Reliable Delivery of Warning Messages in Partitioned Vehicular Ad Hoc Networks

Topology partition imposes significant challenge on reliable delivery of warning messages to vehicles in the zone of relevance (ZOR) in Vehicular Ad Hoc Networks (VANETs). In order to improve the probability of delivering warning messages to all vehicles in the ZOR, VANETs rely on periodic broadcast to disseminate warning messages, which brings the problem of how to set proper message lifetime for the warning message. In this paper, in order to analyze this warning message propagation process and suggest a proper message lifetime for the V2V network, we first propose analytical models to study the warning message propagation process in the connected and partitioned network. Then, based on the proposed models, we derive the delivery probability under different traffic conditions. Finally, through numerical results, we evaluate the impact of traffic characteristics on the setting of the message lifetime. Our results show that the warning message propagation process depends on some vehicle traffic characteristics, e.g., vehicle density, speed and dangerous time. Our results also show that when the message lifetime increases to certain values under different traffic conditions, it will not increase the delivery reliability, but only cause serious redundancy.