Joint Waveform and Phase Shift Design for RIS-Assisted Integrated Sensing and Communication Based on Mutual Information

In this letter, we propose using a reconfigurable intelligent surface (RIS) to improve the performance of integrated sensing and communication (ISAC) systems since it can customize the wireless propagation environment by tuning phase shifts. However, it is not straightforward to integrate the RIS into ISAC systems. As the waveform design for the ISAC system is highly dependent on the channel conditions, the phase shift design of the RIS is fully coupled with the waveform design at the base station (BS). To address this challenge, we jointly optimize the beamformer at the BS and the phase shifts at the RIS in order to maximize the communication data rate and the mutual information (MI) for sensing, and then develop an efficient algorithm to solve this problem. Simulation results show that the proposed algorithm can effectively improve both sensing and communication performance.