Table Of ContentCARRIER RECOVERY IN BURST-MODE 16-QAM
A Thesis Submitted to the College of
Graduate Studies and Research
in Partial Fulfillment of the Requirements
for the Degree of Master of Science
in the Department of Electrical Engineering
University of Saskatchewan
Saskatoon, Saskatchewan
by
Jingxin Chen
June 2004
© Copyright Jingxin Chen, 2004. All rights reserved.
PERMISSION TO USE
In presenting this thesis in partial fulfillment of the requirements for a
Postgraduate degree from the University of Saskatchewan, the author agrees that the
Libraries of this University may make it freely available for inspection. The author
further agree that permission for copying of this thesis in any manner, in whole or in
part, for scholarly purposes may be granted by the professor who supervised this thesis
work or, in his absence, by the Head of the Department or the Dean of the College of
Graduate Studies and Research at the University of Saskatchewan. It is understood
that any copying or publication or use of this thesis or parts thereof for financial gain
shall not be allowed without the author’s written permission. It is also understood that
due recognition shall be given to me and to the University of Saskatchewan in any
scholarly use which may be made of any material in my thesis.
Requests for permission to copy or to make other use of material in this thesis in
whole or part should be addressed to:
Head of the Department of Electrical Engineering
University of Saskatchewan
Saskatoon, Saskatchewan, Canada
S7N 5A9
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ABSTRACT
Wireless communication systems such as multipoint communication systems
(MCS) are becoming attractive as cost-effective means for providing network access
in sparsely populated, rugged, or developing areas of the world. Since the radio
spectrum is limited, it is desirable to use spectrally efficient modulation methods such
as quadrature amplitude modulation (QAM) for high data rate channels. Many MCS
employ time division multiple access (TDMA) and/or time division duplexing (TDD)
techniques, in which transmissions operate in bursts. In many cases, a preamble of
known symbols is appended to the beginning of each burst for carrier and symbol
timing recovery (symbol timing is assumed known in this thesis). Preamble symbols
consume bandwidth and power and are not used to convey information. In order for
burst-mode communications to provide efficient data throughput, the synchronization
time must be short compared to the user data portion of the burst.
Traditional methods of communication system synchronization such as phase-
locked loops (PLLs) have demonstrated reduced performance when operated in burst-
mode systems. In this thesis, a feedforward (FF) digital carrier recovery technique to
achieve rapid carrier synchronization is proposed. The estimation algorithms for
determining carrier offsets in carrier acquisition and tracking in a linear channel
environment corrupted by additive white Gaussian noise (AWGN) are described. The
estimation algorithms are derived based on the theory of maximum likelihood (ML)
parameter estimation. The estimations include data-aided (DA) carrier frequency and
phase estimations in acquisition and non-data-aided (NDA) carrier phase estimation in
tracking. The DA carrier frequency and phase estimation algorithms are based on
oversampling of a known preamble. The NDA carrier phase estimation makes use of
symbol timing knowledge and estimates are extracted from the random data portion of
the burst. The algorithms have been simulated and tested using Matlab® to verify their
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functionalities. The performance of these estimators is also evaluated in the burst-
mode operations for 16-QAM and compared in the presence of non-ideal conditions
(frequency offset, phase offset, and AWGN). The simulation results show that the
carrier recovery techniques presented in this thesis proved to be applicable to the
modulation schemes of 16-QAM. The simulations demonstrate that the techniques
provide a fast carrier acquisition using a short preamble (about 111 symbols) and are
suitable for burst-mode communication systems.
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ACKNOWLEDGEMENTS
I would like to express my sincere gratitude to my supervisor, Professor David M.
Klymyshyn, for being the guiding force behind the research necessary for the
completion of this thesis. Without his guidance, encouragement, support, ideas, and
scientific enlightenment this work would not have been possible.
I also extend my sincere gratitude to Professor Ha Nguyen who performed as my
acting supervisor in the final stage of this work, when Professor Klymyshyn was away
and worked on research in Germany. Professor Nguyen has been abundantly helpful
and given me a lot of valuable advice on my final oral exam and thesis.
My great appreciation also goes to the management and staff of TRLabs in
Saskatoon for providing support and wonderful research environment. My thanks
especially go to Jack Hanson, Dan Aspel, Trevor Hamm, and Garth Wells who always
provided me technical help as I needed.
