A reliable advanced-join system for data multicasting in ITS networks

A number of mobile hosts (MHs) might be densely grouped in an area caused by traffic congestion. In such a situation, the greater part of the MHs will require useful data, such as traffic information, parking information, and other driving-related information. Simultaneous data-transmission broadcasts using a common link are regarded as a suitable medium to distribute this location-dependent information. However, there is no guarantee that MHs can finish receiving the information completely within a limited time. In this paper, we propose a reliable multicast system that consists of a multicast-group-management method called "Advanced-Join (AJ) system", a data-retransmission method, and a data-recovery-processing method. A "base station (BS) multicast group" is defined as the set of BSs in a certain area to which MHs belonging to the same multicast group connect. The AJ system allows a BS that is a member of a BS multicast group to make consolidated join requests to a multicast group on behalf of its MHs. The data-retransmission method determines and processes retransmission data by coordinating retransmission requests from two or more MHs that are members of the same multicast group. The data-recovery-processing method performs interactive data recovery between BSs belonging to the same BS multicast group. By controlling the members of the BS multicast group according to the movement of MHs and deciding the retransmission packets, it is expected that message traffic for the multicast-group management will be reduced, and packet loss during an MHs\´ movement between BSs will be eliminated. Evaluation results show that about 86.8% of MHs complete data reception with the proposed system, while only two MHs complete reception with the simple broadcast system. In addition, the proposed system with the data-retransmission method needs only two-thirds of BSs compared with that without retransmissions.