Sum-rate Maximization for RIS-assisted Radar and Communication Coexistence System

Next-generation wireless communication systems are believed to share the same spectrum previously allocated to radar applications. The coexisting communication system will cause harmful interference to the radar system. In this paper, we investigate the deployment of the Reconfigurable intelligent surface (RIS) to improve the performance of a Multiple-Input Multiple-Output (MIMO) Radar and Communication Coexistence (RCC) system. The RIS consists of a large number of nearly passive, and low-cost elements, which provides passive, and a relatively high beamforming gain by controlling the reflecting elements' reflection coefficients. Moreover, the RIS can eliminate the mutual interference between the radar and communication systems. To improve the sum-rate of the communication system subjected to the radar performance constraints, we design the transmit beamforming and the phase shifts for the RIS elements by using the local search approach. Numerical results verify the effectiveness of the utilization of the RIS.