Robust Beamforming with UAV-Assisted Artificial Noise for Secure LEO Communications

With the increasing demand for secure connectivity in non-terrestrial networks, physical layer security (PLS) in Low Earth Orbit (LEO) satellite communications has attracted growing attention. This paper investigates PLS in the presence of uncertain eavesdropper locations, where satellite beamforming is used to enhance signal strength toward legitimate users while suppressing emissions toward potential eavesdropper regions. A joint optimization framework is developed for satellite beamforming and UAV-assisted artificial noise (AN) design to maximize the secrecy capacity. The resulting non-convex problem is addressed using alternating optimization (AO), semidefinite relaxation (SDR), and successive convex approximation (SCA). Numerical results confirm that the proposed method achieves superior secrecy performance compared to baseline approaches. Additionally, we study the impact of region size, relative location, and satellite mobility on the achievable secrecy rate.