Joint Uplink and Downlink 3D Optimization of an UAV Swarm for Wireless-Powered NB-IoT

This study investigates time-division duplex (TDD) orthogonal-frequency-division multiple access (OFDMA) unmanned aerial vehicles (UAVs)-aided wireless-powered Internet-of-Things (IoT) networks. Here, a swarm of UAVs simultaneously charge all IoT devices with constant power during a downlink (DL) phase. Using the harvested energy, each IoT device transmits data to an UAV during an uplink (UL) phase via OFDMA. We propose a novel framework to maximize the UL throughput by formulating and solving a joint optimization problem to find the optimal DL and UL time portions, device-UAV association, and the 3D placement of the UAVs. Using our proposed framework, it is shown that the 3D position of the UAVs will have different trends during the UL communications and the DL charging. The proposed TDD-OFDMA UAVs- aided can significantly improve the sum throughput of the IoT devices compare to the fixed base stations schemes.