Joint Optimization of RIS-User Association and Beamforming Design for Multi-RIS-Assisted Multi-User Systems

Download PDF
Open Webpage

Chen Chen, Fan Wu, Cong Zhang, Diancheng Cheng, Wenhao Fan, Yuan'an Liu

Published: 2025, Last Modified: 07 Jan 2026IEEE Wirel. Commun. Lett. 2025EveryoneRevisionsBibTeXCC BY-SA 4.0
Abstract: The deployment of multiple reconfigurable intelligent surfaces (RISs) can enhance network coverage and capacity of wireless communication systems. This letter investigates a novel selective allocation scheme in which multiple RISs are spatially distributed to serve wireless users by dynamically controlling the RIS-User association for each RIS and user. The problem is formulated as a joint optimization of active beamforming, passive beamforming and RIS-User association, with the objective of maximizing the system sum-rate. To solve this problem, we propose an iterative algorithm that incorporates an enhanced minimum mean square error-user association (MMSE-UA) method to optimize the RIS-User association and active beamforming. Furthermore, fractional programming (FP) and semidefinite relaxation (SDR) are employed to optimize the passive beamforming. Simulation results demonstrate that the proposed algorithm achieves a higher sum-rate compared to benchmark schemes.