A concurrent transmission enabled cooperative MAC protocol for Vehicular Ad Hoc Networks

In the infotainment applications over Vehicular Ad Hoc Networks(VANETs), the Roadside Units (RSUs) often play the roles of data switching centers. However, the RSUs tend to be the bottlenecks in the data dissemination because of the limited channel bandwidth and heavy traffic loads. In order to improve the throughput of the RSUs, we devise a new MAC protocol Mizar from a cross-layer design perspective. Mizar concentrates on improving the spatio-temporal efficiency in disseminating data from an RSU to the moving vehicles. Leveraging the space diversity of wireless signals, Mizar increases the channel utilization by the cooperative transmission. Moreover, motivated by the location distribution characteristics of the vehicles, Mizar seeks to catch the concurrent transmission opportunities generated in the process of the cooperative communication. It is shown from the experimental results that Mizar can increase the throughput and decrease the transmission delay significantly in comparison with the fixed data rate scheme of IEEE 802.11p, the variable data rate scheme and the cooperative transmission scheme in Mizar.