基于服务质量的多媒体组通信目的节点加入与退出算法的研究

路由选择机制是分布多式媒体系统中的重要研究方向。其中，基于服务质量的多媒体通信目的节点加入与退出算法是关键组成部分。该文在基于服务质量的多媒体通信初始路由建立算法的基础上，基于资源共享原则，提出支持成员动态加入与退出多媒体组通信的目的节点加入与退出算法，以增加使用费用最小为目标在满足服务质量约束的条件下完成目的节点加入，在不影响多媒体组通信服务质量的前提下，在完成目的节点退出的同时最大限度地释放已占用资源。文中还探讨了这些算法的有效性。它们和基于服务质量的多媒体通信初始路由建立算法相结合，可以提供对分布式多毁体组应用服务质量保证的支持。

Research on Quality of Service Based Destination Node Joining and Leaving Algorithms for Multimedia Group Communication

QoS(Quality of Service) Routing mechanisms are important research directions in distributed multimedia systems. For multimedia dynamic group communication, routing mechanisms should support the solving of the following three problems: QoS based initial route setup, QoS based group member joining, and QoS based group member leaving. In this paper, with the support of the QoS based initial route setup algorithms, based on resource sharing principles, QoS based destination node joining and leaving algorithms are presented. The key ideas of the proposed QoS based destination node joining algorithm are as follows: under certain constrains and with resource sharing principles obeyed, finding a minimum incremental usage cost path from the source node to the newly joined destination node, at the same time, leading to the optimal resource (such as CPU, buffer, bandwidth) utility and guaranteeing end to end delay and end to end error rate requirements to the maximum degree. It can be called as source node initiated one pass destination node joining algorithm. In addition, it can avoid loop occurrence along the route when new destination nodes joining. The main idea of the proposed QoS based destination node leaving algorithm is as follows: with multimedia dynamic group communication QoS unaffected, trying to release the occupied resources(such as CPU, buffer, bandwidth) by the group along the route to the maximum degree as the destination node leaving from the group. Thus, it can improve the network resource utilization. The correctness of two proposed algorithms is also discussed. Simulation results show that they are effective and efficient. Combined with the QoS based initial route setup algorithms and with the help of other QoS control mechanisms (such as resource reservation, admission control, QoS accounting and QoS negotiation, etc), the QoS guarantees for distributed multimedia group applications could be supported by these proposed algorithms.