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.
VANETs inherit a conservative channel access control mechanism from IEEE 802.11 standard to mitigate the hidden terminal problem on the service channels, i.e., once a service channel is reserved by a node, all its neighbors in 2-hop range are prohibited from initiating the transmission simultaneously. To improve the channel utilization and increase the network capacity, we propose an optimistic distributed power control scheme, which relaxes the limitations on the 2-hop neighbor's data transmission and creates opportunities to start concurrent transmissions. The experimental results indicate that our scheme shows significant advantages over the fixed power scheme of IEEE 802.11p and Density-based Power Control (DBPC) [1] in terms of the average delay and throughput.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.