CTMAC: A cooperative TDMA MAC in vehicular ad hoc networks

This paper proposes a reliable MAC protocol for a fully distributed Vehicular Ad-Hoc Network (VANET) using the slot states sharing scheme. Recently, technology for reliably transmitting safety messages in VANET has become an issue. With VANET (operating on the IEEE 802.11p standard), as the number of vehicles increases on the highway, the network traffic also increases. It causes more frequent packet transmission failures, and communication failures among vehicles can threaten human safety. VANET has a distributed network topology, so the hidden terminal problem is the biggest concern for researchers. In addition, there are other problems that can occur in wireless mobile nodes' environments, called a merging collision and an access collision. Dealing with these problems has required big overheads to exchange the channel usage states including the slot owner's ID. Therefore, we propose a CTMAC(Cooperative TDMA MAC) that shares the states of all time slots which indicates whether the vehicle has received the packet in each time slot or not. Through CTMAC, more nodes can communicate in the channel duration under reliable channel scheduling.