Tradeoff between system profit and user delay/loss in providing near video-on-demand service

In a near video-on-demand (near-VOD) system, requests for a movie arriving in a period of time are grouped (or “batched”) together and served with a single multicast stream. In this paper, we consider providing near-VOD services when there is a cost associated with using a network multicast channel. We address the tradeoff between system profit, given by the total pay-per-view collected minus the total channel cost, and user delay or user loss (due to reneging). We first analyze and compare the tradeoff of two traditional “basic” schemes, namely, the window-based schemes in which a maximum user delay can be guaranteed, and the batch-size based scheme in which system profit can be guaranteed. By combining these basic schemes, we present a scheme which can adaptively balance system profit and user delay when the underlying request rate fluctuates. We then consider the case in which delayed users may renege and determine how system profit can be maximized by sizing the batching period given user’s reneging behavior. We show that maximizing profit can lead to excessively high user loss rate, especially when the channel cost is high and users are not very patient. Therefore, a shorter suboptimal batching period should be used for this case in reality. We finally introduce schemes which are able to offer high profit or low user loss when the underlying arrival rate fluctuates.