Adjustable Broadcast Protocol for Large-scale Near-video-on-demand Systems

Video-on-demand (VOD) is a service allowing customers to select video programs from a central server for viewing on a television or a computer screen. Traditional unicast VOD systems require huge amounts of the server network’s bandwidth, so near-VOD systems using broadcast protocols have been proposed to reduce the bandwidth requirement. Al-though NVOD systems can service many users with less network bandwidth by broadcast-ing popular videos, the popularity of any given video is likely to vary widely as time goes on. However, the broadcast protocols cannot adapt to dynamic environments where the popularity distribution of videos changes, because of their fixed broadcasting schedule. We introduce a dynamic broadcast protocol called Adjustable Broadcast (AB) based on on-line scheduling, which can adjust the number of channels being used on the fly. AB also exploits various prefetching strategies in the broadcast schedule to reduce the required band-width. And, we propose a dynamic channel allocation scheme using AB that minimizes the average viewer’s waiting time. Using extensive simulation, we have demonstrated the ef-fectiveness of AB and the adaptibility of our dynamic channel allocation