Energy Efficient Resource Allocation for Re-configurable Intelligent Surface-Assisted Wireless Networks

Abstract This paper considers energy-efficient resource allocation in reconfigurable intelligent surface (RIS)-assisted multiple-input-single-output (MISO) communication systems. In particular, it revisits the energy efficiency (EE) problem that uses the alternating optimization (AO) approach. In each AO's iteration, RIS phase optimization is achieved using gradient decent method whose convergence is unfortunately not guaranteed. We therefore, discuss the convergence issue herein while proposing two alternatives, namely, the Wolfe based gradient-descent algorithm (GAW) and the trust region (TR) method. However, the optimal transmit power allocation is obtained using Dinkelbach’s algorithm. Our results show that the proposed methods outperform the existing method that uses sequential fractional programming (SFP) for phase optimization and the traditional relay-based method.