Geofences in the sky: herding drones with blockchains and 5G.

Unmanned aerial vehicles (UAVs), typically also referred to as drones, are gaining popularity and becoming ubiquitous. As the number of drones in the sky rapidly grows, managing the expected high-volume air traffic is becoming a critical challenge. It is essential to prevent collisions, and to protect the public from nuisances like noise or invasion of privacy, and shield from hazards like falling debris. UAV traffic management should comply with regulation, spatiotemporal constraints and limitations of drones. Spatiotemporal constraints could be no-flight zones or areas where drone flight times are restricted. Drone limitations could refer to their speed, flight range, telecommunication capabilities, etc. Furthermore, managing air traffic for UAVs is very different from managing the traffic of self-driving ground vehicles. First, there are no clearly-marked roads in the sky. Second, some UAVs cannot hover and must have a cleared flight path. Third, air traffic should be managed in a 3-dimensional space. In this paper we present a vision of air-traffic control based on geofencing. We discuss three operation modes: centralized, decentralized and a hybrid of the two other modes. We present some of the challenges involved in drone traffic control and illustrate how geofencing could be a useful tool for that, while leveraging the emerging 5G networking technology.