Understanding the wireless and mobile network space: a routing-centered classification.

ABSTRACTResearch into wireless data networks with mobile nodes has mostly considered Mobile Ad Hoc Networks (or MANETs). In such networks, it is generally assumed that end-to-end, possibly multi-hop paths between node pairs exist most of the time. Routing protocols designed to operate in MANETs assume that these paths are formed by a set of wireless links that exist contemporaneously. Disruption or delay tolerant networks (DTNs) have received significant attention recently. Their primary distinction from MANETs is that in DTNs links on an end-to-end path may not exist contemporaneously and intermediate nodes may need to store data waiting for opportunities to transfer data towards its destination. We call such DTN paths space-time paths to distinguish them from contemporaneous space paths used in MANETs. We argue in this paper that MANETs are actually a special case of DTNs. Furthermore, DTNs are, in turn, a special case of disconnected networks where even space-time paths do not exist. In this paper we consider the question of how to classify mobile and wireless networks with the goal of understanding what form of routing is most suitable for which network. We first develop a formal graph-theoretic classification of networks based on the theory of evolving graphs. We next develop a routing-aware classification that recognizes that the boundaries between network classes are not hard and are dependent on routing protocol parameters. This is followed by the development of algorithms that can be used to classify a network based on information regarding node contacts. Lastly, we apply these algorithms to a selected set of mobility models in order to illustrate how our classification approach can be used to provide insight into wireless and mobile network design and operation.