Section: New Results

Multicast communications for cooperative vehicular systems

Participants : Ines Ben Jemaa, Oyunchimeg Shagdar, Paul Muhlethaler, Arnaud de La Fortelle.

With the advancement of wireless communications technologies, users can now have multicast services while they are driving. Majority of the multicast services require Internet-to-vehicle multicast message dissemination. 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 configured to receive the service. In addition to this, multicast packets flows follow a fixed routing 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 first issue, we find that neither current multicast addressing nor existing mobility management mechanisms are suitable for VANET. We introduce first a self-configuring multicast addressing scheme that allows the vehicles to auto-configure a dynamic multicast address without a need to exchange signalling messages with the Internet. Second, we propose a simplified approach that extends Mobile IP and Proxy Mobile IP. About message dissemination, we first propose to revisit traditional multicast routing techniques that rely on a tree structure. 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, we propose then Motion-MAODV, an improved version of a tree-based routing mechanism (MAODV) that aims at guaranteeing longer route lifetime. Finally, we also propose a geographic routing protocol Melody that provides a geocast dissemination in urban environments. Through simulations, we show that Melody ensures more reliable and efficient packet delivery to a given geographic area compared to traditional geo-brodcasting schemes in highly dense scenarios. More detail can be found in [28] , [41] , [47] .