Two-stage compensation for non-ideal effects in MIMO-OFDM systems

In this paper, we propose a two-stage estimation and compensation of the carrier frequency offset (CFO) and the IQ imbalance in MIMO-OFDM systems. In the first stage, the receiver IQ imbalance is compensated along with CFO estimation. In the second stage, the transmitter IQ imbalance is compensated by taking advantage of structure of Alamouti space-time block codes. Robust least square estimations are applied for all compensation processes. Compared with the conventional system that only compensates receiver IQ imbalance, simulation results show that BER performance of the proposed system is significantly improved.