Geographical Routing for Delay Tolerant Encounter Networks

Abstract

Delay tolerant networks (DTNs) are intermittently connected networks, where direct end-to-end path between communicating nodes may never exist. To achieve eventual delivery some nodes must store messages and wait opportunity to forward them. In mobile environment, one of the most challenging problems for routing protocols is to decide, which nodes should store the message to achieve eventual delivery as quick as possible. Common approach is to propagate message into large group of nodes, hoping one of them will reach the destination. These solutions, however, are not very scalable as they generate plenty of extra load and traffic to network. Further more, message carriers have no means to detect when one of copies has reached the destination, so they must store unnecessary copies for long periods. In this paper, we introduce a single copy relay for sparse mobile networks. Predictive Graph Relay (PGR) is a routing scheme, which uses movement prediction to achieve message delivery to certain geographical destination. PGR is suitable for applications, where message receivers are static. Such applications are for example sensor networks, where a static sink collects data from several sensors. Our method only requires a fraction of the system resources compared traditional ways of information delivery in a similar environment.