A high-quality video multicast scheme with a time limit

The block-based fast transmission scheme, which is a typical stored video delivery scheme, is reasonable in terms of its bandwidth efficiency. However, it causes packet loss because of its burst data transmission method. Thus, we suggest a slotted multicast scheme for MPEG video based on the block transmission scheme to maintain a higher quality and to include time constraints. We define two delivery units, the "GoPs group" and the "frame type", on the basis of the MPEG characteristics with periodical NACK feedback from the clients. The former is tolerant to burst packet loss, and the latter gives priority to important frames. Block multicast has two phases: a "transmission phase" and a "retransmission phase". In the former, a server multicasts a block, and in the latter, a server retransmits lost packets using multicast according to the proper delivery unit.