Distributed Beam Tracking for Vehicular Communications via UAV-Assisted Cellular Network

In this paper, we propose a distributed beam tracking scheme for millimeter-wave unmanned aerial vehicle (UAV)-assisted communication systems. In the considered systems, aerial node base (aNB) connects the ground vehicles (GV) through directive beams to mitigate the path loss. However, line-of-sight (LoS) blockage may result in the link disconnection, which leads to the corruption of observations. To solve this issue, we extend the one-to-one beam tracking into the multi-node cooperative beam tracking scheme. For the multi-node cooperative problem, we develop the distributed extended Kalman filter (EKF)-based beam tracking to overcome the high nonlinearity and field-of-view (FoV) limitation of the observation model. While the multi-node cooperation scheme alleviates the corruptions of the observations, it may cause the error propagation between neighbor nodes. Thus, we incorporate the resilient network control into the proposed scheme. Consequently, a distributed EKF-based multi-node cooperative beam tracking protocol is proposed for the correction of corrupted observations and link stability. From our comprehensive simulation, the result of the proposed scheme shows 87.07% error reduction compared to the single node method. This improvement is comparable to the result of the centralized method (91.28% error reduction), and the proposed scheme also has the advantage of scalability.