Réseaux de Capteurs Sans Fils Véhiculaire Sûrs de Fonctionnement

Abstract

Aiming to the main purpose of improving road safety and entertainment, Vehicular Ad Hoc Networks (VANETs) have emerged as an open and interesting research topic in the last decade. The deployment of VANET systems coupled with sensor technologies has increased the gained bene ts from the development of these latter. Thus, they enable real-time data gathering and sharing, so that new applications, such as tra c reporting, relief to environmental monitoring and distributed surveillance are promoted. The design of reliable, fault-tolerant, maintainable, safe and secure applications and standard for realistic and large-scale deployment environment, like in VANETs presents extraordinary challenge, especially in the lack of global memory enabling global system state recognition. In this context, the requirement of clock synchronization remains one of the most signi cant issues that should be addressed to the extent of that dependable systems evolve. The focal point of this Doctoral dissertation is to give an analytical study of clock synchronization issue in vehicular communication systems. The intrinsic characteristics of the unstable vehicular environ- ments, such as the high speed of nodes and the lack of permanent network connectivity have created new challenges and requirements, so that the solutions that have already proposed to synchronize nodes in clas- sical networks are no longer appropriate. Consequently, new and adaptive clock synchronization mechanisms should be devised and implemented. Here, we propose a new mechanism for synchronizing clocks in vehicular environments, dealing so with communication and scalability issues. The proposal, named as \O sets Table Robust Broadcasting" (OTRB), exploits the broadcasting channel to spread the time information over the entire network. This protocol is well-adapted to random network topology changes, high node velocity while o ering good precision and robustness against nodes failure and packet loss. The analytical study and protocol simulation for evaluating the system performance, carried out by a combination of VanetMobiSim and NS2 simulators, have yielded convincing results, outperforming those exhibited by the basic referred protocols. keywords Intelligent transportation system, ITS, VANET, WSN, dependability, clock synchronization, fault-tolerant clock synchronization.