Cooperation-Based Estimation of Separated Reflecting Channels over RIS-Assisted MIMO Networks

Reconfigurable intelligent surface (RIS) technologies have drawn significant attention in wireless communications networks. However, the accurate channel estimation of separated reflecting channels in RIS-assisted multi-input multi-output (MIMO) systems is very important, though crucially challenging due to the complex structure of channels and the large number of RIS reflective elements with passive reflective nature. In this paper, we propose a Three-point Cooperative Sensing based Separated Reflecting Channel Estimation (3PC-SRCE) scheme, which is based on the Pilot Reconstruction based Separated Reflecting Channel Estimation (PR-SRCE) scheme and introduces a multi-antenna auxiliary to assist the channel estimation process. The proposed 3PC-SRCE scheme is a three-stage channel estimation scheme, which overcomes the limitation of ambiguities in the existing channel estimation schemes for separated channels. It is able to obtain the full channel state information (CSI) with the assistance of the auxiliary, including the direction and amplitude information of each channel. Simulation results demonstrate the effectiveness of the proposed PR-SRCE scheme and 3PC-SRCE scheme in estimating the CSI of separated reflecting channels.