Evaluation of HSDPA to LTE – From Testbed Measurements to System Level Performance

Dr. Sebastian Caban, University of Technology Vienna, Austria Sebastian Caban finished his PhD with summa cum laude in October 2009 and is now post doctoral fellow at this institute. Christian Mehlfuhrer, University of Technology Vienna, Austria Christian Mehlfuhrer received his Dipl.-Ing. degree in electrical engineering from the Vienna University of Technology. In 2009, he finished his PhD about measurement-based performance evaluation of WiMAX and HSDPA with summa cum laude. Professor Markus Rupp, University of Technology Vienna, Austria Markus Rupp received his Dipl.-Ing. degree in 1988 at the University of Saarbrucken, Germany and his Dr.-Ing. degree in 1993 at the Technische Universitat Darmstadt, Germany, where he worked with Eberhardt Hansler on designing new algorithms for acoustical and electrical echo compensation. Martin Wrulich, University of Technology Vienna, Austria Martin Wrulich received his Dipl.-Ing. degree from Vienna University of Technology in March 2006 (diploma thesis: "Capacity Analysis of MIMO systems").

About the Authors xiii About the Contributors xv Preface xvii Acknowledgments xxiii List of Abbreviations xxv Part I CELLULAR WIRELESS STANDARDS Introduction 3 References 4 1 UMTS High-Speed Downlink Packet Access 5 1.1 Standardization and Current Deployment of HSDPA 5 1.2 HSDPA Principles 6 1.2.1 Network Architecture 7 1.2.2 Physical Layer 9 1.2.3 MAC Layer 13 1.2.4 Radio Resource Management 14 1.2.5 Quality of Service Management 16 1.3 MIMO Enhancements of HSDPA 17 1.3.1 Physical Layer Changes for MIMO 19 1.3.2 Precoding 21 1.3.3 MAC Layer Changes for MIMO 25 1.3.4 Simplifications of the Core Network 26 References 26 2 UMTS Long-Term Evolution 29 Contributed by Josep Colom Ikuno 2.1 LTE Overview 29 2.1.1 Requirements 29 2.2 Network Architecture 31 2.3 LTE Physical Layer 33 2.3.1 LTE Frame Structure 34 2.3.2 Reference and Synchronization Symbols 36 2.3.3 MIMO Transmission 37 2.3.4 Modulation and Layer Mapping 39 2.3.5 Channel Coding 41 2.3.6 Channel Adaptive Feedback 45 2.4 MAC Layer 46 2.4.1 Hybrid Automatic Repeat Request 46 2.4.2 Scheduling 47 2.5 Physical, Transport, and Logical Channels 48 References 51 Part II TESTBEDS FOR MEASUREMENTS Introduction 57 Reference 58 3 On Building Testbeds 59 3.1 Basic Idea 60 3.2 Transmitter 61 3.3 Receiver 63 3.4 Synchronization 65 3.5 Possible Pitfalls 67 3.5.1 Digital Baseband Hardware 67 3.5.2 Tool and Component Selection 68 3.5.3 Analog RF Front Ends 69 3.5.4 Cost 70 3.5.5 Matlab(r) Code and Testbeds 70 3.6 Summary 71 References 72 4 Quasi-Real-Time Testbedding 75 4.1 Basic Idea 75 4.2 Problem Formulation 77 4.3 Employing the Basic Idea 78 4.4 Data Collection 80 4.4.1 More Sophisticated Sampling Techniques 81 4.4.2 Variance Reduction Techniques 84 4.4.3 Bias 85 4.4.4 Outliers 86 4.4.5 Parameter Estimation 87 4.5 Evaluating and Summarizing the Data 88 4.6 Statistical Inference 90 4.6.1 Inferring the Population Mean 90 4.6.2 Precision and Sample Size 91 4.6.3 Reproducibility and Repeatability 92 4.7 Measurement Automation 95 4.8 Dealing with Feedback and Retransmissions 96 References 97 Part III EXPERIMENTAL LINK-LEVEL