Optimal Placement of Low-Altitude Aerial Base Station for Securing Communications

Because of its cost-effective and on-demand deployment, low-altitude aerial base stations (BSs) are capable of providing emergency communication services in many scenarios. This letter investigates the security issue in emergency communications where the aerial BS is deployed optimally to serve ground users in the presence of an eavesdropper. We aim to maximize the probability of non-zero secrecy capacity to improve the possibility of physical-layer security transmission via the optimal placement of the aerial BS. The resulting nonconvex optimization problem will be simplified based on its geometric properties and equivalent transformation. The simplified problem will then be solved by using semidefinite relaxation. Numerical results show that the optimal placement of the aerial BS can significantly improve the probability of non-zero secrecy capacity.