This paper introduces a novel and efficient approach for user cooperation in wireless video multicast using randomized distributed space time codes (R-DSTC), in which the sender first transmits the source packets, and the sender and receivers that have received all source packets then generate and send the parity packets simultaneously using R-DSTC. As more parity packets are delivered, more receivers can recover all source packets and join the parity packet transmission. Four variations of the proposed systems are considered.
The first one requires complete channel information between the sender and all receivers and between all receivers to derive the optimal transmission rates for sending source and parity packets, and employs receiver feedback to determine when to terminate parity transmission. The other three suboptimal systems do not require full channel information and/or receiver feedback, and hence are more feasible in practice. All four versions can support significantly higher video rates and correspondingly higher quality of decoded video, than prior approaches in the literature, which require full channel information but not feedback.