SIGNAL PROCESSING FOR MOBILE COMMUNICATIONS HANDBOOK

Edited by Mohamed Ibnkahla
CRC PRESS 2005.
CONTENTS
Preface 4 Contributors 6 PART I: INTRODUCTION CHAPTER 1. SIGNAL PROCESSING FOR FUTURE MOBILE COMMUNICATIONS SYSTEMS: CHALLENGES AND PERSPECTIVES 1.1 Introduction 12 1.2 Channel Characterizations 12 1.2.1 Large-Scale Propagation Models 12 1.2.1.1 Deterministic Approach 12 1.2.1.1.1 Free-Space Propagation Model 12 1.2.1.1.2 Log-Distance Path Loss Model 13 1.2.1.2 Stochastic Approach 13 1.2.1.2.1 Lognormal Shadowing Model 13 1.2.2 Small-Scale Propagation Models 14 1.2.2.1 Parameters of Mobile Multipath Channel 14 1.2.2.1.1 Fading 14 1.2.2.1.2 Doppler Shift 14 1.2.2.1.3 Excess Delay 14 1.2.2.1.4 Power Delay Profile, I c ( T) 14 1.2.2.1.5 Delay Spread (T m) 15 1.2.2.1.6 Coherence Bandwidth (B 15 1.2.2.1.7 Doppler Spread (Bd) 15 1.2.2.1.8 Coherence Time (Tcoh) 15 1.2.2.2 Types of Small-Scale Fading 15 1.2.2.2.1 Flat Fading 16 1.2.2.2.2 Frequency-Selective Fading 16 1.2.2.2.3 Fast Fading 16 1.2.2.2.4 Slow Fading 16 1.2.2.3 Statistical Representation of the Small-Scale Propagation Channel 17 1.2.2.3.1 Rayleigh Fading Channel 17 1.2.2.3.2 Ricean Fading Channel 17 1.2.2.3.3 Nakagami Fading Channel 17 1.2.2.4 Statistical Models for Multipath Fading Channels 18 1.2.2.4.1 Two-Ray Fading Channel Model 18 1.2.2.4.2 Motif Model 19 1.2.2.4.3 Finite-State Markov Chain Model 19 1.2.2.4.4 Loo's Satellite Channel Model 20 1.2.2.4.5 Multiple-Input Multiple-Output Channel Models 21 1.2.2.4.5.2 Physical Scattering Model 22 1.2.2.4.5.1 Matrix Channel Model 21 1.3 Modulation Techniques 23 1.3.1 Modulation Schemes: The Classification 23 1.3.2 Different Modulation Schemes 23 1.3.2.1 Phase Shift Keying 23 1.3.2.10 Challenges in the Next-Generation System Concerning Different Modulation 29 1.3.2.2 Pulse Amplitude Modulation 25 1.3.2.3 Quadrature Amplitude Modulation 25 1.3.2.4 Frequency Shift Keying 26 1.3.2.5 Continuous-Phase FSK 27 1.3.2.6 Continuous-Phase Modulation 28 1.3.2.7 Minimum Shift Keying 28 1.3.2.8 Gaussian MSK 28 1.3.2.9 Orthogonal Frequency Division Multiplexing 28 1.4 Coding Techniques 30 1.4.1 Shannon's Capacity Theorem 30 1.4.2 Different Coding Schemes 31 1.4.2.1 Block Codes 32 1.4.2.1.1 Vector Space and Subspace 32 1.4.2.1.2 Linear Block Code 32 1.4.2.1.3 Coding Gain 32 1.4.2.1.4 Hamming Codes 32 1.4.2.1.5 Hamming Distance 32 1.4.2.1.6 Implementation Complexity 32 1.4.2.1.7 BCH (Bose-Chaudhuri-Hocquenghem)Codes 33 1.4.2.1.8 Reed-Solomon Codes 33 1.4.2.1.9 Interleaving 33 1.4.2.2 Convolutional Codes 34 1.4.2.2.1 Pictorial Representation of Convolutional Encoder 34 1.4.2.2.1.1 State Diagram 35 1.4.2.2.1.2 Tree Diagram 35 1.4.2.2.1.3 Trellis Diagram 36 1.4.2.3 Space-Time Coding 36 1.4.2.4 Turbo Coding 36 1.4.2.5 Coded Modulation Techniques 37 1.4.2.5.1 Trellis Coded Modulation 37 1.4.2.5.2 Block Coded Modulation 37 1.4.2.5.3 Multilevel Coded Modulation 37 1.4.2.5.4 Turbo Coded Modulation 37 1.4.3 Coding in Next-Generation Mobile Communications: Some Research 37 1.5 Multiple Access Techniques 39 1.5 Multiple Access Techniques 11 1.5.1 Fundamental Multiple-Access Schemes 39 1.5.1.1 Frequency Division Multiple Access 39 1.5.1.1.1 Merits 39 1.5.1.1.2 Demerits 39 1.5.1.2 Time Division Multiple Access 40 1.5.1.2.1 Merits 40 1.5.1.2.2 Demerits 40 1.5.1.3 Code Division Multiple Access 40 1.5.1.3.1 Wideband CDMA 40 1.5.1.3.2 Merits 40 1.5.1.3.3 Demerits 41 1.5.2 Combination of OFDM and CDMA Systems 41 1.5.2.1 MT-CDMA Scheme 42 1.5.2.2 MC-CDMA Scheme 42 1.5.2.3 MC-DS CDMA Scheme 42 1.5.3 OFDM/TDMA 43 1.5.3.1 Merits 43 1.5.3.2 Demerits 43 1.5.4 Capacity of MAC Methods 43 1.5.4.1 FDMA Capacity 44 1.5.4.2 TDMA Capacity 44 1.5.4.3 CDMA Capacity 44 1.5.5 Challenges in the MAC Schemes 44 1.6 Diversity Technique 45 1.6.1 Classifications of the Diversity Techniques 45 1.6.2 Classifications of Diversity Combiners 46 1.6.2.1 Predetection Diversity Combiners 46 1.6.2.1.1 Selection Diversity Combining 46 1.6.2.1.2 Maximal Ratio Combining 46 1.6.2.1.3 Equal Gain Combining 46 1.6.2.2 Postdetection Diversity Combiners 46 1.6.3 Diversity for Next-Generation Systems: Some Research Evidence 47 1.6.4 Challenges in the Diversity Area 47 1.7 Conclusions 48 PART II: CHANNEL MODELING AND ESTIMATION CHAPTER 2. MULTIPATH PROPAGATION MODELS FOR BROADBAND WIRELESS SYSTEMS 2.1 Introduction 54 2.2 Narrowband, Wideband, and Directional Channel Modeling 55 2.2.1 Intuitive Description 55 2.2.2 Mathematical Description: Deterministic Case 57 2.2.3 Mathematical Description: Stochastic Case 58 2.2.4 Condensed Parameters 59 2.2.5 Directional Description 60 2.3 Modeling Methods for Multipath Channels 62 2.3.1 Measured Channel Impulse Responses 62 2.3.2 Deterministic Channel Computation 63 2.3.2.1 Full Electromagnetic Description 64 