A Cooperative — Efficient — Reliable MAC protocol for Vehicular Ad hoc Networks

Vehicular Ad hoc NETworks (VANETs), an important part of the Intelligent Transportation System (ITS), should provide the reliable safety message broadcasts and efficient non-safety message transmissions to vehicles. The IEEE 1609.4 MAC is designed for VANETs to support multi-channel operations, but it is neither reliable enough for the safety message broadcast nor efficient enough in the service channel (SCH) resources utilization. In this paper, we propose a Cooperative - Efficient - Reliable multi-channel MAC for VANETs, named CER-MAC, which supports both TDMA and CSMA schemes in accessing the control channel (CCH) and provides cooperation in broadcasting the safety messages. The CER-MAC allows vehicle nodes to send safety messages without collision on the CCH within their reserved time slots or the time slots permitted by the neighbors. Moreover, the CER-MAC utilizes the SCH resources during the control channel interval (CCHI) for the non-safety message transmissions. Compared to the current IEEE 1609.4, the proposed CER-MAC protocol outperforms in the reliability for the safety message broadcast and the efficiency for the service channel utilization.