Joint Compensation of Transmitter and Receiver I/Q Imbalances for SC-FDE Systems

Due to the non-ideality of analog components, transmitters (TXs) and receivers (RXs) suffer from hardware impairments such as in-phase/quadrature (I/Q) imbalance, which manifests itself as the mismatches of amplitude, phase and frequency response between I/Q branches. Without compensation, I/Q imbalance can severely degrade the system performance. This paper addresses the joint compensation of TX and RX I/Q imbalances for single carrier frequency domain equalization (SC-FDE) systems. Specifically, we develop an expectation maximization (EM) based approach to separately estimate TX and RX I/Q imbalances, and the multipath channel. With the obtained estimates, we can readily fulfill the compensation of I/Q imbalances. Unlike previous methods, which only estimate the combined effect of I/Q imbalances and the multipath channel, we are able to obtain the separate estimates of the TX I/Q imbalance, the RX I/Q imbalance and the multipath channel. This will significantly alleviate the computation burden of the proposed compensation scheme in the long run. Simulation results show that the proposed scheme outperforms the counterparts, and can significantly mitigate the adverse effects of I/Q imbalances.