Trajectory Optimization for Channel Knowledge Map Construction in Low-Altitude UAV Systems

Channel knowledge map (CKM) is expected to play an important role for low-altitude unmanned aerial vehicle (UAV) communications and sensing. However, constructing CKM is challenging for UAV due to its limited endurance for data collection. To address this challenge, this paper proposes an information-theoretic framework to design UAV data collection policies. The design aims to guide the measurement devices to those locations where the reduction of the expected uncertainty is maximum. The proposed approach involves two stages: initial location selection and online path planning. The initial location and destination are selected on the basis of the proposed CKM’s uncertainty metrics. An online path planning is developed to update the estimated map and uncertainty metric based on the acquired measurements when the destination is reached. The simulation results show that the proposed scheme can rapidly reduce the uncertainty of the CKM with the channel measurements collected along the designed UAV trajectory.