Unequal error recovery scheme for multimedia streaming in application-level multicast

As a way of implementing multicast delivery, applicationlevel multicast (ALM) is known for its various advantages including high flexibility and easy deployment. However, one of its key limitations in achieving reliability and quality-of-service (QoS) for streaming services is the hierarchical error propagation caused by its tree structure. As a solution to this error propagation problem, we propose an unequal error recovery (UER) scheme where we apply different number of retransmissions to the different levels of the ALM tree. The error recovery scheme is implemented using reliable-UDP (RUDP). For each node of the ALM tree, the optimal number of the maximum retransmissions that minimizes the residual loss rate is obtained using Lagrange theory for a given delay constraint. Compared to the equal error recovery scheme where the equal number of maximum retransmissions is applied throughout the ALM tree, the proposed UER scheme shows up to 10% improvement in residual loss rate while maintaining acceptable delay overhead for real-time streaming applications.