Channel Estimation and Robust Detection for IQ Imbalanced Uplink Massive MIMO-OFDM With Adjustable Phase Shift Pilots

In this paper, we investigate channel estimation and robust detection for uplink massive multi-input multi-output orthogonal frequency division multiplexing (MIMO-OFDM) systems with in-phase quadrature-phase imbalances (IQI). We represent the received signal a real-valued model, where combination of IQI wireless is treated as effective channel. Based on then perform minimum mean square error (MMSE) criterion based use adjustable phase shift pilots (APSPs) to reduce pilot overhead verify that MSE can be minimized by scheduling shifts properly. propose algorithm covariance matrices channels. Since performance might degraded due using APSPs, develop an MMSE data scheme which error. Using operator-valued free probability theory, derive asymptotic deterministic equivalent ergodic achievable sum rate proposed scheme. The APSPs demonstrated via extensive numerical results.