近幾年來，由於OFDM技術成熟，使其廣泛應用於各種的領域範圍。但在應用的過程中乃有同步的問題必須要去克服，包含了頻率偏移、時序的偏移、及取樣的偏移等。本論文主要是針對OFDM同步的研究，大致上我們以IEEE 802.11a之應用為例分成兩大部份來進行。首先針對同步所需之信號的檢測、頻率偏移的估測及時序偏移的更正等三大重點著手，藉由MATLAB模擬的結果來證明所設計的同步方式，實驗結果顯示所提出的方法不但於AWGN的通道有不錯的效能，藉由在多重路徑底的通道條件下也有不錯的效能。

　　其次是針對於IEEE 802.11a的同步能力加以改善，自己設計一個frame的組織架構，使得對於頻率偏移的更正能力可以達到 頻率間隔。最後，我們將所設計的方法與Cox 的方法作比較，其效能比Cox的方法好得很多。

　　In recent years, the technology of orthogonal frequency Division Multiplexing is getting more and more mature and on various applications. However, there exist synchronization problems in OFDM has been employed including the frequency offset, timing clock error and sampling frequency offset ,which should be overcome to fit in different applications.

　　The aim of this thesis is to explore the synchronization problems in OFDM .Based on the　specification of IEEE 802.11a, we first investigate the research topics about the signal detection, frequency offset estimation and timing offset correction .The performance analysis is mainly demonstrated by MATLAB simulation and experimental results exhibit that the presented methods can achieve good bit-error rate under AWGN channel and the multi-path condition as well. To further improve the synchronization of OFDM symbols, we design a new frame format that can extend the correction range of OFDM symbols, we design a new frame format that can extend the correction range of the frequency offset to reach times the frequency spacing, where N denotes the length of FFT window, Simulation results also reveal better performance than that of the Cox’s work.

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