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OFDM for Underwater Acoustic Communications

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A blend of introductory material and advanced signal processing and communication techniques, of critical importance to underwater system and network development

This book, which is the first to describe the processing techniques central to underwater OFDM, is arranged into four distinct sections: First, it describes the characteristics of underwater acoustic channels, and stresses the difference from wireless radio channels. Then it goes over the basics of OFDM and channel coding. The second part starts with an overview of the OFDM receiver, and develops various modules for the receiver design in systems with single or multiple transmitters. This is the main body of the book. Extensive experimental data sets are used to verify the receiver performance. In the third part, the authors discuss applications of the OFDM receiver in i) deep water channels, which may contain very long separated multipath clusters, ii) interference-rich environments, where an unintentional interference such as Sonar will be present, and iii) a network with multiple users where both non-cooperative and cooperative underwater communications are developed. Lastly, it describes the development of a positioning system with OFDM waveforms, and the progress on the OFDM modem development. Closely related industries include the development and manufacturing of autonomous underwater vehicles (AUVs) and scientific sensory equipment. AUVs and sensors in the future could integrate modems, based on the OFDM technology described in this book.

Contents includes: Underwater acoustic channel characteristics/OFDM basics/Peak-to-average-ratio control/Detection and Doppler estimation (Doppler scale and CFO)/Channel estimation and noise estimation/A block-by-block progressive receiver and performance results/Extensions to multi-input multi-output OFDM/Receiver designs for multiple users/Cooperative underwater OFDM (Physical layer network coding and dynamic coded cooperation)/Localization with OFDM waveforms/Modem developments

A valuable resource for Graduate and postgraduate students on electrical engineering or physics courses; electrical engineers, underwater acousticians, communications engineers

Author(s): Shengli Zhou, Zhaohui Wang
Publisher: Wiley
Year: 2014

Language: English
Pages: xxiv+386
Tags: Acoustics Civil Environmental Engineering Transportation Electrical Electronics Circuits Digital Design Electric Machinery Motors Fiber Optics Networks Superconductivity Waves Wave Mechanics Physics Science Math Mathematics Agriculture Astronomy Astrophysics Biology Life Sciences Chemistry Earth Studies New Used Rental Textbooks Specialty Boutique

Preface xvii
Acronyms xix
Notation xxiii

1 Introduction 1
1.1 Background and Context 1
1.1.1 Early Exploration of Underwater Acoustics 1
1.1.2 Underwater Communication Media 2
1.1.3 Underwater Systems and Networks 3
1.2 UWA Channel Characteristics 3
1.2.1 Sound Velocity 3
1.2.2 Propagation Loss 5
1.2.3 Time-Varying Multipath 7
1.2.4 Acoustic Propagation Models 10
1.2.5 Ambient Noise and External Interference 11
1.3 Passband Channel Input–Output Relationship 11
1.3.1 Linear Time-Varying Channel with Path-Specific Doppler Scales 12
1.3.2 Linear Time-Varying Channels with One Common Doppler Scale 13
1.3.3 Linear Time-Invariant Channel 13
1.3.4 Linear Time-Varying Channel with Both Amplitude and Delay Variations 14
1.3.5 Linear Time-Varying Channel with Frequency-Dependent Attenuation 15
1.4 Modulation Techniques for UWA Communications 15
1.4.1 Frequency Hopped FSK 15
1.4.2 Direct Sequence Spread Spectrum 16
1.4.3 Single Carrier Modulation 17
1.4.4 Sweep-Spread Carrier (S2C) Modulation 18
1.4.5 Multicarrier Modulation 18
1.4.6 Multi-Input Multi-Output Techniques 19
1.4.7 Recent Developments on Underwater Acoustic Communications 20
1.5 Organization of the Book 20

2 OFDMBasics 23
2.1 Zero-Padded OFDM 23
2.1.1 Transmitted Signal 23
2.1.2 Receiver Processing 26
2.2 Cyclic-Prefixed OFDM 27
2.2.1 Transmitted Signal 27
2.2.2 Receiver Processing 28
2.3 OFDM Related Issues 28
2.3.1 ZP-OFDM versus CP-OFDM 28
2.3.2 Peak-to-Average-Power Ratio 29
2.3.3 Power Spectrum and Bandwidth 29
2.3.4 Subcarrier Assignment 30
2.3.5 Overall Data Rate 30
2.3.6 Design Guidelines 31
2.4 Implementation via Discrete Fourier Transform 31
2.5 Challenges and Remedies for OFDM 32
2.5.1 Benefits of Diversity Combining and Channel Coding 33
2.6 MIMO OFDM 36
2.7 Bibliographical Notes 38

