Exploring coding benefits in CDN-based VoD systems

Currently, video-on-demand (VoD) streaming over Internet is a popular application. Because of the rapidly growing video population and user population, how to maintain high user quality of experience (QoE) with low cost is a challenging problem for Internet video streaming providers. A promising technique to potentially benefit VoD streaming system is network coding. A number of recent works studied how to use network coding to simplify chunk scheduling strategy to enhance VoD streaming performance. Most of these works only covered extreme cases of pure coding or pure chunk scheduling, emphasizing implementation, and experimentation in peer-to-peer (P2P) scenario without analytically evaluating the realizable performance gains explicitly. In this paper we discuss the strength and weakness of a family of coding strategies for CDN-based VoD streaming systems. The coding schemes are characterized by block sizes while the chunk scheduling strategy is characterized by the order to download chunks. Both pure coding strategy and pure chunk scheduling strategy are special cases of this family of strategies. We then propose a model to evaluate the benefits brought by each strategy. Basically, the coding scheme with larger block size gives more streaming and scheduling benefits with the cost of heavier overheads (e.g., encoding and decoding). System designers can take advantage of our model to balance the tradeoff between coding gain and coding overheads.