DBA-MAC: Dynamic Backbone-assisted Medium Access Control Protocol for Efficient Broadcast in VANETs

Active safety systems based on dissemination of alert messages are one of the most important applications of Vehicular ad Hoc Networks (VANETs). These systems typically require to provide efficient and reliable delivery of safety information to all the vehicles travelling over a geographical area. Reducing the delivery delay is also a crucial issue due to the real-time nature of the communication. To meet these requirements, in this paper we design a cross-layered MAC and clustering solution for the fast propagation of broadcast messages in a VANET. A distributed dynamic clustering algorithm is proposed in order to create a dynamic virtual backbone inside the vehicular network. The vehicle-members of the backbone are responsible for implementing an efficient message propagation. The backbone creation and maintenance are proactively performed aiming to balance the stability of backbone connections as well as cost/efficiency trade-off and hops-reduction when forwarding the broadcast messages. A fast multi-hop MAC forwarding scheme is defined to exploit the role of backbone vehicles, under a cross-layered approach. Simulation results show that our cross-layer scheme guarantees high message delivery ratio, reduces the delivery delay and provides efficient channel utilization when compared with other dissemination schemes for VANETs.