On bounding information dissemination delay in vehicular networks

Supporting QoS for safety-critical applications for intelligent transportation systems accentuates the analytical modeling of delays in vehicular networks. Such analysis is, however, challenging due to the dynamics of such a network. We make progress by deriving lower- and upper-bounds for information dissemination delays in multi-hop vehicular networks using two different routing schemes. In particular, we determine the probability that a message m in a vehicular network will be delivered successfully to a participant at distance x from the source within t time units. Messages are broadcast at each hop after a MAC layer delay and nodes in the transmission neighborhood receive the message with some probability which represents the packet loss probability. Network density and inter-vehicle spacing are based on recent empirical studies of vehicular traffic. Simulation studies indicate that our model, and associated analysis, does capture the delay characteristics of vehicular networks. In addition, we observe a sharp threshold for message delivery in these networks, i.e., for a fixed distance x there exists a t* such that a message is delivered almost surely to a destination node that is at distance x from the source when the time allowed is greater than t* (And, it is almost surely not delivered if the time allotted is less than t*.) We believe that this is a promising step towards accurate characterization of communication delay in vehicular networks.