Multicast vs. Unicast Error Recovery Tradeoffs for Group Correlated IPTV Networks

In IPTV networks, quality of experience (QoE) is typically expressed in terms of perceived packet loss rate and latency performances. As the IPTV content is delivered over diverse transmission channels, to meet the QoE objectives of all the users connected to the same IPTV network, we need to utilize resource efficient error control techniques. Recent research on IPTV error control has mostly focused on the use of a dedicated error recovery server (ERServ) to support reactive and unicast-based error control services. It is known that a unicast-based strategy is typically preferred when the accumulative packet loss rate is small and/or the correlation among the users´ loss processes is negligible. However, if the users start to observe correlated packet losses, then unicast-based strategies may lead to significant performance degradations. For such scenarios, to improve the effectiveness of the error recovery process, we need to also utilize multicast-based repair strategies. In this paper, our objectives are (i) to develop spatial correlation models that are applicable to IPTV networks, (ii) to design an error recovery framework that is capable of exploiting the spatial correlation characteristics of the network, and, finally, using the proposed packet loss models and recovery protocols (iii) to analyze the performance tradeoffs associated with the use of unicast- and multicast-based error recovery strategies for correlated packet loss scenarios in IPTV networks.