【作者】 熊燕；

【导师】 许晓东；

【作者基本信息】 华中科技大学 ， 系统工程， 2005， 硕士

【摘要】 现代远程教育是将数字化技术、网络通信技术、多媒体技术、计算机技术等现代信息技术相结合的新型教育方式。为了解决目前现代远程教育中存在的一些问题,本文就远程教育中基于Web 实现的非实时教学系统的优化与设计问题展开了研究和论述。本文从远程教育的发展及特点出发,介绍了非实时教学系统的结构和功能,阐明国内外研究的现状及本文研究的内容。然后就本文的理论基础——排队理论的相关数学知识作了简要阐述。根据非实时教学系统的网络拓扑结构,可运用排队论对该系统进行系统性能分析。本文研究的重点是系统通信强度ρ,用户到达率λ和系统信道容量n 与系统等待延迟、阻塞概率、平均队长、系统吞吐量等重要性能指标之间的定量关系。由此提出如何在其他参数不变的情况下对服务器台数的配置问题。在非实时教学系统网络性能的优化问题中,本文针对多媒体通信的特点,提出了一种基于服务质量(QoS)的动态路由选择的方法,可实现不同要求的多媒体数据动态路由选择。它能够根据网络现有资源状况来决定多媒体流的路径,在网络层通过路由机制实现了不同的QoS 业务。文章最后集中研究了一个非实时教学系统的实现。其中重点阐述了点播系统的设计和实现,具体针对分布式执行服务器配置问题进行了定量的计算。总之,本文提出对集中式管理分布式点播服务教学系统从系统结构和网络性能两方面的优化,既有模型的理论分析又有实际系统的实现。这一系统在提高资源利用率、减小用户等待时间、增加系统吞吐量方面取得了良好地效果。更多还原

【Abstract】 Modern distance education system is a system, which combines the knowledge of digital technology, network communications technology, multimedia technology and computer technology. In order to solve some problems existing in Distance Education of Network at present, this thesis studies and discusses optimizations and designs of the non-realtime education system which is realized based on web. At first, the overview of development and situation of distance education are firstly demonstrated. Then characteristics of distance education and functions of the non-realtime education system are described. And next,, Queuing theory —the theoretical foundation of this thesis and mathematic theories are introduced in brief. In the part of the optimization of network structure, the thesis has made a detail analysis on the queuing models used in system design and performance of a CODs, the quantitative relationship among the following factors is emphatically studied: traffic ρ, users average arrive λ, system channel capability n, system latency probability, blocking probability, mean queue length, system throughput and so on. Another mainly discusses in this paper is the optimization of network performance. We put forward a dynamic routing method based on QoS for multimedia, which dynamic chooses route for multimedia data according to not only different requirements but also the existence resource status of the net, implement different QoS services in network layer through routing mechanism. Lastly, thesis focuses on the designs and realization of a non-realtime education system. All in all, a distance non-realtime education system with centralized management and distributed Courseware-On-Demand servers is introduced in this thesis. We do the work from theoretical analysis of model to the design and realization of real system. This system improves the utilization ratio of resources, decreases the waiting time of clients, enhances throughput of the system.更多还原