Secrecy Analysis and Optimization of UAV-Assisted Relaying Networks with Hardware Impairments

This paper proposes a half-duplex unmanned aerial vehicle (UAV)-assisted decode-forward relaying network based on the simultaneous wireless information and power transfer (SWIPT) scheme with hardware impairments. We derive an exact expression of intercept probability in the presence of a ground eavesdropper (Eve). In addition, we elaborate an analysis of ergodic secrecy rate and formulate an optimal secrecy rate problem to seek appropriate power splitting (PS) ratio. To address the non-convex problem, equivalent transformations are deduced, an iterative algorithm that merges the bisection search and coordinate descent method is presented. The experimental simulations validate our theoretical results. In particular, the optimal flight altitude of the UAV is related to the distance between the UAV and Eve. Moreover, the proposed optimal secrecy rate scheme outperforms compared with other fixed PS ratio cases.