  Clustering, as a technique for grouping nodes in geographical proximity
together, in vehicular communication networks, is a key technique to enhance
network robustness and scalability despite challenges such as mobility and
routing. This paper presents a robust clustering scheme based on cluster head
backup list algorithm for unmanned aerial vehicles (UAVs)-assisted vehicular
communication network, where multiple UAVs act as communication base stations
for a vehicular network. To tackle the high mobility issues in vehicular
communications, instead of allowing direct communication between all vehicles
to the UAV, clustering methods will potentially be efficient in overcoming
delay limitations, excessive power consumption and resource issues. Using the
clustering technique, neighboring vehicles are grouped into clusters with a
specific vehicle selected as the cluster head (CH) in each cluster. The
selected CH connects directly to the UAV through an infrastructure-to-vehicle
(I2V) link, subsequently establishing vehicle-to-vehicle (V2V) communications
with vehicles in the same cluster. To increase cluster connectivity period, the
proposed clustering scheme is developed based on considering the vehicle
behavior for efficient selection of CHs and providing a CH backup list to
maintain the stability of the cluster structure. Numerical evaluations show
that the proposed system outperforms benchmark schemes in terms of clustering
stability and reliability. It is also shown that the performance of the
proposed scheme is not much affected by the increase in the number of vehicles.
This indicates that the proposed scheme can be efficient in dense vehicular
networks where resource constraints pose significant challenges.
