Retransmission scheduling in layered video caches

In contrast to classical assumptions in video on demand (VoD) research, the main requirements for VoD in the Internet are adaptiveness, support of heterogeneity, and last but not least high scalability. Hierarchically layered video encoding is particularly well suited to deal with adaptiveness and heterogeneity support for video streaming. A distributed caching architecture is the key to a scalable VoD solution in the Internet. Thus, the combination of caching and layered video streaming is promising for an Internet VoD system, yet, requires thoughts about some new issues and challenges. In this paper, we investigate one particular of these issues: how to deal with retransmissions of missing segments for a cached layered video in order to meet user demands to watch high quality video with relatively few quality variations. We devise a suite of fairly simple retransmission scheduling algorithms and compare these against existing ones by simulative experiments.