EVALUATION Introduction 101 5 HSDPA Performance Measurements 103 5.1 Mathematical Model of the Physical Layer 104 5.1.1 System Model for the Channel Estimation 106 5.1.2 System Model for the Equalizer Calculation 106 5.2 Receiver 107 5.2.1 Channel Estimation 107 5.2.2 Equalizer 112 5.2.3 Further Receiver Processing 113 5.3 Quantized Precoding 113 5.4 CQI and PCI Calculation 115 5.4.1 HS-PDSCH Interference 115 5.4.2 Pilot Interference 116 5.4.3 Synchronization and Control Channel Interference 116 5.4.4 Post-equalization Noise and SINR 118 5.4.5 SINR to CQI Mapping 119 5.5 Achievable Mutual Information 121 5.6 Measurement Results 124 5.6.1 Alpine Scenario 125 5.6.2 Urban Scenario 128 5.6.3 Discussion of the Implementation Loss 130 5.7 Summary 131 References 132 6 HSDPA Antenna Selection Techniques 139 Contributed by Jos'e Antonio Garc'ia-Naya 6.1 Existing Research 141 6.2 Receive Antenna Selection 142 6.2.1 Antenna Selection Based on System Throughput 143 6.2.2 Hardware Aspects of Antenna Selection 143 6.3 An Exemplary Measurement and its Results 144 6.3.1 Urban Scenario 144 6.3.2 Experimental Assessment of Antenna Selection in HSDPA 145 6.3.3 Measurement Results and Discussion 147 6.4 Summary 148 References 149 7 HSDPA Antenna Spacing Measurements 153 7.1 Problem Formulation 153 7.2 Existing Research 154 7.3 Experimental Setup 155 7.4 Measurement Methodology 157 7.4.1 Inferring the Mean Scenario Throughput 157 7.4.2 Issues Requiring Special Attention 158 7.5 Measurement Results and Discussion 160 7.5.1 Equal Polarization Versus Cross-Polarization 160 7.5.2 Channel Capacity 160 7.5.3 Channel Capacity Versus Mutual Information 162 7.5.4 Mutual Information Versus Achievable Mutual Information 162 7.5.5 Achievable Mutual Information Versus Throughput 163 7.5.6 Throughput 163 7.6 Different Transmit Power Levels and Scenarios 163 References 164 8 Throughput Performance Comparisons 167 8.1 Introduction 167 8.2 Cellular Systems Investigated: WiMAX and HSDPA 168 8.2.1 WiMAX and HSDPA 168 8.2.2 Throughput Bounds and System Losses 169 8.3 Measurement Methodology and Setup 172 8.4 Measurement Results 173 8.4.1 WiMAX Results 173 8.4.2 HSDPA Results in Standard-Compliant Setting 177 8.4.3 HSDPA Results in Advanced Setting 179 8.5 Summary 179 References 182 9 Frequency Synchronization in LTE 183 Contributed by Qi Wang 9.1 Mathematical Model 184 9.2 Carrier Frequency Offset Estimation in LTE 186 9.2.1 Standardized Training Symbols in LTE 186 9.2.2 Maximum Likelihood Estimators 188 9.3 Performance Evaluation 191 9.3.1 Estimation Performance 192 9.3.2 Post-FFT SINR 194 9.3.3 Post-equalization SINR and Throughput 195 References 199 10 LTE Performance Evaluation 201 Contributed by Stefan Schwarz 10.1 Mathematical Model of the Physical Layer 202 10.2 Receiver 203 10.2.1 Channel Estimation 204 10.2.2 Data Detection 205 10.2.3 Further Receiver Processing 206 10.3 Physical Layer Modeling 206 10.3.1 Post-equalization SINR 207 10.3.2 SINR Averaging 207 10.4 User Equipment Feedback Calculation 208 10.4.1 User Equipment Feedback Indicators 208 10.4.2 Calculation of the CQI, PMI, and RI 210 10.5 Practical Throughput Bounds 216 10.5.1 Channel Capacity 216 10.5.2 Open-Loop Mutual Information 217 10.5.3 