Feedback Scalability for Multicast Videoconferencing

Some type of transmission rate control protocol is required in order to support multicast video applications over the Internet. Previously, we proposed a new protocol, the Layered Multicast Control Protocol (LMCP), which utilizes both the video sender and the receivers to control the rate of the video transmission. One weakness of this approach is that feedback from all receivers is required in order for the video source to determine an optimal transmission rate. In this paper we introduce an algorithm that allows us to determine the video source–s transmission rates based on feedback from a subset or sample of the receiver–s feedback. As our analysis shows this algorithm allows us to support hundreds of receivers and allows the sender to determine transmission rates, which are nearly optimal. Based on the distributions analyzed, we were able to calculate transmission rates that achieved a displayable video rate within 5% of the optimal setting for 500 receivers with a worse case feedback rate at the source of 2kbps.