3 Nonbinary LDPC Coded OFDM 39
3.1 Channel Coding for OFDM 39
3.1.1 Channel Coding 39
3.1.2 Coded Modulation 41
3.1.3 Coded OFDM 42
3.2 Nonbinary LDPC Codes 43
3.2.1 Nonbinary Regular Cycle Codes 44
3.2.2 Nonbinary Irregular LDPC Codes 45
3.3 Encoding 46
3.4 Decoding 48
3.4.1 Initialization 48
3.4.2 Variable-to-Check-Node Update 49
3.4.3 Check-to-Variable-Node Update 50
3.4.4 Tentative Decision and Decoder Outputs 51
3.5 Code Design 52
3.5.1 Design of Regular Cycle codes 53
3.5.2 Design of Irregular LDPC Codes 53
3.5.3 Quasi-Cyclic Nonbinary LDPC codes 55
3.6 Simulation Results of Coded OFDM 58
3.7 Bibliographical Notes 59

4 PAPR Control 63
4.1 PAPR Comparison 63
4.2 PAPR Reduction 65
4.2.1 Clipping 65
4.2.2 Selective Mapping 67
4.2.3 Peak Reduction Subcarriers 69
4.3 Bibliographical Notes 69

5 Receiver Overview and Preprocessing 71
5.1 OFDM Receiver Overview 72
5.2 Receiver Preprocessing 73
5.2.1 Receiver Preprocessing 73
5.2.2 Digital Implementation 74
5.2.3 Frequency-Domain Oversampling 77
5.3 Frequency-Domain Input–Output Relationship 78
5.3.1 Single-Input Single-Output Channel 78
5.3.2 Single-Input Multi-Output Channel 79
5.3.3 Multi-Input Multi-Output Channel 80
5.3.4 Channel Matrix Structure 81
5.4 OFDM Receiver Categorization 82
5.4.1 ICI-Ignorant Receiver 82
5.4.2 ICI-Aware Receiver 83
5.4.3 Block-by-Block Processing 85
5.4.4 Block-to-Block Processing 85
5.4.5 Discussion 85
5.5 Receiver Performance Bound with Simulated Channels 85
5.5.1 Simulating Underwater Acoustic Channels 86
5.5.2 ICI Effect in Time-Varying Channels 86
5.5.3 Outage Performance of SISO Channel 87
5.6 Extension to CP-OFDM 88
5.6.1 Receiver Preprocessing 88
5.6.2 Frequency-Domain Input–Output Relationship 89
5.7 Bibliographical Notes 89

6 Detection, Synchronization and Doppler Scale Estimation 91
6.1 Cross-Correlation Based Methods 92
6.1.1 Cross-Correlation Based Detection 92
6.1.2 Cross-Correlation Based Synchronization and Doppler Scale Estimation 96
6.2 Detection, Synchronization and Doppler Scale Estimation with CP-OFDM 99
6.2.1 CP-OFDM Preamble with Self-Repetition 99
6.2.2 Self-Correlation Based Detection, Synchronization and Doppler Scale Estimation 100
6.2.3 Implementation 101
6.3 Synchronization and Doppler Scale Estimation for One ZP-OFDM Block 103
6.3.1 Null-Subcarrier based Blind Estimation 103
6.3.2 Pilot-Aided Estimation 104
6.3.3 Decision-Aided Estimation 104
6.4 Simulation Results for Doppler Scale Estimation 104
6.4.1 RMSE Performance with CP-OFDM 105
6.4.2 RMSE Performance with ZP-OFDM 106
6.4.3 Comparison of Blind Methods of CP- and ZP-OFDM 107
6.5 Design Examples in Practical Systems 108
6.6 Residual Doppler Frequency Shift Estimation 110
6.6.1 System Model after Resampling 110
6.6.2 Impact of Residual Doppler Shift Compensation 111
6.6.3 Two Residual Doppler Shift Estimation Methods 112
6.6.4 Simulation Results 113
6.7 Bibliographical Notes 115

