Research for quality assurance type multicast systems

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The sender collected all information on the communication quality of each link and the best delivery tree was constructed in an existing quality assurance type multicast system. However, assumption of collecting communication quality information had the problem in the feasibility in a large-scale system. In this research, when the control packet was flood, it proposed a new method to decide the path while spreading adding communication quality information, and the effectiveness was evaluated.Moreover, an efficient retransmission control is needed in the quality assurance type multicast system. Especially, an efficient retransmission control has a big influence in the network quality on a wireless network like an ad hoc network. The feature of this research is a method which retransmits in the path to which the communication link in an ad hoc network disconnects without searching for a past transmission path again by local recovery.We introduced the concept of support group for local recovery. The support group is formed as a by-product of a usual path search algorithm. And, the concept is for the watch of the communication link, the detection of the disconnection, the packet retransmission and to construct an alternative communication path locally. The support group is few the overhead because it is made from the process of a usual path search. Moreover, because recovery to the packet loss is done locally and quickly, the retransmission mechanism can be effective in a real-time data transfer. These algorithms were compared by ODMRP and the simulation which was the past, ad hoc multicast protocol. As a result, the method that we proposed improved the packet arrival rate of the past method. Moreover, it was shown that our method could make the reconstruction interval longer than the past method. This result was presented as an international conference thesis.