Fuzzy Closeness-Based Delegation Forwarding in Delay Tolerant Networks

Delay tolerant networks (DTNs) are envisioned to provide promising applications and services. One critical issue in DTNs is efficiently forwarding the messages within the delay requirements while avoiding the cost associated with blind flooding. To guide the forwarding process, nodes can evaluate their relationships with each other, in terms of ``closeness'', which summarizes both temporal and spacial information, based on contact history. However, due to the uncertainty in nodal mobility, the contact history usually contains fuzziness and incomplete information. In this paper, we first define and utilize a fuzzy trust evaluation system for nodes to summarize their relationships to other nodes, in terms of closeness. We then propose the fuzzy clustering to organize nodes into overlapped fuzzy communities based on nodes' evaluations of closeness. On top of the fuzzy communities, a novel fuzzy-weight-based delegation forwarding scheme is proposed to propagate the messages into all communities while avoiding repeated forwarding in the same community. Extensive simulation results based on real traces are presented to support the effectiveness of our scheme.