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...6] assume knowledge of connectivity patterns where exact timing information of contacts is known and then modifies Dijkstra’s algorithm to compute the cost edges and routes accordingly. Merugu et al. =-=[39]-=- and Handorean et al. [21] likewise make the assumption of detailed knowledge of node future movements. This information is time dependent and routes are computed over the time-varying paths available...

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...aths? To organize the search process, we convert the sequence of node contacts into a space-time graph, which is a special kind of directed weighted graph. Our use of the space-time graph is based on =-=[14]-=-. Time is discretized in increments of ∆. In all our work we use ∆ = 10 sec. Vertices in the space-time graph are pairs (xi, T) with xi ∈ M and T = c∆ for c ∈ {1, 2, . . . , ⌊tmax/∆⌋}. Edges in the sp...

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...des using the store-carry-forward routing mechanism. Routing in DTNs poses some unique challenges compared to conventional data networks due to the uncertain and time-varying network connectivity. In =-=[2, 3]-=-, optimal routes in a DTN can be discovered by constructing a time-space graph with oracles. In practical situations where no oracle is available to reveal future contacts, opportunistic routing [4, 5...

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...duce a good performance in many cases so that the oracles which are difficult to obtain may not be worthwhile. A tree-based approach and a modified space-time routing table were presented in [20] and =-=[21]-=-. If the trajectories of the nodes can actively be modified, it can guarantee that the message be transmitted to its destination in a minimal time [22]. Epidemic routing [23] is an early proposal suit...

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...d-hoc algorithms; indeed, to compute the minimum delay path in the DTN graph, [2] proposes a modified version of the Dijkstra algorithm. An alternative modeling of the routing problem was proposed in =-=[11]-=-, which defines a particular space-time graph on which the minimum delay path can be found exploiting a classic shortest path algorithm. Specifically, the space-time graph holds a layer of the origina...

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...ioned due to the low density of the network and also the movement of nodes. These networks are known as delay-tolerant networks (DTNs) [12], and also disruption-tolerant networks [13]. Several models =-=[14, 15]-=- have been proposed to abstract DTNs in a graph model by incorporating time. More recently, a complete architecture to support various protocols in DTNs was designed [16]. DTNs include some other netw...

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...s clusterhead. In Delay-Tolerant Networks (DTNs) where only intermittent network connectivity is available [8, 9], fine-grained mobility knowledge is used to improve the efficiency of data forwarding =-=[17]-=-. In this paper, we present a novel fine-grained mobility characterization approach. In the narrow sense, fine-grained mobility characterization means the accurate prediction of geographical user move...

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...scheme for DTNs is proposed in [5]. In their work, the DTN routing problem is formulated as moving messages across a graph with time-varying connectivity whose dynamics is predictable. The authors of =-=[10]-=- propose the space-time routing scheme. They assume the network profile can be accurately predicted over certain period of time. The dynamic of the networks is modeled as space-time graph. Finding the...