Operating a UAV mesh & internet backhaul network using temporospatial SDN

In this paper we describe an application of Tem-porospatial Software Defined Networking (TS-SDN) to UAV networks. Airborne platforms (airplanes, balloons, airships) can be used to carry wireless communication nodes to provide direct-to-user as well as backhaul connections. Such networks also include ground nodes typically equipped with highly directional steerable transceivers. The physics of flight as well as state of the atmosphere lead to time-dynamic link metrics and availability. As nodes move around, the network topology and routing need to adjust to maintain connectivity. Further, mechanical aspects of the system, such as time required to mechanically steer antennas, makes the reactive repair approach more costly than in terrestrial applications. Instead, TS-SDN incorporates reasoning about physical evolution of the system to proactively adjust the network topology in anticipation of future changes. Using airborne networks under development at Google as an example, we discuss the benefits of the TS-SDN approach compared to reactive repair in terms of network availability. We also identify additional constraints one needs to account for when computing the network topology, such as noninterference with other stationary and moving sources. Existing SDN standards do not support scheduled updates necessary in a TS-SDN. We describe our extensions to control messages and software implementation used in field tests.