Robust Secure Transmission of UAV-Aided Multiuser Network with Imperfect Location Estimation

In this paper, a novel quality-of-service (QoS)-based robust scheme combining beamforming and artificial noise (AN) is proposed to tackle with imperfect location estimation in UAV-aided secure transmission. In this multi-user network, a UAV equipped with linear antenna array cannot accurately estimate locations of users and eavesdroppers. We mainly Consider imperfect location of desired user, while eavesdropper locations fall into two categories: imperfect and unknown. Based on the analysis of energy leakage, two security QoS indicators, signal to leakage noise ratio (SLNR) and AN to leakage plus noise ratio (ANLNR), are defined to solve the difficulties of non-convex optimization and variable coupling of maximizing secrecy-sum-rate (SSR) problem. Specifically, we define the desired region and wiretap region according to the main lobe coverage range and estimation of direction angle and distance. A main-lobe integration method is adopted to optimize the beamforming vectors and the artificial noise projection matrix respectively, without needing the statistical property or distribution of location measurement errors. Compared with conventional robust methods, simulation results show a significant improvement in communication reliability and security performance towards multiple users in the middle and high signal-to-noise ratio (SNR) regions.