MAC layer extensions for improved QoS in 802.11 based vehicular ad hoc networks

Highway safety, collision avoidance and road traffic congestion control are emerging applications of vehicular ad-hoc networks. Inter-vehicular communication could increase driver awareness and distribution of information among vehicles on the road. The safety messages being transmitted or exchanged between vehicles are usually short and have ephemeral utility. Ad-hoc networks of this kind also tend to have a large number of contending nodes. Our work proposes MAC layer extensions to the 802.11e variant of the 802.11 WiFi standard, applied in such scenarios. We describe possible messages that may be transmitted and classification of messages based on urgency. Our enhancements reduce redundancy in safety message broadcasts, by avoiding multiple transmissions of the same report, providing for more optimized channel utilization, especially in cases when a common obstacle generates a similar message at every vehicle within an area.