Luận Văn Radio Channel Measurements and Modeling for Smart Antenna Array Systems Using a Software Radio Recei

Abstract
This dissertation presents research performed in the areas of radio wave propagation
measurement and modeling, smart antenna arrays, and software-defined radio development. A
four-channel, wideband, software-defined receiver was developed to serve as a test bed for
wideband measurements and antenna array experiments. This receiver was used to perform
vector channel measurements in terrestrial and air-to-ground environments using an antenna
array. Measurement results served as input to radio channel simulations based on three
geometric channel models. The simulation results were compared to measurement results to
evaluate the performance of the radio channel models under test. Criteria for evaluation include
RMS delay spread, excess delay spread, signal envelope fading, antenna diversity gain, and gain
achieved through the use of a two-dimensional rake receiver.
This research makes contributions to the wireless communications field through analysis,
development, measurement, and simulation that builds upon past theoretical and experimental
results. Contributions include a software-defined radio architecture, based on object oriented
techniques, that has been developed and successfully demonstrated using the wideband receiver.
This research has produced new wideband vector channel measurements to provide extensive
characterization results facilitating simulation of emerging wireless technology for commercial
and military communications systems. Original ways of interpreting multipath component
strength and correlation for antenna arrays have been developed and investigated. A novel
geometric air-to-ground ellipsoidal channel model has been developed, simulated, and evaluated.
Other contributions include an evaluation of two popular radio channel models, a geometric
channel simulator for producing channel impulse responses, and analytical derivation results
related to channel modeling geometries and multipath channel measurement processing.
In addition to new results, existing theory and earlier research results are discussed.
Fundamental theory for antenna arrays, vector channels, multipath characterization, and channel
modeling is presented. Contemporary issues in software radio and object orientation are
described, and measurement results from other propagation research are summarized.

Table of Contents
List of Figures xi
List of Tables xxiii
Chapter 1 Introduction .1
1.1 Motivation and Challenges in Wireless 1
1.2 Foundations of Progress in Wireless 4
1.3 Research Issues Covered .5
1.4 Organization of This Dissertation 7
Chapter 2 Signal Fundamentals for Antenna Arrays 9
2.1 Complex Signal Fundamentals 9
2.1.1 The Complex Envelope 10
2.1.2 Converting Bandpass Signals to Complex Envelopes . 11
2.1.3 The Narrowband Approximation . .13
2.2 Signals for Smart Antennas .16
2.2.1 The Purpose of Smart Antennas .16
2.2.2 A Signal Model for Antenna Arrays .18
2.2.3 Vector Channels 23
2.2.4 Array Steering Vectors 25
2.2.5 Spatial Signatures 26
2.3 Channel and Signal Characteristics in Multipath Environments .27
2.3.1 Multipath Amplitude and Time Delay . .28
2.3.2 Number of Multipath Components .30
2.3.3 Fading Envelope 31
2.3.4 Direction of Arrival .33
2.3.5 Signal Envelope Correlation Coefficient 34
2.4 Summary . 35
Chapter 3 A Multi-Channel, Software-Defined Measurement Receiver 37
3.1 Architecture Motivation .37
3.2 The Software Radio Methodology .39
3.2.1 Physical Architecture .40
3.2.2 Division of Hardware and Software .41
3.2.3 Benefits of the Methodology . .42
3.3 The Measurement Receiver Concept . .43
3.3.1 Processing Tradeoffs . .4 3
3.3.2 Examples and Applications 44
3.4 System Specifications and Analysis .45
3.4.1 Target Applications 45
3.4.2 Design Goals .46
3.4.3 RF Specifications .47
3.4.4 System Specifications 48
3.4.5 Link Analysis 49
3.4.6 RF Section Analysis .4 9
3.4.7 Noise Analysis .50
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3.5 Measurement Receiver Hardware 51
3.5.1 RF Front End .52
3.5.2 Sampling Section . 53
3.5.3 Complete System .54
3.6 Theory and Application of Object Orientation .54
3.6.1 Objects 55
3.6.2 Object Orientation Concepts 55
3.6.3 Application of Object-Oriented Methods to Software Radios .57
3.7 Measurement Receiver Software .59
3.7.1 Signal Acquisition with the Hardware-Specific Receiver Object 60
3.7.2 Radio Receiver and Processing Functions 62
3.7.3 Display/File Interface Functions 62
3.7.4 Multithreading and Inter-Object Communications 63
