IEEE 802.11ac: Performance of MU-MIMO interference cancellation detectors with imperfect channel state information at Tx and Rx sides

In this paper we analyze the performance of IEEE 802.11ac downlink multi-user multiple input multiple output (MU-MIMO) transceiver architectures that implement regularized channel inversion minimum mean squared error (RI-MMSE) precoder at transmitter (TX) and interference cancellation (IC) MMSE MIMO detector at receiver (RX). IEEE 802.11ac simulation results, assuming imperfect channel state information (CSI) at both TX and RX sides over spatial-correlated and frequency selective TGac MIMO channels, have shown that the use of spatial degrees of freedom to cancel inter-stream interference can mitigate the negative effects of imperfect synchronization and channel estimation, and channel sounding feedback delays in IEEE 802.11ac systems. Simulation results have also shown that single-user MIMO 802.11ac systems with transmit beamforming achieve higher performance compared to MU-MIMO systems with IC-MMSE MIMO detectors when sounding feedback delays and CSI imperfections are taken into account.