 8.2 The Raised Cosine Pulse 122 8.3 Intersymbol Interference and Eye Diagrams 125 8.4 The Root Raised Cosine Filter 128 8.5 Conclusion 129 Selected Bibliography 130 CHAPTER 9 Bit Error Rate Calculations 131 9.1 The BER Measurement Process 131 9.2 System Group Delay 133 9.3 E/N Calibration 135 b 0 9.3.1 Physical RF World Simulation 135 9.3.2 Standard BER Runs 137 9.4 Conclusion 137 Selected Bibliography 137 CHAPTER 10 Channel Models 139 10.1 Flat Fading 139 10.2 Rician Flat Fade 142 10.3 The Jakes Model 143 10.4 Frequency Selective Fading 144 10.5 Effects of Fading on BER Performance 146 x Contents 10.6 Mitigating Fading 148 10.6.1 Equalizers 148 10.6.2 Diversity 153 10.7 Conclusion 154 Selected Bibliography 154 CHAPTER 11 Nonlinear Amplifiers 155 11.1 Intercept and Compression Points 155 11.2 TWT 159 11.3 Spur Charts 159 11.4 Conclusion 162 Selected Bibliography 162 CHAPTER 12 Baseband Simulation 163 12.1 Basic Concept 163 12.2 Pass-Band Filtering 164 12.3 Baseband Noise 166 12.4 Conclusion 167 Selected Bibliography 167 CHAPTER 13 Ultra-Wideband Systems 169 13.1 Direct Sequence DS-UWB Systems 170 13.1.1 Scrambler 170 13.1.2 Forward Error Correction 171 13.1.3 Puncturing 171 13.1.4 Interleaver 172 13.1.5 Modulation 173 13.2 Multiband OFDM UWB-Multiband OFDM Alliance Systems 178 13.2.1 FEC Coding 180 13.2.2 Puncturing 181 13.2.3 Modulation 181 13.2.4 Carrier Modulation Frequency Agility 184 13.3 Conclusion 184 Selected Bibliography 184 APPENDIX A Table of Laplace Transforms 185 APPENDIX B Elements of Probability Theory and Random Variables 187 B.1 Probability Theory 187 B.1.1 Axioms of Probability 187 B.1.2 Dice Example 187 B.1.3 Conditional Probability 189