Frequency Offset Estimation for OFDM Systems in the Presence of I/Q Mismatch

It is well known that Orthogonal Frequency Division Multiplexing (OFDM) systems are sensitive to carrier frequency offset (CFO), hence frequency offset estimation and compensation is critical in OFDM systems. The performance of general CFO estimation methods will degrade in the presence of hardware distortions, for example, I/Q mismatch. With higher carrier frequencies, both CFO and I/Q mismatch will increase and the performance of CFO estimation will degrade significantly. CFO estimation robust to I/Q mismatch becomes particularly important today because of the demand of broadband wireless communication at higher carrier frequencies. In this paper, we propose a low complexity CFO estimation algorithm which is robust to a large range of I/Q mismatch. The proposed estimator can achieve similar performance with the general CFO estimation method when smaller I/Q mismatch is present while improve the system performance significantly when a larger mismatch is present.