A multicast protocol in ad hoc networks inter-vehicle geocast

The intelligent transportation systems ITS cause a significant passion since the appearance of new inter-vehicles communication mechanisms based on mobile networks. The wireless ad hoc networks, completely distributed and not depending on infrastructures, allow the fast and cheap development of such mechanisms. This article concerns multicast in wireless ad-hoc networks applied to ITS. We propose a new protocol called IVG inter-vehicles geocast which consists in informing all the vehicles of a highway about any danger such as an accident or any other obstacle. In this case, risk areas are determined according to the driving direction and the positioning of the vehicles. These vehicles define a restricted broadcast group, so-called, multicast group. Multicast group, contrary to the classical methods, which use node identities, is defined temporally and dynamically by the location, speed and driving direction of vehicles. Some simulations thanks to Glomosim tool, for which we have defined a model for the road transport, and studies of the complexity are given. The results show that IVG is an efficient broadcast method for secure highway transportation and reduces the number of useful messages.