The dedicated short range communications (DSRC) system is applicable to the various fields, such as parking lot management and drive-through system, by making use of the spot zone service characteristics and electronic toll collection (ETC) technology. On the other hand, the cellular networks and the car navigation systems are very popular and cover wide service area; therefore the intelligent transportation systems (ITS) networks using DSRC system should be cooperated with the above existing system efficiently in order to give drivers many sophisticated ITS services. In ITS services, there are many cases of transferring the same data such as traffic information and navigation map requested by many users. The authors propose the "Pull-data type" and "Push-data type" ITS multicast service and its realizing mechanism. These multicast services can reduce the communication traffic, therefore save the rather network resources efficiently, moreover can inform the nearby drivers quickly and precisely by making use of the short range communication characteristic. To accomplish these ITS multicast services, the authors adopt "multicast LID" and "multicast routing" mechanism in DSRC networks and on-board equipment (OBEs). This mechanism is similar to IP multicasting protocol in the Internet and multicast service in the cellular and satellite communication networks. But DSRC service zone is very narrow and servicing RSU may change frequently depending on high-speed driving; moreover almost ITS information such as traffic and weather information should be transmitted cyclically as a uni-directional renewal data in order to announce the current status. So they propose a unique register and handover mechanism which is different in the cellular communication system.
Abstract