Contention window analysis for beaconing in VANETs

The recently standardised IEEE 802.11p Wireless Access in Vehicular Environment (WAVE) protocol is envisioned to be used for Vehicle-to-Vehicle and Vehicle-to-Infrastructure communications. We provide an analysis of 802.11p´s performance when used for the exchange of small status messages known as beacons. These beacons enable vehicles to establish a Cooperative Awareness from which many applications can draw their inputs. Applications have been proposed to increase safety, efficiency and comfort of future road traffic. This paper investigates the impact of adapting settings for the Contention Window (CW) based on the traffic density in order to increase the efficiency of the 802.11p broadcasts w.r.t. reception probability and delay with a focus on real-time vehicle control. In contrast to the literature available on adapting CW settings in unicast, we find that the initial CW value of 15 proposed in the IEEE 802.11p standard performs significantly well under almost all studied circumstances.