Sum-Rate Maximization in RIS-Aided Wireless-Powered D2D Communication Networks

Abstract

The transmission performance of an reconfigurable intelligent surface (RIS)-aided device-to-device (D2D) communication network is fundamentally limited by the devices' energy. To address this challenge, in this paper, the joint radio resource allocation of D2D users (DUs) with piece-wise linear energy harvesting (EH) models and passive beamforming of the RIS is investigated to maximize the sum rate of DUs for an RIS-aided wireless-powered D2D communication underlaying a cellular network. Specifically, multiple wireless-powered DUs harvest radio-frequency energy from a hybrid access point (HAP) with the help of an RIS during the EH phase and achieve data transmission by using the harvested energy during information transmission phase. The optimization problem is formulated by jointly optimizing the transmit power of DUs, transmission time, the active beamforming vector of the HAP, and the passive beamforming matrix of the RIS. An alternating optimization-based algorithm is designed to solve the non-convex problem by using the variable substitution approach and the Lagrangian dual method. Simulation results have shown that our proposed algorithm provides a significant improvement in data rates over the existing algorithm without the RIS.