On the optimal rate allocation for layered video multicast

Layered transmission has been recommended as one of the solutions to the inherent heterogeneity problem of video multicast over the Internet. Unlike traditional sender-driven adaptation schemes, current layered multicast protocols usually use distributed control algorithms which perform adaptation on the receiver side. With the assumption that the layer rates are fixed, the control granularity of such protocols is considerably coarse and there is usually a mismatch between the fixed rates and the requirements of the receivers. In this paper, we argue that dynamically allocating layer rates by the sender can minimize this mismatch. We study the optimization criteria for layer rate allocation, and propose a novel metric, Application-aware Fairness Index, to fairly reflect the degree of the receiver's satisfaction. We then formulate the problem of optimal allocation for heterogeneous receivers, and derive an efficient algorithm for solving it. The algorithm is highly scalable and outperforms the traditional static allocation schemes by 10% or more.