Avoiding Collisions at Any (Low) Cost: ADS-B like Position Broadcast for UAVs

Abstract

Unmanned Aerial Vehicles (UAVs), a.k.a. drones, are increasingly used for different tasks. With more drones in the sky, the risk of accidents rises, sparking the need for conflict management solutions. Aircraft use a system called Automatic Dependent System-Broadcast (ADS-B) to continuously broadcast their position and speed but this system is not suitable for small drones because of its cost, complexity and capacity limitations. Broadband technologies such as Wi-Fi beacons are more suited for such dense scenarios, and they also offer the benefit of wide availability and low cost. The main challenges for Wi-Fi are (a) the multichannel nature of the technology makes transmitter and receiver coordination difficult, and (b) standard chipsets are not designed for frequent broadcast transmission and reception. In this paper, we propose and analyse a multichannel position broadcast solution that is robust against jamming and achieves a reliable location update within 125 ms. In addition, we implement the protocol on inexpensive embedded Wi-Fi modules and analyse the hardware limitations of such devices. Our conclusions are that, even on the simplest Wi-Fi chipsets, our protocol can be implemented to achieve a realistic location broadcast solution that still perfectly mimics simulation and analytical results on the lab bench and still can achieve approximately 4 message/s throughput at a distance of 900 m on flying UAVs.