An Efficient Time Slot Acquisition on the Hybrid TDMA/CSMA Multi-channel MAC in VANETs

The multi-channel MACs increase the throughput and reduce the collision probability compared to the singlechannel MACs. However, coordination of multiple nodes across multi-channels is non-trivial. Recently, a multi-channel MAC, called HER-MAC, uses both TDMA and CSMA schemes to improve reliability in broadcasting safety messages and efficiency in service channel utilization. Nevertheless, HER-MAC suffers a high collision probability for a large number of vehicle nodes. In this paper, we propose a hybrid TDMA/CSMA multi-channel MAC protocol for VANETs that allows efficient broadcasting of messages and increases throughput on the control channel. Further, our proposed MAC eliminates unnecessary control packet such as HELLO and SWITCH packets in HER-MAC. Analysis and simulation results show that the proposed MAC can provide faster time slot acquisition on the control channel than HER-MAC.