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CONTENTS List of Figures xiii List of Tables xvii Preface xix 1 Introduction 1 1.1 Overview of UWB 1 1.2 Advantages of UWB 3 1.3 UWB Applications 4 1.4 UWB Transmission Schemes 5 1.5 Challenges for UWB 7 2 Channel Characteristics 9 2.1 Large-Scale Models 10 2.1.1 Path Loss Models 10 2.1.2 Shadowing 11 2.2 Small-Scale Models 12 2.2.1 Tap-delay line fading model 12 2.2.2 ? ? K model 14 2.2.3 Saleh?Valenzuela (S-V) model 14 2.2.4 Standard UWB Channel Model 15 vii viii CONTENTS 3 UWB: Single Band Approaches 17 3.1 Overview of Single Band Approaches 18 3.2 Modulation Techniques 19 3.2.1 Pulse Amplitude Modulation (PAM) 19 3.2.2 On-Off Keying (OOK) 20 3.2.3 Phase Shift Keying (PSK) 20 3.2.4 Pulse Position Modulation (PPM) 20 3.3 Multiple Access Techniques 21 3.3.1 Time-Hopping UWB 21 3.3.2 Direct Sequence UWB 23 3.4 Demodulation Techniques 23 3.4.1 Received Signal Model 24 3.4.2 Correlation Receiver 25 3.4.3 Rake Receiver 26 3.5 MIMO Single Band UWB 28 3.5.1 MIMO Space-Time Coded Systems 28 3.5.2 Space-Time Coded UWB Systems 29 3.6 Performance Analysis 33 3.6.1 TH-BPPM 35 3.6.2 TH-BPSK 38 3.6.3 DS-BPSK 38 3.7 Simulation Results 40 3.8 Chapter Summary 48 4 UWB: Multiband OFDM Approach 49 4.1 Overview of Multiband OFDM Approach 50 4.1.1 Fundamental Concepts 50 4.1.2 Signal Model 50 4.2 IEEE 802.15.3a WPAN Standard Proposal 53 4.2.1 OFDM Parameters 53 4.2.2 Rate-Dependent Parameters 54 4.2.3 Operating Band Frequencies 55 4.2.4 Channelization 55 4.3 Physical Layer Design 56 4.3.1 Scrambler and De-scrambler 57 4.3.2 Convolutional Encoder and Viterbi Decoder 58 4.3.3 Bit Interleaver and De-interleaver 59 4.3.4 Constellation Mapper 62 4.3.5 OFDM Modulation 62 4.4 MAC Layer Design 64 4.4.1 Network Topology 64 CONTENTS ix 4.4.2 Frame Architecture 65 4.4.3 Network Operations 66 4.5 Chapter Summary 67 5 MIMO Multiband OFDM 69 5.1 MIMO-OFDM Communications 70 5.2 MIMO Multiband OFDM System Model 72 5.2.1 Transmitter Description 72 5.2.2 Channel Model 73 5.2.3 Receiver Processing 74 5.3 Performance Analysis 75 5.3.1 Independent Fading 76 5.3.2 Correlated Fading 79 5.4 Simulation Results 82 5.5 Chapter Summary 87 6 Performance Characterization 89 6.1 System Model 90 6.2 Performance Analysis 91 6.2.1 Average PEP Analysis 92 6.2.2 Approximate PEP Formulation 94 6.2.3 Outage Probability 98 6.3 Analysis for MIMO Multiband OFDM Systems 101 6.3.1 MIMO Multiband OFDM System Model 101 6.3.2 Pairwise Error Probability 102 6.3.3 Example: Repetition STF Coding based on Alamouti?s Structure 104 6.4 Simulation Results 105 6.5 Chapter Summary 109 7 Performance under Practical Considerations 113 7.1 System Model 114 7.2 Average Signal-to-Noise Ratio 116 7.2.1 Expressions of Fading Term, ICI, and ISI 116 7.2.2 Variances of Fading Term, ICI, and ISI 119 7.2.3 Average Signal-to-Noise Ratio and Performance Degradation 123 7.3 Average Bit Error Rate 124 7.3.1 Overall Spreading Gain of 1 125 7.3.2 Overall Spreading Gain of 2 127 7.3.3 Overall Spreading Gain of 4 128 7.4 Performance Bound 131 7.5 Numerical and Simulation Results 133 x CONTENTS 7.5.1 Numerical Results 133 7.5.2 Simulation and Numerical Results 136 7.6 Chapter Summary 137 Appendix: Derivations of A1, A2, B1, and B2 138 8 Differential Multiband OFDM 143 8.1 Differential Modulation 144 8.1.1 Single-Antenna Systems 144 8.1.2 MIMO Systems 145 8.2 Differential Scheme for Multiband OFDM Systems 147 8.2.1 System Model 147 8.2.2 Differential Encoding and Transmit Signal Structure 148 8.2.3 Multiband Differential Decoding 149 8.3 Pairwise Error Probability 151 8.4 Simulation Results 154 8.5 Chapter Summary 155 9 Power Controlled Channel Allocation 157 9.1 System Model 158 9.2 Power Controlled Channel Allocation Scheme 160 9.2.1 Generalized SNR for Different Transmission Modes 161 9.2.2 PER and Rate Constraint 162 9.2.3 Problem Formulation 163 9.2.4 Subband Assignment and Power Allocation Algorithm 164 9.2.5 Joint Rate Assignment and Resource Allocation Algorithm 165 9.3 Simulation Results 167 9.3.1 Subband Assignment and Power Allocation 