Finally, I would like to thank my parents, Shang Xun Chen and Yi Wen Rong, my
parents-in-law, my husband Peter, and my friends for all the encouragement and
support they have provided me throughout my academic career. No words can express
my gratitude to them.
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DEDICATION
To my adorable daughter, Yuan Yuan
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TABLE OF CONTENTS
PERMISSION TO USE................................................................................................i
ABSTRACT..................................................................................................................ii
ACKNOWLEDGEMENTS........................................................................................iv
DEDICATION..............................................................................................................v
TABLE OF CONTENTS............................................................................................vi
LIST OF FIGURES.....................................................................................................x
LIST OF TABLES....................................................................................................xiii
LIST OF ABBREVIATIONS..................................................................................xiv
LIST OF SYMBOLS................................................................................................xvi
1 INTRODUCTION...................................................................................................1
1.1 Background.........................................................................................................1
1.2 Motivation...........................................................................................................3
1.3 Objectives............................................................................................................5
1.4 Literature Review................................................................................................6
1.5 Thesis Organization.............................................................................................8
2 MODULATION AND DEMODULATION FOR THE AWGN CHANNEL..10
2.1 Overview...........................................................................................................10
2.2 Digital Modulation............................................................................................11
2.2.1 QAM.......................................................................................................12
2.2.2 16-QAM..................................................................................................14
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2.3 Channel..............................................................................................................17
2.4 Coherent Demodulation....................................................................................19
2.5 Performance of the Optimum Detection...........................................................22
2.6 Filtering and Intersymbol Interference..............................................................24
2.7 Summary...........................................................................................................30
3 CARRIER RECOVERY SYSTEM DESIGN....................................................31
3.1 Carrier Recovery Description............................................................................31
3.1.1 Carrier Rcovery Parameters....................................................................32
3.1.2 Carrier Recovery Processes.....................................................................34
3.2 Design Considerations.......................................................................................36
3.2.1 Preamble Selection..................................................................................36
3.2.2 Synchronizer Structure Selection............................................................38
3.3 System Design...................................................................................................39
3.3.1 Carrier Acquisition Estimator.................................................................40
3.3.2 Carrier Tracker........................................................................................41
3.4 Summary...........................................................................................................43
4 CARRIER RECOVERY ALGORITHMS.........................................................45
4.1 The Received Signal Model..............................................................................45
4.2 ML Parameter Estimation.................................................................................47
4.2.1 MAP and ML..........................................................................................47
4.2.2 Likelihood Function................................................................................48
4.2.3 ML Condition..........................................................................................51
4.3 Carrier Acquisition............................................................................................52
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4.3.1 DA Frequency Offset Estimation............................................................52
4.3.2 DA Phase Offset Estimation...................................................................55
4.4 Carrier Tracking................................................................................................58
4.4.1 Overview.................................................................................................58
4.4.2 NDA Carrier Phase Estimation...............................................................59
4.4.3 Window Size Selection...........................................................................62
4.5 Summary...........................................................................................................63
5 SIMULATION RESULTS AND PERFORMANCE EVALUATION OF
CARRIER RECOVERY SYSTEM..........................................................................65
5.1 Performance Measurement of Estimators.........................................................65
5.1.1 Estimation Error Measurement...............................................................66
5.1.2 BER Measurement..................................................................................66
5.1.3 BER Degradation due to Synchronization Errors...................................68
5.2 Simulation Issues...............................................................................................71
5.2.1 Baseband Simulation...............................................................................72
5.2.2 Simulation Setup.....................................................................................73
5.3 Performance Evaluation of Carrier Recovery System......................................79
5.3.1 DA Frequency Estimator........................................................................79
5.3.2 DA Phase Estimator................................................................................88
5.3.3 NDA Phase Tracker................................................................................91
5.4 Summary...........................................................................................................94
6 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS......................96
6.1 Summary...........................................................................................................96
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6.2 Conclusions.......................................................................................................98
6.3 Recommendations for Future Study..................................................................99
REFERENCES.........................................................................................................101
APPENDIX A MATLAB MODULES FOR SIMULATION BLOCKS.......104
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