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系統識別號 U0002-1806200822334400
中文論文名稱 以中繼站為基礎的合作式通訊系統中 通道估測之研究
英文論文名稱 Channel Estimation for Relay Based Cooperative Communication Systems
校院名稱 淡江大學
系所名稱(中) 電機工程學系碩士班
系所名稱(英) Department of Electrical Engineering
學年度 96
學期 2
出版年 97
研究生中文姓名 顏進益
研究生英文姓名 Chin-Yi Yen
學號 695441054
學位類別 碩士
語文別 英文
口試日期 2008-06-13
論文頁數 60頁
口試委員 指導教授-易志孝
委員-嚴雨田
委員-趙亮琳
中文關鍵字 通道估測  合作式通訊  中繼傳輸  導引符號輔助調變  效能分析 
英文關鍵字 channel estimation  cooperative communication systems  relay-based transmission  pilot symbol assisted modulation (PSAM)  performance analysis 
學科別分類 學科別應用科學電機及電子
中文摘要 雖然許多探討基於中繼站的同調合作式通訊系統的研究已經顯示其可達到如多天線技術般使用空間分集之效益,稱之為合作分集;但是,這些研究分析主要是基於接收端可獲得完美的通道狀態資訊之假設。在實際應用情形下,通道狀態資訊必須經由估計取得且非完美通道狀態資訊對系統效能的影響也需要加以分析。在本篇論文中,我們探討採用放大轉傳模式的中繼站為基礎之合作式通訊系統並研究其通道估測問題。對於放大轉傳的傳輸機制而言,中繼站可以固定增益或變動增益來放大接收來自源端的訊號再進而傳送到終端。取決於中繼站的移動性,我們考慮固定端至移動端間通道之模型以及移動端至移動端間通道之模型。我們利用導引符號輔助調變(PSAM)來落實通道估測的工作,並把線性最小均方誤差(LMMSE)視為估測準則,再加以電腦模擬舉例說明非完美通道狀態資訊對採用放大轉傳模式的中繼站為基礎之合作式通訊系統所產生的影響。
英文摘要 Although many researches on relay-based cooperative coherent communication systems have shown that the benefits of spatial diversity, saying cooperative diversity, can be achieved as the multi-antenna technologies do, the analyses primarily rely on the assumption that the perfect channel state information (CSI) is available at the receiver. In practical scenarios, the CSI has to be estimated and the effect of imperfect CSI on system performance needs to be analyzed. In this thesis, we study the channel estimation problem for amplify-and-forward (AF) relay-based cooperative communication systems. For AF transmission scheme, the relay amplifies the received signal from the source by a fixed or variable gain and forwards it to the destination. Depending on the mobility of the relay, we consider both the fixed-to-mobile channel model and the mobile-to-mobile channel model. To facilitate the channel estimation task, we employ the pilot symbol assisted modulation (PSAM) and consider the linear minimum mean-squared error (LMMSE) as the estimation criterion. Computer simulations are conducted to illustrate the influences of the imperfect CSI on the performance of AF relay-based communication systems.
論文目次 TABLE OF CONTENTS

ACKNOWLEDGENMENTS I
中文摘要 II
ABSTRACT III
TABLE OF CONTENTS IV
LIST OF FIGURES VI
CHAPTER 1 INTRODUCTION 1
CHAPTER 2 WIRELESS TRANSMISSION ENVIRONMENTS 5
2.1 Radio Propagation Phenomena 5
2.1.1 Large scale fading: pathloss and shadowing 5
2.1.2 Small scale fading: multipath scattering 7
2.1.3 Line-of-sight and non line-of-sight surroundings 9
2.2 Wireless Mobile Channel Characteristics 10
2.2.1 Multipath delay spread and coherence bandwidth 10
2.2.2 Doppler spread and coherence time 13
2.3 Diversity Techniques for Multipath Fading Channel 14
2.3.1 Diversity types 14
2.3.2 Combining techniques 14
CHAPTER 3 WIRELESS MOBILE CHANNEL MODELS 15
3.1 Fixed-to-Mobile Channel Models 15
3.2 Mobile-to-Mobile Channel Models 19
3.3 Wireless Relay Channel Models 22
3.4 Simulation Results 27
CHAPTER 4 CHANNEL ESTIMATION AND ESTIMATOR CRITERIA 32
4.1 System Model 32
4.2 Channel Estimation Design 34
4.2.1 Pilot symbol assisted modulation 34
4.2.2 Estimator criteria 36
4.3 Estimation of the AF Relay Channel 41
4.3.1 Fixed gain case 41
4.3.1.1 Stationary relay 42
4.3.1.2 Mobile relay 43
4.3.2 Variable gain case 44
4.3.2.1 Stationary relay 45
4.3.2.2 Mobile relay 47
4.4 Maximal Ratio Combining 48
4.5 Numerical Results 49
4.5.1 Performance of the LMMSE estimator 49
4.5.2 Pilot insertion period 51
4.5.3 The number of pilots 54
4.5.4 Doppler spread 54
4.5.5 The effect of MRC 55
CHAPTER 5 CONCLUSIONS AND FUTURE WORK 57
5.1 Conclusions 57
5.2 Future Work 57
REFERENCES 58


LIST OF FIGURES

Figure 1.1 The three-node channel model of the cooperative system 3
Figure 3.1 The single-ring model 16
Figure 3.2 Sketch of the double-ring model 20
Figure 3.3 Sketches of the AoA and the AoD 21
Figure 3.4 AF relay channel model 23
Figure 3.5 Pdfs of the envelope of the fixed-to-mobile channel model 27
Figure 3.6 Correlation functions of the simulated fixed-to-mobile channel model 28
Figure 3.7 Correlation functions of the simulated mobile-to-mobile channel model 28
Figure 3.8 Pdfs of the envelope of the mobile-to-mobile channel model 29
Figure 3.9 Comparison of the envelopes’ pdfs between the fixed-gain and the variable-gain AF relay channel models 29
Figure 3.10 Correlation functions of a stationary relay with fixed gain 30
Figure 3.11 Correlation functions of a stationary relay with variable gain 30
Figure 3.12 Correlation functions of a mobile relay with fixed gain 31
Figure 3.13 Correlation functions of a mobile relay with variable gain 31
Figure 4.1 Sketch of the pilot symbol assisted modulation 35
Figure 4.2 LMMSE estimator performances for a stationary relay 50
Figure 4.3 LMMSE estimator performances for a mobile relay 50
Figure 4.4 The average MSE in estimating the composite AF relay channel 51
Figure 4.5 Influence of pilot spacing on estimator performances (fixed gain) 52
Figure 4.6 Influence of pilot spacing on estimator performances (variable gain) 52
Figure 4.7 Influence of pilot numbers on estimator performances (fixed gain) 53
Figure 4.8 Influence of pilot numbers on estimator performances (variable gain) 53
Figure 4.9 Effects of Doppler spreads on estimator performances (fixed gain) 54
Figure 4.10 Effects of Doppler spreads on estimator performances (variable gain) 55
Figure 4.11 LMMSE estimator performances when a direct link is available 56
Figure 4.12 LMMSE estimator performances when a weaker direct link is available 56

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