OFDM for Underwater Acoustic Communications

S. Zhou, Associate Professor, Department of Electrical and Computer Engr., University of Connecticut, Storrs, USAShengli Zhou received his Ph.D. degree in electrical engineering from the University of Minnesota (UMN), Minneapolis, in 2002. Dr. Zhou is a senior member of IEEE, and a member of Connecticut Academy of Science and Engineering (CASE). His general research interests lie in the areas of wireless communications and signal processing. For the last six years, he has focused on underwater acoustic communications and networking. For his work on underwater acoustic communications, he received the 2007 Office of Naval Research (ONR) Young Investigator Program (YIP) award and the 2007 Presidential Early Career Award for Scientists and Engineers (PECASE). He is so far the only UCONN faculty member to ever receive the prestigious PECASE award. Z.-H. Wang, Ph.D Student, Department of Electrical and Computer Engineering, University of Connecticut, Storrs, USAMs. Wang is a student member of IEEE. She serves as a technical reviewer for IEEE Journal of Oceanic Engineering, IEEE Transactions on Signal Processing, IEEE Transactions on Wireless Communications, and various conferences. Her research interests lie in the areas of communications, signal processing and detection, with recent focus on multicarrier modulation algorithms and signal processing for underwater acoustic communications and networking.

• Preface xvii Acronyms xixNotation xxiii1 Introduction 11.1 Background and Context 11.1.1 Early Exploration of Underwater Acoustics 11.1.2 Underwater Communication Media 21.1.3 Underwater Systems and Networks 31.2 UWA Channel Characteristics 31.2.1 Sound Velocity 31.2.2 Propagation Loss 51.2.3 Time-Varying Multipath 71.2.4 Acoustic Propagation Models 101.2.5 Ambient Noise and External Interference 111.3 Passband Channel Input–Output Relationship 111.3.1 Linear Time-Varying Channel with Path-Specific Doppler Scales 121.3.2 Linear Time-Varying Channels with One Common Doppler Scale 131.3.3 Linear Time-Invariant Channel 131.3.4 Linear Time-Varying Channel with Both Amplitude and Delay Variations 141.3.5 Linear Time-Varying Channel with Frequency-Dependent Attenuation 151.4 Modulation Techniques for UWA Communications 151.4.1 Frequency Hopped FSK 151.4.2 Direct Sequence Spread Spectrum 161.4.3 Single Carrier Modulation 171.4.4 Sweep-Spread Carrier (S2C) Modulation 181.4.5 Multicarrier Modulation 181.4.6 Multi-Input Multi-Output Techniques 191.4.7 Recent Developments on Underwater Acoustic Communications 201.5 Organization of the Book 202 OFDMBasics 232.1 Zero-Padded OFDM 232.1.1 Transmitted Signal 232.1.2 Receiver Processing 262.2 Cyclic-Prefixed OFDM 272.2.1 Transmitted Signal 272.2.2 Receiver Processing 282.3 OFDM Related Issues 282.3.1 ZP-OFDM versus CP-OFDM 282.3.2 Peak-to-Average-Power Ratio 292.3.3 Power Spectrum and Bandwidth 292.3.4 Subcarrier Assignment 302.3.5 Overall Data Rate 302.3.6 Design Guidelines 312.4 Implementation via Discrete Fourier Transform 312.5 Challenges and Remedies for OFDM 322.5.1 Benefits of Diversity Combining and Channel Coding 332.6 MIMO OFDM 362.7 Bibliographical Notes 383 Nonbinary LDPC Coded OFDM 393.1 Channel