2.3.2.2 High-Frequency Approximations 64 2.3.3 Tapped Delay Lines 66 2.3.4 Stochastic MIMO Models 67 2.3.5 Geometry-Based Stochastic Channel Models 68 2.4 Propagation Aspects and Parameterization 69 2.4.1 Amplitude Statistics 70 2.4.2 Arrival Times 71 2.4.3 Average Time Dispersion 72 2.4.4 Average Angular Dispersion at the BS 73 2.4.5 Average Angular Dispersion at the MS 74 2.4.6 MIMO Parameters 75 2.4.7 Polarization 75 2.4.8 Millimeter Wave Propagation 75 2.4.9 Ultrawideband Systems 76 2.5 Standard Models 76 2.5.1 The COST 207 Model 76 2.5.2 The ITU-R Models 77 2.5.3 IEEE 802.11/HIPERLAN Models 79 2.5.4 The 802.15 Ultrawideband Channel Model 79 2.5.5 The 3GPP-3GPP2 Model 81 2.5.6 The COST 259 Model 82 2.6 Conclusions 83 CHAPTER 3. MODELING AND ESTIMATION OF MOBILE CHANNELS 3.1 Introduction 97 3.2 Channel Models 99 3.2.1 Time-Variant Channels 99 3.2.1.1 Tapped Delay Line Model 99 3.2.1.2 Basis Expansion Models 101 3.2.2 Time-Invariant Channels 102 3.3 Channel Estimation 104 3.3.1 Training-Based Channel Estimation 105 3.3.1.1 Time-Variant Channels 105 3.3.2 Blind Channel Estimation 106 3.3.2.1 Combined Channel and Symbol Estimation 106 3.3.2.1.1 Stochastic Maximum Likelihood Estimation 106 3.3.2.1.2 Deterministic Maximum Likelihood Estimation 107 3.3.2.2 The Methods of Moments 108 3.3.2.2.1 SISO Channel Estimation 108 3.3.2.2.1.1 Indirect Channel Estimation 108 3.3.2.2.2 SIMO Channel Estimation 109 3.3.2.2.2.3 Multistep Linear Prediction 113 3.3.2.2.2.2 Noise Subspace Approach 112 3.3.2.2.2.1 The Cross-Relation Approach 111 3.3.3 Semiblind Approaches 115 3.3.4 Hidden Pilot-Based Approaches 115 3.3.4.1 Equalization 117 3.4 Simulation Examples 118 3.4 Simulation Examples 97 3.4.1 Example 1 118 3.4.2 Example 2 119 3.5 Conclusions 121 CHAPTER 4. MOBILE SATELLITE CHANNELS: STATISTICAL MODELS AND PERFORMANCE ANALYSIS 4.1 Introduction 125 4.2 Statistical Propagation Models 126 4.2.1 Narrowband Statistical Models 128 4.2.1.1 Single-State Statistical Models 128 4.2.1.1.1 Single-State First-Order Characterization 129 4.2.1.1.1.9 Patzold et al. Distribution 132 4.2.1.1.1.6 Suzuki Distribution 130 4.2.1.1.1.10 GRLN Distribution 133 4.2.1.1.1.11 Xie and Fang Distribution 133 4.2.1.1.1.4 Nakagami Distribution 130 4.2.1.1.1.5 Norton Distribution 130 4.2.1.1.1.2 Rayleigh Distribution 129 4.2.1.1.1.7 Loa Distribution 131 4.2.1.1.1.3 Rice Distribution 129 4.2.1.1.1.1 Lognormal Distribution 129 4.2.1.1.1.12 Other Models 134 4.2.1.1.1.8 RLN Distribution 131 4.2.1.1.2 Single-State Second-Order Characterization 134 4.2.1.1.2.1 Doppler Spectrum 135 4.2.1.1.2.2 Level Crossing Rate and Average Fade Duration 136 4.2.1.1.2.3 Fade and Non-fade Duration Statistics 137 4.2.1.1.2.4 Shadowing Correlation Function 138 4.2.1.2 Multistate Statistical Models 138 4.2.1.2.1 Lutz Model 138 4.2.1.2.2 Barts and Stutzman Model 140 4.2.1.2.3 Vucetic and Du Model 140 4.2.1.2.4 Rice and Humphreys Model 141 4.2.1.2.5 Karasawa et al. Model 141 4.2.1.2.6 Fontan et al. Model 141 4.2.1.2.7 Wakana model 141 4.2.2 Wideband Statistical Models 142 4.2.2.1 DLR Wideband Model 142 4.2.2.2 Saunders et al. 143 4.2.2.3 IMR Channel Model 143 4.3 Detection Performance Analysis 125 4.3 Detection Performance Analysis 144 4.3.1 Uncoded Transmission over LMS Channels 144 4.3.1.1 M-ary Coherent Detection 145 4.3.1.2 M-ary Orthogonal Noncoherent Detection 145 4.3.2 Coded Transmission over LMS Channels 146 4.3.2.1 Pseudo-coherent BPSK Detection 147 4.3.2.2 Non-coherent M-ary Detection 149 4.3.2.3 Convolutional Code Performance Analysis 150 4.3.2.4 Turbo Code Performance Analysis 154 4.4 Conclusions 155 CHAPTER 5. MOBILE VELOCITY ESTIMATION FOR WIRELESS COMMUNICATIONS 5.1 Introduction 161 5.1.1 Importance of Velocity Estimation 161 5.1.2 Existing Velocity Estimators 163 5.1.3 Structure of the Chapter 164 5.2 Received Signal Model and Statistics 164 5.2.1 Received Signal Model 164 5.2.2 Multipath Component Model 165 5.2.3 The Scattering Distribution 166 5.2.4 Statistics of the Multipath Fading 166 5.3 Principles of Mobile Velocity Estimation 168 5.3.1 Examples of Derivations of the Velocity 168 5.3.2 Examples of Velocity Estimators 170 5.4 Performance Analysis of Velocity Estimators 171 5.4.1 Effect of Shadowing 172 5.4.2 Effect of AWGN and Nonisotropic Scattering 172 5.4.2.1 Derivation of the Normalized Bias 172 5.4.2.2 Performance in the Presence of AWGN and Isotropic Scattering 173 5.4.2.3 Performance in the Presence of Nonisotropic Scattering 174 5.5 Performance Analysis Using Simulations 176 5.5.1 Simulations of the Received Signal 176 5.5.2 Simulation Results 177 5.6 Rice Factor Estimation 180 5.6.1 Existing Methods 180 5.6.2 Envelope-Based Estimators 181 5.6.3 Simulation Results 184 5.7 Application on Handover Performance 184 5.7.1 Handover