一种移动流媒体分层协同缓存系统

随着移动互联网的发展和用户数量的增加，网络中的音视频服务普遍采用动态缓存机制来减轻回程主干网的带宽压力和提高用户的观影体验。如何根据网络和用户需求，调整不同节点的缓存内容，以减少主干网的带宽压力，是当前缓存部署迫切需要解决的问题。基于子模函数理论，本文提出主动和被动资源分配调整方案及其算法。主动方案根据资源的流行度把视频文件部署到缓存节点上，以达到用户访问代价的最小化；被动方案根据音视频流行度的变化对节点上缓存的内容进行实时调整，以提高缓存资源的利用率和用户体验，降低主干网的带宽消耗。最小访问代价算法的复杂度与缓存空间容量大小相关，在缓存空间紧张时能快速迭代出资源的分配方案。数值仿真表明，主动和被动分配资源分配方案能有效降低远程服务器的带宽压力和提高用户体验。

A Hierarchical Cooperative Caching System in Mobile Streaming Media

With the development of mobile Internet and the increase of the number of users, dynamic caching mechanism is widely used in audio & video services to reduce the data traffic going through backhaul backbone links and improve the viewing experience. How to adjust the cache content of multiple nodes according to the network and user demand to cut down the traffic in backbone links is an important problem to be solved in current cache deployment. Based on the submodular function theory, the proactive and reactive resource allocation adjustment schemes and their algorithms are proposed. According to the popularity of the content, the proactive scheme puts the video files to the cache space to minimize overhead of obtaining them. The reactive one adjusts the content in the space of the node in time to cater to the popularity’s change, so as to improve the utilization of the cache resources and user experience, and reduce the rate of occupied bandwidth in the backbone links. The complexity of the minimum access cost algorithm is related to the size of the cache space, which can quickly iterate out the resource allocation scheme when the cache space is tight. Numerical simulation shows that the proactive and reactive resource allocation schemes can effectively alleviate the traffic load of the remote server and improve the user’s experience.