摘要近年来，基于HTTP的动态自适应流媒体(DASH)已经被广泛部署在因特网上。然而，基于多服务器的DASH研究还比较有限。与传统的基于单服务器的DASH相比，多服务器DASH具有带宽可扩展、链路多样性和更高的可靠性等特点。同时，多个服务器的带宽多样性与时变性，也对数据片段调度带来巨大的挑战。由于视频播放的时序特性，当多服务器并行顺序下载时，将导致播放片段的乱序。21451
为了解决这个问题，本文主要了研究多服务器的情况下，如何对视频片段的请求进行调度，从而保证视频片段下载的顺序性，从而提高视频播放的连续性。本文提出了一种基于概率论的多服务器调度方法。首先，为了避免视频播放停顿，我们需要确保视频片段在其播放截止时间之前完成下载。随后，我们提出一种新的调度机制，旨在为每个片段请求分配一个合适的服务器，以确保片段下载完成时的有序。本文通过仿真实验验证了我们的调度方法的有效性，实验结果表明，与已有方法相比，我们的方法显著提高了顺序下载片段所占的比例，改善了视频的播放质量。
关键词 动态HTTP流媒体 多服务器 概率方法 片段请求调度
毕业论文设计说明书（论文）外文摘要
Title The study of chunk download scheduling schemes
for DASH with multiple servers
Abstract
Recently, Dynamic Adaptive Streaming over HTTP (DASH) has been widely used for video streaming services over the Internet. However, there are limited researches have been concerned on DASH over multiple servers, and it is still a challenge to guarantee the order of video chunks due to the heterogeneous and time-varying bandwidth of multiple servers. To solve this problem, in this work, we propose a probabilistic approach to chunk request scheduling for DASH with multiple servers. First, to avoid playback delay, we need to guarantee that the chunks are completely downloaded before their playback deadline. Then, our proposed scheduling scheme aims to assign the video chunks to the appropriate servers so that the video chunks are completely downloaded in order. We formulate the scheduling scheme into an optimization problem which is hard to be solved. Then, under some approximation, a near-optimal solution is found that we iteratively assign each video chunk request to the server, from which the chunk can be downloaded at the earliest time under the constraint that the chunks are completely downloaded before their playback deadline. Compared with the existing schemes, the emulation results show that our proposed scheme greatly improves the proportion of chunks that are received orderly.
Keywords DASH; Multiple Servers; Probabilistic Approach; Chunk Request Scheduling
目 次
1 绪论1
1.1 研究背景1
1.2 国内外研究现状3
1.3 本文主要工作4
1.4 本文结构安排5
2 动态HTTP流媒体技术6
2.1 动态HTTP流媒体概述6
2.2 片段下载调度策略7
2.3 码率动态调整策略8
2.4 多服务器DASH11
2.5 小结12
3 基于概率的片段下载调度策略13
3.1 问题描述13
3.2 问题求解14
3.3算法描述16
3.4 小结17
4 仿真系统中的相关算法与优化策略18
4.1 码率调整18
4.2 状态切换18
4.3 超时重传18
4.4 小结19
5 系统实现与仿真实验20
5.1系统实现20
5.2 运行测试20
5.3 仿真实验24
5.4 小结27
结论 28
致谢 29
参考文献30
1 绪论
本章首先论述了本文的研究背景，随后分析了动态HTTP流媒体技术的国内外研究现状，最后给出了本文的主要工作和结构安排。 基于多服务器的动态HTTP流媒体调度策略研究:http://www.youerw.com/jisuanji/lunwen_13660.html