Direct-conversion-based wireless communication systems suffer from I/Q imbalances in the front-end analog processing. In this study, the authors investigate the impact of frequency-independent (FI) I/Q imbalance on the channel reciprocity of time-division-duplexing (TDD) multiple-input multiple-output (MIMO) systems over frequency flat-fading channels. Moreover, in order to compensate the channel non-reciprocity caused by FI I/Q imbalance, the authors propose two pre-compensation algorithms with and without I/Q imbalance parameters. The performance of the TDD MIMO system under study is evaluated in terms of downlink capacity and bit-error rate. Simulation results show that the proposed algorithms can effectively mitigate the negative effect of FI I/Q imbalance on the channel reciprocity.
