optimizing UAVtoCar Communications in 3D Environments Through Dynamic UAV Positioning Unmanned Aerial Vehicles (UAVs) can act as relays in areas with limited infrastructure to support cartocar communications. Prior studies on UAVtocar communications showed that the irregularity of the terrains has a significant impact on link quality. Thus, in this paper, we propose a positioning technique that relies on Particle Swarm optimization (PSO) to optimize the positioning of a UAV in the vehicular environment by considering the irregularities of the terrains that might hinder LineofSight (LOS) conditions. The proposed technique takes into account the path loss caused by the terrains. Simulation results show that the optimization algorithm allows us to determine the best position for the deployed UAVs throughout time by considering the movement of the cars, and also accounting for adjustments in terms of flight altitude. In particular, the latter is adjusted by considering the position of the cars on the ground and the profile of surrounding terrains to determine potential communications blockages, while respecting international regulations regarding flight altitude restrictions.

Three Dimensional UAV Positioning for Dynamic UAVtoCar Communications In areas with limited infrastructure, Unmanned Aerial Vehicles (UAVs) can come in handy as relays for cartocar communications. Since UAVs are able to fully explore a threedimensional environment while flying, communications that involve them can be affected by the irregularity of the terrains, that in turn can cause path loss by acting as obstacles. Accounting for this phenomenon, we propose a UAV positioning technique that relies on optimization algorithms to improve the support for vehicular communications. Simulation results show that the best position of the UAV can be timely determined considering the dynamic movement of the cars. Our technique takes into account the current flight altitude, the position of the cars on the ground, and the existing flight restrictions.