提高P2P视频点播系统服务性能的关键技术研究
文献类型：学位论文
| 作者 | 齐卫宁 |
| 学位类别 | 博士 |
| 答辩日期 | 2008-06-02 |
| 授予单位 | 中国科学院声学研究所 |
| 授予地点 | 声学研究所 |
| 关键词 | 对等网络 视频点播系统 服务质量保证 大规模应用 |
| 其他题名 | Research on Key Techniques to Improve Performances of Service for Peer-to-Peer based Video-on-Demand Systems |
| 学位专业 | 信号与信息处理 |
| 中文摘要 | 流媒体应用是当前互联网领域研究的热点问题之一。视频点播（VoD）改变了传统的用户被动接收的方式，而代之以交互的方式，丰富了人们的娱乐空间，具有极为广阔的应用前景，成为流媒体研究领域的一大热点。传统的C/S模式的VoD系统已经不能够满足现在的需求，无法实现大规模的应用。对等网络（P2P）作为一种新兴的网络模型，为VoD的大规模应用提供了解决方案。充分利用普通节点（Peer）的带宽和缓存资源，提高VoD系统的视频服务质量（QoS），是实现VoD系统全面推广的一个重要前提。但P2P固有的一些特性，如网络的动态变化性、节点的异构性等；和VoD系统的一些特有需求，如大量并发请求问题、节目点播不均匀问题、难以开展大规模测试等为VoD系统的QoS保证带来困难。本文的研究内容就是解决上述问题，为用户提供有质量保证的视频点播服务。研究目标是在改善系统带宽资源利用效率、减少用户点播响应时间、提高系统吞吐量、降低用户撤销概率、提高系统并发量和增强系统交互能力等方面探索领先的理论、方法和实现技术，为大规模高性能有QoS保证的视频服务系统提供理论依据和关键性实现技术。 本文的主要贡献和创新工作如下： 1、对于基于树的P2P VoD系统结构进行了比较深入的研究，并通过仿真对基于树的分代系统P2VoD协议进行了性能分析。仿真结果表明，这种基于树的VoD系统具有数据调度简单，数据传输效率高的优点，但是在大量节点同时加入系统时，系统性能下降明显。 2、针对相同数据的并发请求问题，提出了一种高效、低带宽消耗、低延迟的数据分发算法。该算法在所有节点的输出带宽只满足一个节点的下载需求带宽的情况下，能够以Td+log2N*Tc的延迟让N个节点收到数据时长为Td、最小数据片段长度为Tc的数据。 3、针对VoD系统节目点播的不均匀特性，设计了一种多层次的网络拓扑组织结构，包括：链网状拓扑结构、基于服务频道的块状分群拓扑结构、以及DHT查询存储结构，以保证不同点播频率的节目都能获得较好的服务质量保证。 4、提出了一种基于按位运算的数据片段信息选择计算方法。使用二进制序列存储并交互节点可共享的数据片段的信息，使得信息的获取具有可结合性。该算法具有计算复杂度低，计算速度快的特点。仿真结果表明，该算法和循环查找算法相比，服务器压力降低了50%左右。 5、基于eMule系统，设计实现了一种WINCE嵌入式平台上的P2P文件共享系统。该系统的实现，为P2P VoD系统的大规模测试和推广奠定了基础。针对嵌入式平台的特点，对该文件共享系统进行了优化，提出了多种优化方法。充分利用内存资源解决嵌入式平台I/O操作速度慢的问题、改善排队算法解决嵌入式系统Socket资源受限的问题。测试结果表明，这些优化方法有效的改善了嵌入式文件共享系统的性能。 |
| 英文摘要 | With the widespread penetration of broadband access, streaming services, especially Video-on-Demand services, over Internet have been one of the most popular Internet applications. Video-on-Demand services change the way that users have to watch what’s on, and enrich people’s entertainment spaces by providing an interactive fashion, showing an attractive economic future. The traditional client/server architecture can hardly cope with the ever-growing client population due to its limited service capacity. Recently, overlay networks based on P2P computing have shown a promising approach to offer media streaming services high scalability. But some inherent characters of P2P networks, such as dynamics of networks, resource heterogeneity of peers etc, and some particular requirements of VoD systems, such as lots of concurrent queries, asymmetry requests of programs, difficulty of highly scalable tests etc, bring huge challenges to QoS guarantees of VoD systems. Research contents of the thesis are to resolve the above problems and to provide VoD services with QoS guarantees. Research targets include that exploring advanced theories, methods and practical techniques to improve the efficiency of bandwidth utilization, reduce the start-up delay, increase the throughput of the systems, reduce the probability of user leaving, increase the concurrent capability of the system and enhance the interactive ability etc. The main contributions and innovative works of the thesis include: (1) Structures of tree-based P2P VoD systems are analyzed. And a tree-based protocol P2VoD is investigated by simulations. Simulation results show that tree-based VoD systems have the advantages of conciseness for data scheduling and high efficiency for data distribution. But when a large number of nodes join the system almost at the same time, its performances fall distinctly. (2) A new algorithm with high efficiency, low bandwidth requirement and low delay is presented in this thesis to settle the large scale concurrent querying problem in media streaming systems. With a well designed node selection algorithm, even though each node’s output bandwidth can only satisfy one node’s downloading bandwidth requirement, all nodes can receive the required data block with length Td within the delay of Td+log2N*Tc seconds, where N is the number of peers, and Tc is the least data piece’s time. (3) To resolve the asymmetry request problems of VoD programs, a new network framework of multiple levels is designed, which include a chain-mesh topology structure, a block-clustered topology structure based on serving-channel, and a DHT-based lookup-storage topological structure. It ensures that the system can provide QoS guarantees for programs with different ordering probability. (4) A new selection algorithm based on BIT operation for data-piece information is presented. The storage overhead and communication overhead of peers is reduced by using binary sequences to store and change information of available data-pieces between peers. And the algorithm is of low complexity and of high efficiency. Simulation results show that the server stress is reduced to 50% percent. (5) A file sharing system based on eMule and Windows CE embedded platform has been realized, which laid the foundations of large scale testing and extention for P2P VoD systems. It has been optimized according to the characteristics of the embedded platform, and two kinds of optimized methods have been proposed. The problem of slow-speed I/O operation in the embedded platform is improved by making the best of the memory resources. And the problem of limited Sockets is resolved by improving the queue algorithm. Test results show that performances of the system have been effectively improved by our optimized methods. |
| 语种 | 中文 |
| 公开日期 | 2011-05-07 |
| 页码 | 131 |
| 源URL | [http://159.226.59.140/handle/311008/358]  |
| 专题 | 声学研究所_声学所博硕士学位论文_1981-2009博硕士学位论文 |
| 推荐引用方式 GB/T 7714 | 齐卫宁. 提高P2P视频点播系统服务性能的关键技术研究[D]. 声学研究所. 中国科学院声学研究所. 2008. |
入库方式： OAI收割
来源：声学研究所
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