Decision Algorithms 184 5.7.2 Effect of an Error in Velocity Estimation on the System's 185 5.8 Conclusions and Perspectives 187 PART III: MODULATION TECHNIQUES FOR WIRELESS COMMUNICATIONS CHAPTER 6. ADAPTIVE CODED MODULATION FOR TRANSMISSION OVER FADING CHANNELS 6.1 Introduction 195 6.2 Adaptive System Model 197 6.2.1 Model for a Wireless Link 197 6.2.2 Adaptation in Response to Path Loss/Shadowing 198 6.2.3 Analytic Model for Fine-Scale Adaptation 199 6.3 Adaptivity in Single-Input Single-Output Systems 201 6.3.1 Information Theoretic Bounds 201 6.3.2 Design for Uncoded Systems 202 6.3.2.1 Design Rules 203 6.3.2.2 Numerical Results 204 6.3.3 Coded Modulation Structures 205 6.3.3.1 Coding Structures with (Nearly) Perfect Prediction 205 6.3.3.2 Coding Structures with Moderate Prediction Error Statistics 205 6.3.3.3 Coding Structures with Large Prediction Error Statistics 206 6.3.4 Designing with a Given Coded Modulation Structure 206 6.3.4.1 Design Rules 206 6.3.4.2 Performance Results 206 6.4 Adaptivity in Multiantenna Systems 207 6.4.1 Information Theoretic Considerations 207 6.4.1.1 MIMO Single-User Systems 207 6.4.1.2 Multiuser MIMO Systems 208 6.4.2 Adaptive Coded Modulation for MIMO Systems 208 6.5 Conclusions 209 CHAPTER 7. SIGNALING CONSTELLATIONS FOR TRANSMISSION OVER NONLINEAR CHANNELS 7.1 Introduction 214 7.2 System Model 215 7.3 Craig's Method 216 7.4 probability of Symbol Error for 16-ary QAM Format 217 7.4.1 The (8,8) Constellation Format 217 7.4.1.1 The Structure 217 7.4.1.2 Probability of Error Analysis 218 7.4.2 The (4,12) Constellation Format 219 7.4.2.1 The Structure 219 7.4.2.2 Probability of Error Analysis 219 7.4.3 The (S,II) Constellation Format 220 7.4.4 The (6,10) Constellation Format 221 7.4.5 16-Rectangular Constellations with a Circular Format 222 7.4.5.1 The Structure 222 7.4.5.2 Probability of Error Analysis 223 7.4.6 The Effect of Nonlinearity and the Application 224 7.4.7 Total Degradation 226 7.4.8 Results and Discussions 227 7.5 probability of Symbol Error for the Circular 232 7.5.1 The (4,11,17) Constellation Format 232 7.5.2 The (5,11,16) Constellation Format 234 7.5.3 32-Rectangular Constellations with a Circular Format 235 7.5.3.1 The Structure 235 7.5.3.2 Probability of Error Analysis 236 7.5.4 The Effect of Nonlinearity and the Application 240 7.5.5 Results and Discussions 240 7.6 Conclusions 242 CHAPTER 8. CARRIER FREQUENCY SYNCHRONIZATION FOR OFDM SYSTEMS 8.1 Introduction 244 8.10 Conclusions 262 8.2 Basics of OFDM 245 8.2.1 OFDM Modulation 246 8.2.2 Demodulation 247 8.3 Effect of CFO on System Performance 249 8.4 Carrier Frequency Offset Estimation 250 8.5 Repetitive Slots-Based CFO Estimation 251 8.5.1 Nonlinear Least Squares Method 251 8.5.2 Computationally Simpler Estimators 252 8.5.2.1 Approximate NLS Estimator 252 8.5.2.2 BLUE Estimator 253 8.6 Null-Subcarrier-Based CFO Estimation 253 8.6.1 Deterministic Maximum Likelihood Estimation 254 8.6.2 Special Case: Repetition of Identical Slots 255 8.6.2.1 Virtual Subcarriers Absent 255 8.6.2.2 Virtual Subcarriers Present 255 8.7 Identifiability 256 8.8 Performance Analysis 258 8.8.1 The Conditional CRB 258 8.8.2 The Unconditional CRB: Rayleigh Channel 259 8.8.3 Optimal Choice of Null-Subcarriers 259 8.9 Simulation Results 260 CHAPTER 9. FILTER-BANK MODULATION TECHNIQUES FOR TRANSMISSION OVER FREQUENCY-SELECTIVE CHANNELS 9.1 Introduction 267 9.2 Critically Sampled Filter Banks 269 9.2.1 Orthogonality Conditions 269 9.2.2 Efficient Implementation 270 9.2.3 Example of Critically-Sampled Filter Bank 273 9.3 Discrete Multitone Modulation 274 9.4 O-QAM OFDM Modulation 276 9.5 Discrete Wavelet Multitone Modulation 281 9.6 Filtered Multitone Modulation 282 9.6.1 Filter-bank Design 286 9.6.2 Per-Subchannel Adaptive Equalization and Precoding 289 PART IV: MULTIPLE ACCESS TECHNIQUES CHAPTER 10. SPREAD-SPECTRUM TECHNIQUES FOR MOBILE COMMUNICATIONS 10.1 A Brief History of Wireless Communications 296 10.1.1 The Wireless Revolution 296 10.1.2 2G and 3G Cellular Systems 296 10.1.3 DSP Components for Wireless Communications 297 10.2 Fundamentals of Digital Spread-Spectrum Signaling 298 10.2.1 Narrowband 298 10.2.10 Short Code 301 10.2.11 Long Code 301 10.2.12 Processing Gain 301 10.2.13 Pseudorandom Sequence Generators 302 10.2.14 Basic Architecture of a DS/SS Modem 302 10.2.2 Spread-Spectrum 299 10.2.3 Frequency-Hopping Spread Spectrum 299 10.2.4 Direct-Sequence Spread Spectrum 299 10.2.5 DS/SS Signal Model 300 10.2.6 Real Spreading 300 10.2.7 Complex Spreading 300 10.2.8 DS/SS Bandwidth Occupancy 300 10.2.9 Spreading Factor 301 10.3 Code-Division Multiple Access 304 10.3.1 Frequency-, Time-, and Code-Division Multiplexing 304 10.3.2 Multirate Code-Division Multiplexing 306 10.3.3 Multiple Access