Combined cellular/direct method of inter-vehicle communication

The use of inter-vehicle communication (IVC) is considered as an integral part of future intelligent transportation systems. However, most research has focused on communications for the purpose of controlling vehicles to improve safety. Along with this kind of communications, direct high-speed links between specific vehicles should also be considered. For point-to-point communication links between vehicles, communication is difficult when vehicles are far apart. Use of the cellular network (such as IMT-2000) for inter-vehicle communication is possible, but the speed of the link is limited to 144-384 kbps. Furthermore, the cost of continuous communication is extremely high. A combined cellular/direct link would provide a high-quality link, while at the same time reduce the transmission costs. In this paper, the hand-off rate of such a system is examined and a hysteresis factor is proposed to reduce the number of hand-offs when switching between the direct link and the cellular system.