Channel Estimation for Reconfigurable Intelligent Surface-Assisted Multiple Antennas Communication Systems

Reconfigurable intelligent surfaces (RISs) have a large number of reflection units, and the manufacturing and deployment costs are much lower than those of large base stations (BSs). Moreover, in the millimeter-wave (mmWave) communication system, the direct path from the BS to the user (UE) may be blocked, and the RIS is an ideal scheme to reshape the wireless propagation path. How to obtain the channel state information (CSI) of the RIS-assisted communication system is still a problem worthy of attention at present, and the accurate acquisition of CSI is an important prerequisite for beamforming design. In this paper, we propose a new channel estimation (CE) scheme in RIS-assisted multiple-input multiple-output (MIMO) millimeter-wave communication system. Firstly, the CSI between the BS and the RIS is calculated based on the location information, then the beamforming design is carried out for the transmitted signal at BS according to the calculated CSI, and then the CSI between the RIS and the UE is estimated by orthogonal matching pursuit (OMP) algorithm.