Secrecy Transmission Capacity of Large-Scale UAV-Enabled Wireless Networks

This paper considers the secrecy transmission in a large-scale unmanned aerial vehicle (UAV)-enabled wireless network, in which a set of UAVs in the sky transmit confidential information to their respective legitimate receivers on the ground, in the presence of another set of randomly distributed suspicious ground eavesdroppers. We assume that the horizontal locations of legitimate receivers and eavesdroppers are distributed as two independent homogeneous Possion point processes (PPPs), and each of the UAVs is positioned exactly above its corresponding legitimate receiver for efficient secrecy communication. Furthermore, we consider an elevation-angle-dependent line-of-sight (LoS)/non-LoS (NLoS) path-loss model for air-to-ground (A2G) wireless channels and employ the wiretap code for secrecy transmission. Under this setup, we first characterize the secrecy communication performance (in terms of the connection probability (CP), secrecy outage probability (SOP), and secrecy transmission capacity (STC)) in mathematically tractable forms. Next, we optimize the system configurations (i.e., the wiretap code rates and UAV positioning altitude) to maximize the STC, subject to a maximum SOP constraint. Finally, we present numerical results to validate the theoretical analysis.