Power Allocation and Phase Shift Optimization for RIS-Assisted UAV-Enabled WPCN

To hardware complexity and expensive hardware costs, a Reconfigurable Intelligent Surface (RIS)-assisted wireless powered communication network (WPCN) is investigated in this study, where the unmanned aerial vehicle (UAV) acts as a hybrid access point to improve the efficiency of both the downlink (DL) and the uplink (UL). In the proposed framework, an efficient modeling method is proposed for jointly optimizing time allocation, transmit power and RIS reflection coefficient. To reduce the computational complexity, an alternating direction algorithm is developed by utilizing the minimum throughput of sstem. Specifically, we establish the lower bound of the composite channel constraint and optimize the UAV's position using successive convex approximation (SCA). We then obtain closed-form solutions for transmit power and reformulate a linear programming problem to solve the time allocation. Numerical results demonstrate the effectiveness of the proposed method, outperforms traditional WPCNs.