Precoding and Trajectory Design for UAV-Assisted Integrated Communication and Sensing Systems

Benefited from the characteristics of high mobility, low cost and convenient deployment, unmanned aerial vehicles (UAVs) can be deployed in wireless communication systems as mobile base stations (BSs) to improve the communication performance of users. In addition, by deploying communication and sensing equipment and supporting efficient resource sharing of communication and sensing technologies, UAVs are expected to act as high-performance aerial platforms which integrate communication and sensing technologies. In this paper, a multi-antenna UAV-enabled joint communication and sensing scenario is examined by jointly considering the flight energy of the UAV, multi-antenna transmissions, and the user service requirements. Two optimization problems are respectively formulated for various UAV states. In particular, the problem of communication precoding and UAV flight trajectory optimization is formulated as a minimum user rate maximization problem and the joint optimization problem of UAV sensing position, communication and sensing precoding is formulated as a minimum target detection probability maximization problem. Since the minimum-rate maximization problem is a non-convex optimization problem, which is difficult to solve directly, we decompose the original optimization problem into a communication precoding design subproblem and a UAV trajectory design subproblem, and solve the two subproblems successively by applying an alternate iteration method. Specifically, a zero forcing (ZF) algorithm is put forward for solving the communication precoding design subproblem. A successive convex approximation (SCA) algorithm is applied to determine the optimal trajectory of the UAV. Based on the optimal trajectory of the UAV, the sensing position optimization problem is modeled as a weighted distance minimization problem, and then a heuristic algorithm is proposed to obtain the optimal positions. Finally, a ZF algorithm-based joint communication and sensing precoding is presented. The effectiveness of the proposed algorithm is verified by simulations.