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論文名稱 Title |
在多重路徑衰退通道下OFDM系統之盲蔽式時間同步 Blind Timing Synchronization for OFDM Systems in Multipath Fading Channels |
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系所名稱 Department |
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畢業學年期 Year, semester |
語文別 Language |
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學位類別 Degree |
頁數 Number of pages |
49 |
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研究生 Author |
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指導教授 Advisor |
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召集委員 Convenor |
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口試委員 Advisory Committee |
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口試日期 Date of Exam |
2010-07-08 |
繳交日期 Date of Submission |
2010-08-23 |
關鍵字 Keywords |
盲蔽式、符號同步、多重路徑衰退通道、時間同步、循環字首 symbol synchronization, timing synchronization, cyclic prefix, multipath fading channels, blind |
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統計 Statistics |
本論文已被瀏覽 5666 次,被下載 2687 次 The thesis/dissertation has been browsed 5666 times, has been downloaded 2687 times. |
中文摘要 |
在多重路徑衰退通道(multipath fading channel)的情形下,本篇論文針對正交分頻多工(Orthogonal Frequency-Division Multiplexing,OFDM)系統提出了一個利用循環字首(cyclic prefix)來進行盲蔽式(blind)符號時間同步(symbol timing synchronization)的演算法,它從通道延遲的特性設計出了適當的權重來找尋符號時間起始點的方法。傳統的最大概似(maximum likelihood,ML)演算法在多重路徑衰退通道下因為通道延遲展開的影響,估測會偏差而且變動性很大。所提出的指數權重方法不只解決了以上的問題,而且提升了符號時間的準確度,尤其是此方法不需要知道訊雜比以及通道的長度。電腦模擬的結果證明了所提出的方法比其他傳統演算法更佳,且可對抗多路徑衰退通道的影響。 |
Abstract |
In this thesis, a blind symbol timing synchronization algorithm based on cyclic prefix for OFDM systems in multipath fading channels is proposed. It finds the starting point of symbol timing for using appropriate weights which are designed from channel delay spread characteristics. In multipath fading channels, the conventional ML (maximum likelihood) algorithm estimate is biased and has a large variance due to the effect of channel delay spread. The proposed exponential weighting methods not only solve the above problems but also improve the accuracy of symbol timing. Particularly, the proposed method does not require the information of SNR and channel length. From computer simulation results, the proposed method outperforms the other conventional algorithms and is also robust against the effect of multipath fading channels. |
目次 Table of Contents |
第一章 簡介 1 1.1 研究動機 1 1.2 論文簡介 1 1.3 論文架構 3 第二章 系統模型 5 2.1 正交分頻多工技術概念 5 2.2 循環字首 8 2.3 正交分頻多工之架構 9 2.4 同步之議題 11 2.5 傳統符號時間同步演算法 12 2.5.1 最大相關演算法 13 2.5.2 最大概似演算法 14 2.5.3 最小均方誤差演算法 17 2.5.4 傳統演算法之模擬比較 18 2.6 多重路徑衰退通道 19 第三章 權重之符號時間同步演算法 21 3.1 接收訊號分析 21 3.2 簡化方法 22 3.3 加入權重之符號時間同步演算法 23 3.4 具有通道資訊的權重 25 第四章 系統模擬 26 4.1 傳統符號時間演算法之模擬 26 4.1.1 簡化方法之模擬 28 4.2 指數衰退通道模型 29 4.2.1 加入權重之符號時間同步演算法 30 4.3 實際通道模擬 32 第五章 結論 36 參考資料 37 |
參考文獻 References |
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