Robust Beamforming Under Channel Prediction Errors for Time-Varying MIMO System

Abstract: The accuracy of acquired channel state information (CSI) for beamforming design is essential for achievable performance in multiple-input multiple-output (MIMO) systems. However, in a high-speed moving scene with time-division duplex (TDD) mode, the acquired CSI depending on the channel reciprocity is inevitably outdated, leading to outdated beamforming design and then performance degradation. In this paper, a robust beamforming design under channel prediction errors is proposed for a time-varying MIMO system to combat the degradation further, based on the channel prediction technique. Specifically, the statistical characteristics of historical channel prediction errors are exploited and modeled. Moreover, to deal with random error terms, deterministic equivalents are adopted to further explore potential beamforming gain through the statistical information and ultimately derive the robust design aiming at maximizing weighted sum-rate performance. Simulation results show that the proposed beamforming design can maintain outperformance during the downlink transmission time even when channels vary fast, compared with the traditional beamforming design.

Keywords: time-varying channels; time-division duplex; robust beamforming; channel prediction errors; weighted sum-rate maximization