Cost-Efficient Topology Design Problem in Time-Evolving Delay-Tolerant Networks

In this paper, we study the cost efficient topology design (CETD) problem in a predictable delay tolerant networks (DTN) where the time-evolving network topology is known a priori or can be predicted. We model such time-evolving network as a weighted space-time graph which includes both spacial and temporal information. The aim of CETD is to build a sparse structure from the original space-time graph such that (1) the network is still connected over time between any two nodes, (2) the cost of the least cost path for any two nodes in this constructed structure is at most δ times of that in the original graph, i.e., cost efficient DTN routing is possible between any two nodes; and (3) the total cost of the structure is minimized. We first show that classic topology control methods for static graph do not work for this new problem and then propose three efficient topology control methods which can significantly reduce the total cost of topology while maintain the connectivity and cost-efficiency over time. Extensive simulations have been conducted on random DTN networks and results demonstrate the efficiency of the proposed methods.