167 9.3.2 Joint Rate Assignment and Resource Allocation 170 9.4 Chapter Summary 171 10 Cooperative UWB Multiband OFDM 175 10.1 Cooperative Communications 176 10.2 System Model 177 10.2.1 Non-Cooperative UWB 177 10.2.2 Cooperative UWB 179 10.3 SER Analysis for Cooperative UWB 180 10.3.1 Cooperative UWB 180 10.3.2 Comparison of Cooperative and Non-Cooperative UWB 185 10.4 Optimum Power Allocation for Cooperative UWB 186 10.4.1 Power Minimization using Cooperative Communications 187 10.4.2 Coverage Enhancement using Cooperative Communications 191 CONTENTS xi 10.5 Improved Cooperative UWB 193 10.6 Simulation Results 196 10.7 Chapter Summary 200 References 203 Index 211 LIST OF FIGURES 1.1. UWB spectral mask for indoor communication systems. 2 1.2. Spectrum of UWB and existing narrowband systems. 3 1.3. UWB transmission approaches: single band and multiband approaches. 5 2.1. Principle of the Saleh-Valenzuela fading model. 15 3.1. Pulse train with low duty of cycle, where Tf is pulse repetition time and Tw is pulse duration 18 3.2. An example of 4-ary PAM signal. 19 3.3. An example of OOK signal. 20 3.4. An example of binary PSK signal. 20 3.5. An example of 4-ary PPM signal. 21 3.6. A pulse train with TH sequence f1; 0; 3; : : :g. 22 3.7. An example of TH-UWB signals with different modulation 23 3.8. An example of DS-UWB signal with BPSk modulation. 24 3.9. A correlator with reference signal v(1) k0 (t) 25 3.10. A Rake receiver with reference signals v(1) k0 (t ? ? (1)(l)) 26 3.11. A MIMO space-time coded system. 28 xiii xiv LIST OF FIGURES 3.12. A multi-user space-time coded UWB system. 30 3.13. (a) Second derivative of the Gaussian monocycle waveform used at the receiver. (b) Its autocorrelation function. 41 3.14. Performance of TH and DS UWB systems 43 3.15. Performance of TH and DS UWB systems with respect to number of users. 45 3.16. Performance of TH and DS UWB-MIMO systems with various number of Rake fingers, L. 46 3.17. Performance of TH and DS UWB-MIMO systems with ROD space-time codes of different rates. 47 4.1. Multiband spectrum [Dis03] 51 4.2. Multiband signals transmitted at different times [Dis03]. 51 4.3. Illustration of UWB Multiband OFDM Spectrum. 52 4.4. Transmitter and receiver of an OFDM system. 52 4.5. Band division in multiband OFDM standard proposal. 53 4.6. Time-frequency spreading (a) Low rates (b) Middle rates (c) High rates. 55 4.7. Operating band frequencies in mandatory mode. 55 4.8. A time-frequency representation of multiband OFDM signal with timefrequency code f1 3 2 1 3 2g [Bat03] 56 4.9. Multiband OFDM system (a) Transmitter; (b) Receiver [Bat03] 57 4.10. Convolutional encoder (mother code) [Bat03]. 58 4.11. Input-output relation of convolutional encoder [Bat03]. 58 4.12. Puncturing patterns for rate 11/32 [Bat03]. 59 4.13. Puncturing patterns for rate 1/2 [Bat03]. 60 4.14. Puncturing patterns for rate 5/8 [Bat03]. 60 4.15. Puncturing patterns for rate 3/4 [Bat03]. 61 4.16. Interleaver: (a) Symbol interleaver; (b) Tone Interleaver [Bat03]. 61 4.17. QPSK constellation bit encoding [Bat03]. 62 4.18. Subcarrier frequency allocation [Bat03]. 63 4.19. An illustration of piconet topology in UWB WPAN 64 4.20. A superframe structure for UWB WPAN specified in the IEEE 802.15.3 standard [TG3]. 65 5.1. A MIMO-OFDM communications system 70 LIST OF FIGURES xv 5.2. MIMO multiband OFDM system. 72 5.3. Time-frequency representation of multiband OFDM symbols with K = 2 and fast band-hopping rate. 73 5.4. Time-frequency representation of multiband OFDM symbols with K = 2 and slow band-hopping rate. 81 5.5. Power delay profile based on statistical channel model in [Tar03]. 82 5.6. Performance of multiband OFDM with different coding schemes (K = 1). 84 5.7. Performance of multiband OFDM with different diversity orders. 85 5.8. Performance of multiband OFDM with different time spreading factors. 86 5.9. Performance of multiband OFDM with different hopping rates. 87 6.1. One realization of UWB channel generated using the parameters for CM 1 and CM 4 99 6.2. Probability density function. 