7 Channel and Noise Variance Estimation 117
7.1 Problem Formulation for ICI-Ignorant Channel Estimation 118
7.1.1 The Input–Output Relationship 118
7.1.2 Dictionary Based Formulation 118
7.2 ICI-Ignorant Sparse Channel Sensing 120
7.2.1 Dictionary Resolution versus Channel Sparsity 121
7.2.2 Sparsity Factor 122
7.2.3 Number of Pilots versus Number of Paths 123
7.3 ICI-Aware Sparse Channel Sensing 124
7.3.1 Problem Formulation 124
7.3.2 ICI-Aware Channel Sensing 124
7.3.3 Pilot Subcarrier Distribution 125
7.3.4 Influence of Data Symbols 126
7.4 Sparse Recovery Algorithms 127
7.4.1 Matching Pursuit 127
7.4.2 1-Norm Minimization 128
7.4.3 Matrix-Vector Multiplication via FFT 129
7.4.4 Computational Complexity 131
7.5 Extension to Multi-Input Channels 131
7.5.1 ICI-Ignorant Sparse Channel Sensing 131
7.5.2 ICI-Aware Sparse Channel Sensing 132
7.6 Noise Variance Estimation 134
7.7 Noise Prewhitening 134
7.7.1 Noise Spectrum Estimation 135
7.7.2 Whitening in the Frequency Domain 136
7.8 Bibliographical Notes 136

8 Data Detection 137
8.1 Symbol-by-Symbol Detection in ICI-Ignorant OFDM Systems 139
8.1.1 Single-Input Single-Output Channel 139
8.1.2 Single-Input Multi-Output Channel 140
8.2 Block-Based Data Detection in ICI-Aware OFDM Systems 141
8.2.1 MAP Equalizer 142
8.2.2 Linear MMSE Equalizer with A Priori Information 142
8.2.3 Extension to the Single-Input Multi-Output Channel 145
8.3 Data Detection for OFDM Systems with Banded ICI 145
8.3.1 BCJR Algorithm and Log-MAP Implementation 145
8.3.2 Factor-Graph Algorithm with Gaussian Message Passing 148
8.3.3 Computations related to Gaussian Messages 149
8.3.4 Extension to SIMO Channel 150
8.4 Symbol Detectors for MIMO OFDM 151
8.4.1 ICI-Ignorant MIMO OFDM 151
8.4.2 Full-ICI Equalization 152
8.4.3 Banded-ICI Equalization 152
8.5 MCMC Method for Data Detection in MIMO OFDM 153
8.5.1 MCMC Method for ICI-Ignorant MIMO Detection 153
8.5.2 MCMC Method for Banded-ICI MIMO Detection 154
8.6 Bibliographical Notes 155

9 OFDM Receivers with Block-by-Block Processing 157
9.1 Noniterative ICI-Ignorant Receiver 158
9.1.1 Noniterative ICI-Ignorant Receiver Structure 158
9.1.2 Simulation Results: ICI-Ignorant Receiver 159
9.1.3 Experimental Results: ICI-Ignorant Receiver 160
9.2 Noniterative ICI-Aware Receiver 161
9.2.1 Noniterative ICI-Aware Receiver Structure 162
9.2.2 Simulation Results: ICI-Aware Receiver 163
9.2.3 Experimental Results: ICI-Aware Receiver 164
9.3 Iterative Receiver Processing 164
9.3.1 Iterative ICI-Ignorant Receiver 165
9.3.2 Iterative ICI-Aware Receiver 165
9.4 ICI-Progressive Receiver 166
9.5 Simulation Results: ICI-Progressive Receiver 168
9.6 Experimental Results: ICI-Progressive Receiver 171
9.6.1 BLER Performance 171
9.6.2 Environmental Impact 171
9.6.3 Progressive versus Iterative ICI-Aware Receivers 174
9.7 Discussion 175
9.8 Bibliographical Notes 175

10 OFDM Receiver with Clustered Channel Adaptation 177
10.1 Illustration of Channel Dynamics 177
10.2 Modeling Cluster-Based Block-to-Block Channel Variation 178
10.3 Cluster-Adaptation Based Block-to-Block Receiver 180
10.3.1 Cluster Offset Estimation and Compensation 181
10.3.2 Cluster-Adaptation Based Sparse Channel Estimation 184
10.3.3 Channel Re-estimation and Cluster Variance Update 186
10.4 Experimental Results: MACE10 186
10.4.1 BLER Performance with an Overall Resampling 187
10.4.2 BLER Performance with Refined Resampling 188
10.5 Experimental Results: SPACE08 190
10.6 Discussion 193
10.7 Bibliographical Notes 193

