An Adaptive Approach to Estimation and Compensation of Frequency-Dependent I/Q Imbalances in MIMO-OFDM Systems

In this paper, a novel adaptive approach based on Alamouti scheme is proposed to estimate and compensate frequency-dependent in-phase/quadrature-phase (I/Q) imbalances in space-time coded MIMO-OFDM communication systems. The I/Q imbalances may be present at both ends of transmitter (TX) and receiver (RX). Although different methods have been proposed to utilize the Alamouti scheme in order to obtain spatial diversity in a MIMO-OFDM system, the inaccurate channel estimation caused by I/Q imbalances degrades the system performance. A new combining scheme is introduced to overcome this significant drawback by using joint estimation and compensation of the multipath fading channel and I/Q imbalances. The simulation results show that the proposed adaptive method can effectively mitigate the effect of the frequency-dependent TX and RX I/Q imbalances in the MIMO-OFDM systems.