Delivery likelihood based spraying in Delay Tolerant Networks

Delay Tolerant Networks (DTNs) are intermittently connected mobile networks, in which a fully connected path from source to destination does not exist. Therefore in these networks, message delivery relies on opportunistic routing where nodes use store-carry-and-forward paradigm to route the messages. However, effective forwarding based on a limited knowledge of contact behavior of nodes is challenging. There exist schemes where the number of times a message can be replicated is pre-specified. Example includes Spray and Wait [4] that limits the total number of copies created initially (spray phase). A number of different spraying heuristics can be envisioned. Traditional spraying heuristics naively split copies between source node and encountered nodes. For instance, binary spraying halves copies, but do not necessarily use other available information. Moreover, these heuristics do not evaluate the encountered node in terms of delivery likelihood. If node A encounters node B which might have never contacted with any other nodes, handing over half of the copies to such a node means those copies will probably not be transmitted to the destination which is very inefficient. In this paper we propose two efficient spraying heuristics based on delivery likelihood.