Interference 306 10.3.4 Capacity of a CDMA System 307 10.3.5 Cellular Networks and the Universal Frequency Reuse 308 10.4 A Review of 2G and 3G Standards for CDMA 308 10.4 A Review of2G and 3G Standards for CDMA 295 10.4.1 IS-95 309 10.4.2 UMTS/UTRA 309 10.4.3 cdma2000 311 10.5 Synchronization for Spread-Spectrum and CDMA Signals 312 10.5.1 Synchronization Functions 312 10.5.2 Code Synchronization 312 10.5.3 Carrier Frequency and Phase Synchronization 314 10.6 Architecture of DSP-Based DS/SS and CDMA Receivers 315 10.6.1 IF vs. Baseband Sampling 315 10.6.2 Correlation Receiver 316 10.6.3 Rake Receiver 316 10.7 Multiuser Detection 318 10.7.1 Multiuser Detection in the UL 318 10.7.2 The Decorrelating and MMSE Detectors 320 10.8 Perspectives and Conclusions 321 10.8.1 The Challenge to Mobile Spread-Spectrum Communications 321 10.8.2 4G Wireless Communications Systems 322 10.8.3 Concluding Remarks 323 CHAPTER 11. MULTIUSER DETECTION FOR FADING CHANNELS 11.1 Introduction 327 11.2 Signal and Channel Model 327 11.2.1 The Fading Channel Model 327 11.2.2 Transmitted Signal Model 329 11.2.3 Continuous-Time Received Signal Model 330 11.3 Multiuser Detection with Known CSI 331 11.3.1 Conventional Single-User Detection 332 11.3.2 Optimum Multiuser Detection 333 11.3.3 Linear Multiuser Detection 335 11.3.3.1 The Decorrelating Detector 335 11.3.3.2 Remarks 337 11.3.3.3 The MMSE Detector 338 11.3.3.4 Remarks on the MMSE Detector 339 11.3.4 Approximate MMSE Detection: Linear Serial 340 11.3.5 Constrained ML Detection: Nonlinear Serial 341 11.3.6 Performance Results 342 11.3.6.1 Analysis 342 11.3.7 Some Numerical Results 347 11.3.8 Sliding-Window One-Shot Multiuser Receivers 349 11.4 Multiuser Detection with Unknown CSI 350 11.4.1 Signal Representation in Unknown CSI 350 11.4.2 Available Strategies to Cope with Missing CSI 353 11.4.3 Channel Estimation Based on the Least Squares Criterion 353 11.4.4 Trained Adaptive Code-Aided Symbol Detection 355 11.4.5 Code-Aided Joint Blind Multiuser Detection and Equalization 358 11.4.6 Subspace-Based Blind MMSE Detection 359 11.4.7 Minimum Variance Blind Detection 360 11.4.8 Two-Stage Blind Detection 360 11.4.9 Performance Results 361 11.5 Conclusions 363 PART V: MIMO SYSTEMS CHAPTER 12. PRINCIPLES OF MIMO-OFDM WIRELESS SYSTEMS 12.1 Introduction 365 12.2 The Broadband MIMO Fading Channel 366 12.2.1 Basic Assumptions 366 12.2.2 Array Geometry 367 12.2.3 Fading Statistics 367 12.2.4 Ricean Component 368 12.2.5 Comments on the Channel Model 368 12.3 Capacity of Broadband MIMO-OFDM Systems 368 12.3.1 MIMO-OFDM 368 12.3.2 Capacity of MIMO-OFDM Spatial Multiplexing Systems 370 12.3.3 Impact of Propagation Parameters on Capacity 370 12.3.3.1 Impact of Cluster Angle Spread and Antenna Spacing 371 12.3.3.2 Impact of Total Angle Spread 371 12.3.3.3 Ergodic Capacity in the SISO and MIMO Cases 371 12.3.4 Numerical Results 373 12.4 Space-Frequency Coded MIMO-OFDM 373 12.4.1 Space--Frequency Coding 373 12.4.2 Error Rate Performance 375 12.4.3 Maximum Diversity Order and Coding Gain 375 12.4.3.1 Rayleigh Fading 375 12.4.3.1.1 Receive Correlation Only 376 12.4.3.1.2 Transmit Correlation Only 376 12.4.3.1.3 Joint Transmit-Receive Correlation 377 12.4.3.2 Ricean Fading 377 12.5 Impact of Propagation Parameters 378 12.5.1 Impact of Propagation Parameters 378 12.5.1.1 Impact of Cluster Angle Spread 378 12.5.1.2 Impact of Total Angle Spread 379 12.5.2 Simulation Results 380 12.5.2.1 Simulation Example 1 380 12.5.2.2 Simulation Example 2 380 12.5.2.3 Simulation Example 3 382 12.5.2.4 Simulation Example 4 382 12.5.2.4.1 Spatial Multiplexing 384 12.5.2.4.2 Delay Diversity Combined with Convolutional Code 384 CHAPTER 13. SPACE-TIME CODING AND SIGNAL PROCESSING FOR BROADBAND WIRELESS COMMUNICATIONS 13.1 Introduction 387 13.2 Broadband Wireless Channel Model 387 13.2 Broadband Wireless Channel Model 389 13.3 Information- Theoretic Considerations 391 13.3 Information- Theoretic Considerations 387 13.3.1 Shannon Capacity of Fading ISI Channels 391 13.3.2 Diversity Order 391 13.3.3 Design Criteria for Space-Time Codes over Flat-Fading Channels 392 13.4 Signal Transmission Issues 393 13.4.1 Transmitter Techniques 393 13.4.1.1 Spatial Multiplexing (BLAST) 393 13.4.1.2 Transmit Diversity Techniques 394 13.4.1.3 Space-Time Coding 395 13.4.1.3.1 Space-Time Trellis Codes 396 13.4.1.3.2 Alamouti-Type Space-Time Block Codes 397 13.4.1.4 Diversity vs. Throughput Trade-Off 398 13.4.1.5 Orthogonal Frequency Division Multiplexing 399 13.4.2 Receiver Techniques 399 13.4.2.1 Coherent Techniques 400 13.4.2.1.1 Channel Estimation for Quasi-Static Channels 400 13.4.2.1.2 Channel Estimation and Tracking for Rapidly Time- Varying Channels 401 13.4.2.1.3 Joint Equalization/Decoding of Space-Time Trellis Codes 