Coding for OFDM 393.1.1 Channel Coding 393.1.2 Coded Modulation 413.1.3 Coded OFDM 423.2 Nonbinary LDPC Codes 433.2.1 Nonbinary Regular Cycle Codes 443.2.2 Nonbinary Irregular LDPC Codes 453.3 Encoding 463.4 Decoding 483.4.1 Initialization 483.4.2 Variable-to-Check-Node Update 493.4.3 Check-to-Variable-Node Update 503.4.4 Tentative Decision and Decoder Outputs 513.5 Code Design 523.5.1 Design of Regular Cycle codes 533.5.2 Design of Irregular LDPC Codes 533.5.3 Quasi-Cyclic Nonbinary LDPC codes 553.6 Simulation Results of Coded OFDM 583.7 Bibliographical Notes 594 PAPR Control 634.1 PAPR Comparison 634.2 PAPR Reduction 654.2.1 Clipping 654.2.2 Selective Mapping 674.2.3 Peak Reduction Subcarriers 694.3 Bibliographical Notes 695 Receiver Overview and Preprocessing 715.1 OFDM Receiver Overview 725.2 Receiver Preprocessing 735.2.1 Receiver Preprocessing 735.2.2 Digital Implementation 745.2.3 Frequency-Domain Oversampling 775.3 Frequency-Domain Input–Output Relationship 785.3.1 Single-Input Single-Output Channel 785.3.2 Single-Input Multi-Output Channel 795.3.3 Multi-Input Multi-Output Channel 805.3.4 Channel Matrix Structure 815.4 OFDM Receiver Categorization 825.4.1 ICI-Ignorant Receiver 825.4.2 ICI-Aware Receiver 835.4.3 Block-by-Block Processing 855.4.4 Block-to-Block Processing 855.4.5 Discussion 855.5 Receiver Performance Bound with Simulated Channels 855.5.1 Simulating Underwater Acoustic Channels 865.5.2 ICI Effect in Time-Varying Channels 865.5.3 Outage Performance of SISO Channel 875.6 Extension to CP-OFDM 885.6.1 Receiver Preprocessing 885.6.2 Frequency-Domain Input–Output Relationship 895.7 Bibliographical Notes 896 Detection, Synchronization and Doppler Scale Estimation 916.1 Cross-Correlation Based Methods 926.1.1 Cross-Correlation Based Detection 926.1.2 Cross-Correlation Based Synchronization and Doppler Scale Estimation 966.2 Detection, Synchronization and Doppler Scale Estimation with CP-OFDM 996.2.1 CP-OFDM Preamble with Self-Repetition 996.2.2 Self-Correlation Based Detection, Synchronization and Doppler Scale Estimation 1006.2.3 Implementation 1016.3 Synchronization and Doppler Scale Estimation for One ZP-OFDM Block 1036.3.1 Null-Subcarrier based Blind Estimation 1036.3.2 Pilot-Aided Estimation 1046.3.3 Decision-Aided Estimation 1046.4 Simulation Results for Doppler Scale Estimation 1046.4.1 RMSE Performance with CP-OFDM 1056.4.2 RMSE Performance with ZP-OFDM 1066.4.3 Comparison of Blind Methods of CP- and ZP-OFDM 1076.5 Design Examples in Practical Systems 1086.6 Residual Doppler Frequency Shift Estimation 1106.6.1 System Model after Resampling 1106.6.2 Impact of Residual Doppler Shift Compensation 1116.6.3 Two Residual Doppler Shift Estimation Methods 1126.6.4 Simulation Results 1136.7 Bibliographical Notes 1157 Channel and Noise Variance Estimation 1177.1 Problem Formulation for ICI-Ignorant Channel Estimation 1187.1.1 The Input–Output Relationship 1187.1.2 Dictionary Based Formulation 1187.2 ICI-Ignorant Sparse Channel Sensing 1207.2.1 Dictionary Resolution versus Channel Sparsity 1217.2.2 Sparsity Factor 1227.2.3 Number of Pilots versus Number of Paths 1237.3 ICI-Aware Sparse Channel Sensing 1247.3.1 Problem Formulation 1247.3.2 ICI-Aware Channel Sensing 1247.3.3 