Reliable mobicast via face-aware routing

This work presents a novel protocol for a spatiotemporal variant of multicast called mobicast, designed to support message delivery in ad hoc sensor networks. The spatiotemporal character of mobicast relates to the obligation to deliver a message to all the nodes that will he present at time t in some geographic zone Z, where both the location and shape of the delivery zone are a function of time over some interval (t/sub start/, t/sub end/). The protocol, called face-aware routing (FAR), exploits ideas adapted from existing applications of face routing to achieve reliable mobicast delivery. The key features of the protocol are a routing strategy, which uses information confined solely to a node's immediate spatial neighborhood, and a forwarding schedule, which employs only local topological information. Statistical results shows that, in uniformly distributed random disk graphs, the spatial neighborhood size is usually less than 20. This suggests that FAR is likely to exhibit a low average memory cost. An estimation formula for the average size of the spatial neighborhood in a random network is another analytical result reported in this paper. This paper also presents a novel and low cost distributed algorithm for spatial neighborhood discovery.