Characterizing the connectivity of large scale Vehicular Ad-Hoc Networks

Modeling complicated vehicular mobility behavior and the associated network connectivity in large scale vehicular ad hoc network has been a challenging problem for the past several years. In this paper, we carry out extensive experiments involving thousands of operational taxies in Shanghai and Beijing cities. Studying the taxi traces on the vehicular connectivity, we observe that the vehicle isolation probability exhibits an exponential decay with the increase of transmission range. This observation is in sharp contrast to the most widely used system models such as Random Way Point and Random Walk, where the vehicle isolation probability changes with transmission range as exp(-λR²), where R is the transmission range. We propose a simple theoretical model to explain the exponential decay of vehicle isolation. Validation of our model is carried through comparisons between the synthetic trace and the real trace, and the results show that our mobility model has a good approximation to the real scenario. Our results give insights on the behavior of connectivity, thus providing fundamental guidelines on design of new vehicular mobility models, new data forwarding protocols and their performance analysis.