Characterization of a large-scale Delay Tolerant Network

In this paper, we present a thorough characterization of the spatio-temporal communication graph of a large-scale real-world vehicle-based Delay Tolerant Network (DTN). Unlike previous studies which either use synthetic mobility traces or data from small networks (<; 50 nodes), our analysis is based on the mobility patterns of a large scale (~ 1200 nodes) real-world public transport network. In particular, we examine the node degree distribution, encounter patterns, periodicity and clustering behavior, properties that are particularly relevant in the context of data forwarding in DTN. Moreover, we also study the impact of different radio propagation models on these properties. Our extensive study demonstrates that public transport networks exhibit repetitive patterns and corroborates the existence of few highly connected nodes, termed as hubs, in these networks. We have also found that the degree distribution of nodes and the inter-contact durations follow the properties of power-law distributions. We provide insights on how these properties can be leveraged to design effective communication protocols for such large-scale DTN.