On the Feasibility of Position-Flooding in Urban UAV Networks

While the capabilities of Unmanned Aerial Vehicles (UAVs) lay the foundation for exciting new applications, many communication challenges remain unsolved. To make UAV operation safer and more reliable, the establishment of an Unmanned Aerial Traffic Management (UTM) is necessary. The most important functions of such a system are Airspace Monitoring (AM) and Communication Aided Detect and Avoid (CADA). To realize CADA, UAVs must timely communicate their position to other UAVs nearby to avoid collisions. For AM, positions must be forwarded to a ground station e.g. through an ad-hoc network. In this work, we evaluate whether these two functions can be realized for dense urban UAV networks in a decentralized way by using position-flooding. To measure this, we select three flooding protocols from the literature. Further, we propose Rate Decay Flooding (RDF) as a novel flooding protocol, that leverages the fact, that position updates become less urgent the further they have travelled. RDF reduces the traffic density by lowering the data rate with which traffic is forwarded on every hop. All four protocols are evaluated in an open-source simulator. The results show that RDF can support position-flooding in networks more than twice the size compared to the next best protocol. In doing so, it generates 52% less data traffic and thereby allows for the concurrent use of the ad-hoc network for other use-cases such as remote control. Using RDF improves the position uncertainty of neighbors at a distance of 2500m by 180m.