WDM Multicast Tree Construction Algorithms for Minimizing Blocking Probability under a Delay Constraint

We propose novel tree construction algorithms for multicast communication in photonic networks. Since multicast communications consume many more link resources than unicast communications, effective algorithms for route selection and wavelength allocation are required. We propose novel tree construction algorithms called the weighted Steiner tree (WST) algorithm and the composite weighted Steiner tree (CWST) algorithm. Since the proposed Weighted Steiner Tree algorithm takes account of the number of wavelengths available for each link, this algorithm can select those links which have larger number of available wavelengths. By using this link selection technique, this algorithm can accept many more multicast requests than other multicast tree construction algorithms. However, under certain delay constraints, the blocking characteristics of the proposed weighted Steiner tree algorithm deteriorate since some light paths between source and destination use long hops and cannot satisfy the delay constraint. In order to adapt the approach to the delay-sensitive environments, we have devised the composite weighted Steiner tree algorithm comprising the weighted Steiner tree algorithm and the Dijkstra algorithm for use in a delay constrained environment such as an IPTV application. In this paper, we also give the results of simulation experiments which demonstrate the superiority of the proposed composite weighted Steiner tree algorithm compared with the distributed minimum hop tree (DMHT) algorithm, from the viewpoint of the light-tree request blocking probability.