OFDM and MC-CDMA A Primer

Transcription

1 OFDM and MC-CDMA A Primer L. Hanzo University of Southampton, UK T. Keller Analog Devices Ltd., Cambridge, UK IEEE PRESS IEEE Communications Society, Sponsor John Wiley & Sons, Ltd

2 Contents About the Authors Other Wiley and IEEE Press Books on Related Topics Acknowledgements xv xvii xix 1 Introduction Motivation of the Book Orthogonal Frequency Division Multiplexing History Early Classic Contributions and OFDM Standards Peak-to-Mean Power Ratio Synchronisation OFDM/CDMA Decision-Directed Channel Estimation Uplink Detection Techniques for Multi-User SDMA-OFDM OFDM Applications Outline of the Book Chapter Summary and Conclusion 18 1 OFDM System Design 19 2 Introduction to Orthogonal Frequency Division Multiplexing Introduction PrinciplesofQAM-OFDM Modulation by DFT Transmission via Bandlimited Channels Basic OFDM Modem Implementations Cyclic OFDM Symbol Extension Decision-Directed Adaptive Channel Equalisation OFDM Bandwidth Efficiency Chapter Summary and Conclusion 39 vii

3 OFDM Transmission over Gaussian Channels Orthogonal Frequency Division Multiplexing Choiceofthe OFDM Modulation OFDM System Performance over AWGN Channels Clipping Amplification OFDM Signal Amplitude Statistics Clipping Amplifier Simulations Introduction to Peak-Power Reduction Techniques BER Performance Using Clipping Amplifiers Signal Spectrum with Clipping Amplifier Clipping Amplification - Summary Analogue-to-Digital Conversion Phase Noise Effects of Phase Noise Phase Noise Simulations White Phase Noise Model Serial Modem OFDM Modem Coloured Phase Noise Model Phase Noise - Summary Chapter Summary and Conclusion 60 OFDM Transmission over Wideband Channels The Channel Model The Wireless Asynchronous Transfer Mode System The WATM Channel The Shortened WATM Channel The Wireless Local Area Network The WLAN Channel UMTS System The UMTS Type Channel Effects of Time-Dispersive Channelson OFDM Effects of the Stationary Time-Dispersive Channel Non-Stationary Channel Summary of Time-Variant Channels Signalling over Time-Dispersive OFDM Channels Channel Transfer Function Estimation Frequency Domain Channel Transfer Function Estimation Pilot Symbol-Assisted Schemes Linear Interpolation for PSAM Ideal Lowpass Interpolation for PSAM Summary Time Domain Channel Estimation System Performance Static Time-Dispersive Channel Perfect Channel Estimation 78

4 ix Differentially Coded Modulation PSAM Aided Channel Transfer Function Estimation Slowly Varying Time-Dispersive Channel Perfect Channel Estimation Pilot Symbol-Assisted Modulation Summary Intersubcarrier Interference Cancellation Motivation The Signal Model Channel Estimation Cancellation Schemes ICI Cancellation Performance Conclusions on ICI Cancellation Chapter Summary and Conclusion OFDM Time and Frequency Domain Synchronisation System Performance with Frequency and Timing Errors Frequency Shift The Spectrum ofthe OFDM Signal Effects of Frequency Mismatch on Different Modulation Schemes Coherent Modulation Pilot Symbol Assisted Modulation Differential Modulation Frequency Error - Summary Time Domain Synchronisation Errors Coherent Demodulation Pilot Symbol-Assisted Modulation Differential Modulation Time Domain Synchronisation Errors - Summary Synchronisation Algorithms Coarse Frame and OFDM Symbol Synchronisation Review Fine Symbol Tracking Review Frequency Acquisition Review Frequency Tracking Review Synchronisation based on Auto-Correlation Multiple Access Frame Structure The Reference Symbol The Correlation Functions Frequency Tracking and OFDM Symbol Synchronisation OFDM Symbol Synchronisation Frequency Tracking Studies Frequency Acquisition and Frame Synchronisation Studies Frame Synchronisation Studies Frequency Acquisition Studies Block Diagram of the Synchronisation Algorithms Frequency Acquisition Using Pilots 123

5 The Reference Symbol Frequency Acquisition Performance of the Pilot-Based Frequency Acquisition in AWGN Channels Alternative Frequency Error Estimation for Frequency Domain Pilot Tones Comparison of the Frequency Acquisition Algorithms BER Performance with Frequency Synchronisation Chapter Summary and Conclusion Appendix: OFDM Synchronisation Performance Frequency Synchronisation in an AWGN Channel One Phasor in AWGN Environment Cartesian Coordinates Polar Coordinates ProductofTwoNoisyPhasors Joint Probability Density Phase Distribution Numerical Integration 141 Adaptive Single- and Multi-user OFDM Techniques Introduction Motivation Adaptive Techniques Channel Quality Estimation Parameter Adaptation Signalling the AOFDM Parameters System Aspects Adaptive Modulation for OFDM System Model Channel Model Channel Transfer Function Variations Choice of the Modulation Modes Fixed Threshold Adaptation Algorithm Sub-Band BER Estimator Adaptation Algorithm Constant Throughput Adaptive OFDM AOFDM Mode Signalling and Blind Detection Signalling Blind Detection by SNR Estimation Blind Detection by Multi-Mode Trellis Decoder Sub-Band Adaptive OFDM and Turbo Channel Coding Effects of the Doppler Frequency Channel Transfer Function Estimation Adaptive OFDM Speech System Introduction System Overview System Parameters 169

