A Mesh Architecture for Robust Packet Delivery in Airborne Networks

As a special subset of ad hoc networks, airborne networks aim to provide efficient network access for airborne and ground assets in a tactical environment. Conventional ad hoc routing protocols face some difficulties in such networks. First, significant overhead may be generated due to the high node mobility and dramatic topology changes. Second, temporary link failure may abort the delivery of a packet in some intermediate router. In this thesis, we propose a cluster-based reactive routing protocol to alleviate these problems. Our solution takes advantage of mesh routers installed in unmanned aerial vehicles or aircraft capable of hovering, when such airborne assets are available. As those mesh points usually have relatively stable connections among themselves, they play the role of cluster heads, forming a hierarchical routing structure. A simple self-organizing rule is introduced in cluster management to limit the cluster control overhead and route discovery flooding. In addition, a disruption tolerant mechanism (DTM) is deployed in the routing protocol to increase resilience to temporary link or node failure. The DTM utilizes the location, bearing and speed information provided by each node and intelligently maintains a buffer of packets that cannot be immediately delivered. If a temporary link failure occurs in the intermediate router during delivery, the packet is then buffered in that router up to a maximum time-to-live. The DTM also keeps track of link changes and tries to deliver the message as soon as a new path toward the destination is found. If the buffered messages are about to time out and the destination is still unreachable, the DTM still makes an effort to deliver the packet to another router with higher probability of eventually reaching the destination.