在這篇論文中，主要是有關無線通訊系統裡正交分頻多工(OFDM)同步的議題，包含了二項主要的內容。第一、我們提出了在正交分頻多工(OFDM)系統中結合最大相似性偵測(MLE)和最小均分差錯誤(MMSE)的同步演算法，用來同時估測時間偏移與頻率偏移。第二，我們提出了在正交分頻多工系統中利用領航訊號消除頻率偏移所造成的子載波干擾(ICI)之問題，主要解決了ICI自我消除機制在頻率偏移較大時就無法有效地改善系統效能。

In this paper, there are two major contents about OFDM synchronization issue in wireless communication. The first of all, a joint MLE and MMSE synchronization scheme is proposed for OFDM timing and frequency offset. Secondly, a novel pilot-aided inter-carrier interference (ICI) self-cancellation scheme is proposed for use in orthogonal frequency division multiplexing (OFDM) systems. The proposed scheme maps both modulated data symbols and pre-defined pilot symbols onto non-neighboring sub-carriers with weighting coefficients of +1 and -1. With the aid of pilot symbols, a more accurate estimation of frequency offsets can be obtained, and the ICI self-cancellation demodulation can be operated properly.

圖目錄
第一章 導論...1
1.1 研究動機...1
1.2 論文架構...2
第二章 正交分頻多工基本原理與介紹...3
2.1 OFDM基本原理與介紹...3
2.2 傳統的OFDM的傳送與接收端...4
2.3 基於離散傅立葉轉換的OFDM架構...5
2.4 OFDM系統特性及優缺點...6
2.4.1 防護區間(Guard Interval，GI)...6
2.4.2 OFDM 正交性...7
2.4.3 OFDM優缺點...8
第三章 結合MLE和MMSE之同步演算法...10
3.1 傳統MLE和MMSE演算法...10
3.1.1 傳統利用訓練符元之MLE演算法...10
3.1.2 利用訊號自相關運算之MMSE演算法...12
3.2 無線區域網路IEEE802.11a中結合最大相似性偵測與最小均方差錯誤之同步演算法...13
3.2.1 IEEE 802.11a規格介紹以及通道模型...13
3.2.2 應用在IEEE 802.11a結合最大相似性偵測與最小均方差錯誤之同步演算法...16
3.2.2.1 利用最大相似性偵測之時間偏移估測器...16
3.2.2.2 利用最小均方差錯誤之頻率偏移估測器...18
3.2.2.3 估測器之效能分析...19
3.2.3 電腦模擬結果...20
3.3 正交分頻多工中結合最大相似性偵測與最小均方差錯誤同步演算法
3.3.1 以最大相似性偵測為基礎之時間偏移估測器...27
3.3.2 以最小均方差錯誤為基礎之頻率偏移估測器...29
3.3.3 電腦模擬結果...30
第四章 具有領航訊號之子載波自我消除機制...35
4.1 頻率偏移對於OFDM系統之影響...35
4.2 傳統子載波干擾消除方法...36
4.2.1 相鄰子載波干擾自我消除方法...36
4.2.2 非相鄰子載波干擾自我消除方法...39
4.3 具有領航訊號之非相鄰子載波干擾自我消除方法...41
4.4 電腦模擬結果...46
第五章 結論與未來展望...49
參考文獻...50

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