Joint Compensation of Transmitter and Receiver IQ Imbalance for MIMO-OFDM Over Doubly Selective Channels

Multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM), as a viable technique, is being widely considered for high data rate and bandwidth efficient wireless communications. However, analog impairments like in-phase/quadrature (IQ) imbalance decrease the performance of this technique. Furthermore, time variations of a doubly selective channel cause intercarrier interference (ICI) which again degrades the performance. In this paper, the digital compensation of both the transmitter and the receiver IQ imbalances in MIMO-OFDM transmission over doubly selective channels is studied. In particular, basis expansion model is employed to develop a novel IQ formulation for a time-varying channel. Using this formulation, two receiver schemes are suggested to jointly mitigate the IQ imbalance and channel time variation effects. In deriving one of these schemes, the general case of an insufficient cyclic prefix (CP) for OFDM modulation is also considered. An insufficient CP results in interblock interference (IBI). The proposed approach for insufficient CP case, unifies several existing methods for IQ imbalance compensation and IBI/ICI cancellation. Simulation results show that this approach considerably improves the achievable bit-error-rate performance.