Joint Beamforming Design for Multi-Functional RIS-Aided Uplink Communications

This letter investigates the joint beamforming design problem in a multi-functional reconfigurable intelligence surface (MF-RIS)-aided uplink communication system. Specifically, each element of the MF-RIS is able to switch between the reflection and refraction modes, while achieving power amplification of incident signals. By jointly optimizing the transmit power of users, MF-RIS coefficients, and the receive beamforming of the base station, we formulate a mixed-integer non-linear programming (MINLP) problem to maximize the uplink sum-rate. To solve this challenging MINLP problem, we propose an iterative algorithm by using the successive convex approximation and penalty function methods, where the optimal transmit power is derived. Numerical results show the effectiveness of our proposed algorithm and the superiority of the MF-RIS compared to other RIS counterparts.