Securing UAV Communications via Joint Trajectory and Power Control

TLDR

UAV communication is expected to be widely used in 5G networks because of its low cost, high mobility, and on‑demand deployment, yet its broadcast and line‑of‑sight channels create a new security challenge. This study addresses that challenge by applying physical‑layer security techniques. The authors formulate non‑convex problems to maximize average secrecy rates for both UAV‑to‑ground and ground‑to‑UAV links by jointly optimizing the UAV’s trajectory and transmit power, and solve them with iterative block‑coordinate descent and successive convex optimization that alternately update power and trajectory until convergence. Simulation results demonstrate that the proposed joint trajectory and power control algorithms outperform benchmark schemes lacking such optimization in terms of secrecy rates for both communication directions.

Abstract

Unmanned aerial vehicle (UAV) communication is anticipated to be widely applied in the forthcoming fifth-generation wireless networks, due to its many advantages such as low cost, high mobility, and on-demand deployment. However, the broadcast and line-of-sight nature of air-to-ground wireless channels give rise to a new challenge on how to realize secure UAV communications with the destined nodes on the ground. This paper aims to tackle this challenge by applying the physical layer security technique. We consider both the downlink and uplink UAV communications with a ground node, namely, UAV-to-ground (U2G) and ground-to-UAV (G2U) communications, respectively, subject to a potential eavesdropper on the ground. In contrast to the existing literature on the wireless physical layer security only with the ground nodes at fixed or quasi-static locations, we exploit the high mobility of the UAV to proactively establish favorable and degraded channels for the legitimate and eavesdropping links, through its trajectory design. We formulate new problems to maximize the average secrecy rates of the U2G and G2U transmissions, by jointly optimizing the UAV's trajectory, and the transmit power of the legitimate transmitter over a given flight period of the UAV. Although the formulated problems are non-convex, we propose iterative algorithms to solve them efficiently by applying the block coordinate descent and successive convex optimization methods. Specifically, both the transmit power and UAV trajectory are optimized, with the other being fixed in an alternating manner, until the algorithms converge. The simulation results show that the proposed algorithms can improve the secrecy rates for both U2G and G2U communications, as compared to other benchmark schemes without power control and/or trajectory optimization.