CMAC: A cluster based MAC protocol for VANETs

The messages in a VANET environment are short with limited time value. The aim of a MAC protocol is to deliver these messages with high reliability and low delay. To guarantee this in a high mobility and fluid topology environment, the contention period over the shared wireless channels must be minimized. In this work, an RSU centric cluster based MAC (CMAC) protocol has been proposed. In this protocol, the channel allocation and management is transferred to the RSU to obviate channel contention for reliable delivery of messages. The RSU region is divided into prefixed clusters with frequency reuse in non adjacent clusters. The frequency reuse increases the available bandwidth and reduces the waiting time of a node for channel allocation. The traffic and the VANET topology is generated separately and used to determine the effectiveness of CMAC protocol. Results indicate that the protocol has high throughput even when the number of vehicles is high and also for large clusters in an RSU region. This high packet reception ratio indicates the efficacy of the protocol for high reliability low delay delivery of messages in a VANET environment.