They are ready - are they? Examining 802.11n aerial communications of search and rescue UAVs

In search and rescue (SAR) missions, small unmanned aerial vehicles (UAVs) equipped with cameras allow for efficient scanning of large areas. At the same time, UAVs may act as flexible network relays and data ferries, thus, providing ad-hoc aerial wireless communications for SAR teams. Still, in particular the delivery of high resolution images challenges common wireless protocols, which have not been designed for highly mobile nodes.

In this talk, we describe the UAV networking approach followed by the SWARMIX [1] project. For image transfer, we use multi-hop ad-hoc WLAN 802.11n, and, in addition, XBee-PRO 802.15.4 as a control channel. In extensive experiments, we found that the otherwise promising 802.11n performs poorly in highly mobile aerial scenarios. This is partially due to the limitations of the embedded hardware in use, but also a result of network dynamics. We discuss potential causes for throughput degradation and increase of packet loss when distance and speed increase. Finally, we draw conclusions how to use these insights to improve UAV to UAV communications.