On improving delay performance of IEEE 802.11p vehicular safety communication

Abstract

In this work, we present the design of an efficient Deterministic medium Access DA for Dedicated Short-Range Communication DSRC vehicular safety communication over IEEE 802.11p, called Vehicular DA VDA. VDA supports two types of safety services emergency and routine safety messages with different priorities and strict requirements on delay, especially for emergency safety messages. VDA processes both types of safety messages to maintain a balance between two conflicting requirements: reducing chances of packets collisions and lowering the transmission delay. VDA allows vehicles to access the wireless medium at selected times with a lower contention than it would otherwise be possible within two-hop neighbourhood with the classical 802.11p EDCA or DCF schemes. Besides, we propose an improvement of VDA called Dynamic VDA opportunities Re-assignment DVR to avoid network performance degradation caused by interference outside the two-hops. Particularly, our scheme provides an efficient adaptive adjustment of the Contention Free Period CFP duration to establish a priority between emergency and routine messages. Simulations show that the VDA scheme, used with 802.11p, clearly outperforms 802.11p alone in high-offered load conditions while bounding the transmission delay of safety messages. Furthermore, beyond two-hops, DVR is able to efficiently tackle the interference phenomenon by reducing losses and delays of safety applications.