Characterizing Multihop Aerial Networks of COTS Multirotors

Unmanned aerial vehicles (UAVs) recently enabled a myriad of new applications spanning domains from personal entertainment to surveillance and monitoring. In this paper, we focus on using several small UAVs collaboratively to provide extended reach to an online video monitoring system for inspection of industrial installations. We make use of 802.11 radios on low-cost commercial-off-the-shelf UAVs, set up a time-division multiple access overlay protocol to avoid mutual interference, and enable high channel utilization in multihop networks. In particular, we provide a model for the quality of the UAV-to-UAV link, in terms of packet delivery ratio as a function of distance, packet size, and orientation, based on an extensive measurement campaign. We show that this platform is not omnidirectional in the horizontal plane and that UAV-to-UAV communication ceases around 75 m. Concerning the operation in a multihop mode to allow extending the network, the paper derives the optimal number of hops that maximize the end-to-end throughput, as well as the corresponding hop lengths. We validate our mathematical model with extensive experimental measurements transmitting payloads up to 200 m (over 802.11 g at 54 MBps).