DSearching: Distributed searching of mobile nodes in DTNs with floating mobility information

In delay tolerant networks (DTNs), enabling a node to search and find an interested mobile node is an important function in many applications. However, the movement of nodes in DTNs makes the problem formidable. Current methods in disconnected networks mainly rely on fixed stations and infrastructure-based communication to collect node position information, which is difficult to implement in DTNs. In this paper, we present DSearching, a distributed mobile node searching scheme for DTNs that requires no infrastructure except the GPS on mobile nodes. In DSearching, the entire DTN area is split into sub-areas, and each node summarizes its mobility information as both transient sub-area visiting record and long-term movement pattern among sub-areas. Each node distributes its transient visiting record for a newly entered sub-area to nodes that are likely to stay in the sub-area that it just moves out, so that the information flows in the network for the locator to trace it along its actual movement path. Each node also stores different parts of its long-term mobility pattern to long-staying nodes in different sub-areas for the locator to trace it when visiting records are absent. Considering that nodes in DTNs usually have limited resources, DSearching constrains the communication and storage cost in the information distribution process. Extensive trace-driven experiments with real traces demonstrate the high efficiency and high effectiveness of DSearching.