Video multicast through cooperative incremental parity packet transmission

In this paper, a cooperative multicast scheme that uses Randomized Distributed Space Time Codes (R-DSTC), along with packet level Forward Error Correction (FEC), is studied. Instead of sending source packets and parity packets through two hops using R-DSTC as proposed in our prior work, the new scheme delivers both source packets and parity packets using only one hop. The source station (access point, AP) first sends all the source packets, then the source as well as all nodes that have received all source packets together send the parity packets using R-DSTC. As more parity packets are transmitted, more nodes can decode all source packets and join the parity packet transmission. The process continues until all nodes acknowledge (through feedback) the receipt of enough packets for recovering the source packets. For each given node distribution, the optimum transmission rates for source and parity packets, are determined such that the video rate that can be sustained at all nodes is maximized. This new scheme can support significantly higher video rates (and correspondingly higher PSNR of decoded video) than the prior approaches. We further present two suboptimal approaches, which do not require full information about user distribution and feedback, and hence are more feasible in practice. The new scheme using only the node count information and without feedback still outperforms our prior approach that assumes full channel information and no feedback, when the node density is sufficiently high.