Pilot Subcarrier Distribution 1257.3.4 Influence of Data Symbols 1267.4 Sparse Recovery Algorithms 1277.4.1 Matching Pursuit 1277.4.2 1-Norm Minimization 1287.4.3 Matrix-Vector Multiplication via FFT 1297.4.4 Computational Complexity 1317.5 Extension to Multi-Input Channels 1317.5.1 ICI-Ignorant Sparse Channel Sensing 1317.5.2 ICI-Aware Sparse Channel Sensing 1327.6 Noise Variance Estimation 1347.7 Noise Prewhitening 1347.7.1 Noise Spectrum Estimation 1357.7.2 Whitening in the Frequency Domain 1367.8 Bibliographical Notes 1368 Data Detection 1378.1 Symbol-by-Symbol Detection in ICI-Ignorant OFDM Systems 1398.1.1 Single-Input Single-Output Channel 1398.1.2 Single-Input Multi-Output Channel 1408.2 Block-Based Data Detection in ICI-Aware OFDM Systems 1418.2.1 MAP Equalizer 1428.2.2 Linear MMSE Equalizer with A Priori Information 1428.2.3 Extension to the Single-Input Multi-Output Channel 1458.3 Data Detection for OFDM Systems with Banded ICI 1458.3.1 BCJR Algorithm and Log-MAP Implementation 1458.3.2 Factor-Graph Algorithm with Gaussian Message Passing 1488.3.3 Computations related to Gaussian Messages 1498.3.4 Extension to SIMO Channel 1508.4 Symbol Detectors for MIMO OFDM 1518.4.1 ICI-Ignorant MIMO OFDM 1518.4.2 Full-ICI Equalization 1528.4.3 Banded-ICI Equalization 1528.5 MCMC Method for Data Detection in MIMO OFDM 1538.5.1 MCMC Method for ICI-Ignorant MIMO Detection 1538.5.2 MCMC Method for Banded-ICI MIMO Detection 1548.6 Bibliographical Notes 1559 OFDM Receivers with Block-by-Block Processing 1579.1 Noniterative ICI-Ignorant Receiver 1589.1.1 Noniterative ICI-Ignorant Receiver Structure 1589.1.2 Simulation Results: ICI-Ignorant Receiver 1599.1.3 Experimental Results: ICI-Ignorant Receiver 1609.2 Noniterative ICI-Aware Receiver 1619.2.1 Noniterative ICI-Aware Receiver Structure 1629.2.2 Simulation Results: ICI-Aware Receiver 1639.2.3 Experimental Results: ICI-Aware Receiver 1649.3 Iterative Receiver Processing 1649.3.1 Iterative ICI-Ignorant Receiver 1659.3.2 Iterative ICI-Aware Receiver 1659.4 ICI-Progressive Receiver 1669.5 Simulation Results: ICI-Progressive Receiver 1689.6 Experimental Results: ICI-Progressive Receiver 1719.6.1 BLER Performance 1719.6.2 Environmental Impact 1719.6.3 Progressive versus Iterative ICI-Aware Receivers 1749.7 Discussion 1759.8 Bibliographical Notes 17510 OFDM Receiver with Clustered Channel Adaptation 17710.1 Illustration of Channel Dynamics 17710.2 Modeling Cluster-Based Block-to-Block Channel Variation 17810.3 Cluster-Adaptation Based Block-to-Block Receiver 18010.3.1 Cluster Offset Estimation and Compensation 18110.3.2 Cluster-Adaptation Based Sparse Channel Estimation 18410.3.3 Channel Re-estimation and Cluster Variance Update 18610.4 Experimental Results: MACE10 18610.4.1 BLER Performance with an Overall Resampling 18710.4.2 BLER Performance with Refined Resampling 18810.5 Experimental Results: SPACE08 19010.6 Discussion 19310.7 Bibliographical Notes 19311 OFDM in Deep Water Horizontal Communications 19511.1 System Model for Deep Water Horizontal Communications 19611.1.1 Transmitted Signal 19711.1.2 Modeling Clustered Multipath Channel 19711.1.3 Received Signal 19811.2 Decision-Feedback Based Receiver Design 19911.3 Factor-Graph Based Joint IBI/ICI