Resource Allocation in a RIS-Assisted TDMA Wireless Powered Sensor Network Using UAV

This paper studies an RIS-assisted wireless powered sensor network (WPSN) where sensors harvest energy from a UAV and transmit data to the fusion center (FC) using TDMA, aided by an RIS mounted on the UAV. In the proposed model, the wireless power transfer (WPT) time is predetermined as a fraction of the total data transmission time and is excluded from the optimization variables. The goal is to maximize sum throughput by efficiently allocating sensor time and adjusting the phase shifts of the RIS. The resulting non-convex optimization problem is solved by decomposing it into two subproblems: first, determining the optimal phase shifts; and second, developing an algorithm for optimal time allocation using the Lagrange dual method. Excluding the WPT time from the optimization variables enables us to develop an efficient algorithm for time allocation with significantly reduced execution time compared to scenarios where WPT time is also an optimization variable, while maintaining comparable performance. Numerical results demonstrate that the proposed method significantly improves the network’s performance.