An Uplink Access Scheme for Cell-Free MIMO System with Channel Aging

The mismatches between the estimated channels and real channels caused by channel aging will increase significantly over time in cell-free multiple-input multiple-output (MIMO), and user mobility exacerbates this variation. In this paper, we investigate the impact of user-access point (UE-AP) matching strategies in mobile communications on the performance of cell-free MIMO systems affected by channel aging. First, we construct a real-time channel estimation scheme, which combines CSI with real-time environmental feedback to alleviate the effects of channel aging caused by Doppler drift on system performance. The application of the MMSE estimator under channel aging is also rederived. Then we propose a user-centric, energy-efficient dynamic UE-AP allocation scheme to adapt to the dynamic propagation environment. Simulation results show that the scheme we propose can improve the energy utilization significantly, thereby achieving the goal of green communication, and outperforms other alternatives in terms of resource utilization, without compromising communication quality.