本論文裡，我們提出了一個應用在正交分頻多工系統中的符元時間與載波頻率誤差估測器。此估測器結合了循環字首的冗餘與被用來做通道估測的領航符元的資訊進行同步演算法。由於在本論文中所加入的領航符元具有在時域良好的自相關特性，故能增進時間同步上的效能，進而也提升了載波頻率誤差估測的準確度。在此系統中的領航符元是在頻域中疊加在資料符元上，因此必須找到一較好的領航符元功率對資料符元功率的比例，使得系統的錯誤率最低，在論文中，此比例是藉由模擬得到的。此外，領航符元經由反離散傅立葉轉換後在時域具有等振福的性質，能有效的抑制峰值對平均功率比。此外，在我們提出的架構之中，頻寬使用效率因不需要額外的子載波分配給領航符元使用而獲得提升。

In this thesis, a joint symbol timing and carrier frequency offset estimator is proposed for orthogonal frequency division multiplexing (OFDM) systems. The estimator exploits both redundancy in the cyclic prefix and pilot symbols for channel estimation. The proposed scheme includes a transparent sequence that is added to the OFDM symbol in frequency domain. Comparing with conventional methods, the proposed architecture has the advantage of better bandwidth usage since it does not require extra sub-carriers. The PAPR problem can be suppressed due to constant envelope property of the added sequence in time domain. Moreover, the optimal power allocation ratio of the transparent sequence is determined by minimizing the bit error rate of the system using simulation experiments.

致謝 I
中文摘要 II
ABSTRACT III
目錄 IV
圖目錄 VI
中英對照表 VIII
第一章 導論 1
1.1 研究動機 1
1.2 論文章節介紹 2
第二章 正交分頻多工系統簡介 3
2.1 正交分頻多工系統介紹 3
2.2 傳統的正交分頻多工系統架構 5
2.3 利用離散傅立葉轉換的正交分頻多工系統架構 8
2.4 保護區間與循環字首 10
2.5 正交分頻多工系統的優缺點 13
第三章 正交分頻多工系統中現有時間同步方法介紹 15
3.1 同步概念簡介 15
3.2 利用循環字首特性的同步演算法 17
3.3 利用循環字首與領航符元的符元時間估測演算法 20
第四章 新的同步架構介紹與分析 24
4.1 新的同步機制架構 24
4.2 疊加序列的特性 27
4.3 載波頻率誤差估測之效能分析 28
4.4 新架構的頻寬使用效率與PAPR 30
第五章 電腦模擬結果 33
第六章 結論 38
附錄A 39
附錄B 41
參考文獻 44

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