6 xi Constant Throughput Adaptive Modulation Constant-Rate BER Performance Multimode Adaptation Mode Switching Simulation Results Frame Error Results Audio Segmental SNR Pre-equalisation Motivation Pre-equalisation with Sub-Band Blocking Adaptive Modulation with Spectral Predistortion Comparison of the Adaptive Techniques Near-Optimum Power-and Bit Allocation in OFDM State of the Art Problem Description Power and Bit Allocation Algorithm Multi-User AOFDM Introduction Adaptive Transceiver Architecture AnOverview The Signal Model The SMI Algorithm The Adaptive Bit-Assignment Algorithm The Channel Models Simulation Results - Perfect Channel Knowledge General Remarks Two-Branch Maximum-Ratio Combining SMI Co-Channel Interference Suppression Pilot-Based Channel Parameter Estimation System Description Simulation Results Chapter Summary and Conclusion 201 II OFDM versus MC-CDMA Systems OFDM versus MC-CDMA Amalgamating DS-CDMA and OFDM The DS-CDMA Component The OFDM Component Multi-Carrier CDMA MC-CDMA MC-DS-CDMA MT-CDMA Further Research Topics in MC-CDMA Chapter Summary and Conclusion 217

7 8 Basic Spreading Sequences PN Sequences Maximal Length Sequences Gold Codes Kasami Sequences Orthogonal Codes Walsh Codes Orthogonal Gold Codes Multi-Rate Orthogonal Gold Codes Chapter Summary and Conclusion MC-CDMA Performance in Synchronous Environments The Frequency Selective Channel Model The System Model Single User Detection Maximal Ratio Combining Equal Gain Combining Orthogonality Restoring Combining Multi-User Detection Background Maximum Likelihood Detection Concatenated Space-Time Block Coded and Turbo Coded Symbolby-Symbol Adaptive OFDM and Multi-Carrier CDMA Chapter Summary and Conclusion 250 III Advanced Topics: Multi-User OFDM Systems Maximum-Likelihood Enhanced Sphere Decoding of MIMO-OFDM Classification of Smart Antennas Introduction to Space-Time Processing SDM-OFDM System Model MIMO Channel Model SDM-OFDM Transceiver Structure Optimised Hierarchy Reduced Search Algorithm-Aided SDM Detection OHRSA-Aided ML SDM Detection Search Strategy GeneralisationoftheOHRSA-MLSDMDetector Bitwise OHRSA ML SDM Detection Generalisationofthe BW-OHRSA-ML SDM Detector OHRSA-Aided Log-MAP SDM Detection Soft-Output OHRSA-Aided Approximate Log-MAP Detection Complexity Analysis Performance Analysis Chapter Summary and Conclusion 300

8 xüi 11 Genetic Algorithm Aided Joint Channel Estimation and MUD for SDMA OFDM Introduction SDMA MIMO Channel Model System Overview GA-Aided Iterative Joint Channel Estimation and Multi-User Detection Pilot-Aided Initial Channel Estimation Generating Initial Symbol Estimates GA-Aided Joint FD-CHTF and Data Optimisation Providing Soft Outputs Extended GA Individual Structure for MIMO Systems Initialisation Joint Genetic Optimisation Cross-Over Operator Mutation Operator Comments on the Joint Optimisation Process Generating the GA's Soft Outputs Simulation Results Effects of the Maximum Mutation Step Size Effects of the Doppler Frequency Effects of the Number of GA-JCEMUD Iterations Effects of the Pilot Overhead Joint Optimisation versus Separate Optimisation ComparisonofGA-JCEMUDsHaving Soft and Hard Outputs MIMO Robustness Chapter Summary and Conclusion Multi-User OFDM Employing Genetic Algorithm Aided Minimum Bit Error Rate Multi-User Detection Introduction Minimum Bit Error Ratio Detection of OFDM System Model Space Division Multiple Access Error Probability of a BPSK System Exact MBER Multi-User Detection Genetic Algorithm Overview of GAs Employing GAs in the MBER MUD Aided SDMA OFDM System Simulation Results Performance ofafour-user and Four-Receiver Antenna Scenario Performance of the Four-Antenna Scenario versus the Number of Users Complexity Comparison Chapter Summary and Conclusion 346

9 13 Conclusion and Further Research Problems Summary and Conclusions of Parti Summary of Parti Conclusions of Parti Summary and Conclusions of Part II Summary of Part II Conclusions of Part II Summary and Conclusions of Part III Near-ML Enhanced Sphere Detection of MIMO-OFDM GA-Aided Joint MUD and Channel Estimation GA-Aided MBER MUD Closing Remarks 3^6 Glossary 359 Bibliography ^6^ Subject Index AuthorIndex