Dynamic ISAC Beamforming Design for UAV-Enabled Vehicular Networks

Utilizing unmanned aerial vehicles (UAVs) as aerial platforms to provide both sensing and communication services is envisioned as a promising paradigm, due to their inherent flexibility and maneuverability. In this paper, we propose a UAV-enabled sensing-assisted communication scheme for vehicular networks using the integrated sensing and communication (ISAC) technique. Specifically, we consider the geometry of vehicles as extended targets with multiple resolvable scatters and adjust beamwidth to cover the entire vehicle in the ISAC duration. Based on the reflected signals, the UAV can predict the state of vehicle, which is then exploited to generate tailored beams to effectively track the vehicle. To address the asymmetric sensing and communication requirements, a three-stage ISAC scheme with dynamic sensing duration and frequency is proposed according to the communication/sensing performance in real time. The initial state of vehicle is estimated in the first stage, followed by the use of ISAC wide beams in the second stage to achieve the vehicle coverage, employing an extended Kalman filtering (EKF) approach for state tracking and prediction. In the third stage, the UAV selectively transmits either an ISAC beam or a communication-only beam based on monitored sensing and communication performance metrics. Finally, simulation results are provided to evaluate the efficacy of the proposed scheme as compared to other benchmarks and also shed light on the tradeoff between communication and sensing.