Equalization 20011.3.1 Probabilistic Problem Formulation 20011.3.2 Factor-Graph Based Equalization 20211.4 Iterative Block-to-Block Receiver Processing 20311.5 Simulation Results 20511.6 Experimental Results in the AUTEC Environment 20811.7 Extension to Underwater Broadcasting Networks 21111.7.1 Underwater Broadcasting Networks 21111.7.2 Emulated Experimental Results: MACE10 21111.8 Bibliographical Notes 21412 OFDM Receiver with Parameterized External Interference Cancellation 21512.1 Interference Parameterization 21512.2 An Iterative OFDM Receiver with Interference Cancellation 21712.2.1 Initialization 21912.2.2 Interference Detection and Estimation 21912.2.3 Channel Estimation, Equalization and Channel Decoding 22112.2.4 Noise Variance Estimation 22112.3 Simulation Results 22112.3.1 Time-Invariant Channels 22212.3.2 Time-Varying Channels 22312.3.3 Performance of the Proposed Receiver with Different SIRs 22412.3.4 Interference Detection and Estimation 22512.4 Experimental Results: AUTEC10 22512.5 Emulated Results: SPACE08 22712.6 Discussion 22912.7 Bibliographical Notes 22913 Co-located MIMO OFDM 23113.1 ICI-Ignorant MIMO-OFDM System Model 23213.2 ICI-Ignorant MIMO-OFDM Receiver 23313.2.1 Noniterative ICI-Ignorant MIMO-OFDM Receiver 23313.2.2 Iterative ICI-Ignorant MIMO-OFDM Receiver 23413.3 Simulation Results: ICI-Ignorant MIMO OFDM 23413.4 SPACE08 Experimental Results: ICI-Ignorant MIMO OFDM 23713.5 ICI-Aware MIMO-OFDM System Model 23713.6 ICI-Progressive MIMO-OFDM Receiver 23713.6.1 Receiver Overview 23913.6.2 Sparse Channel Estimation and Noise Variance Estimation 24013.6.3 Joint ICI/CCI Equalization 24013.7 Simulation Results: ICI-Progressive MIMO OFDM 24113.8 SPACE08 Experiment: ICI-Progressive MIMO OFDM 24213.9 MACE10 Experiment: ICI-Progressive MIMO OFDM 24413.9.1 BLER Performance with Two Transmitters 24413.9.2 BLER Performance with Three and Four Transmitters 24613.10 Initialization for the ICI-Progressive MIMO OFDM 24613.11 Bibliographical Notes 24614 Distributed MIMO OFDM 24914.1 System Model 25014.2 Multiple-Resampling Front-End Processing 25114.3 Multiuser Detection (MUD) Based Iterative Receiver 25214.3.1 Pre-processing with Frequency-Domain Oversampling 25214.3.2 Joint Channel Estimation 25414.3.3 Multiuser Data Detection and Channel Decoding 25514.4 Single-User Detection (SUD) Based Iterative Receiver 25514.4.1 Single-User Decoding 25514.4.2 MUI Construction 25614.5 An Emulated Two-User System Using MACE10 Data 25714.5.1 MUD-Based Receiver with and without Frequency-Domain Oversampling 25814.5.2 Performance of SUD- and MUD-Based Receivers 25814.6 Emulated MIMO OFDM with MACE10 and SPACE08 Data 26014.6.1 One Mobile Single-Transmitter User plus One Stationary Two-Transmitter User 26114.6.2 One Mobile Single-Transmitter User plus One Stationary Three-Transmitter User 26214.6.3 Two Mobile Single-Transmitter Users plus One Stationary Two-Transmitter User 26314.7 Bibliographical Notes 26315 Asynchronous Multiuser OFDM 26515.1 System Model for Asynchronous Multiuser OFDM 26615.2 Overlapped Truncation and Interference Aggregation 26715.2.1 Overlapped Truncation 26715.2.2 Interference Aggregation 26815.3 An Asynchronous Multiuser OFDM Receiver 26915.3.1 The Overall Receiver