Research for quality assurance type multicast systems

发送者收集关于每条链路的通信质量的所有信息，并在现有的质量保证型组播系统中构建最佳递送树。然而，收集通信质量信息的假设在大规模系统中的可行性存在问题。在控制报文泛洪的情况下，提出了一种在传播过程中加入通信质量信息的路径选择方法，并对其有效性进行了评估，同时在质量保证型组播系统中需要一种有效的重传控制。特别是在像自组织网络这样的无线网络上，有效的重传控制对网络质量有很大的影响。该研究的特点是在自组织网络中通信链路断开的路径上进行重传，而不需要通过本地恢复来重新搜索过去的传输路径。支持组是作为通常的路径搜索算法的副产品形成的。并且，该概念用于监视通信链路、检测断开连接、分组重传以及在本地构建替代通信路径。支持组很少开销，因为它是从通常的路径搜索过程中产生的。此外，由于对分组丢失的恢复是在本地且快速地完成的，因此重传机制在实时数据传输中可以是有效的。通过ODMRP和仿真实验对这些算法进行了比较。因此，我们提出的方法提高了过去方法的分组到达率。此外，实验结果表明，该方法可以使重建间隔比以往的方法更长。这一结果被作为国际会议论文提交。

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.