Sum-Rate Maximization for UAV-Mounted STAR-RIS-Assisted Wireless Powered Communications Networks

In this paper, we consider an unmanned aerial vehicle mounted simultaneously transmitting and reflecting reconfigurable intelligent surfaces (UAV-mounted STAR-RIS)-assisted wireless powered communications network that includes an access point, a UAV-mounted STAR-RIS, and two ground users located on different sides of the STAR-RIS. Specifically, the ground users first harvest energy via the UAV-mounted STAR-RIS-assisted downlink and then transmit information to access point via the UAV-mounted STAR-RIS-assisted uplink. We formulate the sum-rate maximization problem by jointly optimizing the location of UAV-mounted STAR-RIS, the time allocation, and the STAR-RIS phase shift while considering the quality of service requirements of the ground users. Further, we first derive the optimal phase shift of STAR-RIS and then employ an alternating method to find the optimal time assigned to the two users and the optimal location of the UAV. Finally, we compare the performance in simulation results against other benchmark schemes to assess the effectiveness of our proposed scheme.