Optimal Relay Node Selection in Two-Hop Routing for Intermittently Connected MANETs

Recently, many researchers have been attracted to intermittently connected mobile ad-hoc networks (MANETs), which are a type of DTN (delay/disruption/disconnect tolerant network). To achieve end-to-end communication between a source node and a destination node in the networks, storecarry-forward routing has been considered as a promising solution. In this paper, we propose an algorithm for optimal relay node selection in two-hop store-carry-forward routing schemes, where only the source node can generate relay nodes (nodes with a copy of the message). When the routing scheme restricts the maximum number of relay nodes, its performance is highly dependent on the selection of relay nodes so that the algorithm is important. The routing scheme according to our method of relay node selection can minimize the mean delivery delay. In this paper, we first straightforwardly formulate a system dynamics model from generating an original message to its destination, and then show that it is difficult to derive the optimal relay node selection for the system dynamics model. To construct the algorithm, we consider an system model equivalent to the original system model, and show that the relay node selection can be obtained easily for the equivalent system model. Through numerical experiments, we evaluate the performance of the routing scheme according to our method of relay node selection.