在本論文中，我們考量了兩個正交分頻多工系統中的非理想效應：載波頻率偏移(Carrier Frequency Offset)與IQ不平衡 (IQ imbalance)。此兩種非理想效應都會對系統效能產生嚴重影響。現有的各種聯合估測演算法通常需要做迭代運算才能在估測中收斂，或是其計算複雜度太高。因此，我們根據序文內兩段相同的序列，提出一個以最小平方法 (Least Square)為基礎的演算法來聯合估測載波頻率偏移與IQ不平衡。從模擬結果可得知，我們提出的演算法在不同的SNR情況下，估測載波頻率偏移與IQ不平衡的效能都是強健的。在IQ不平衡的估測中，即使在振幅誤差3dB，相位誤差20度的情況下，也能維持強健的估測效能。此外，我們所提出的演算法其複雜度也比EM-based之演算法來的低。

In this thesis, we consider two non-ideal effects in orthogonal frequency division multiplexing (OFDM) system: carrier frequency offset (CFO) and IQ imbalance. Both CFO and IQ imbalance degrade the system performance seriously. Current joint estimation algorithms need iterations to converge in the estimation, or their computational complexity are considerably high. As a result, we proposed a LS-based method to estimate both CFO and IQ imbalance based on the two identical sequences in the preamble. Simulation results show that it is robust for a wide SNR range both in CFO and IQ imbalance estimation. The performance of IQ imbalance estimation is robust even with gain error 3dB, phase error 20°. Moreover, the proposed method has much lower complexity than the EM-based approach.

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