Multicast communications for cooperative vehicular systems

With the advancement of wireless communications technologies, users can now have multicast services while they are driving. In adding to the traditional multicast applications, developments in vehicular communications allow new multicast emerging applications such as eet management and point of interest (POI). Fleet management, including route guidance of a eet of vehicles, often requires a control/service center, which resides in the Internet, to communicate and provide information to eets of vehicles. Point of Interest refers to a speci c point location (e.g., parking lots, restaurants, or other local facilities) that may be of interest or use to road users in the area. Both of these mentioned applications require Internet-to-vehicle multicasting. Conventional group management approaches in Internet is relatively simple because it is performed on the local networks of the multicast members which are usually a priori con gured to receive the service. In addition to this, multicast packets ows follow a routing structure (usually a tree structure) that is built between the source and the destinations. These approaches could not be applied to vehicular networks (VANET) due to their dynamic and distributed nature. In order to enable such multicasting, our work deals with two aspects. First, reachability of the moving vehicles to the multicast service and second, multicast message dissemination in the VANET. Regarding the rst issue, we nd that neither current multicast addressing nor existing mobility management mechanisms are suitable for VANET. This is because not only they do not t to applications that have a geographic scope but also they do not allow spontaneous joining and they may create routing problems. We introduce rst a self-con guring multicast addressing scheme that allows the vehicles to auto-con gure a dynamic multicast address without a need to exchange signalling messages with the Internet. Second, we propose a simpli ed approach that extends Mobile IP and Proxy Mobile IP. This approach aims at optimizing message exchange between vehicles and entities responsible for managing their mobility in Internet. To study the dissemination mechanisms that are suitable for eet management applications, we propose to revisit traditional multicast routing techniques that rely on a tree structure. For this purpose, we study their application to vehicular networks. In particular, as vehicular networks are known to have changing topology, we present a theoretical study of the link lifetime between vehicles in urban environments. Then, using simulations, we study the application of Multicast Adhoc On Demand Vector, MAODV. We propose then Motion-MAODV, an improved version of MAODV that aims at enhancing routes built by MAODV in vehicular networks and guarantee longer route lifetime. Finally, to enable geographic dissemination as required by POI applications, we propose a routing protocol Melody that provides a geocast dissemination in urban environments. Through simulations, Melody ensures more reliable and ecient packet delivery to a given geographic area compared to traditional geo-brodcasting schemes in highly dense scenarios.