Towards supporting GPS-unequipped vehicles in inter-vehicle geocast

IVG (inter vehicle geocast) is a GPS-based inter-vehicle communication mechanism used for alarm message dissemination among vehicles in a highway in risk situations. In this paper, we propose an improvement to IVG towards supporting its interoperability in environments where "GPS-U" GPS-unequipped vehicles are present. They are vehicles that are not equipped with GPS devices or they have some problems to obtain their positions, via GPS, due to some obstacles. The proposed solution allows GPS-U vehicle to compute its position with the help of its neighbors that are equipped with GPS devices, called GPS-E neighbors. Analyses show that the optimal performances of IVG can be reached even when the rate of GPS-U vehicle is 40%.