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研究生:陳柏宇
研究生(外文):Bo-Yu Chen
論文名稱:正交分頻多工系統低複雜度訊框同步演算法之效能分析與改進
論文名稱(外文):Performance Analysis and Improvement of the Low-Complexity Frame Synchronization Algorithm for OFDM Systems
指導教授:呂振森呂振森引用關係
口試委員:郭天穎陳伯岳
口試日期:2008-07-25
學位類別:碩士
校院名稱:國立臺北科技大學
系所名稱:電機工程系所
學門:工程學門
學類:電資工程學類
論文種類:學術論文
論文出版年:2008
畢業學年度:96
語文別:中文
論文頁數:70
中文關鍵詞:訊框同步演算法正交分頻多工系統循環前置
外文關鍵詞:Frame Synchronization AlgorithmOFDMCyclic Prefix
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本論文主要是探討正交分頻多工系統下快速且低複雜度訊框同步演算法效能分析與改良。在正交分頻多工系統中訊框同步是系統能維持有效運作的關鍵因素。在正交分頻多工系統訊框同步的相關研究中,已被證明可以在不使用任何外加符號的情況下,以循環前置的相關性達到同步的目地,但此方法複雜度相對較高。因而有後續先將接收訊號量化再計算同步位置的低複雜度同步演算法,但其準確度也相對偏低。在本論文中,將針對前述所提出的低複雜度同步演算法做進一步探討與改進,並結合外加符號的使用,發展出一個低複雜度的訊框同步演算法,先使用低複雜度訊框同步演算法去做訊框起始點範圍的粗略定位,再使用外加符號做小範圍精確定位,此一方法,可在不增加太多計算量的前提下,有效改進系統訊框同步之效能。
In the thesis, we research into the performance of the low-complexity frame synchronization algorithm for OFDM systems and improve it. The frame synchronization of OFDM systems is a critical factor for effective operations of the above system. The relative research shows that the frame synchronization can be achieved by using correlation of cyclic prefix without additional adding symbols, but the computation complexity of this algorithm is high. Thus a low-complexity synchronization algorithm had been proposed. It used the quantized version of the received signal to compute synchronization position with less accuracy. In the thesis, we develop a low complexity synchronization algorithm based on the low-complexity algorithm described above by combining the method of adding extra symbols. In this method, first we use low-complexity frame synchronization algorithm to find coarse synchronization position, and then use additional symbols to find accuracy synchronization position. In this way, our proposed method can improve the performance of frame synchronization at the expense of increasing a little complexity.
中文摘要 i
英文摘要 ii
誌謝 iii
目錄 iv
表目錄 v
圖目錄 vi
第一章 緒論 1
1.1 前言 1
1.2 研究動機與方法 2
1.3 各章內容 3
第二章 OFDM系統原理與錯誤率分析 4
2.1 OFDM系統運作原理 4
2.1.1 基於FFT之OFDM系統架構 6
2.1.2 正交性 7
2.1.3 保護區間與頻率偏移 8
2.1.4 OFDM系統的優點與缺點 14
2.2 OFDM位元錯誤率分析 16
2.2.1 QPSK-OFDM系統於AWGN通下之錯誤率分析 16
2.2.2 QPSK-OFDM系統於雷利通道下之錯誤率分析 17
2.3 同步錯誤的影響 21
2.3.1 時間偏移的影響 21
2.3.2 同步錯誤下產生的相位旋轉效應 23
2.4 訊框同步下的OFDM系統模型 25
2.4.1 最佳化同步演算法 27
2.4.2 低複雜度同步演算法 28
第三章 低複雜度訊框同步之改良 34
3.1 低複雜度演算法之簡化 34
3.1.1 移動和簡化 34
3.1.2 對數概似函數簡化 37
3.1.3 結合移動和與對數概似函數之簡化 39
3.2 低複雜度演算法之效能改良 40
3.2.1 機率最大值平均法 40
3.2.2 結合m-序列與低複雜度訊框同步法 42
3.2.2.1 m-序列同步演算法 42
3.2.2.2 改良式低複雜度同步演算法 47
3.3 使用改良式演算法之錯誤率分析 64
第四章 結論與未來發展 67
參考文獻 69
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