Using EDCA to improve vehicle safety messaging

The effectiveness of DSRC for collision avoidance depends on the communication performance of safety messages. EDCA, the standard IEEE 802.11 QoS capability, was designed for networks with a mix of voice, video and best effort traffic. This paper examines how to use EDCA to reduce frame collisions for a channel dominated by periodic safety messages. The paper makes two main contributions: Access Category (AC) Isolation and Virtual Division. AC Isolation eliminates inter-AC countdown collisions, dramatically improving the success rate for high priority packets. Virtual Division uses isolation in a novel way that also reduces collisions for lower priority packets. Both techniques are consistent with the 802.11 standard. The paper includes both detailed analysis and insightful NS-2 simulations.