A Control-based Design of Beamforming and Trajectory for UAV-Enabled ISAC System

We study a control-based design of beamforming and trajectory that incorporates the dynamic model, focusing on a scenario where a multi-antenna unmanned aerial vehicle (UAV) simultaneously performs radar sensing of multiple targets in a specific region and communication with multiple ground users. Two optimization problems are formulated for the three-degree-of-freedom (3-DoF) and six-degree-of-freedom (6-DoF) dynamic models of UAV, which are often overlooked in existing designs. These problems aim to maximize the average weighted communication rate while maintaining the dynamic constraints and the sensing service requirements by designing the UAV trajectory and the communication and sensing beamforming vectors. To deal with the challenges posed by the UAV dynamic constraints, we decompose the original problem into two subproblems: the communication and sensing beamforming design subproblem, and the UAV trajectory optimization subproblem. Given the UAV trajectory, we employ the sequential convex approximation (SCA) and semi-definite relaxation (SDR) methods to transform the beamforming design subproblem into a convex problem. Given the communication and sensing beamforming vectors, we propose a control-based approach with piecewise parameterization and exact penalty function strategies to transform the UAV trajectory optimization subproblem into a static nonlinear program, which can be efficiently solved by sequential quadratic programming (SQP). Numerical simulations indicate that the proposed scheme is more feasible in terms of the UAV control than the existing scheme in practical systems, with less performance loss or even no performance degradation.