CHANNEL ALLOCATION UNDER BATCHING AND VCR CONTROL IN VIDEO-ON-DEMAND SYSTEMS

In order to guarantee continuous delivery of a video stream in an on-d emand video server environment, a collection of resources (referred to as a logical channel) are reserved in advance. To conserve server res ources, multiple client requests for the same video can be batched tog ether and served by a single channel. Increasing the window over which all requests for a particular video are batched results in larger sav ings in server capacity; however, it also increases the reneging proba bility of a client. A complication introduced by batching is that if a batched client pauses, a new stream (which may not be immediately ava ilable) needs to be started when the client resumes. To provide short response time to resume requests, some channels are set aside and are referred to as contingency channels. To further improve resource utili zation, even when a nonbatched client pauses, the channel is released and reacquired upon resume. In this paper, we first develop an analyti cal model that predicts the reneging probability and expected resume d elay, and then use this model to optimally allocate channels for batch ing, on-demand playback, and contingency. The effectiveness of the pro posed policy over a scheme with no contingency channels and no batchin g is also demonstrated. (C) 1995 Academic Press, Inc