401 13.4.2.1.4 Joint Equalization/Decoding of Space-Time Block Codes 402 13.4.2.1.5 OFDM with Fast Channel Variations 404 13.4.2.1.6 Joint Equalization and Interference Cancellation 404 13.4.2.1.7 Adaptive Techniques 406 13.4.2.2 Noncoherent Techniques 407 13.5 Summary and Future Challenges 409 CHAPTER 14. LINEAR PRECODING FOR MIMO SYSTEMS 14.1 Introduction 414 14.1.1 System Model 415 14.2 Optimum precoding 416 14.2.1 Jointly Optimum Design and Performance Bounds 417 14.2.1.1 MMSE Criterion under Transmit Power and Maximum Eigenvalue Constraint 418 14.2.1.2 Maximum Amin(SNR(F, G)) under Power and Maximum 419 14.2.1.3 Equivalent Decomposition into Independent Sub channels 420 14.2.1.4 Performance Measures 421 14.3 Performance Analysis and Random Matrices 423 14.3.1 Differential Forms and Random Matrix Techniques 423 14.3.2 The Statistics of the Capacity 427 14.4 Channel Estimation for MIMO Systems 432 14.4 Channel Estimation for MIMO Systems 414 14.4.1 Channel Estimation Algorithm 433 14.4.2 Cramer-Rao Lower Bound 435 14.4.3 Numerical Results 436 14.5 Conclusions 437 CHAPTER 15. PERFORMANCE ANALYSIS OF MULTIPLE ANTENNA SYSTEMS 15.1 Introduction 441 15.2 MIMO Systems without Co-Channel Interference 442 15.2.1 System Model and Problem Statement 442 15.2.2 MIMO Channel Capacity without Channel State Information 442 15.2.2.1 Rician Fading 442 15.2.2.2 l.i.d. Rician Fading and LLd. Rayleigh Fading Channels 443 15.2.2.3 Correlated Rayleigh Fading Channels 444 15.2.2.4 Capacity CCDF 449 15.2.3 Capacity/Outage Probability of MIMO MRC (Beam-Forming) Systems 451 15.2.3.1 System Models and Problem Statement 451 15.2.3.2 MIMO MRC Systems Outage Probability 452 15.2.3.3 Capacity CCDF of MIMO MRC Systems 453 15.2.4 Water-Filling Capacity and Beam Forming Performance of Correlated 453 15.2.4.1 Water-Filling Capacity 453 15.2.4.2 Beam-Forming Performance 455 15.3 MIMO Systems in the Presence 458 15.3.1 Problem Statement 458 15.3.2 Capacity CCDF of MIMO Optimum Combining Scheme 459 15.3.2.2 Capacity of Optimum Combining 463 15.3.3 Statistics of the MIMO Capacity with Co-Channel Interference 463 15.3.3.1 Problem Statement 463 15.3.3.2 Capacity MGF 464 15.3.4 RicianjRayleigh Fading Scenarios 467 PART VI: EQUALIZATION AND RECEIVER DESIGN CHAPTER 16. EQUALIZATION TECHNIQUES FOR FADING CHANNELS 16.1 Introduction 472 16.2 Wireless Channel Model 473 16.2.1 TIV Channels 475 16.2.2 TV Channels 475 16.3 System Model 477 16.3.1 TIV Channels 478 16.3.2 TV Channels 478 16.4 Block Equalization 478 16.4.1 Block Linear Equalization 479 16.4.2 Block Decision Feedback Equalization 480 16.5 Serial Linear Equalization 481 16.5.1 TIV Channels 481 16.5.2 TV Channels 483 16.5.3 Equalizer Design 484 16.6 Serial Decision Feedback Equalization 485 16.6.1 TIV Channels 486 16.6.2 TV Channels 486 16.6.3 Equalizer Design 487 16.7 Frequency-Domain Equalization for TIV Channels 488 16.7.1 FD Linear Equalization 489 16.7.2 FD Decision Feedback Equalization 489 16.8 Existence of Zero-Forcing Solution 492 16.8.1 Linear Equalizers 492 16.8.2 Decision Feedback Equalizers 492 16.9 Complexity 493 16.9.1 Design Complexity 493 16.9.2 Implementation Complexity 494 CHAPTER 17. LOW-COMPLEXITY DIVERSITY COMBINING SCHEMES FOR MOBILE COMMUNICATIONS 17.1 Introduction 503 17.2 System and Channel Models 504 17.2.1 System Model 504 17.2.2 Channel Model 505 17.3 Dual-Branch Switch and Stay Combining 505 17.3.1 Dual-Branch sse Schemes 506 17.3.2 Markov Chain-Based Analysis 507 17.3.3 Statistics of Overall Combiner Output 509 17.3.4 Application to Performance Analysis and Comparisons 511 17.4 Multibranch Switched Diversity 515 17.4.1 L-Branch sse 515 17.4.2 L-Branch SEC 516 17.5 Generalized Switch and Examine Combining (GSEC) 521 17.5.1 Mode of Operation of GSEC 521 17.5.2 MGF of Combiner Output 522 17.5.3 Application to Performance Analysis 524 17.5.4 Complexity Savings over GSC 527 17.6 Further Remarks 529 CHAPTER 18. OVERVIEW OF EQUALIZATION TECHNIQUES FOR MIMO FADING CHANNELS 18.1 Introduction 531 18.2 Frequency-Selective MIMO Channel Model 531 18.2 Frequency-Selective MIMO Channel Model 532 18.2.1 General Framework 532 18.2.2 Simulation Framework 533 18.3 Block Linear and Decision-Feedback Equalizers 534 18.3.1 Block Linear Equalizers 534 18.3.2 Block Decision-Feedback Equalizers 535 18.3.2.1 Simulation Results 537 18.4 List-Type Equalizers 538 18.4.1 The Single Antenna Case 538 18.4.1.1 Viterbi Algorithm 538 18.4.1.2 Generalized Viterbi Algorithm 538 18.4.1.3 List-Type MAP Algorithm 539 18.4.2 Generalization to the MIMO Case 540 18.4.3 Simulation Results 541 18.5 The Multidimensional Whitened Matched Filter 531 18.5 The Multidimensional Whitened Matched Filter 542 18.5.1 Whitened Matched Filter 542 18.5.2 Prefiltered List-Type MAP Equalizer 