Layered Multicast Group Construction for Reliable Multicast Communications

In reliable multicast communications, transmission rate of a sender should be restricted to the node capability of the lowest node in order to support reliable transmission of packets to all receivers in a multicast group. Even a node of high capability should receive packets at lower rate when there are lower capability nodes in a corresponding multicast group. In reliable multicast communications, heterogeneity of node capability degrades total performance of a multicast group. In the paper, we present the layered multicast group construction, which is one of technical solutions for performance degradation caused by heterogeneity. The basic concept of the layered multicast group construction is to divide a multicast group into multiple subgroups and order them based on node capability. This reduces diversity of node capability inside each sugbroup, which improves delay performance of a whole multicast group. We investigate optimal construction of the layered multicast group construction, i.e. optimal dividing points of subgroups. Numerical examples show that average delay performance is remarkably improved by the layered multicast group construction compared with a conventional single multicast group construction and performance improvement obtained by two or three subgroups is sufficient for practical use.