Scheduling video streams in video-on-demand systems: A survey

Developments in multimedia technology over the past decade has caused video-on-demand services to emerge as a new paradigm in home entertainment. Because of the large volume of data involved in the process and stringent continuity and real-time constraints, these services pose challenges that are different from the standard file transfer operations in the network. The necessity of efficient usage of scarce resources like network bandwidth and server capacity (in terms of I/O bandwidth) demands novel and easy-to-use schemes for scheduling continuous video streams. This paper presents an overview of the major scheduling policies that have emerged in the recent past. In particular, the paper provides detailed discussion on policies based on principles of broadcasting, batching, caching, and piggybacking or merging. Policies like look-ahead scheduling schemes that are designed exclusively to provide certain interactive VCR-like control operations are also covered. A conceptual comparison between the various classes of scheduling policies is carried out to identify common threads and key concepts. Performance of these policies in terms of bandwidth demand reduction, customer waiting time reduction, provision of interactive control by the user, and fairness of service are given special emphasis. The paper concludes with a discussion on the possible avenues of further reasearch and development in this potentially interesting and challenging field.