From ground to aerial communication

Micro Unmanned Aerial Vehicles (UAVs) employed in civil missions are receiving remarkable attention from both research and industry. UAVs embed more and more sensor technology, and their small mounted cameras allow for efficient mapping of large areas in short time. Yet, civil missions such as rescue operations would need a timely delivery of high-resolution images, which calls for high-speed communication such as provided by WLAN IEEE 802.11n. Driven by extensive experiments, the key finding of this contribution is that 802.11n performs poorly in highly mobile and aerial scenarios, as the throughput between UAVs drops far below the theoretical maximum as soon as they become airborne. This is partially caused by the limitations of the embedded hardware, but also a result of the network dynamics of the aerial links. In order to dissect the origins of the low performance figures, we isolate the potential causes of degradation by analyzing our data of throughput, packet loss, aircraft and antenna orientation, and cruise speed. We discuss quantitatively how practical it is to deliver high-resolution images when being exposed to aerial throughput. We believe that it will be a long way until micro UAVs transferring large-size data become reality and argue for a new amendment of IEEE 802.11 addressing the communication among highly-mobile UAVs.