Broadcasting Approaches for VOD Services

Abstract

A VoD system is typically implemented by a client-server architecture supported by certain transport networks such as telecom, CATV, or satellite networks. The simplest scheme is to dedicate a channel to each client. Many VCR-like functions may be provided (e.g., forward, rewind, pause, search, etc.). Since video is an isochronous medium, the video server has to reserve a sufficient amount of network bandwidth and I/O bandwidth for each video stream before committing to a client’s request. Apparently, such systems may easily run out of channels because the growth of the number of channels can never keep up with the growth of the number of clients. To solve this problem, many schemes have been proposed to resolve the bandwidth problem. In this chapter, we review two kinds of broadcasting schemes. The first one is the batching scheme, in which a set of viewers arriving close in time will be collected and grouped together. Then the video server will serve them altogether with one channel. The second one is the periodic broadcasting approach. The server uses multiple dedicated channels to cooperatively broadcast one video. Each channel is responsible for broadcasting some portion of the video. Each client follows some reception rule to grab data from appropriate channels so as to play the whole video continuously. The server’s broadcasting activity is independent of the arrivals of requests. Such an approach is more appropriate for popular or “hot” videos that may interest many viewers during a certain period of time.