對於無線通訊系統來說，正交分頻多工(Orthogonal Frequency Division Multiplexing, OFDM)技術是現行最流行且較優異的技術，由於OFDM子載波間的正交性讓頻寬可以有效的運用，循環字首(Cycle prefix, CP)的運用可以抵抗多重路徑通道的衰減。頻率偏移會破壞子載波間的正交性，會降低系統效能；通道估測在通訊系統架構中是很重要的步驟，估測的準確度大大地影響訊號錯誤率，在合作式通訊這種較複雜的環境下，通道估測就更為重要。 本篇論文同時考慮頻率偏移和通道這兩個影響系統的因素，利用最大事後機率法(Maximum a posteriori) 推導出聯合估計器，並期望能運用在合作式通訊環境中，比較在放大並傳送和解碼並傳送的傳輸協定下的估測效能比較，甚至將此擴展到分時多工的並列式多中繼站的合作通訊環境。 ;Up to now, orthogonal frequency division multiplexing (OFDM) was a current and outstanding technique of wireless communication. Bandwidth can be used effectively through orthogonality of OFDM subcarriers. The usage of CP can resist multipath effect. The CFOs can destroy orthogonality of OFDM subcarriers and degrade system performance; Channel estimation is very important step in communication system structure. The accuracy of channel estimation influences bit error rate (BER) significantly. Channel estimation is highly significant in complex cooperative communication system. CFOs and channel estimation are considered to the factors for communication system. We derived the joint estimator by maximum a posteriori method. We expect that it can be applied in cooperative communication environment with comparison of estimation performance based on amplify and forward as well as decode and forward transmission protocol, even in TDM parallel multiple relays cooperative communication environment.
