在本篇論文中，我們提出兩種可以應用於正交分頻多工系統之載波頻率飄移估測演算法。正交分頻多工技術在高速傳輸之無線通訊系統是一種常見的傳輸技術，它的主要缺點是對於載波頻率飄移的高敏感度，這飄移主要是由頻率震盪器的不穩定與都普勒頻率飄移所造成。而載波頻率飄移的存在會造成載波間干擾進而降低系統效能。一般而言，常見的載波頻率飄移估測演算法可分為三類: 基於pilot資訊之PTA估算法、 基於cyclic prefix資訊之CPB估算法與基於training symbol資訊之TSB估算法。此外載波頻率飄移可分為整數部分與分數部分。在這篇論文中我們著重於處理後者。然而，以上所介紹的估算法有一些缺點: 降低傳輸頻寬或時間誤差的高敏感度。於是在此篇論文中，我們提出了兩種基於PTA與CPB之改良式載波頻率飄移估測演算法來改善上述缺點。而此改良式載波頻率飄移估測演算法的主要是利用傳輸資料資訊來輔助估測，並希望藉此來提供更佳的系統效能與更準確的頻率同步。接下來我們將在AWGN與超寬頻系統通道的影響下作出模擬，在模擬結果中考慮這兩種改良式載波頻率飄移估測演算法與三種傳統估測方式的系統效能，並比較系統效能的改善與討論pilot個數的使用量。最後模擬結果指出此論文所提出的估測方式皆能有效地提升系統效能與傳輸頻寬

In this thesis, we present two carrier frequency offset estimation algorithms applied to OFDM system. OFDM is popular transmitting technology for high data rate wireless communication systems. One of the major drawbacks is its high sensitivity to carrier frequency offset (CFO) due to the Doppler frequency and oscillator instability. The existence of a CFO brings about reduction of system performance due to the occurrence of inter-carrier interference (ICI). Geneally, the CFO estimation algorithms can be classified into three categories, which are pilot tone aided (PTA), cyclic prefix based (CPB), and training symbols based (TSB). Moreover, CFO can be divided into: integral and fractional part. In this thesis, we focus on the later. However, above estimation methods have some drawbacks: reduction of transmitted data rate or sensitivity of timing error. Here we propose two midified methods for estimating CFO based on PTA and CPB method, and desire to improve the principal drawbacks of original method. The key opinion of our proposed algorithms is exploitation of the data-carriers to provide more accurate frequency synchronization and provide better performance. Specifically, the effects of estimator are discussed and compared by simulation result in AWGN and UWB channel

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