An Adaptive Surface Design for Energy-Aware Hybrid RIS Communications

This paper presents a low-complexity joint optimization framework for hybrid reconfigurable intelligent surface (RIS) systems, where each element can operate in either passive or active mode. The objective is to maximize energy efficiency by jointly determining the active element configuration and phase shifts across the RIS. A two-stage algorithm is developed: the first stage estimates the minimum number of active elements required to meet a target SNR, while the second performs phase alignment for coherent signal combining. Simulation results show that the proposed approach achieves near-optimal performance with significantly lower computational complexity compared to existing solutions.