Enhanced DCF MAC scheme for providing differentiated QoS in ITS

Road-to-vehicle communication (RVC) system supports multiple services in future intelligent transportation systems (ITS). To meet different QoS requirements especially on delay, it is important to differentiate data traffic of different applications. However the upcoming Northern American DSRC standard based on IEEE 802.11a specification uses legacy DCF MAC and it lacks support for QoS differentiation, which is crucial in future multi-service RVC system. We analyzed different QoS requirements of the various possible applications in ITS and propose to use enhanced DCF (EDCF) for future RVC systems. We compared performance of EDCF vs. DCF in ITS RVC system and also evaluated different contention parameters' impact in EDCF. Simulation result showed that under most situations, EDCF gives prioritized access to different traffic and meets the QoS requirements for the delay-sensitive applications, which cannot be met using legacy DCF. However, a proper and adaptive parameter setting is necessary to achieve the performance especially under high system load situations.