Metrics for Vehicle Density in Urban Environment

Vehicular Ad Hoc Networks (VANETs) have received a great interest either form academia and from industry since a decade because of their potential for Cooperative-Intelligent Transportation Systems (C-ITS). Then many issues have been investigated in order to improve performances of such networks as packet delay, throughput,.. As a consequence, such systems could participate in the future to reduce accidents on the roads and traffic jams. Unicast forwarding over VANETs are usually geographic for one main reason: the nodes are dynamic, then their location change in a continous manner and the network topology is never stable. As a consequence, packet loss is a serious issue which has to be considered with care. Among known solutions to solve this issue, we have to find appropriate metrics to measure paths to be used in order to forward packet in the network. This paper aims to propose a new metrics called Link Connectivity (LC) in order to find the path with the highest connectivity between the source vehicle and the destination vehicle. Then this metrics is a basis for a unicast routing protocol over VANETs in city environment. The proposed approach is able to find the path with higher connectivity in urban environments which guarantees a high packet delivery. This metric has been integrated into a greedy based routing algorithm which has been developed over the simulator OMNET++ and a comparison to the eGyTAR [9] (which is an extension to GyTAR protocol [6]) is discussed We have conducted extensive simulations with different scenarios to evaluate the scalability of the approach and the robustness against frequent topology changes. As a conclusion, we have observed that this metrics has a positive impact on some performance indicators as packet delivery ratio, end-to-end delay and overhead compared to eGyTAR protocol.