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研究生：	林良徽 Lin, Liang-Huei
論文名稱：	增進效能之盲閉式OFDM訊號偵測 Improved Blind Detection of OFDM Signals
指導教授：	張名先 Chang, Ming-Xian
學位類別：	碩士 Master
系所名稱：	電機資訊學院 - 電腦與通信工程研究所 Institute of Computer & Communication Engineering
論文出版年：	2012
畢業學年度：	100
語文別：	英文
論文頁數：	37
中文關鍵詞：	通道估測、通道脈衝響應、盲閉式偵測、正交分頻多工系統
外文關鍵詞：	estimation, channel impulse response, blind detection, OFDM
相關次數：	點閱：82 下載：0
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由於正交分頻多工系統(OFDM)在多路徑環境之下十分穩定，而且在頻域做等化的複雜度低，使得OFDM經常被用於無線通訊的傳輸上。為了達到更高的資料傳輸量跟頻寬效益，我們使用盲閉式(Blind)偵測來取代原來的引導訊號(Pilot Signal)偵測。
本篇論文我們提出符號正規化之盲閉式OFDM訊號偵測。使用通道脈衝響應(CIR)來模擬OFDM系統中各子頻道的通道響應(CR)，再加上使用branch-and-bound 原理，來解決非線性的整數規劃問題。
透過本篇論文所提出的方法，可以有效的減少拜訪點數，同時也可利用多項式來近似每個子通道的時變通道響應。接著，可利用預先估計的通道響應，來找尋較佳的起始資料串，此資料串用來做為 branch-and-bound 演算法的初始值，可大量地減少所需的拜訪點數。模擬結果證明使用符號正規化可以有效地降低搜尋的複雜度。

For wireless communications, the orthogonal-frequency division multiplexing (OFDM) system is frequently applied due to its robustness to the multipath environment and its low-complexity frequency-domain equalization. In order to increase the data throughput, we can use the blind method instead of the pilot-assisted method for the signal detection in OFDM systems.
In this thesis, we propose a blind detection algorithm for the OFDM system with normalized symbol amplitudes. We use channel impulse response (CIR) to model the channel response (CR) variation across sub-channels. Then we apply the branch-and-bound principle to solve the non-linear integer programming problem.
The proposed blind detection algorithm can effectively reduce the number of visiting nodes. We also use a polynomial to model the time variation of CRs in every sub-channel, such that we can use the predicted CRs to obtain a better initial data sequence in the blind detection algorithm. The better data sequence can obviously reduce the number of visiting nodes in the tree search. Simulation results validate that the proposed blind detection algorithm can reduce the complexity while maintain the same error rates.

中文摘要	                                                   I
Abstract	                                          II
Acknowledgement	                                         III
Content	                                                  IV
List of Figures	                                          VI
Chapter 1	                                           1
Introduction	                                           1
Chapter 2	                                           3
System and Channel Model	                           3
2.1 System Model	                                   3
2.2 Channel Model	                                   5
2.2.1 Modification of Jake’s Rayleigh Fading Model	   5
Chapter 3	                                           8
Blind Detection	                                           8
3.1 CIR Model	                                           8
3.2 Blind Detection	                                  11
3.2.1 Integer Programming	                          11
3.2.2 Branch-and-Bound Algorithm	                  13
3.2.3 Recursive Formula	                                  18
Chapter 4	                                          21
Complexity Reduced Method	                          21
4.1 Motive	                                          21
4.2 Calculating Node-Value with Normalized Symbol Amplitudes	                                                  22
4.3 Channel Prediction by Curve Fitting	                  25
4.4 Simulation Results	                                  30
Chapter 5	                                          35
Conclusion	                                          35
Chapter 6	                                          36
Bibliography	                                          36


                                    

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[6] M. X. Chang and Y. T. Su, “2-D regression channel estimation for equalizing OFDM signals,” Proc IEEE 51th Vehicular Technology Conference, Tokyo, pp. 240-244, May 2000.
[7] M. X. Chang and Y. T. Su, “Model-based channel estimation for equalizing OFDM signal,” IEEE Trans. Commun., vol. 50, pp. 240-544, Apr. 2002.
[8] M. X. Chang and Y. T. Su, “Performance Analysis of Equalized OFDM System in Rayleigh Fading,” IEEE Trans. Commun., vol. 1, NO. 4, October 2002.
[9] M. Russell and G. L. Stüber, “Interchannel interference analysis of OFDM in a mobile environment,” in Proc. IEEE VTC’95, Chicago, IL, July 1995, pp. 820-824.
[10] G. Strang, Linear Algebra and Its Applications, 3rd ed. Philadelphia, PA: Saunders, 1988.
[11] Ming-Xian Chang and Yu T. Su, “Blind and Semiblind Detections of OFDM Signals in Fading Channels” IEEE Trans. Commun., VOL. 52, NO. 5, MAY 2004.

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