Algorithms for the Base Node Location Problem in the Virtual Segment Method in Store-Carry-Forward Routing Schemes

The message deliveries based on the store-carry-forward routing schemes, such as epidemic spraying, Message Ferrying and so on, are one of the fundamental and useful methods for establishing communications under Delay/Disruption/Disconnect Tolerant Networking (DTN) environments. However, these methods for message deliveries commonly have their own limitations in reach ability of message to destinations and scalability of networking. For example, the propagation delay of message between source and destination nodes generally becomes longer as the distance to the destination increases and as the density of nodes covering an area decreases. To overcome these problems, Yamamura et al. proposed the method of Virtual Segment (VS) which combined the epidemic routing and the Message Ferrying with multiple base nodes (BN) connected with a wired/wireless high-speed core network. They showed experimentally that the method improved both the reach ability and the scalability as well. However, their study didn't mention how to locate base nodes in the Virtual Segments for achieving efficient message delivery. In this paper, we consider the Base Node Location Problem (BNLP) to find the optimal solution of locating base nodes in the Virtual Segments. We propose two heuristic algorithms to approach this problem and show the effectiveness of them by numerical simulations.