Adapting network video to multi-time scale bandwidth fluctuations

Examines the issue of adapting network video to bandwidth fluctuations on different time scales. We observe that fluctuations in shared packet switching networks occur on different time scales, from less than a microsecond up to minutes and longer. Sources of bandwidth fluctuations arise from noise in physical devices and communication channels, link-layer routing and multiplexing, and connection migrations among heterogeneous networks. The magnitudes of such fluctuations, measured by peak-to-average rate ratio, vary up to several hundred-fold. Since the sources of such fluctuations exist in today's Internet and will again appear in the next-generation Internet based on the IETF proposal of the Diff-Serv (differential service) model, there is no hope that these orders-of-magnitude fluctuations will go away by themselves. Network video applications must face the challenge and adapt to such fluctuations. Our investigation on this issue yields the conclusion that a scalable solution is achievable through layered video coding techniques. This paper presents our finding by first discussing the sources of the fluctuations on slow, medium and fast time scales. Layered coding techniques, although they were originally developed for different purposes, can be integrated into a single framework to effectively treat each level of fluctuation. The paper presents this framework and concludes with a mapping between layered video techniques and fluctuation levels.