Characterization and modeling in large-scale urban DTNs

In Delay Tolerant Networks (DTNs), characteristics of mobility model have essential impact on routing protocols design and verification. Most of current studies about network characteristics are derived from theoretical models or small-scale real network traces. Properties of nodes in those networks are simple and can not reflect features in large-scale applications. In addition, few studies focus on modeling large-scale urban DTNs based on the network characteristics. In this paper, we analyze a large-scale urban DTN including traces from 12096 taxies in Beijing City. We observed that inter contact time (ICT) between two nodes satisfies exponential distribution, and the network forms a number of hotspot areas in which the vehicles tend to cluster. Based on the observation, we design a DTN mobility model by introducing characteristics of hotspot area and prove that distribution of ICT in this model also exhibits exponential nature as it is in real urban DTNs. Our further simulation experiment reveals the similarity between the proposed model and urban DTNs. This result thus demonstrates that the model is rational to guide DTN protocols design and verification in large-scale applications.