Developing real-time safety and nonsafety applications for vehicular ad hoc networks (VANETs) requires understanding of the dynamics of the network topology characteristics since these dynamics determine both the performance of routing protocols and the feasibility of an application over VANETs. Using various key metrics of interest, including node degree, neighbor distribution, number of clusters, and link duration, we provide a realistic analysis of the VANET topology characteristics over time and space for a highway scenario. In this analysis, we integrate real-world road topology and real-time data extracted from the freeway Performance Measurement System (PeMS) database into a microscopic mobility model to generate realistic traffic flows along the highway.
Moreover, we use a more realistic, recently proposed, obstacle-based channel model and compare the performance of this sophisticated model to the most commonly used and more simplistic channel models, including unit disk and lognormal shadowing models. Our investigation on the key metrics reveals that both lognormal and unit disk models fail to provide realistic VANET topology characteristics. We therefore propose a matching mechanism to tune the parameters of the lognormal model according to the vehicle density and a correlation model to take into account the evolution of the link characteristics over time. The proposed method has been demonstrated to provide a good match with the computationally expensive and difficult-to-implement obstacle-based model. The parameters of the proposed model have been validated to depend only on the vehicle traffic density based on the real data of four different highways in California.