543 18.5.3 WMF Implementation Using Linear Prediction 543 18.5.4 Energy Concentration 544 18.5.5 Simulation Results 546 18.6 The Block Equalizers vs. the Prefiltered 531 18.6 The Block Equalizers vs. the Prefiltered List-Type MAP 547 18.6.1 Complexity Comparison 547 18.6.2 Performance Comparison 548 18.7 Conclusion 549 CHAPTER 19. NEURAL NETWORLZS FOR TRANSMISSION OVER NONLINEAR CHANNELS 19.1 Introduction 552 19.2 Identification of Memoryless Nonlinear Amplifiers 555 19.2.1 Natural Gradient Learning 556 19.2.2 Influence of the HP A Modeling Error 558 19.2.3 Application to Adaptive Predistortion 561 19.3 Modeling and Identification of Nonlinear 566 19.3.1 Neural Network Channel Identification 566 19.3.2 Learning Algorithm 567 19.3.3 Application to MLSE Receiver Design 568 19.3.4 Simulation Examples 568 19.4 Channel Equalization 572 19.4.1 Neural Network Structure 572 19.4.2 BP Algorithm 574 19.4.3 NG Algorithm 574 19.4.4 Simulation Examples 575 19.5 Conclusion 575 PART VII: VOICE OVER IP CHAPTER 20. VOICE OVER IP AND WIRELESS: PRINCIPLES AND CHALLENGES 20.1 Introduction 581 20.2 Speech Coding for IP and Wireless: Principles 581 20.2.1 Some Preliminary Notions 581 20.2.2 Speech Coding Basics 582 20.2.2.1 Differential Coding 582 20.2.2.2 Adaptive Quantization 583 20.2.2.3 Noise Masking 583 20.2.2.4 Quality Measures 584 20.2.3 Speech Coding for IP and Wireless 584 20.2.3.1 Waveform Coders 584 20.2.3.2 Parametric Coders 584 20.2.3.3 Hybrid Coders 584 20.2.3.4 Relevant Coder Attributes 585 20.2.3.4.1 Bit Rate 585 20.2.3.4.2 Complexity 586 20.2.3.4.3 Delay 586 20.2.3.4.4 Robustness 586 20.3 Voice over IP 586 20.3.1 An Overview 586 20.3.2 Technological Barriers 587 20.3.2.1 End-to-End Delay and Jitter 587 20.3.2.2 Packet Loss 587 20.3.2.3 Throughput 587 20.3.2.4 Internet Availability and Reliability 588 20.3.2.5 Security and Confidentiality 588 20.3.3 Quality of Service 588 20.3.4 Standard Speech Coders for VoIP 588 20.3.5 Packet loss Recovery Techniques 589 20.3.6 Other Packet-Based Alternatives for Voice Transport: Trends 590 20.4 Voice over Wireless 590 20.4.1 Wireless Voice Communications Systems 590 20.4.2 Fundamental Issues in Speech Coding for Wireless 591 20.4.2.1 Channel Quality and Adaptive Operation 591 20.4.2.2 Background Noise 591 20.4.2.3 Tandeming 591 20.4.2.4 Voice Activity Detection 591 20.4.2.5 Unequal Error Protection (UEP) 591 20.4.2.6 Frame Erasures 592 20.4.3 Standard Speech Coders for Wireless 592 20.4.3.1 European GSM and UMTS Standards 592 20.4.3.2 North American Cellular Systems 593 20.4.4 Some Trends 593 20.4.4.1 Joint Channel-Source Coding 593 20.4.4.2 Robustness Issues for Low-Bit-Rate Coders 594 20.4.4.3 Selectable Mode Vocoder (SMV [18]) 594 20.5 Voice over IP over Wireless 594 20.6 Voice-Enabled Services over IP and Wireless 595 20.6.1 Introduction 595 20.6.2 Technologies for Voice-Enabled Interfaces 595 20.6.3 Architectures for Automatic Speech Recognition 596 20.6.3.1 Local or Terminal-Based Speech Recognition 596 20.6.3.2 Remote or Network-Based Speech Recognition 597 20.6.3.3 Distributed Speech Recognition 597 20.6.4 ASR over IP 598 20.6.4.1 Coding Distortion 598 20.6.4.2 Packet Loss 598 20.6.5 ASR over Wireless 598 20.6.5.1 Noisy Scenarios 599 20.6.5.2 The Influence of Coding Distortion on Speech Recognition 599 20.6.5.3 Transmission Errors and Lost Frames 599 20.7 Conclusions and Challenges 580 20.7 Conclusions and Challenges 600 PART VIII: WIRELESS GEOLOCATION TECHNIQUES CHAPTER 21. GEOLOCATION TECHNIQUES FOR MOBILE RADIO SYSTEMS 21.1 Introduction 605 21.1.1 FCC Regulations for E-911 606 21.1.2 Location-Based Services (LBS) 606 21.2 Geolocation Methods 607 21.3 Geolocation Algorithms 609 21.3.1 Geometric Solutions 609 21.3.2 Least Squares Estimation 611 21.3.3 Other Location Algorithms 613 21.3.4 Hybrid Location Methods 613 21.3.5 Performance 614 21.4 Location Parameter Estimation 616 21.4.1 ADA Estimation 616 21.4.2 Range Estimation 617 21.4.3 Range Difference Estimation 617 21.4.4 Joint Parameter Estimation 618 21.5 Impairments to Accuracy 618 21.5 Impairments to Accuracy 605 21.5.1 Multipath Propagation 618 21.5.2 Hearability 619 21.5.3 Non-Line-of-Sight Propagation 619 21.6 Provisions in the Standards 621 21.6.1 3G Location Solutions 621 21.6.2 Locating Legacy Terminals 622 21.7 Summary 622 CHAPTER 22. ADAPTIVE ARRAYS FOR GPS RECEIVERS 22.1 Introduction 628 22.2 GPS Signal Model 632 22.3 Interference Suppression Techniques in GPS 633 22.3.1 Broadband Interference Suppression Using Space-Time Array 633 22.3.1.1 MSINR 634 22.3.1.2 MMSE 634 22.3.1.3 MOP 635 22.3.1.4 Signal Distortion Introduced by Processor 635 22.3.2 Narrowband FM Interference Suppression 636 22.3.3 A Self-Coherence Antijamming GPS Receiver 640 22.4 Multipath Mitigation in