Two-Phase Efficient Channel Estimation for Passive Double-RIS Assisted MIMO Systems

Zhiqing Ding, Wanguo Jiao, Chao Xu

Abstract: In order to improve communication quality in some heavily blocking scenarios, the double-reconfigurable intelligent surface (RIS) is introduced, then there are more channel coefficients to be estimated. To reduce the pilot overhead, an efficient two-phase channel estimation scheme is proposed for passive double-RIS assisted MIMO systems to estimate the dual-reflection cascaded channels. Specifically, RIS 1 operates in a known fixed mode, and RIS 2 operates in a dynamically adjustable mode with the time slot, which can reduce the number of channel coefficients to be estimated. Then, the dual-reflection cascaded channel property is utilized to further reduce pilot overhead. Simulation results illustrate that the proposed scheme significantly reduces the pilot overhead and achieves superior estimation performance simultaneously.