論文摘要 此篇論文中，我們討論在多載波分碼多重進接(MC-CDMA)的系統架構中，下傳通道（Downlink）由於系統的震盪器校正偏移(System Mismatch)以及都普勒效應（Doppler Effect）所造成的系統在頻率上的偏移效應，而為了維持載波間的正交性，去除通道間干擾(ICI)對系統效能嚴重的破壞，故頻率偏移校正為維持系統服務重要的課題。在本篇論文中，我們比較幾種目前廣為討論的頻率偏移估測方法，並應用在多載波分碼多重進接系統中。主要的估測演算法分為訓練符號元基礎與隱蔽估測架構兩類，並利用多重天線接收的系統架構增進估測演算法的精準度。在本篇文章末節，針對電腦模擬各演算法效能的結果，作一詳細的分析與比較，並針對各演算法在不同系統參數的優缺點做一詳細說明討論。 Abstract— In orthogonal frequency-division multiplex (OFDM) systems, it provides a great ability in protecting against channel selective attenuation. And the code-division multiple accesses (CDMA) system is well known and employed in the 3G personal communication system. While the system communicates in the narrow band interference, CDMA systems could still have good performance in such channel influence. An OFDM-CDMA system is just as clear and easy to be understood by its name, and is a combination of these different system structures and greatly unites both the advantage of them. However, maintaining the orthogonality does play an important point in the OFDM-CDMA system. A lot of frequency offset estimation algorithm is proposed and discussed. In this paper we propose multiple receiver structure to improve the estimation performance and also analyze these algorithm performance and compare the computation complexity of different algorithm in different system parameter.