GPS 646 22.4.1 Bias Due to Signal Multipath 646 22.4.1.1 Early-Late Discrimination Functions 647 22.4.1.2 Time-Delay Estimation 648 22.4.2 Single-Antenna Multipath Mitigation Techniques 649 22.4.2.1 Narrow Correlator 649 22.4.2.2 Multipath Elimination Delay Lock Loop 649 22.4.3 Time-Delay and Carrier-Phase Estimation Using Antenna Array 649 22.5 Conclusions 651 PART IX: POWER CONTROL AND WIRELESS NETWORKING CHAPTER 23. TRANSMITTER POWER CONTROL IN WIRELESS NETWORLZING: BASIC PRINCIPLES AND CORE ALGORITHMS 23.1 Intoduction 654 23.2 Power Control for Streamed Continuous Traffic 656 23.2.1 The Target SIR Formulation of the Power Control Problem 656 23.2.1.1 Example of the Simple Two-Link Network 657 23.2.1.2 The Optimal Power Vector P* 659 23.2.2 Autonomous Distributed Power Control 660 23.2.3 DPC with Active Link Protection 661 23.2.4 Admission Control under DPC/ ALP 663 23.2.4.1 Voluntary Dropout 666 23.2.4.2 Forced Dropout 666 23.2.4.3 Initial Power Level of New Links 667 23.2.5 Noninvasive Channel Probing and Selection 667 23.3 Power Control for Packetized Data Traffic 668 23.3.1 Power-Controlled Multiple Access: The Basic Model 668 23.3.2 Optimally Emptying the Transmitter Buffer 669 23.3.3 The Case of Per-Slot-Independent Interference 670 23.3.4 Structural Properties: Backlog Pressure and Phased Back-Off 671 23.3.5 Design of PCMA Algorithms: Responsive Interference 672 23.4 Final Remarks 673 CHAPTER 24. SIGNAL PROCESSING FOR MULTIACCESS COMMUNICATION NETWORKS 24.1 Introduction 675 24.2 MPR at the Physical Layer 676 24.2.1 The Model 676 24.2.2 Assumptions and Properties 678 24.2.3 The Training-Based Zero-Forcing Receiver 678 24.2.4 The Semiblind Least Squares Smoothing Receiver 679 24.2.5 Further Remarks 681 24.3 The Interface between the Physical Layer and the MAC 682 24.3.1 Channel Reception Matrix 682 24.3.2 Resolvability 683 24.3.3 From Resolvability Function to Reception Matrix 684 24.3.4 Further Remarks 684 24.4 Impact of MPR on the Performance of Existing 685 24.4.1 Resolvability Comparison 685 24.4.2 Network Performance Comparison 685 24.4.3 Further Remarks 686 24.5 MAC Layer Design for Networks with MPR 687 24.5.1 The Network Model 687 24.5.2 The Multiqueue Service Room Protocol 687 24.5.3 The Dynamic Queue Protocol 688 24.5.4 Further Remarks 689 24.6 Approach High Performance from Both Physical 690 24.7 Conclusion 691 PART X: EMERGING TECHNIQUES AND APPLICATIONS CHAPTER 25. TIME-FREQUENCY SIGNAL PROCESSING FOR WIRELESS COMMUNICATIONS 25.1 Introduction 694 25.2 Time-Frequency Signal Processing Tools 695 25.2.1 Limitations of Traditional Signal Representations 695 25.2.2 Joint Time-Frequency Representations 695 25.2.2.1 Finding Hidden Information Using Time-Frequency Representations 695 25.2.2.2 What Is a Time-Frequency Representation? 696 25.2.2.2.1 Physical Interpretation of TFDs 698 25.2.2.2.2 Instantaneous Frequency and Group Delay 698 25.2.3 Quadratic Time-Frequency Distributions 699 25.2.3.1 Time-Varying Spectrum and the Wigner- Ville Distribution 699 25.2.3.2 Time-Varying Spectrum Estimates and Quadratic TFDs 700 25.2.3.3 Time, Lag, Frequency, and Doppler Domains and the Ambiguity Function 701 25.2.3.4 Quadratic TFDs, Multicomponent Signals, Cross-Terms Reduction, 703 25.2.3.4.1 Reduced Interference Distributions 704 25.2.3.4.2 Comparison of Quadratic TFDs 704 25.2.3.5 Time-Frequency Signal Synthesis 705 25.2.3.6 Other Properties 705 25.3 Spread-Spectrum Communications Systems Using TFSP 705 25.3.1 Channel Modeling and Identification 705 25.3.1.1 Wireless Communication LTV Channel Model 706 25.3.1.2 Estimation of LTV channels 708 25.3.1.3 Estimation of Scattering Function 709 25.3.2 Interference Mitigation 710 25.3.2.1 TV-NBI Suppression in DS-CDMA 710 25.3.2.2 Signal Modulation Design for ISI Mitigation 711 25.3.2.3 Multiple-Access Interference in MC-CDMA 713 25.4 Time-Frequency Array Signal Processing 714 25.4.1 The Spatial Time-Frequency Distributions 715 25.4.1.1 Structure under linear model 716 25.4.1.2 Structure under Unitary Model 716 25.4.2 STFD Structure in Wireless Communications 717 25.4.3 Advantages of STFDs over Covariance Matrix 717 25.4.4 Selection of Autoterms and Cross-Terms 718 25.4.5 Time-Frequency Direction-of-Arrival Estimation 719 25.4.5.1 Data Model 720 25.4.5.2 TF-MUSIC 720 25.4.6 Time-Frequency Source Separation 720 25.4.6.1 Separation of Instantaneous Mixture 721 25.4.6.2 Separating More Sources Than Sensors 722 25.4.6.3 Separation of Convolutive Mixtures 722 25.4.6.4 STFD-Based Separation 723 25.5 Other TFSP Applications in Wireless Communications 724 25.5.1 Precoding for LTV Channels 724 25.5.2 Signaling Using Chirp Modulation 724 25.5.3 Detection of FM Signals in Rayleigh Fading 725 25.5.4 Mobile Velocity/Doppler Estimation 726 25.6 