Robust Symbol-Level Precoding for MIMO Downlink Transmission With Channel Aging.

This paper investigates the robust design of symbollevel precoding (SLP) for multiuser multiple-input multipleoutput (MIMO) downlink transmission with imperfect channel state information (CSI) caused by channel aging. By utilizing the a posteriori channel model based on the widely adopted jointly correlated channel model, the imperfect CSI is modeled as the statistical CSI incorporating the channel mean and channel variance information with spatial correlation. With the signal model in the presence of channel aging, we formulate the signal-to-noise-plus-interference ratio (SINR) balancing problem for robust SLP design, which targets to maximize the minimum SINR and can be transformed into a typical max-min fractional programming (MMFP). In the scenario of massive MIMO, we simplify the objective function of the SINR balancing problem and further derive a low-complexity SLP scheme. Simulation results confirm the superiority of the proposed schemes over the state-of-the-art SLP schemes.