Luận Văn Semi-blind signal detection for mimo and mimo-ofdm systems

Introduction

With the growth of broadband internet access and the development of multimedia
services in cellular mobile wireless communications, an ever-increasing demand for
high capacity and high speed transmission with good Quality-of-Service (QOS) has
been created. To meet this demand, various techniques have been proposed.

MIMO

In the 1st generation (1G) mobile communication system, frequency domain is
exploited to achieve the desired system capacity by FDM (Frequency Division
Multiplexing), while time domain is exploited by TDM (Time Division Multiplexing)
in the 2nd generation (2G) mobile communication system. To improve the system
capacity, code domain is exploited by CDM (Code Division Multiplexing) in some
2G and current 3rd generation (3G) mobile communication systems. However, the
data rate which can be achieved in the current and extended 3G systems is only as
high as 14.4Mbps.
To further improve the system capacity, space domain, which is regarded as the
"last frontier" that can substantially improve the capacity, is exploited in the 3.5G
such as HSDPA (High Speed Downlink Packet Access) system and being considered
for the next generation mobile communication systems. As a capacity boosting
technique, MIMO (Multiple Input Multiple Output) utilizes multiple antennas at both
ends of a wireless link as shown in Fig. 1.1. A number of signals are simultaneously
transmitted from different transmit antennas onto the same physical channel and then
separated by multiple receive antennas and signal processing techniques at the
receiver. Independent studies have shown that the capacity of MIMO systems can
grow linearly with the number of transmit and receive antennas [Winters, Salz and
Gitlin, 1994; Foschini and Gans, 1998; Paulraj, Gore, Nabar and Bolcskei, 2004]. A
lot of research interest has thus been attracted to MIMO systems due to their high
capacity and spectral efficiency in recent years [Dai, Molisch and Poor, 2004; Chizhik,
Ling, Wolniansky, Valenzuela, Costa and Huber, 2003; Chizhik, Foschini, Gans and
Valenzuela, 2002].


Contents
Declaration i
Acknowledgements ii
Table of Contents .iii
List of Figures . .vi
Abbreviations . viii
Chapter 1
Introduction 1
1.1 MIMO 1
1.2 MIMO-OFDM 3
1.3 Semi-blind signal detection .4
1.4 Motivation and organization of the thesis .6
Chapter 2
Semi-Blind Rake-Based Multi-User Detection for Quasi-
Synchronous MIMO Systems 9
2.1 Introduction .9
2.2 System model .12
2.3 Semi-blind Rake-based multi-user detection technique .14
2.3.1 Multi-user single-path signal separation 15
2.3.2 Time delay estimation .17
2.3.3 Multi-path combining .19
2.3.4 Channel noise consideration 21
2.3.5 Performance analysis 22
iii
2.4 Examples and simulation results 25
2.4.1 Time delay estimation .25
2.4.2 Semi-blind Rake-based multi-user detection technique .27
2.4.2.1 Example 1 .2 7
2.4.2.2 Example 2 .3 0
2.5 Summary .33
Chapter 3
Time Domain Semi-blind Signal Detection for MIMO-
OFDM Systems with Short Cyclic Prefix 35
3.1 Introduction 35
3.2 System Model 38
3.3 Time Domain Semi-Blind Signal Detection 41
3.3.1
Zero-noise case .43
3.3.1.1 Equalization and signal detection 44
3.3.1.2 H part estimation 47
3.3.1.3 Remark .48
3.3.2 Channel noise consideration .49
3.3.3 Computational complexity .50
3.4 Simulation results 51
3.4.1
The case where the channel length is shorter than or equal to
the CP length: L ≤ D .52
3.4.2
The case where the channel length is longer than the CP
length: L > D 54
3.4.3 Comparison .56
3.4.4 Data length effect 57
3.5 Summary .58
iv
Chapter 4
Two-Step Semi-Blind Signal Detection for MIMO-OFDM
Systems without Cyclic Prefix 60
4.1 Introduction .60
4.2 System Model .62
4.3 Two-Step Semi-blind Signal Detection .66
4.3.1 Blind ICI and ISI cancellation .67
4.3.2 Signal detection in the presence of MAI 70
4.3.3 Effect of channel noise 71
4.3.4 Implementation 72
4.4 Simulation Results .73
4.4.1 Effect of SNR 73
4.4.2 Effect of the parameter K 76
4.4.3 Effect of channel length overestimation 78
4.5 Summary .79
Chapter 5
Conclusions and suggestions for future research 80
Reference 83
Publications 89