PSCAR: a proactive-optimal-path selection with coordinator agents assisted routing for vehicular ad hoc networks

In this paper, we propose the Proactive-optimal-path Selection with Coordinator Agents Assisted Routing (PSCAR) protocol for Vehicular Ad hoc NETworks (VANETs) in an urban environment. The main idea of PSCAR is to contribute static nodes as coordinator agents placed at each intersection, in order to improve the routing performance and to deal with radio obstacles (buildings, trees...) and voids as encountered in urban environments. Since the coordinator agents are static nodes, each one knows all the paths to any other coordinator agent in the network. Thus, instead of searching an optimal path toward the destination node, PSCAR will determine an optimal path to the nearest coordinator agent to the destination node so as to better anticipate any change of the destinations position. The optimal path is selected according to two criteria: the total physical distance and the vehicle density on the path. The vehicle density is estimated based on a fundamental diagram of the traffic that allows estimating the vehicular traffic density on each road segment. To evaluate the performance of PSCAR we used the Network Simulator 2 (ns-2) and the mobility simulator SUMO. We compare our scheme with some existing solutions with the aim of showing its effectiveness, in terms of packet delivery ratio, end-to-end delay, and network overhead.