Probability Delegation Forwarding in Delay Tolerant Networks

Delay tolerant networks are a type of wireless mobile networks that do not guarantee the existence of a path between a source and a destination at any time. In such a network, one of the critical issues is to reliably deliver data with a low latency. Naive forwarding approaches, such as flooding and its derivatives, make the routing cost (here defined as the number of copies duplicated for a message) very high. Many efforts have been made to reduce the cost while maintaining performance. Recently, an approach called delegation forwarding (DF) caught significant attention in the research community because of its simplicity and good performance. In a network with N nodes, it reduces the cost to O(radic(N)) which is better than O(N) in other methods. In this paper, we extend the DF algorithm by putting forward a new scheme called probability delegation forwarding (PDF) that can further reduce the cost to O(N^{log 2+2p (1+p)}), p isin (0, 1). Simulation results show that PDF can achieve similar delivery ratio, which is the most important metric in DTNs, as the DF scheme at a lower cost if p is not too small. In addition, we propose the threshold probability delegation forwarding (TPDF) scheme to close the latency gap between the DF and PDF schemes.