OFDM for Underwater Acoustic Communications

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

Auteur

S. Zhou, Associate Professor, Department of Electrical and Computer Engr., University of Connecticut, Storrs, USA
Shengli 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, USA
Ms. 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.

Contenu
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 InputOutput 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 InputOutput 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...