Energy Minimization for Active RIS-Aided UAV-Enabled SWIPT Systems

In this letter, we consider an active reconfigurable intelligent surface (RIS)-aided unmanned aerial vehicle (UAV)-enabled simultaneous wireless information and power transfer (SWIPT) system. Compared with the conventional passive RIS, the active RIS deploying the internally integrated amplifiers can offset part of the multiplicative fading. In this system, we deal with an optimization problem of minimizing the total energy cost of the UAV. Specifically, we alternately optimize the trajectories, the hovering time, and the reflection vectors at the active RIS by using the successive convex approximation (SCA) method. Simulation results show that the active RIS performs better in energy saving than the conventional passive RIS.