Outage and throughput analysis of UAV-assisted wireless-powered IoT sensor networks over Nakagami-m fading channel with non-linear energy harvester

In modern wireless-powered communication networks (WPCNs) like Internet of Things (IoT) and wireless sensor networks (WSNs), the usage of Unmanned Aerial Vehicle (UAV) as a cooperative relay node is seen as a promising technique. In this paper we analyse the performance of a dual-hop decode and forward (DF) UAV-assisted system, which consists of a set of energy-constrained IoT sensor nodes (SNs), a UAV working as a relay between SNs and the desired destination user (D). For the considered system set-up, SNs first harvest the energy using the wireless power transfer (WPT) link from UAV and then transmit back the information signal to UAV and to the desired user using wireless information transfer (WIT) link. Here, we consider a non-linear energy harvesting mechanism that is more practical compared with the conventional linear energy harvesting system. Closed-form expressions for the outage probability and average throughput of the system are derived, by considering the key parameters such as transmit power, time switching factor, UAVs height and different fading environments. A suboptimal value of time switching factor between WPT and WIT is studied using a numerical search algorithm. Finally, the numerical simulation results demonstrate the average system throughput and exhibit how the proposed non-linear energy harvesting system is quite different from conventional linear energy harvesting systems.