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研究生:許堯勝
研究生(外文):Hsu, Yao-Shang
論文名稱:零填補之正交分頻多工系統的盲蔽式通道估計
論文名稱(外文):Blind Channel Estimation for Zero-Padding Orthogonal Frequency Division Multiplexing Systems
指導教授:吳卓諭
指導教授(外文):Wu, Jwo-Yuh
學位類別:碩士
校院名稱:國立交通大學
系所名稱:電機學院IC設計產業專班
學門:商業及管理學門
學類:其他商業及管理學類
論文種類:學術論文
論文出版年:2009
畢業學年度:97
語文別:中文
論文頁數:54
中文關鍵詞:正交分頻多工系統零填補盲蔽式通道估計最佳週期性編碼序列
外文關鍵詞:orthogonal frequency division multiplxingzero-paddingblind channel estimationperiodic modulating sequence
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本論文提出一個經由盲蔽判別一個零填補之正交分頻多工系統通道以還原符元的方法。其判別方式是利用所接收訊號形成的自相關矩陣,計算出其通道係數乘積矩陣,再對一個由通道係數乘積矩陣所形成的厄米特矩陣作特徵分解。其通道係數向量,即為此厄米特矩陣經特徵分解後的最大特徵值所對應的特徵向量。所得的特徵向量與真實向量之間,存在了一個常數倍數的關係。而本文也提出了經由設計訓練符元的方式來得到真實的系統通道係數向量與計算而得的特徵向量之間的常數倍數。
為了減少通道雜訊對於估計通道準確度的影響,本文提出了利用觀察雜訊子空間與系統通道係數乘積子空間的相關程度來設計零填補之正交分頻多工系統的最佳週期性編碼序列。應用了最佳週期性編碼序列計算出通道之後,本篇論文以強制歸零等化器來還原符元。將實證結果與子空間方法比較後,首先,比起子空間法,本篇論文所提出的方法在計算上更為簡單。在低訊雜比與低傳送區塊的情況下,得到了較準確的通道估計與較低的錯誤率。
In this thesis, we proposed a blind channel identification scheme for zero-padding orthogonal frequency division multiplexing systems with periodic modulating sequence. The proposed method uses the block system model and exploits the channel matrix when some zeros are padded into the source block signal. When block signal is received, we can use its autocorrelation matrix to compute the products of channel coefficient. The channel impulse response vector can be identified, up to a scalar ambiguity, by computing the eigenvector associated with the maximal eigenvalue of a Hermitian matrix, which is formed by the products of channel coefficient. To remove the scalar ambiguity, we design the training symbols which are inserted in the data blocks.
To minimize the decrease of channel estimation accuracy caused by channel noise, we design the optimal periodic modulating sequence for zero-padding orthogonal frequency division multiplexing by observing the orthogonality between the noise subspace and the channel product coefficient subspace. After applying the optimal periodic modulating sequence to identify the channel impulse response, zero-forcing equalizer is used to recover the symbol. Comparing to the subspace method, the proposed method is simpler in computation. In the low SNR regime and less data blocks, the proposed method has better performance in channel estimation accuracy and lower symbol error rate.
摘要 i
誌謝 iii
目錄 iv
圖目錄 vi
名詞縮寫表 viii
運算符號表 ix
第一章 緒論 1
第二章文獻回顧與系統模型 3
2.1 正交分頻多工系統傳輸原理 4
2.1.1 子載波的正交性 6
2.1.2 保護區間與循環字首 7
2.1.3 正交分頻多工系統的優缺點 8
2.2 基本假設 10
2.3 循環字首傳送之正交分頻多工系統 11
2.4 零填補傳送之正交分頻多工系統 14
2.5 循環字首與零填補之正交分頻多工系統優缺點比較 16
2.6 子空間法 17
第三章 盲蔽式通道估計 19
3.1 零填補之正交分頻多工系統的盲蔽式通道估計 19
3.1.1 通道判別方程式 19
3.1.2 通道係數乘積的計算 22
3.1.3 通道脈衝響應的判別 24
3.2 最佳週期性編碼序列設計 25
3.2.1 最佳化的條件 25
3.2.2 最佳解 27
3.3 訓練符元的設計 33
3.3.1 常數倍數的確定 33
3.4 演算法 35
3.5 模擬結果 36
第四章 符元還原 45
4.1 強制歸零等化器 45
4.2 模擬結果 46
第五章 結論 52
參考文獻 53
[1] Zhengdao Wang, Xiaoli Ma, and Georgios B. Giannakis, “OFDM or Single-Carrier Block Transmission?” IEEE Transactions on Communications, vol. 52, no. 3, March 2004.
[2] Xenofon G. Doukopoulos, and George V. Moustakides, “Blind Adaptive Channel Estimation in OFDM Systems,” IEEE Transactions on Wireless Communications, vol. 5, no. 7, July 2006.
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[4] Yi-Sheng Chen and Ching-An Lin, “Blind-Channel Identification for MIMO Signal-Carrier Zero-Padding Block-Transmission Systems,” IEEE Transactions on Circuits and Systems- I: Regular papers, vol. 55,no. 6, July 2006.
[5] Jwo-Yuh Wu, and Ta-Sung Lee, “Periodic-Modulation-Based Blind Channel Identification for Signal-Carrier Block Transmission with Frequency-Domain Equalization,” IEEE Transactions on Signal Processing, vol. 54, no. 3, March 2006.
[6] Khaled Amleh, and Hongbin Li, “Blind-Channel Estimation and Interference Suppression for Signal-Carrier and Multicarrier Block Transmission System,” IEEE Transactions on vehicular technology, vol. 57, no. 5, September 2008.
[7] Andrea Goldsmith, Wireless Communications, Cambridge University Press, 2005.
[8] Simon Haykin, Communication systems, John Wiley & Sons, Inc., 3rd edition, 1994.
[9] Richard van Nee, Ramjee Prasad, OFDM wireless multimedia communication, Artech House Boston London, 2000.
[10] C. A. Lin and J. Y. Wu, “Blind identification with periodic modulation: a time-domain approach,” IEEE Transactions on Signal Processing, vol. 50, no. 11, pp. 2875–2888, November 2002.
[11] Zhengdao Wang and Georgios B. Giannakis, “Wireless Multicarrier Communications,” IEEE Signal Processing Magazine, vol. 17, no. 3,May 2000.
[12] R. A. Horn and C. R. Johnson, Topics in Matrix Analysis, Cambridge, U.K.: Cambridge Univ. Press, 1991.
[13] P.J.Davis, Circulant Matrix, New York: Wiley, 1979.
[14] Hua Zhang, Ye Li, Anthony Reid, and John Terry, “Optimum Training Symbol Design for MIMO OFDM in Correlated Fading Channels,” IEEE Transactions on Wireless Communications, vol. 5, no. 9, September 2006.
[15] Upamanyu Madhow, Fundamentals of Digital Communication, Cambridge Univ. Press, 2008.
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