  Wireless networks consisting of low SWaP, FW-UAVs are used in many
applications, such as monitoring, search and surveillance of inaccessible
areas. A decentralized and autonomous approach ensures robustness to failures;
the UAVs explore and sense within the area and forward their information, in a
multihop manner, to nearby aerial gateway nodes. However, the unpredictable
nature of the events, relatively high speed of UAVs, and dynamic UAV
trajectories cause the network topology to change significantly over time,
resulting in frequent route breaks. A holistic routing approach is needed to
support multiple traffic flows in these networks to provide mobility- and
congestion-aware, high-quality routes when needed, with low control and
computational overheads, using the information collected in a distributed
manner. Existing routing schemes do not address all the mentioned issues.
  We present a hybrid reactive routing protocol for decentralized UAV networks.
Our scheme searches routes on-demand, monitors a region around the selected
route (the pipe), and proactively switches to an alternative route before the
current route's quality degrades below a threshold. We empirically evaluate the
impact of pipe width and node density on our ability to find alternate
high-quality routes within the pipe and the overhead required to maintain the
pipe. Compared to existing reactive routing schemes, our approach achieves
higher throughput and reduces the number of route discoveries, overhead, and
resulting flow interruptions at different traffic loads, node densities and
speeds. Despite having limited network topology information, and low overhead
and route computation complexity, our proposed scheme achieves superior
throughput to proactive optimized link state routing scheme at different
network and traffic settings. We also evaluate the relative performance of
reactive and proactive routing schemes.
