Stochastic Broadcast for VANET

Abstract

Vehicular ad-hoc networks (VANETs) are an emerging important type of wireless ad-hoc network. Unlike many other types of MANETs, VANET applications such as traffic data dissemination are inherently broadcast oriented and require communication protocols to be anonymous and scalable. Simple broadcast flooding satisfies these requirements, but its performance is highly dependent on network density and may lead to the broadcast storm problem. This work is the first we are aware of to propose stochastic broadcast as a solution for VANET. Stochastic broadcast instructs nodes to rebroadcast messages according to a retransmit probability. Such a scheme is private since node identification is unnecessary, however it has an undesirable dependency on vehicle density in the same manner as simple flooding. To solve this problem, we demonstrate the link between the mathematical science of continuum percolation and stochastic broadcast. Specifically, that the critical percolation threshold in continuum percolation (¿ 4.5 expected neighbors) translates to the wireless broadcast context. Then we show that nodes can tune the performance of the broadcast system to efficient levels by adjusting the retransmit probability so the apparent density of the network approaches the critical threshold.