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

379 Pages·2003·8.03 MB·English

by  William G. Newhall

Radio Channel Measurements and Modeling for
Smart Antenna Array Systems Using a
Software Radio Receiver

William G. Newhall

Dissertation submitted to the Faculty of
Virginia Polytechnic Institute and State University
in partial fulfillment of the requirements for the degree of

Doctor of Philosophy
in
Electrical and Computer Engineering

Committee
Jeffrey H. Reed (Chairman)
Warren L. Stutzman
William H. Tranter
Brian D. Woerner
C. Patrick Koelling

April 2003
Blacksburg, Virginia

© 2003 William G. Newhall

Keywords: Propagation Measurement, Channel Modeling, Vector Channels, Smart Antenna, Software Radio,
Multipath, Wireless Communications.

Radio Channel Measurements and Modeling for
Smart Antenna Array Systems Using a
Software Radio Receiver
William G. Newhall
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.

To those who steadfastly encourage life accomplishments.
Family, and friends close enough to call family.

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Acknowledgements

I have received an enormous amount of support from colleagues, friends, and family throughout
my graduate work. I would like to thank Jeff Reed, Bill Tranter, Brian Woerner, Warren
Stutzman, and Pat Koelling for their direction and participation on my committee. I also greatly
appreciate many other professors and staff at Virginia Tech for their input and support,
especially Tim Pratt, Bill Davis, Charles Bostian, Bob Boyle, Dennis Sweeney, and Krishnan
Ramu.

I am thankful for the friendship and assistance of my fellow graduate students and Virginia Tech
graduates, including Max Robert, James Hicks, Fakhrul Alam, Sesh Krishnamoorthy, Raqib
Mostafa, Ramesh Palat, Mostafa Howlader, Roger Skidmore, Ran Gozali, Tom Biedka, Chris
Anderson, Jody Neel, Philip Balister, Carl Dietrich, Gaurav Joshi, Kai Dietze, Neiyer Correal,
Matt Valenti, and Kathyayani Srikanteswara. I greatly appreciate the help of the MPRG staff,
including Jenny Frank, Hilda Reynolds, Shelby Smith, Beth Huffman, and Cindy Graham.

I could not have accomplished so much without my colleagues and friends at Grayson Wireless.
I thank Ken Talbott, Greg Bump, Jon Dubovsky, Casey Elder, Ron Bryan, Mark Priest, Steve
Trice, Tom Conley, Tim Garrett, and Terry Garner.

To my terrific friends, Mike Metzgar, Jennifer Lesser, Michele Kolet, and Neal Kegley, I owe
thanks for your friendship and a space in your lives.
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Bob Newhall and Barbara Ruebush, my brother and sister, have provided an immeasurable
amount of encouragement, and I thank them for being there for me.

I would mostly like to thank my parents, Robert and Roberta Newhall, whose constant and
limitless support, encouragement, and advice had a great part in bringing my work and dreams to
completion.
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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..........................................................................................43
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...........................................................................................49
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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