Structure 26915.3.2 Interblock Interference Subtraction 27015.3.3 Time-to-Frequency-Domain Conversion 27115.3.4 Iterative Multiuser Reception and Residual Interference Cancellation 27315.3.5 Interference Reconstruction 27415.4 Investigation on Multiuser Asynchronism in an Example Network 27515.5 Simulation Results 27615.5.1 Two-User Systems with Time-Varying Channels 27715.5.2 Multiuser Systems with Time-Invariant Channels 27915.6 Emulated Results: MACE10 28115.7 Bibliographical Notes 28416 OFDM in Relay Channels 28516.1 Dynamic Coded Cooperation in a Single-Relay Network 28516.1.1 Relay Operations 28616.1.2 Receiver Processing at the Destination 28816.1.3 Discussion 28916.2 A Design Example Based on Rate-Compatible Channel Coding 28916.2.1 Code Design 28916.2.2 Simulation Results 29116.3 A Design Example Based on Layered Erasure- and Error-Correction Coding 29216.3.1 Code Design 29216.3.2 Implementation 29316.3.3 An Experiment in Swimming Pool 29316.3.4 A Sea Experiment 29616.4 Dynamic Block Cycling over a Line Network 29916.4.1 Hop-by-Hop Relay and Turbo Relay 29916.4.2 Dynamic Block-Cycling Transmissions 30016.4.3 Discussion 30216.5 Bibliographical Notes 30217 OFDM-Modulated Physical-Layer Network Coding 30317.1 System Model for the OFDM-Modulated PLNC 30517.2 Three Iterative OFDM Receivers 30617.2.1 Iterative Separate Detection and Decoding 30617.2.2 Iterative XOR-ed PLNC Detection and Decoding 30717.2.3 Iterative Generalized PLNC Detection and Decoding 30917.3 Outage Probability Bounds in Time-Invariant Channels 30917.4 Simulation Results 31017.4.1 The Single-Path Time-Invariant Channel 31117.4.2 The Multipath Time-Invariant Channel 31117.4.3 The Multipath Time-Varying Channel 31317.5 Experimental Results: SPACE08 31417.6 Bibliographical Notes 31518 OFDM Modem Development 31718.1 Components of an Acoustic Modem 31718.2 OFDM Acoustic Modem in Air 31818.3 OFDM Lab Modem 31818.4 AquaSeNT OFDM Modem 32018.5 Bibliographical Notes 32119 Underwater Ranging and Localization 32319.1 Ranging 32419.1.1 One-Way Signaling 32419.1.2 Two-Way Signaling 32419.1.3 Challenges for High-Precision Ranging 32519.2 Underwater GPS 32519.2.1 System Overview 32519.2.2 One-Way Travel Time Estimation 32619.2.3 Localization 32719.2.4 Tracking Algorithms 32919.2.5 Simulation Results 33419.2.6 Field Test in a Local Lake 33519.3 On-Demand Asynchronous Localization 33619.3.1 Localization Procedure 33719.3.2 Localization Algorithm for the Initiator 33819.3.3 Localization Algorithm for a Passive Node 34019.3.4 Localization Performance Results in a Lake 34119.4 Bibliographical Notes 344Appendix A Compressive Sensing 345A.1 Compressive Sensing 346A.1.1 Sparse Representation 346A.1.2 Exactly and Approximately Sparse Signals 346A.1.3 Sensing 346A.1.4 Signal Recovery and RIP 347A.1.5 Sensing Matrices 348A.2 Sparse Recovery Algorithms 348A.2.1 Matching Pursuits 349A.2.2 1-Norm Minimization 349A.3 Applications of Compressive Sensing 350A.3.1 Applications of Compressive Sensing in Communications 350A.3.2 Compressive Sensing in Underwater Acoustic Channels 351Appendix B Experiment Description 353B.1 SPACE08 Experiment 353B.2 MACE10 Experiment 354B.2.1 Experiment Setup 355B.2.2 Mobility Estimation 356References 359Index 383