Dynamic backbone for fast information delivery in vehicular ad hoc networks: an evaluation study

Fast delivery and high reliability are two of the main requirements which must be guaranteed by multi-hop broadcast protocols of alert messages in VANETs. Most of the existing schemes work by selecting the optimal forwarder vehicle at each hop through a distributed contention phase, thus introducing an additional delay in the forwarding process. An alternative approach is to identify the optimal set of relay vehicles before the actual dissemination of the alert messages, by creating and maintaining a virtual backbone of vehicles inside the VANET. For this purpose, we propose here an extended version of the Dynamic Backbone-Assisted MAC (DBA-MAC) scheme which supports fast and efficient multi-hop broadcast communication in VANETs. The DBA-MAC scheme comprises two main components: (i) a distributed clustering scheme, which builds a virtual backbone of vehicles, and a (ii) fast multihop forwarding scheme, which provides contention-free forwarding of the alert messages among the backbone vehicles. Compared to our previous works on DBA-MAC, we proposes here additional metrics for backbone creation which account for the channel receiver characteristics of each vehicle, through the estimation of the Link Budget (LB) between communicating vehicles. Moreover, we show through analytical and simulation results that the performance of the DBA-MAC in terms of delivery delay can be bounded between those of a static backbone with nodes placed at the optimal distance and those of a traditional contention-based scheme, which attempts to select the farthest vehicle at each hop. Finally, through the OMNET++ and SUMO tools, we propose an extended evaluation of the DBA-MAC scheme over realistic urban scenarios by modeling the impact of vehicular mobility and shadowing effects on the protocol performance.