3.7.5 Automatic Gain Control . 65
3.7.6 Example of Measurement Receiver Software Application 66
3.8 FPGA-Based Transmitter 69
3.8.1 Transmitter Hardware 69
3.8.2 Transmitter Verification .70
3.9 Summary . 72
Chapter 4 Multipath Channel Models for Antenna Arrays 75
4.1 The Purpose of Radio Channel Models 76
4.2 Channel Model Classification 78
4.3 Existing Geometric Channel Models 79
4.3.1 Multipath Channel Impulse Response 79
4.3.2 Geometrically Based Single-Bounce Elliptical Model 81
4.3.3 Geometrically Based Single-Bounce Circular Model .86
4.3.4 Elliptical Sub-Regions Model 88
4.3.5 Other Channel Models .92
4.4 Three-Dimensional Ellipsoidal Channel Model . .95
4.4.1 The Ellipsoidal Scattering Region 95
4.4.2 Applications of the Bounded Ellipsoid .96
4.4.3 Axis Lengths and Normalized Excess Delay 99
4.5 Geometric Air-to-Ground Ellipsoidal Channel Model . .101
4.5.1 Analytical Specification of Scattering Region 103
4.5.2 Generating the Ellipsoid and Scatterers on the Rotated Axes 107
4.5.3 Direction-of-Arrival Statistics 111
4.5.4 Joint Direction-of-Arrival and Time-Delay Statistics .114
4.6 Summary . 119
Chapter 5 Channel Measurements .121
5.1 Survey of Radio Channel Measurements .121
5.1.1 Terrestrial Measurements .122
5.1.2 Air-to-Ground Measurements 127
5.2 Rooftop-Level Measurement Campaign .131
5.2.1 Measurement Overview .131
5.2.2 Multipath RMS Delay Spread 132
5.2.3 Distribution of Multipath Components .135
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5.2.4 Multipath Strength Correlation Coefficients Versus Delay .137
5.3 Dense Scatterer Measurement Campaign .148
5.3.1 Measurement Overview .148
5.3.2 Multipath RMS Delay Spread 151
5.3.3 Multipath Excess Delay Spread 160
5.3.4 Distribution of Multipath Components .161
5.3.5 Strength of Multipath Components Versus Delay . 169
5.3.6 Multipath Strength Correlation Coefficients Versus Delay .186
5.4 Air-to-Ground Measurement Campaign .188
5.4.1 Measurement Overview .190
5.4.2 Multipath RMS Delay Spread 191
5.4.3 Multipath Excess Delay Spread 194
5.4.4 Distribution of Multipath Components .195
5.5 Summary . 200
Chapter 6 Wideband Vector Channel Simulation .203
6.1 Simulation Overview .204
6.2 Simulation Geometries 207
6.2.1 Simulating the ESR Model Geometry 207
6.2.2 Simulating the GBSBE Model Geometry .209
6.2.3 Simulating the GAGE Model Geometry .209
6.3 Multipath Component Distribution, Strength, and Delay 213
6.3.1 Distribution of Multipath Components in Delay . 213
6.3.2 Multipath Delay . 214
6.3.3 Strength Modeling for ESR and GBSBE . .216
6.3.4 Strength Modeling for GAGE 218
6.3.5 Line of Sight Components .220
6.3.6 Log-Normal Multipath Strength Variation .221
6.3.7 Rayleigh Fading .223
6.4 Direction of Arrival .226
6.4.1 Direction of Arrival for ESR and GBSBE 226
6.4.2 Direction of Arrival for GAGE 228
6.5 Summary . 228
Chapter 7 Channel Model Evaluation 229
7.1 Elliptical Sub-Regions Channel Model 231
7.1.1 Simulation Parameters .231
7.1.2 Multipath Signal Strength 233
7.1.3 RMS Delay Spread 242
7.1.4 Excess Delay Spread 246
7.1.5 Multipath Fading .248
7.1.6 Antenna Diversity . .250
7.1.7 Two-Dimensional Rake Receiver .256
7.1.8 ESR Comparison Summary .264
7.2 Geometrically Based Single-Bounce Elliptical Channel Model 266
7.2.1 Simulation Parameters .266
7.2.2 Multipath Signal Strength 268
7.2.3 RMS Delay Spread 275
x
7.2.4 Excess Delay Spread 278
7.2.5 Multipath Fading .280
7.2.6 Antenna Diversity . .281
7.2.7 Two-Dimensional Rake Receiver .288
7.2.8 GBSBE Comparison Summary . .295
7.3 Geometric Air-to-Ground Ellipsoidal Channel Model . .296
7.3.1 Simulation Parameters .297
7.3.2 RMS Delay Spread 299
7.3.3 Multipath Signal Strength 301
7.3.4 Excess Delay Spread 304
7.3.5 Multipath Fading .305
7.3.6 Antenna Diversity . .305
7.3.7 Two-Dimensional Rake Receiver .308
7.3.8 GAGE Comparison Summary . .311
7.4 Summary . 312
Chapter 8 Conclusion 315
8.1 Summary of Research 315
8.2 Original Contributions .317
8.3 Future Work 319
8.4 Closing . .320
Epilogue 321
Appendix A Measurement Receiver MATLAB Signal Interface .323
A.1 MATLAB Interface Overview .323
A.2 Workspace Variables . 324
A.3 Real-Time Plotting 32 5
A.4 Example M-File .326
A.5 Steps for Developing m-files for the Measurement Receiver 329
Appendix B VT-STAR Development . 331
B.1 Overview .331
B.2 VT-STAR Transmitter . 331
B.3 VT-STAR Receiver .333
Appendix C Channel Model Simulator Parameters 337
C.1 Top Level Structures .337
C.2 Channel Parameters Structure . .338
C.3 Intermediate Plots . .339
C.4 Vector Channel Structure . 34 0
C.5 Multiple Simulation Runs 341
References .343
Author Biographical Notes .3 51