Efficient Reliable Multicast Using FEC and Limited Retransmission for HDTV IP Broadcasting

IP multicast technology enables simultaneous delivery of multimedia content to numerous users. However, the quality of experience (QoE) is subject to degradation due to packet loss because quality of service (QoS) is not guaranteed in best-effort IP networks. To maintain good QoE, streaming applications typically use an application-layer FEC (forward error correction) technique. Conventional FEC techniques always transfer redundant packets, but these redundant packets are only used when packet loss has occurred. This causes inefficiency in networks where packets are not often lost. To avoid filling network paths with unnecessary redundant packets, we developed a new application-layer packet loss recovery mechanism based on layered multicast using FEC and ARQ. This mechanism divides redundant packets into fundamental and supplementary redundant packet groups and sends them in separate multicast sessions. The supplementary redundant packets are received only by receivers participating in the multicast session of them or requesting retransmission. This mechanism realizes efficient reliable multicast for HDTV IP broadcasting by reducing unnecessary redundant packets and preventing an explosion of requests. We tested the effectiveness of our mechanism in streaming HDTV experiments over a commercial best-effort IP network. The results of experiment show that the proposed mechanism avoids transferring wasteful, redundant packets and efficiently maintains reliability with preventing an explosion of requests.