A Probability Based MAC Channel Congestion Control Mechanism for VANET

A significant issue in VANETs (Vehicular Ad Hoc Networks) is the design of an effective MAC (Medium Access Control) or broadcast scheme which can facilitate the fast and reliable dissemination of critical safety messages to neighboring vehicles in case of an unexpected event. Broadcasting of data and control packets is expected to be crucial in vehicular environment. Most of the broadcasting packet is designed to be delivered on a given frequency during the control channel (CCH) interval set by the IEEE 1609.4 standard [1] (which provides enhancements to the IEEE 802.11p MAC by supporting multi-channel operation). In this paper, the probability based MAC channel congestion control mechanism is developed to cope with rapid topology changes, i.e., vehicles entering and leaving the network, as well as overloaded situations in terms of increased number of vehicles and/or increased amount of data traffic injected without collapsing. Method is also based on the estimation of potential neighboring vehicles through broadcasting Hello messages, and then based on probability model to calculate the expected offset slots for reduce the collision situations, and thus improve transmission performance.