Phase Transition Behavior of Message Propagation in Delay Tolerant Vehicular Ad Hoc Networks
Ashish Agarwal, David Starobinski · 2008
The vehicular networking environment is characterized by time-varying traffic density and relatively high vehicular mobility rates. Enabling networking in the vehicular environment is challenging due to the rapidly changing topology and the vast network of roadways. In this article, we present an analytical model to describe the behavior of message propagation in a delay tolerant network formed over moving vehicles. We describe a model where partitioning between connected subnets exists in a network with time-varying topology. A messaging scheme exploits the time-varying partitioning to enable data exchange in a delay tolerant network setting. We derive the bounds for performance of message propagation in the vehicular networking environment. The analytical bounds derived are compared with simulation results for characteristics of the vehicular networking environment such as vehicular traffic density, transmission range and vehicular speed. The results depict the observation of phase transition in message propagation rate with increasing vehicle traffic density. Importantly, we are able demonstrate the limits of densities of bi-directional vehicle traffic at which the transitions occur. The results show that the delay tolerant networking assumption provides gains for message propagation over traditional ad hoc networking schemes that rely on path formation. Finally, we show that increased mobility of vehicles actually aids in message propagation, contrary to the expectation that it would be a hindrance due to frequent topology changes. This work is supported by the NSF under grant No. CNS-0435353. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science