Throughput Maximization for Active Hybrid RIS-Assisted WPCN-NOMA Systems

In this letter, an active hybrid reconfigurable intelligent surface (A-HRIS)-assisted wireless-powered communication network (WPCN) is considered. In the downlink, the A-HRIS harvests a part of radio frequency (RF) signals emitted by base station (BS), while reflecting a part of RF signals to devices for energy harvesting. In the uplink, all devices transmit signal to the A-HRIS with non-orthogonal multiple access (NOMA) strategy, then the A-HRIS amplifies the received signals and forwards them to the BS. To maximize the sum achievable throughput of the system, a two-stage optimization solution is proposed to jointly optimize the energy beamforming matrix, transmission timeslot allocation, reflected matrix and received vector of A-HRIS. Numerical results demonstrate the effectiveness of the proposed A-HRIS structure and optimization solution in enhancing the sum achievable throughput.