Distance-Adaptive Spectrum Resource Allocation Using Subtree Scheme for All-Optical Multicasting in Elastic Optical Networks

We propose and investigate a subtree scheme for all-optical multicast routing, modulation level and spectrum allocation (AOM-RMSA) in elastic optical networks. A multicast request is accommodated by several light-trees and each light-tree covers only a part of the destination set. We assume that all nodes are multicast capable and investigate the subtree scheme over the single light-tree scheme for the AOM-RMSA problem under both static and dynamic traffic scenarios. In the static scenario, we formulate an integer linear programming model to obtain the optimal solution. Then, we propose two time-efficient heuristic algorithms that construct subtrees according to the link-sharing ratio between the paths from source to two distinct destinations. The proposed algorithms improve the spectrum utilization by building subtrees that have smaller tree-spanning size and adopt higher level modulation formats. They have also effectively reduced the blocking probability compared to single light-tree schemes.