Impact and compensation of I / Q imbalance on channel reciprocity of time‐division‐duplexing multiple‐input multiple‐output systems

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.