Energy-harvesting aided unmanned aerial vehicles for reliable ground user localization and communications under lognormal-Nakagami-m fading channels

In this paper, we propose a wireless localization system based on energy-harvesting aided unmanned aerial vehicles (UAV). Our proposed system consists of a ground station (GS), a UAV, and multiple users located on the ground, in which both the ground station and all the ground users (GUs) want to know the locations of the ground users. To this end, the UAV first harvests energy from the GS, and then broadcasts signals to the GUs for localization. Each GU will estimate its location, and then transmits data, including its location information, to the GS with the help of the UAV. The links between nodes experience both large-scale lognormal shadowing and small-scale Nakagami-m fading. We first derive the Cramer-Rao lower bound (CRLB) under spatially correlated shadowing for localization performance evaluation. Next, we analyze the system throughput under delay-limited and delay-tolerant transmission modes. To derive exact closed-form expressions as well as high signal-to-noise ratio (SNR) approximations of the performance metrics, we consider a mixture gamma distribution approximation for the probability density functions (PDF) of the composite fading channels. We evaluate the impact of several key system parameters such as the number of waypoints and the altitude of the UAV, correlated shadowing and energy-harvesting time both on the localization performance and on the achievable throughput. Simulations are provided to validate the theoretical analysis.