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系統識別號 U0002-1806200815554400
中文論文名稱 在頻率選擇性通道中使用最小平方法於正交分頻多工通道估測
英文論文名稱 A Least-Squares Approach for OFDM Channel Estimation in Frequency-Selective Channels
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 楊國豐
研究生英文姓名 Kuo-Feng Yang
學號 695440015
學位類別 碩士
語文別 英文
口試日期 2008-06-16
論文頁數 58頁
口試委員 指導教授-嚴雨田
委員-易志孝
委員-劉鴻裕
中文關鍵字 正交分頻多工  最大可能估計  頻率選擇通道  最佳訓練序列  通道估計 
英文關鍵字 Orthogonal frequency division multiplexing (OFDM)  least squares (LS) estimation  frequency-selective channels  optimum training sequence  channel estimation 
學科別分類 學科別應用科學電機及電子
中文摘要 通道估計器通常對於實際通道的長度是未知的,設計時常以通
道的最大可能長度作通道估測。本篇論文針對這種在估計器中,含有
多餘估計參數的情況,討論其對於估計準確度的影響,並依此推導出
最佳估計器的訓練序列之設計準則。估計的方法為最大可能估計,精
確的數學分析公式被提出,並與電腦模擬做比較,驗證出理論與實際
模擬結果吻合。此結果可作為將來進一步在改進通道估計準確度的先
導研究,藉以提出新的通道參數估計器。
英文摘要 The practical channel length for a channel estimator is usually unknown. The maximum possible channel length is therefore assumed a priori. In this paper, we explore the effect of channel information redundancy on the channel estimation accuracy in orthogonal frequency division multiplexing (OFDM) systems. The optimum training sequence for channel estimation is discussed. Theoretical analysis and Monte Carlo simulation are compared and show great agreement. Maximum-likelihood (ML) estimation is used for the channel estimation. The study leads to a novel channel estimator design.
論文目次 CONTENTS

ACKNOWLEDGEMENT I
CHINESE ABSTRACT II
ENGLISH ABSTRACT III
CONTENTS IV
LIST OF FIGURES VI
CHAPTER1 INTRODUCTION 1
CHAPTER2 OFDM PRINCIPLE AND STRUCTURE 4
2.1 Data and System Structure for OFDM 4
2.2 Mathematical Description 7
CHAPTER 3 MULTIPATH PROPAGATION AND FADING CHANNELS 13
3.1 Multi-path Propagation 13
3.2 Free Space Propagation Model 14
3.3 Rayleigh Fading Model 15
3.4 Rice fading 17
3.5 Nakagami fading 19
3.6 Shadowing 20
3.7 Parameters of Mobile Multipath Channels 21
3.7.1 Time dispersion parameters 21
3.7.2 Coherence bandwidth 23
3.7.3 Doppler spread and coherence Time 24
3.8 Small-Scale Fading 25
CHAPTER 4 ANALYSIS OF LEAST SQUARES CHANNEL ESTIMATION FOR OFDM SYSTEMS 31
4.1 System Model 31
4.2 Least Squares Channel Estimation 34
4.3 Channel Estimator Performance 36
CHAPTER 5 SIMULATION RESULTS AND DISCUSSION 38
CHAPTER 6 CONCLUSIONS 48
APPENDIX 49
A.1 Optimum Training Sequence Design 50
REFERENCES 53

LIST OF FIGURES

Figure 2.1.1 Data structure with the use of the guard interval 5
Figure2.1.2 Channel dispersion effect 6
Figure 2.1.3 Data structure with the use of cyclic prefix 6
Figure 2.2.1 Source data structure 8
Figure 2.2.2 OFDM system structure 12
Figure 3.1 Types of small-scale fading 26
Figure 5.1 Comparisons between the LS estimate of and the true (solid lines) Channel length is assumed known. 40
Figure 5.2 Comparisons between the estimate of and the true (solid lines). Channel length is assumed known. 41
Figure 5.3 Comparison of experimental estimation variance and theoretical variance for . Channel length is assumed known. 42
Figure 5.4 Comparison of experimental estimation variance and theoretical variance for . Channel length is assumed known. 43
Figure 5.5 Comparisons between the LS estimate of and the true (solid lines). Channel length is assumed unknown. 44
Figure 5.6 Comparisons between the estimate of and the true (solid lines). Channel length is assumed unknown.. 45
Figure 5.7 Comparison of experimental estimation variance and theoretical variance for . Channel length is assumed unknown. 46
Figure 5.8 Comparison of experimental estimation variance and theoretical variance for . Channel length is assumed unknown. 47


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