UAV-mounted intelligent reflecting surface in maritime wireless powered communication network

Intelligent reflecting surface (IRS) assisted with the wireless powered communication network (WPCN) can enhance the desired signal energy and carry out the power-sustaining problem in ocean monitoring systems. In this paper, we investigate a reliable communication structure where multiple buoys transmit data to a base station (BS) with the help of the unmanned aerial vehicle (UAV)-mounted IRS and harvest energy from the base station simultaneously. To organically combine WPCN with maritime data collection scenario, a scheduling protocol that employs the time division multiple access (TDMA) is proposed to serve multiple buoys for uplink data transmission. Furthermore, we compare the full-duplex (FD) and half-duplex (HD) mechanisms in the maritime data collection system to illustrate different performances under these two modes. To maximize the fair energy efficiency under the energy harvesting constraints, a joint optimization problem on user association, BS transmit power, UAV's trajectory and IRS's phase shift is formulated. To solve the non-convex problem, the original problem is decoupled into several subproblems, and successive convex optimization and block coordinate descent (BCD) methods are employed obtain the near-optimal solutions alternatively. Simulation results demonstrate that the UAV-mounted IRS can significantly improve energy efficiency in our considered system.