Buffer Control for Guaranteeing User-Level QoS of Continuous Media Flows

Abstract

研究了缓存控制对媒体流用户层QoS 的影响.多媒体系统信宿端通常采用播放缓存来补偿时延抖动,提高媒体流播放的连续性.缓存控制虽然能够降低时延抖动的影响,却增加了端到端时延.时延或时延抖动是用户可感知的QoS 参数,缓存控制对用户层QoS 的影响究竟如何呢?利用已有的应用层向用户层QoS 映射的研究结果,分析缓存控制参数与端到端QoS 参数、应用层QoS 参数的关系,获得了缓存控制参数与用户层QoS 参数的关系.从理论上深入挖掘缓存控制对用户层QoS 参数的作用,给出了提供确定时延和时延抖动保障的缓存容量值,论证了在网络环境一定时存在提供最佳用户层QoS 的缓存容量值.实验结果验证了分析.;A study on the effect of buffer control on user-level QoS of media flows is presented. In multimedia systems, playout buffer at the destination site is often adopted to compensate the delay jitter and improve the continuity of information playback. Buffer contol can reduce the effect of the delay jitter but increase the end-to-end delay. As delay and delay jitter are both the user-perceived QoS parameters, how does buffer control affect user-level QoS? By utilizing the former results on QoS mapping from application-level to user-level, and by investigating the relation between the buffer control parameter, end-to-end-level QoS parameters and application-level QoS parameters, the relationship between the buffer control parameter and user-level QoS parameter is obtained. The effect of buffer control on user-level QoS having been studied in-depth with theoretical analysis. The buffer size providing determinate delay and delay jitter guarantee is found and the buffer size providing the optimal user-level QoS for a certain network condition is demonstrated. Experimental results validate the analysis.