Empirical study on taxi GPS traces for Vehicular Ad Hoc Networks

Inter-contact time (denoted as T_I) between mobile nodes that captures the temporal characteristics of Vehicular Ad Hoc Networks (VANETs) has been intensively studied. Whereas the node spatial distribution is ignored in most existing mobility schemes, which is also worthy of investigation, particularly for real applications. Moreover, the node spatial distribution has a significant influence on the inter-contact time. In this paper, we study the empirical data acquired from taxis in Shanghai city. We find that most taxis distribute on some hot roads which makes the node spatial distribution appear power law. Based on this observation, we propose the concepts of indirect contact and heterogeneous inter-contact time (represented as T_H) to reveal how hot roads can change the distribution of inter-contact time. By investigating the empirical data, we show that the T_H distribution also appears power law.