Frequency-Limited Beamforming Optimization for RIS-Assisted Integrated Radar and Communication System

Abstract

This letter investigates a reconfigurable intelligent surface (RIS)-assisted integrated radar and multi-user communication system with frequency-limited beamforming optimization, where the radar mean square error (MSE) between the actual and desired beampatterns and the multi-user interference (MUI) are simultaneously minimized. Besides, considering the variability of frequency bands employed by individual communication users, we develop a weighted framework under the frequency spectrum limited and power constraints. The degrees of freedom for system design are the communication multi-user beamforming vectors and the RIS phase configuration. To solve the nonconvex framework, we derive an efficient alternating optimization algorithm combining the majorization-minimization-based alternating direction penalty method (MMADPM) and the element-wise block coordinate descent (E-BCD) design. Numerical simulations validate the effectiveness of the proposed method, demonstrating significant performance improvements in terms of radar MSE minimization, communication MUI suppression, and convergence speed.