Optimal transmission probabilities in VANETs with inhomogeneous node distribution

In a Vehicular Ad-hoc Network (VANET), the amount of interference from neighboring nodes to a communication link is governed by the vehicle density dynamics in vicinity and transmission probability of terminals. It is obvious that vehicles are distributed non-homogeneously along a road segment due to traffic controls and speed limits at different portions of the road, the common assumption of homogeneous node distribution in the network in most of the previous work in mobile ad-hoc networks thus appears to be inappropriate in VANETs. To capture the density dynamics in generic urban routes, we utilize a fluid model to characterize the general vehicular traffic flow, and a stochastic model to capture the randomness of individual vehicles, from which we can acquire respectively the densities of the mean number of vehicles along the road and the probability distribution. With the knowledge of the vehicular density dynamics from the stochastic traffic model, we determine the throughput and progress performances of a routing strategy, and confirm the accuracy of the analytical results through simulations. The analytical model proposed in this paper serves as a fundamental building block for performance analysis of other transmission protocols and network configurations, we also demonstrate that the optimal transmission probability for optimized network performance can be found from our results, which provides insights into system engineering and protocol designs in VANETs.