Joint Beamforming and Phase-Shifting Optimization in MISO with RIS-Assisted Communication

In this paper, we jointly investigate beamforming and phase shift of reconfigurable intelligent surface (RIS) for energy efficiency (EE) maximization in an MISO downlink system with multiple users. Specially, we assume that we only know the channel statistics information between RIS to users. The formulated problem is formulated to a non-convex one such that it is difficult to obtain the optimal solution. To tackle this nonconvexity, we decouple the original problem to two subproblems and further propose two iterative suboptimal algorithms based on the successive convex approximation (SCA) to solve the two subproblems, respectively. Then we propose an iterative algorithm to obtain a suboptimal solution of original problem in polynomial time. The numerical results verifies the effectiveness of our proposed algorithm.