Joint Allocation of Bandwidth and FEC Across Layers for Video Multicast over Wired and Wireless Networks

Layered multicast is an e cient technique to deliver video to users over wired and wireless networks. In this paper, we consider such a multicast system in which the server adapts the bandwidth and FEC of each layer so as to maximize overall video quality, given the heterogeneous user characteristics in terms of their end-to-end bandwidth, packet drop rate over the wired network, and bit error rate in the wireless hop. In terms of FEC, we also study the value of a gateway which \transcodes" packet-level FEC to byte-level FEC before forwarding packets from the wired network to the wireless users. We present an analysis on the system, propose an e cient algorithm on FEC allocation for the base layer, and formulate a dynamic program with a fast and accurate approximation for the joint bandwidth and FEC allocation of the enhancement layers. Our results show that a transcoding gateway performs only slightly better than the non-transcoding one, and our allocation is e ective in terms of FEC overhead and bandwidth served to each user.