106 6.3. Performances of single-antenna multiband OFDM system with BPSK symbols. 107 6.4. Performances of single-antenna multiband OFDM system with QPSK symbols. 108 6.5. Outage probability of single-antenna multiband OFDM system. 110 6.6. Performances of MIMO multiband OFDM system with QPSK symbols. 111 7.1. System model. 114 7.2. (a) Timing synchronization error; (b) Frequency synchronization error. 115 7.3. The average BER of multiband OFDM systems for the high data rate mode in channel model CM1. 131 7.4. The multiband OFDM system model. 132 7.5. The average BER of multiband OFDM systems in perfect frequency and timing synchronization: (a) CM1; (b) CM2; (c) CM3; and (d) CM4. 133 7.6. The average BER of multiband OFDM systems for low-rate mode in imperfect timing synchronization: (a) CM1; (b) CM2; (c) CM3; and (d) CM4. 134 7.7. The degradation ratio of multiband OFDM systems for low-rate mode in imperfect frequency synchronization: (a) CM1; (b) CM2; (c) CM3; and (d) CM4. 135 7.8. The degradation ratio of multiband OFDM systems for low-rate mode in imperfect frequency and timing synchronization (a) CM1; (b) CM2; (c) CM3; and (d) CM4. 136 7.9. The average BER of multiband OFDM systems for the high data rate mode in channel model CM1. 137 8.1. Descriptions of the differential unitary space-time modulation scheme. 146 xvi LIST OF FIGURES 8.2. Example of differential encoded signal matrix and transmit signal structure for UWB multiband OFDM system with K = 2, G = 2, and Mt = 2. 149 8.3. Performance under CM 1, Mt = 1, Mr = 1, R = 1 b/s/Hz. 154 8.4. Performance under CM 1 and CM 2, Mt = 1, Mr = 1, R = 1=K b/s/Hz. 155 8.5. Performance comparison of the DMB-OFDM scheme under CM 1 employing SISO and MIMO processing, K = 1 and R = 1 b/s/Hz. 156 9.1. Flow chart of the joint rate assignment and resource allocation algorithm. 165 9.2. Performances of three-user system with random location. 168 9.3. Performances of multiple-user system. 169 9.4. One realization of rate adaptation for two-user system. 170 9.5. Average rate and standard deviation of multiple-user system. 172 10.1. A simplified cooperation model. 177 10.2. Illustrations of non-cooperative and cooperative UWB multiband OFDM systems with the same data rate. 178 10.3. Comparison of the SER formulations and the simulation result for the cooperative UWB system. We assume that ?2 s;d = ?2 s;r = ?2 r;d = 1, and P1 = P2 = P=2. 184 10.4. Coverage enhancement using cooperative UWB multiband OFDM 191 10.5. Illustration of an improved cooperative UWB multiband OFDM scheme. 193 10.6. Comparison of the SER formulations and the simulation result for the improved cooperative UWB multiband OFDM system. We assume that ?2 s;d = ?2 s;r = ?2 r;d = 1, and P1 = P2 = P3 = P=3. 195 10.7. SER performance of UWB systems versus P=N0. 197 10.8. P=N0 versus destination location. 198 10.9. P=N0 versus destination location for UWB systems with power limitation. 198 10.10. Distance between source and destination versus distance between source and relay. 199 10.11. Maximum transmission range versus P=N0. 200 LIST OF TABLES 2.1. Multipath channel model parameters 16 4.1. Timing parameters 53 4.2. Rate-dependent parameters 54 4.3. Time-frequency codes for different piconets[Bat03] 56 4.4. Scrambler seed selection [Bat03]. 58 4.5. QPSK encoding [Bat03]. 62 7.1. Data-rate modes 124 10.1. Comparisons between optimum power allocation obtained via exhaustive search and analytical results. 189 10.2. Power ratio of cooperative and non-cooperative UWB multiband OFDM systems 189 10.3. Power allocation, relay location, and maximum coverage of cooperative UWB multiband OFDM systems with frequency spreading gain: gF = 1. 193 10.4. Power allocation, relay location, and maximum coverage of cooperative UWB multiband OFDM systems with frequency spreading gain: gF = 2 193 10.5. Comparisons between optimum power allocation obtained via exhaustive search and analytical results. 197

Library of Congress Subject Headings for this publication:

Orthogonal frequency division multiplexing.

Ultra-wideband devices.