這篇論文探討了在多重輸入多重輸出之正交分頻多工系統中利用最大可能性準則做載波頻率偏移和通道響應的聯合估測。初步介紹此系統的訊號模型以及基於最大可能性的聯合估測器推導，此演算法可以分成兩大部分，第一部分是利用旋轉觀念對載波頻率偏移作初始的估測，再利用初始結果設計頻域等化器。第二部分則是利用疊代的觀念來找出真正最大的頻率波峰，使載波頻率偏移估測的效果能更好。此疊代演算法可以正確收斂至全域最大值而不是區域最大值，且與格子搜尋法相比減少計算複雜度，模擬效能表現出來在均方誤差精確度上也貼近於克拉瑪界線。

In this thesis, we present a joint carrier frequency offset (CFO) and frequency selective channel response estimation in multiple input multiple output-orthogonal frequency division multiplexing (MIMO-OFDM) systems. The signal model of MIMO-OFDM is introduced and the joint estimator is derived based on the maximum likelihood criterion. The proposed algorithm can be separated into two major portions. In the first part of proposed algorithm, we estimate an initial CFO by using the rotation concept and utilize the result to design the frequency domain equalizer. The second part is to employ iterative concept to find the true frequency peak for better CFO estimation performance. The proposed method can surely converge to the global maximum solution step by step. In addition, the computation complexity is less than the grid-search method. The MSE performance of the proposed algorithm shown in the simulation result is close to the Cramer-Rao Lower bound (CRB).

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