Energy-Efficient Secure Transmission for UAV-enabled Wireless Powered Communication

This paper investigates an uplink transmission of Internet of Things (IoT) in an unmanned aerial vehicle (UAV)enabled wireless powered communication (WPC) network, where a source sensor and multiple intermediate sensors harvest energy from a dedicated power transmitter deployed at the UAV. In order to help the source sensor transmit the data packet to the access point, an intermediate sensor is selected as a relay based on their links with source. Then, we derive the closed-form expressions of secrecy outage probability (SOP) and secure energy efficiency (SEE). Furthermore, we formulate the SEE optimization problem to find the optimal transmit power and location for the UAV power transmitter. Simulation results show that the best position of UAV is closer to the relays with the increasing of the number of relays. In addition, the decreasing of the UAV height contributes to the improvement of SEE.