CM-MAC: A Cluster-Based Multi-Channel MAC Protocol for VANET

VANET (vehicular ad hoc network) is a new kind of MANET (mobile ad hoc network) for ITS (intelligent transportation system). With the development of vehicles and mobile ad hoc network technology, VANET has become an emerging field of research, which is envisioned to provide a variety of safety applications (such as collision avoidance and warning systems) that require high reliability and bounded delay and non-safety applications (such as Internet access and electronic commerce) that are throughput sensitive. This paper proposes a stable clustering algorithm according to VANET features. On the basis of this algorithm, according to DSRC (dedicated short range communication) allocation of CCH (control channel) and SCH (service channel), considering the wireless communication interference between vehicles and the QoS requirements for different applications, the paper also proposes a cluster-based multi-channel hybrid MAC protocol. The non-competition based TDMA scheme is taken for intra-cluster communications and the competition based CSMA/CA scheme is taken for inter-cluster communications. The different SCHs are allocated for neighbor clusters. Such a concept is attractive as it can be combined with cluster-based routing strategies. So the overhead introduced by the clustering process is beneficial not only on one layer, but for the whole communication process. Simulation experiments show that the protocol is superior to the current MAC protocol in the delay requirement of safety applications and the throughput of non-safety applications.