On the use of destination set grouping to improve fairness in multicast video distribution

In a fair multicast video distribution scheme each receiver should receive a video stream with a quality that is commensurate with its capabilities or the capabilities of the path leading to it, regardless of other receivers or network paths. This fairness problem results from the fact that multicast communication trades economy of bandwidth with granularity of control. Distributing video using individual feedback-controlled point-to-point streams results in high bandwidth utilization but the granularity of control is high as communication parameters can be negotiated individually with each receiver. In contrast, using a single multicast stream has good bandwidth economy, but very low granularity of control. In this paper we propose, implement and experiment with a system that spans the spectrum represented by the two extremes above. In the scheme, called destination set grouping (DSG), a source maintains a small number of video streams, carrying the same video but each targeted at receivers with different capabilities. Each stream is feedback-controlled within prescribed limits by its group of receivers. Receivers may move among streams as their capabilities or the capabilities of the network paths leading to them change. The scheme is shown to improve fairness significantly at a small bandwidth cost.