Closed-Loop Mutual Information 218 10.5.4 BICM Bounds 219 10.5.5 Achievable Throughput Bounds 222 10.5.6 Prediction of the Optimal Performance 223 10.6 Simulation Results 224 10.6.1 SISO Transmission 225 10.6.2 OLSM Transmission 227 10.6.3 CLSM Transmission 229 References 230 Part IV SIMULATORS FOR WIRELESS SYSTEMS Introduction 237 References 240 11 LTE Link- and System-Level Simulation 243 Contributed by Josep Colom Ikuno 11.1 The Vienna LTE Link Level Simulator 245 11.1.1 Structure of the Simulator 245 11.1.2 Complexity 247 11.2 The Vienna LTE System Level Simulator 250 11.2.1 Structure of the Simulator 250 11.2.2 Simulator Implementation 252 11.2.3 Complexity 253 11.3 Validation of the Simulators 255 11.3.1 3GPP Minimum Performance Requirements 257 11.3.2 Link- and System-Level Cross-Comparison 257 11.4 Exemplary Results 259 11.4.1 Link-Level Throughput 259 11.4.2 LTE Scheduling 262 References 265 12 System-Level Modeling for MIMO-Enhanced HSDPA 271 12.1 Concept of System-Level Modeling 271 12.2 Computationally Efficient Link-Measurement Model 273 12.2.1 Receive Filter 274 12.2.2 WCDMA MIMO in the Network Context 276 12.2.3 Equivalent Fading Parameters Description 278 12.2.4 Generation of the Equivalent Fading Parameters 284 12.2.5 Influence of Non-Data Channels 286 12.2.6 Resulting SINR Description 287 12.3 Link-Performance Model 288 12.3.1 Link-Performance Model Concept 289 12.3.2 Training and Validation of the Model 293 References 296 Part V SIMULATION-BASED EVALUATION FOR WIRELESS SYSTEMS Introduction 301 13 Optimization of MIMO-Enhanced HSDPA 303 13.1 Network Performance Prediction 303 13.1.1 Simulation Setup 303 13.1.2 Single Network Scenario Investigation 304 13.1.3 Average Network Performance 306 13.2 RLC-Based Stream Number Decision 310 13.2.1 UE Decision 310 13.2.2 RLC Decision 311 13.2.3 System-Level Simulation Results 311 13.3 Content-Aware Scheduling 313 13.3.1 Video Packet Prioritization in HSDPA 313 13.3.2 Content-Aware Scheduler 314 13.3.3 Simulation Results 315 13.4 CPICH Power Optimization 316 13.4.1 System-Level Modeling of the CPICH Influence 317 13.4.2 CPICH Optimization in the Cellular Context 318 References 321 14 Optimal Multi-User MMSE Equalizer 325 14.1 System Model 326 14.2 Intra-Cell Interference Aware MMSE Equalization 330 14.2.1 Interference Suppression Capability 332 14.3 The Cell Precoding State 334 14.3.1 Training-Sequence-Based Precoding State Estimation 336 14.3.2 Blind Precoding State Estimation 337 14.3.3 Estimator Performance 339 14.4 Performance Evaluation 340 14.4.1 Physical-Layer Simulation Results 340 14.4.2 System-Level Simulation Results 341 References 343 15 LTE Advanced Versus LTE 347 Contributed by Stefan Schwarz 15.1 IMT-Advanced and 3GPP Performance Targets 348 15.2 Radio Interface Enhancements 349 15.2.1 Bandwidth Extension 349 15.2.2 Enhanced MIMO 350 15.2.3 Uplink Improvements 351 15.2.4 Beyond Release 10 352 15.3 MIMO in LTE Advanced 354 15.3.1 Codebook-Based Precoding 354 15.3.2 Non-Codebook-Based Precoding 356 15.4 Physical-Layer Throughput Simulation Results 359 15.4.1 Eight-Antenna Transmission 359 15.4.2 Comparison between LTE and LTE Advanced 363 15.4.3 Comparison of SU-MIMO and MU-MIMO 363 References 366 Index 369