Statistical CSI-Based Two-Stage Beamforming Scheme for Massive MIMO with Channel Aging

In this paper, we propose a two-stage beamforming (TSB) scheme for frequency division duplex (FDD) massive MIMO systems with channel aging. The proposed scheme utilizes statistical channel state information (CSI) and the channel aging coefficient to design the prebeamforming matrix to sparsify the channel matrix, so as to reduce pilot overhead while enhancing spectral efficiency. Specifically, a Gauss-Markov fading model is used to describe channels with aging effects. We derived the formulas for received energy of each user from each beam per slot. In the first stage of TSB, the prebeamforming matrix design is modeled as a 0-1 integer programming problem. The problem is used to maximize the received energy and solved using the branch-and-bound method. Subsequently, in the second stage of TSB, the beamforming matrix is designed with zero-forcing criterion, significantly reducing inter-user interference. Simulation results demonstrate that the proposed scheme effectively mitigates the impact of channel aging on system performance.