Evaluation of MAC contention techniques for efficient geo-routing in vehicular networks

In this paper we provide a novel performance evaluation methodology and fair comparison of the most relevant MAC-network cross-layer proposals for efficient geo-routing in the context of vehicular networks. In particular, GeoNetworking, the standard European network layer protocol for vehicle-to-vehicle (V2V) communications, proposes Contention-Based Forwarding (CBF) as basic forwarding mechanism, which can be also implemented at MAC layer in order to optimize its operation. A categorization and unified formal description of different proposals for such contention-based mechanisms is provided. We not only qualitatively discuss them, but also derive a more precise mathematical description of the operation of the proposals. Then we put forward a common framework for the analysis of their performance in the critical scenario of emergency warning delivery. Interestingly, with this model the performance metrics can be computed even when each vehicle selects its contention slot in a different way, unlike other models. This approach is validated by a thorough evaluation of the selected proposals in single-hop and multi-hop scenarios under ideal propagation conditions with both the proposed model and simulations. Finally, these techniques are also evaluated under more realistic fading conditions and compared with the purely network-layer implementation of CBF.