[计算机]流媒体论文：基于前缀缓存和指数分段的代理缓存算法研究.doc

流媒体论文：基于前缀缓存和指数分段的代理缓存算法研究【中文摘要】随着网络和多媒体技术的发展,流媒体应用越来越流行。然而现有的互联网络缺乏对实时通信的良好支持,影响了流媒体的传输性能。同时,流媒体传输对系统I/O和网络带宽的高要求,使得服务器和网络带宽成为系统的瓶颈。流媒体代理缓存技术通过缓存热门节部分或全部数据,为就近的客户端请求提供服务,可以有效的解决上述问题。因此,针对流媒体应用的特点,研究高效的代理缓存策略,以提高缓存命中率、减小客户端启动延迟、降低服务器负载和网络资源消耗,是流媒体代理缓存技术的重要研究内容。如何替换缓存的对象以便用户直接从缓存中访问是缓存替换算法研究的主要内容。现有缓存替换算法主要以媒体访问次数和访问频率来计算缓存效能值,并未考虑对象未来被访问的概率,对效能值评价不够精确,并且效能值的计算也局限于整个媒体对象而没有精确到段。针对这些问题,本文提出了基于前缀缓存的改进替换算法,该算法以指数分段为基础,细化了对于缓存空间的调度粒度,效能值的计算细化到段,考虑了媒体部分有效性、段未来被访问的概率、段的访问频率、段已缓存长度对缓存效能值的影响和段平均访问长度,因而提高了缓存性能。实验结果表明：本文的流媒体代理缓存算法在提高缓存单位字节的命中率、降低启动延迟率等方面有较好的性能,能够提高流媒体的播放质量和传输效率。【英文摘要】As the development of the Internet and multimedia technology, the application of streaming media is becoming more and more popular. However, the current Internet lacks support for real-time communication, which influencing the performance of media transmission. Furthermore, due to the high demands of streaming media transmission on system I/O and network bandwidth, the server and network and width turn into the bottleneck of the whole system. While such problems can be effectively solved by the proxy caching technology, which caches part or all of the data of hot programs so as to offer services to the users nearby. Therefore, based on the main features of the application of streaming media, studies on efficient proxy caching strategy to increase caching hit rate, decrease the client startup latency and reduce server overloads and network resource consumption are of great significance to the research of proxy caching technology of streaming media.The main research on cache replacement algorithms is how to replace cache object. Existing cache replacement algorithms have the problem of inaccurate evaluation of the caching utility because their standards are access times and frequency of the media, additionally they dont consider the probability of access objects in the future, and the evaluation of cache utility is not accurate, the calculation of cache utility is constrained to the whole media object but not accurately to the segment. To solve these problems, the paper presents the cache replacement algorithm based on LRV. This algorithm builds the base on exponential segmentation, refines the scheduling granularity of cache space, and the calculation of cache utility is based on segments, the media partial validity, the probability of access to segment in the future, segment access frequency, segment average access length and the influence of cached segment size to cache utility are all considered in this algorithm, which enhances the cache performance.The results of simulation experiments show that the streaming media proxy cache algorithm we proposed has better performance on increasing cache byte hit rate and reducing client startup latency than the existing ones, and helps to improve the transmission efficiency and the quality of streaming media service.【关键词】流媒体 指数分段 代理缓存 缓存替换算法【英文关键词】streaming media Index segmented Prefix caching Cache replacement algorithm【目录】基于前缀缓存和指数分段的代理缓存算法研究摘要4-5Abstract5第一章 绪论8-161.1 研究背景和意义8-101.2 国内外研究现状10-141.2.1 流媒体缓存系统结构的研究10-121.2.2 缓存策略研究121.2.3 流调度技术的研究12-131.2.4 替换算法的研究131.2.5 预取技术的研究13-141.2.6 流媒体代理缓存国内研究现状141.3 本论文的主要研究工作和组织结构14-161.3.1 主要研究工作14-151.3.2 论文的组织结构15-16第二章 流媒体代理服务器系统理论基础16-302.1 流媒体理论16-172.1.1 流媒体简述16-172.1.2 流媒体技术172.2 流媒体系统架构17-242.2.1 流媒体系统基本组成部分17-182.2.2 流媒体系统基本架构18-242.3 流媒体代理服务器缓存模型24-292.3.1 带宽与流媒体的关系24-252.3.2 流媒体代理缓存25-262.3.3 VOD系统26-282.3.4 流媒体代理服务器缓存模型28-292.4 小结29-30第三章 基于前缀缓存和指数分段的代理缓存算法研究30-393.1 解决缓存策略的关键问题30-313.2 基于前缀缓存和指数分段的代理缓存算法研究31-383.2.1 缓存的重要性和考虑因素313.2.2 已有缓存算法分析比较31-333.2.3 分段策略33-343.2.4 缓存管理策略分析34-353.2.5 缓存效能值的依据35-373.2.6 算法描述37-383.3 小结38-39第四章