Conclusion 727 CHAPTER 26. MONTE CARLO SIGNAL PROCESSING FOR DIGITAL COMMUNICATIONS: PRINCIPLES AND APPLICATIONS 26.1 Introduction 735 26.2 MCMC Methods 736 26.2.1 General MCMC Algorithms 736 26.2.1.1 Metropolis-Hastings Algorithm 736 26.2.1.2 Gibbs Sampler 737 26.2.1.3 Other Techniques 737 26.2.2 Applications of MCMC in Digital Communications 738 26.2.2.1 MCMC Detectors in AWGN Channels 738 26.2.2.2 MCMC Equalizers in ISI Channels 740 26.2.2.3 MCMC Multiuser Detector in CDMA Channels 742 26.2.3 Other Applications 744 26.3 SMC Methods 744 26.3.1 General SMC Algorithms 744 26.3.1.1 Sequential Importance Sampling 744 26.3.1.2 SMC for Dynamic Systems 746 26.3.1.3 Mixture Kalman Filter 747 26.3.2 Resampling Procedures 748 26.3.3 Applications of SMC in Digital Communications 750 26.3.3.1 SMC Receiver in Flat-Fading Channels 750 26.3.3.2 SMC Receiver in MIMO ISI Channels 752 26.4 Concluding Remarks 756 CHAPTER 27. PRINCIPLES OF CHAOS COMMUNICATIONS 27.1 What Is Chaos? 759 27.1.1 Nonlinear Dynamic Systems 759 27.1.2 Statistical Analysis of Chaotic Signals 761 27.1.2.1 Probability Density Functions 761 27.1.2.2 Autocovariance and Autocorrelation Function 762 27.1.3 Realization of Chaos Generators 765 27.1.3.1 Discrete-Time Systems 765 27.1.3.2 Bit Stream Generators 765 27.1.3.3 Continuous-Time Systems 766 27.1.3.4 Distributed Systems 766 27.1.3.5 Digital Realizations 766 27.1.4 Properties of Chaotic Signals 766 27.2 Communication: Requirements and Resources 759 27.3 Chaos in Communications 759 27.3 Chaos in Communications 768 27.3.1 The Broadband Aspect 768 27.3.2 The Complexity Aspect 768 27.3.3 The Orthogonality Aspect 768 27.4 Communication Using Broadband Chaotic Carriers 768 27.4.1 Chaos-Based Transmitters 769 27.4.1.1 Static Encoding/Modulation Methods 769 27.4.1.1.1 Chaotic Masking 769 27.4.1.1.2 Chaos Shift Keying 770 27.4.1.1.3 Chaotic On-Off Keying 770 27.4.1.1.4 Transmitted Reference Methods and Differential Chaos Shift Keying 771 27.4.1.1.5 Analysis of Schemes with Static Encoding/Modulation 771 27.4.1.2 Dynamic Encoding/Modulation Methods 772 27.4.1.2.1 Chaotic Modulation/Chaotic Switching 772 27.4.1.2.2 Encoding Messages into the Symbolic Dynamics of Chaos Generators 772 27.4.2 Receiver Design in Chaos Communications 773 27.4.2.1 Message Detection Using a Reference Signal 773 27.4.2.1.1 Reference Generation by Drive Response Synchronization 773 27.4.2.1.2 Reference Generation by Controlling Chaotic Systems 774 27.4.2.1.3 Demodulation Using Reference Signals: Application Examples 774 27.4.2.2 Message Detection Based on Signal Statistics 776 27.4.2.3 Inverse System Principles 776 27.4.2.4 Other Detection Principles 777 27.5 Chaos for Spreading Code Generation 777 27.6 Chaotic vs. Classical Communications 27.6.1 The Analysis of Chaos Communication Schemes in AWGN 778 27.6.1.1 The Analysis Problem 778 27.6.1.2 Analysis Methods 779 27.6.1.2.1 Discrete-Time Baseband Modeling 779 27.6.1.2.2 Statistical Analysis of Nonlinear Discrete-Time Baseband Models 780 27.6.1.3 Analysis Example 781 27.6.1.3.1 Baseband Model 781 27.6.1.3.2 Baseband Signal Models 781 27.6.1.3.3 Results of the Statistical Analysis: Gaussian Approximation 782 27.6.1.3.4 Results of the Statistical Analysis: Exact Solutions 782 27.6.2 Chaos Communication Methods in Comparison to Classical Solutions 783 CHAPTER 28. ADAPTATION TECHNIQUES AND ENABLING PARAMETER ESTIMATION ALGORITHMS FOR WIRELESS COMMUNICATIONS SYSTEMS 28.1 Introduction 787 28.2 Overview of Adaptation Schemes 789 28.2.1 Link and Transmitter Adaptation 790 28.2.2 Adaptive System Resource Allocation 791 28.2.3 Receiver Adaptation 791 28.3 Parameter Measurements 792 28.3 Parameter Measurements 787 28.3.1 Channel Selectivity Estimation 792 28.3.1.1 Time Selectivity Measure: Doppler Spread 792 28.3.1.2 Frequency Selectivity Measure: Delay Spread 794 28.3.1.3 Spatial Selectivity Measure: Angle Spread 795 28.3.2 Channel Quality Measurements 796 28.3.2.1 Measures before Demodulation 797 28.3.2.2 Measures during and after Demodulation 797 28.3.2.3 Measures after Channel Decoding 799 28.3.2.4 Measures after Speech or Video Decoding 799 28.4 Applications of Adaptive Algorithms: Case Studies 800 28.4.1 Examples for Adaptive Receiver Algorithms 800 28.4.1.1 Channel Estimation with A Priori Information 800 28.4.1.2 Adaptive Channel Length Truncation for Equalization 801 28.4.1.3 Adaptive Interference Cancellation Receivers 801 28.4.1.4 Adaptive Soft Information Generation and Decoding 802 28.4.2 Examples for Link Adaptation and Adaptive Resource Allocation 803 28.4.2.1 Adaptive Power Control 803 28.4.2.2 Adaptive Modulation and Channel Coding 803 28.4.2.3 Adaptive Cell and Frequency Assignment 805 28.5 Future Research for Adaptation 806 28.6 Conclusion 808 // @