On the Relation between the Communications System and the Collision Probability in Massive UAV Scenarios

In this contribution we take a look into the future and investigate so-called massive UAV (unmanned aerial vehicle) scenarios in the VLL (very low level) airspace with UAV densities ranging from 50 to 500 UAVs per km². We predict that UAVs will fly autonomously and use a beaconing system similar to that used today in road and maritime traffic to warn of collisions. For this purpose, UAVs regularly broadcast short beacon messages which include their current positions and trajectories. However, beacon messages may not be received correctly due to congestion on the radio channel. As in vehicular environments, the loss of several successive beacon messages sent by a certain UAV can have dramatic consequences, since conflicting trajectories cannot be identified. In our work, we derive the relation between failures on the communications channel and the probability of collisions between UAVs. Eventually, we show that an ALOHA type beaconing system with a bandwidth of 1 MHz can handle massive UAV scenarios.