11 OFDM in Deep Water Horizontal Communications 195
11.1 System Model for Deep Water Horizontal Communications 196
11.1.1 Transmitted Signal 197
11.1.2 Modeling Clustered Multipath Channel 197
11.1.3 Received Signal 198
11.2 Decision-Feedback Based Receiver Design 199
11.3 Factor-Graph Based Joint IBI/ICI Equalization 200
11.3.1 Probabilistic Problem Formulation 200
11.3.2 Factor-Graph Based Equalization 202
11.4 Iterative Block-to-Block Receiver Processing 203
11.5 Simulation Results 205
11.6 Experimental Results in the AUTEC Environment 208
11.7 Extension to Underwater Broadcasting Networks 211
11.7.1 Underwater Broadcasting Networks 211
11.7.2 Emulated Experimental Results: MACE10 211
11.8 Bibliographical Notes 214

12 OFDM Receiver with Parameterized External Interference Cancellation 215
12.1 Interference Parameterization 215
12.2 An Iterative OFDM Receiver with Interference Cancellation 217
12.2.1 Initialization 219
12.2.2 Interference Detection and Estimation 219
12.2.3 Channel Estimation, Equalization and Channel Decoding 221
12.2.4 Noise Variance Estimation 221
12.3 Simulation Results 221
12.3.1 Time-Invariant Channels 222
12.3.2 Time-Varying Channels 223
12.3.3 Performance of the Proposed Receiver with Different SIRs 224
12.3.4 Interference Detection and Estimation 225
12.4 Experimental Results: AUTEC10 225
12.5 Emulated Results: SPACE08 227
12.6 Discussion 229
12.7 Bibliographical Notes 229

13 Co-located MIMO OFDM 231
13.1 ICI-Ignorant MIMO-OFDM System Model 232
13.2 ICI-Ignorant MIMO-OFDM Receiver 233
13.2.1 Noniterative ICI-Ignorant MIMO-OFDM Receiver 233
13.2.2 Iterative ICI-Ignorant MIMO-OFDM Receiver 234
13.3 Simulation Results: ICI-Ignorant MIMO OFDM 234
13.4 SPACE08 Experimental Results: ICI-Ignorant MIMO OFDM 237
13.5 ICI-Aware MIMO-OFDM System Model 237
13.6 ICI-Progressive MIMO-OFDM Receiver 237
13.6.1 Receiver Overview 239
13.6.2 Sparse Channel Estimation and Noise Variance Estimation 240
13.6.3 Joint ICI/CCI Equalization 240
13.7 Simulation Results: ICI-Progressive MIMO OFDM 241
13.8 SPACE08 Experiment: ICI-Progressive MIMO OFDM 242
13.9 MACE10 Experiment: ICI-Progressive MIMO OFDM 244
13.9.1 BLER Performance with Two Transmitters 244
13.9.2 BLER Performance with Three and Four Transmitters 246
13.10 Initialization for the ICI-Progressive MIMO OFDM 246
13.11 Bibliographical Notes 246

14 Distributed MIMO OFDM 249
14.1 System Model 250
14.2 Multiple-Resampling Front-End Processing 251
14.3 Multiuser Detection (MUD) Based Iterative Receiver 252
14.3.1 Pre-processing with Frequency-Domain Oversampling 252
14.3.2 Joint Channel Estimation 254
14.3.3 Multiuser Data Detection and Channel Decoding 255
14.4 Single-User Detection (SUD) Based Iterative Receiver 255
14.4.1 Single-User Decoding 255
14.4.2 MUI Construction 256
14.5 An Emulated Two-User System Using MACE10 Data 257
14.5.1 MUD-Based Receiver with and without Frequency-Domain Oversampling 258
14.5.2 Performance of SUD- and MUD-Based Receivers 258
14.6 Emulated MIMO OFDM with MACE10 and SPACE08 Data 260
14.6.1 One Mobile Single-Transmitter User plus One Stationary Two-Transmitter User 261
14.6.2 One Mobile Single-Transmitter User plus One Stationary Three-Transmitter User 262
14.6.3 Two Mobile Single-Transmitter Users plus One Stationary Two-Transmitter User 263
14.7 Bibliographical Notes 263

