Signal Processing for Future MIMO-OFDM Wireless Communication Systems
Thesis submitted to Cardiff University in candidature for the degree of Doctor of Philosophy.
CardiffUNi VS Ri f T V
P R I F V 5 G O I
Centre of Digital Signal Processing Cardiff University
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The combination of multiple-input multiple-output (MIMO) technol
ogy and orthogonal frequency division multiplexing (OFDM) is likely
to provide the air-interface solution for future broadband wireless sys
tems. A major challenge for MIMO-OFDM systems is the problem
of multi-access interference (MAI) induced by the presence of multiple
users transmitting over the same bandwidth. Novel signal processing
techniques are therefore required to mitigate MAI and thereby increase
A background review of space-time block codes (STBCs) to lever
age diversity gain in MIMO systems is provided together with an in
troduction to OFDM. The link performance of an OFDM system is
also shown to be sensitive to time-variation of the channel. Iterative
minimum mean square error (MMSE) receivers are therefore proposed
to overcome such time-variation.
In the context of synchronous uplink transmission, a new two-step
hard- decision interference cancellation receiver for STBC MIMO-OFDM
is shown to have robust performance and relatively low complexity. Fur
ther improvement is obtained through employing error control coding
methods and iterative algorithms. A soft output multiuser detector
based on MMSE interference suppression and error correction coding
at the first stage is shown by frame error rate simulations to provide
significant performance improvement over the classical linear scheme.
Finally, building on the uturbo principle , a low-complexity iterative
interference cancellation and detection scheme is designed to provide a
good compromise between the exponential computational complexity of
the soft interference cancellation linear MMSE algorithm and the near
capacity performance of a scheme which uses iterative turbo processing
for soft interference suppression in combination with multiuser detec
To my parents for their unconditional support
and my wife Jie Zhuang for her love and encouragement
I would like to give my great thanks to my supervisor Prof. Jonathon
A. Chambers, who spent much time consulting with me. Thanks for his
great enthusiasm and patience with me. W ithout his invaluable support
and encouragement, this thesis would have not been accomplished. I
feel lucky to have been inspired by his extraordinary motivation, great
intuition and hard work. He is an example for my future career and
has my deepest respect professionally and personally.
I would also like to thank my second supervisor in Belfast, Northern
Ireland, Dr. Mathini Sellathurai, who has supervised me during my
second and third year PhD study. She contributed greatly to every
paper I have written, and to every progress step I have made. Dr.
Saeid Sanei, Dr. Sangarapillai Lambotharan and Dr. Zhuo Zhang have
given much help and many suggestions on not only my research and
study, but also my life in Cardiff. I would also like to express sincere
gratitude to them.
The thanks also go to my dear colleagues in the center of digital
signal processing (CDSP). It has been my great honour to work with
them: Andrew Aubrey, Clive Cheong Took, Yonggang Zhang, Cheng
Shen, Qiang Yu, Yue Zheng, Min Jing, Lay Teen Ong and many others.
Cardiff has been wonderful for me mainly because of all these friends.
My wife Jie Zhuang who accompanied me in Cardiff during the last
two years, is greatly appreciated. I would like to thank for her love and
Finally, I would like to thank my parents for their unconditional
patience and support while we have been separated for many years.
L. Zhang, C. Shen, M. Sellathurai, and J. A. Chambers,Low
Complexity Sequential Iterative Cancellation Technique for Multi
user MIMO-OFDM Systems, IEEE Signal Processing Lett., sub
mitted, Sept. 2008.
L. Zhang, M. Sellathurai, and J. A. Chambers, A Joint Coded
Two-Step Multiuser Detection Scheme for MIMO-OFDM Sys
tem, Proc. IEEE International Conference on Acoustics, Speech
and Signal Processing, 2007 (IC ASSP 2007), Vol. 3, pp. 111-85 -
111-88, Hawaii, USA, April 2007.
L. Zhang, M. Sellathurai, and J. A. Chambers, A Two-Step
Multiuser Detection Scheme for Space-Time Coded MIMO-OFDM
Systems, Proc. 10th IEEE Singapore International Conference
on Communication systems, 2006 (ICCS 2006), Singapore, Oct.
L. Zhang, M. Sellathurai, and J. A. Chambers, A Space-Time
Coded MIMO-OFDM Multiuser Application With Iterative MMSE-
Decision Feedback Algorithm, Proc. 8th IEEE International
Conference on Signal Processing (ICSP2006), Guilin, P.R.China,
L. Zhang, M. Sellathurai, and J. A. Chambers, An Iterative
Multiuser Receiver for Space-Time Coded MIMO-OFDM Sys
tems, Proc. 7th International Conference on Mathematics in
Signal Processing (IMA2006), pp. 182-184, Cirencester, UK, Dec.
C. Shen, L. Zhang, and J. A. Chambers, A Two-Step Interfer
ence Cancellation Technique for a MIMO-OFDM System with
Four Transmit Antennas, Proc. 2007 15th International Con
ference on Digital Signal Processing, pp. 351-354, Cardiff, UK,
LIST OF ACRONYMS
3GPP 3rd Generation Partnership Project
AMPS Advanced Mobile Phone System
AWGN Additive White Gaussian Noise
BER Bit Error Rate
bps Bits Per Second
CCM Circulant Channel Matrix
CDMA Code Division Multiple Access
CSD Circuit Switched D ata
DFT Discrete Fourier Transform
DVB Digital Video Broadcasting
FFT Fast Fourier Transform
FER Frame Error Rate
FFT Inverse Fast Fourier Transform
GPRS General Packet Radio Service
GSM Global System for Mobile communications
List of Acronyms xi
HDTV High Definition Television
HIPERLAN High Performance Radio Local Access Network
HSPA High Speed Packet Access
i.i.d. Independent and Identically Distributed
iDEN Integrated Digital Enhanced Network
I DFT Inverse Discrete Fourier Transform
IMT-2000 International Mobile Telecommunications 2000
IS-95 Interim Standard 95
ITU International Telecommunication Union
ITU-R ITU Radiocommunication Sector
JTACs Japanese Total Access Communications
LS Least Squares
LTE Long Term Evolution
MIMO Multiple-Input M ultiple-Output
MLE Maximum Likelihood Estimation
MLSE Maximum Likelihood Sequence Estimation
MMS Multimedia Messaging Service
MMSE Minimum Mean Squared Error
NMT Nordic Mobile Telephone
List of Acronyms Xll
OFDM Orthogonal Frequency Division Multiplexing
OFDMA Orthogonal Frequency-Division Multiple Access
PDC Personal Digital Cellular
pdf Probability Density Function
PHS Personal Handy-phone System
PSK Phase Shift Keying
QAM Quadrature Amplitude Modulation
RTMI Radio Telefono Mobile Integrato
SIMO Single-Input M ultiple-Output
SNR Signal to Noise Ratio
TACS Total Acce