Multi-UAV-Enabled Integrated Sensing and Communications: Joint Beamforming and UAV Placement Design

This paper studies a scenario when multiple un-manned aerial vehicle (UAV)-mounted dual-functional access points (APs) collaboratively provide integrated sensing and communications (ISAC) services for ground subscribers. It is assumed that the UAVs are equipped with a vertically oriented uniform linear array (ULA). These UAVs simultaneously transmit information signals to communicate with their respective ground users (GUs) and cooperatively detect a ground target within an interested area. With this configuration, we aim to maximize the minimum detection probability over the target area by designing the transmit beamforming at these UAVs and their placement locations, while ensuring the GUs' individual minimum signal-to-interference-plus-noise ratio (SINR) constraints, the minimum inter-Uav distance constraints for collision avoidance, and the maximum transmit power constraints at UAVs. It is challenging to solve the highly non-convex problem because of the ULA configuration on the UAV s. Towards this end, we propose an iterative algorithm to obtain a high-quality solution to this problem based on alternating optimization and semidefinite relaxation (SDR). Finally, we provide numerical results to confirm the effectiveness of our proposed design in comparison with other benchmark schemes. It is demonstrated that our proposed joint transmit beamforming and UAV placement design efficiently balances the trade-off between communication and sensing performances.