Optimal Transcoding and Caching for Adaptive Streaming in Media Cloud: an Analytical Approach
Optimal Transcoding and Caching for Adaptive Streaming in Media Cloud: an Analytical Approach
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DOI：
10.1109/tcsvt.2015.2402892
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发表时间：
2015-02
影响因子：
8.4
通讯作者：
Yichao Jin;Yonggang Wen;C. Westphal
中科院分区：
文献类型：
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作者：
Yichao Jin;Yonggang Wen;C. Westphal
如今，大规模视频分发占据了全球互联网流量的很大一部分。然而，现有的内容交付网络可能不足以分发自适应视频流，这主要是由于缺乏对存储、计算和带宽资源的协调。在本文中，我们利用Media Cloud提供按需自适应视频流服务，其中这些资源可以按需方式动态调度。我们的目标是通过优化协调多种资源来最大限度地降低总运营成本。具体地说，我们通过检查每个边缘服务器的缓存、代码转换和带宽成本之间的三向权衡来制定优化问题。然后，我们采用两步法解析地推导出每个边缘服务器的最优转码配置和缓存空间分配的闭合解。最后，我们通过大量的仿真验证了我们的解决方案。结果表明，与现有的内容分发网络中使用的方法相比，我们的方法实现了显著的成本节约。此外，我们还发现最优策略及其收益会受到一系列系统参数的影响，包括不同资源的单位成本、到源站的跳距、用户请求模式的Zipf参数以及针对一个网段的不同码率版本的设置。
Nowadays, large-scale video distribution feeds a significant fraction of the global Internet traffic. However, existing content delivery networks may not be cost efficient enough to distribute adaptive video streaming, mainly due to the lack of orchestration on storage, computing, and bandwidth resources. In this paper, we leverage Media Cloud to deliver on-demand adaptive video streaming services, where those resources can be dynamically scheduled in an on-demand fashion. Our objective is to minimize the total operational cost by optimally orchestrating multiple resources. Specifically, we formulate an optimization problem, by examining a three-way tradeoff between the caching, transcoding, and bandwidth costs, at each edge server. Then, we adopt a two-step approach to analytically derive the closed-form solution of the optimal transcoding configuration and caching space allocation, respectively, for every edge server. Finally, we verify our solution throughout extensive simulations. The results indicate that our approach achieves significant cost savings compared with the existing methods used in content delivery networks. In addition, we also find the optimal strategy and its benefits can be affected by a list of system parameters, including the unit cost of different resources, the hop distance to the origin server, the Zipf parameter of users' request patterns, and the settings of different bitrate versions for one segment.