Improving Physical Layer Security Using UAV-Enabled Mobile Relaying

TLDR

Mobile relaying using UAVs has attracted attention in wireless communications, yet the secrecy‑rate maximization problem remains nonconvex and hard to solve. This letter demonstrates the utility of mobile relaying for secure wireless communications by aiming to maximize the secrecy rate in a four‑node channel. The authors employ a difference‑of‑concave program to devise an iterative, water‑filling‑based algorithm that converges to a KKT point, with a closed‑form solution available for a special case to reduce complexity. Simulations show that the proposed mobile relaying scheme significantly outperforms static relaying in secrecy enhancement.

Abstract

Mobile relaying has aroused great interest in wireless communications recently, thanks to the rapid development and evolvement of unmanned aerial vehicles. This letter establishes the utility of mobile relaying in facilitating secure wireless communications. In particular, we consider transmit optimization in a four-node (source, destination, buffer-aided mobile relay, and eavesdropper) channel setup, wherein we aim at maximizing the secrecy rate of this system. However, the secrecy rate maximization problem is nonconvex and intractable to solve. To circumvent the nonconvexity, we exploit the difference-of-concave (DC) program to develop an iterative algorithm, which is proven to have Karush-Kuhn-Tucker point convergence guarantee. The algorithm conducts a water-filling-based solution in each DC iteration, and thus is computationally efficient to implement. In addition, for a given special case, we show that each DC iteration could yield a closed-form solution, which further reduces the computational complexity. Simulation results demonstrate that the proposed mobile relaying scheme could significantly outperform the static relaying scheme in terms of secrecy enhancement.