DSearching: Using Floating Mobility Information for Distributed Node Searching in DTNs

In delay tolerant networks (DTNs), enabling a mobile node to search and find another interested mobile node is an important function in many applications. However, the movement of nodes in DTNs makes the problem formidable. Current node searching methods in disconnected networks mainly rely on fixed stations in the network 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. 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. Upon arriving at a sub-area, a node generates a new visiting record for the sub-area and distributes it to nodes that are likely to stay in the previous sub-area, so that visiting records form a chain for the locators to trace the node. Each node also stores different parts of its long-term mobility pattern to long-staying nodes in different sub-areas for others 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 while enabling efficient node searching. Advanced extensions that can further improve the searching efficiency is also proposed in this paper. Extensive trace-driven experiments with real traces demonstrate the high efficiency and high effectiveness of DSearching.