Energy Efficiency Method for RIS-Aided NOMA-SWIPT System

Due to the uncontrollability of the channel caused by the uncontrollability of the wireless transmission environment, the introduction of Reconfigurable intelligent surface (RIS) is needed to intelligently control the wireless propagation environment. We use RIS to improve the performance of non-orthogonal multiple access (NOMA)-based Simultaneous wireless information and power transfer (SWIPT) systems. This is done by maximizing the efficiency of energy transfer while ensuring the quality nature of NOMA-based information transmission. To achieve these objectives, we find the optimal phase shift of the RIS using the Semi-Definite Program (SDP) method and determine the optimal NOMA power distribution coefficient using a search approach. The simulation results demonstrate that our scheme improves the energy transfer efficiency compared to the conventional method without RIS.