15 Asynchronous Multiuser OFDM 265
15.1 System Model for Asynchronous Multiuser OFDM 266
15.2 Overlapped Truncation and Interference Aggregation 267
15.2.1 Overlapped Truncation 267
15.2.2 Interference Aggregation 268
15.3 An Asynchronous Multiuser OFDM Receiver 269
15.3.1 The Overall Receiver Structure 269
15.3.2 Interblock Interference Subtraction 270
15.3.3 Time-to-Frequency-Domain Conversion 271
15.3.4 Iterative Multiuser Reception and Residual Interference Cancellation 273
15.3.5 Interference Reconstruction 274
15.4 Investigation on Multiuser Asynchronism in an Example Network 275
15.5 Simulation Results 276
15.5.1 Two-User Systems with Time-Varying Channels 277
15.5.2 Multiuser Systems with Time-Invariant Channels 279
15.6 Emulated Results: MACE10 281
15.7 Bibliographical Notes 284

16 OFDM in Relay Channels 285
16.1 Dynamic Coded Cooperation in a Single-Relay Network 285
16.1.1 Relay Operations 286
16.1.2 Receiver Processing at the Destination 288
16.1.3 Discussion 289
16.2 A Design Example Based on Rate-Compatible Channel Coding 289
16.2.1 Code Design 289
16.2.2 Simulation Results 291
16.3 A Design Example Based on Layered Erasure- and Error-Correction Coding 292
16.3.1 Code Design 292
16.3.2 Implementation 293
16.3.3 An Experiment in Swimming Pool 293
16.3.4 A Sea Experiment 296
16.4 Dynamic Block Cycling over a Line Network 299
16.4.1 Hop-by-Hop Relay and Turbo Relay 299
16.4.2 Dynamic Block-Cycling Transmissions 300
16.4.3 Discussion 302
16.5 Bibliographical Notes 302

17 OFDM-Modulated Physical-Layer Network Coding 303
17.1 System Model for the OFDM-Modulated PLNC 305
17.2 Three Iterative OFDM Receivers 306
17.2.1 Iterative Separate Detection and Decoding 306
17.2.2 Iterative XOR-ed PLNC Detection and Decoding 307
17.2.3 Iterative Generalized PLNC Detection and Decoding 309
17.3 Outage Probability Bounds in Time-Invariant Channels 309
17.4 Simulation Results 310
17.4.1 The Single-Path Time-Invariant Channel 311
17.4.2 The Multipath Time-Invariant Channel 311
17.4.3 The Multipath Time-Varying Channel 313
17.5 Experimental Results: SPACE08 314
17.6 Bibliographical Notes 315

18 OFDM Modem Development 317
18.1 Components of an Acoustic Modem 317
18.2 OFDM Acoustic Modem in Air 318
18.3 OFDM Lab Modem 318
18.4 AquaSeNT OFDM Modem 320
18.5 Bibliographical Notes 321

19 Underwater Ranging and Localization 323
19.1 Ranging 324
19.1.1 One-Way Signaling 324
19.1.2 Two-Way Signaling 324
19.1.3 Challenges for High-Precision Ranging 325
19.2 Underwater GPS 325
19.2.1 System Overview 325
19.2.2 One-Way Travel Time Estimation 326
19.2.3 Localization 327
19.2.4 Tracking Algorithms 329
19.2.5 Simulation Results 334
19.2.6 Field Test in a Local Lake 335
19.3 On-Demand Asynchronous Localization 336
19.3.1 Localization Procedure 337
19.3.2 Localization Algorithm for the Initiator 338
19.3.3 Localization Algorithm for a Passive Node 340
19.3.4 Localization Performance Results in a Lake 341
19.4 Bibliographical Notes 344

Appendix A Compressive Sensing 345
A.1 Compressive Sensing 346
A.1.1 Sparse Representation 346
A.1.2 Exactly and Approximately Sparse Signals 346
A.1.3 Sensing 346
A.1.4 Signal Recovery and RIP 347
A.1.5 Sensing Matrices 348
A.2 Sparse Recovery Algorithms 348
A.2.1 Matching Pursuits 349
A.2.2 1-Norm Minimization 349
A.3 Applications of Compressive Sensing 350
A.3.1 Applications of Compressive Sensing in Communications 350
A.3.2 Compressive Sensing in Underwater Acoustic Channels 351

Appendix B Experiment Description 353
B.1 SPACE08 Experiment 353
B.2 MACE10 Experiment 354
B.2.1 Experiment Setup 355
B.2.2 Mobility Estimation 356

References 359
Index 383