An adaptive and reliable integrated MAC mechanism for VANETs

In this paper, we propose a reliable MAC protocol that combines carrier sensing multiple access (CSMA) with self-organizing TDMA specifically for the vehicular ad hoc networks (V ANETs). In this mechanism, the dwelling time ratio between the control channel and service channel can be adjusted according to the vehicle density, so that the wireless resources can be fully utilized. Meanwhile, the distributed MAC mechanism is priority based: it guarantees the QoS requirement for both emergency messages and beacon messages. We verified our scheme through extensive simulations under the IEEE 802.11p setting, and the results demonstrate the superiority of our scheme in the reduction of transmission delay and the packet loss rate, and improvement of throughput 802.11p/1609.4 and SOFT MAC protocols. To the best of our knowledge, this is the first attempt to design an integrated MAC mechanism by considering the access scheme, channel switching and priority setting concurrently.