A TDMA-Based MAC Protocol for Efficient Delivery of Emergency Messages in VANETs

It is very necessary to timely report critical events in vehicular ad hoc networks (VANETs) in order to ensure road safety and avoid catastrophic situation. To report critical events within a minimum possible latency, we present a time division multiple access (TDMA) based medium access control (MAC) protocol for efficient delivery of emergency messages (EDEM-TMAC) in VANETs. Instead of relying only on periodic messages, which is commonly adopted by the existing TDMA-based MAC protocols for VANETs, we intelligently employ event-driven messages to optimize efficiency. Access collision problem between event-driven messages and association request messages is resolved by dynamically partitioning the free channel. Simulation results show that compared with the existing MAC protocol, EDEM-TMAC can reduce the delay of reporting critical events up to 99%, and remain enough high packet delivery ratio of emergency messages even at high node density.