Joint Waveform Design for RIS-Aided Dual-functional Radar-Communication System

In this paper, we consider the waveform design for Dual-functional Radar-Communication System (DFRC) with the assistance of a Reconfigurable Intelligent Surface (RIS). We investigate the joint optimization of the transmit waveform and RIS phase shift matrix to improve the radar detection and communication quality. The optimization problem is formulated as the weighted summation of communication and radar metrics under both radar sensing and RIS constraints, which is a non-convex problem. To address this problem, we propose an alternating method to decouple the optimization variables and decompose this intractable problem as three sub-problems. However, it is still challenging to obtain the optimal RIS phase shift matrix due to the unit-modulus constraint. To solve this problem, we developed an Riemannian trust-region (RTR) algorithm based on the complex circle manifold. Numerical results show that RIS can help improve the performance of DFRC system, and the proposed algorithm shows fast convergence.