Performance Analysis of Massive MIMO Systems with Nonlinear Reciprocity Mismatch

Time-division-duplexing massive multiple-input multiple-output (MIMO) systems estimate the channel state information (CSI) by leveraging the uplink-downlink channel reciprocity, which is no longer valid when the mismatch arises from the asymmetric uplink and downlink radio frequency (RF) chains. Existing works treat the reciprocity mismatch as constant for simplicity. However, practical RF chains consist of nonlinear components, which leads to nonlinear reciprocity mismatch. In this work, we examine the impact of the nonlinear reciprocity mismatch on the performance of massive MIMO systems. To evaluate the impact of the nonlinear mismatch, we first derive the closed-form expression of the ergodic achievable rate for the multi-user massive MIMO system. Then, we analyze the performance loss caused by the nonlinear mismatch to show that the impact of the mismatch at the base station (BS) side is much larger than that at the user equipment side. Simulation results are presented to examine the system performance and to verify the analytical results.