Grooming of multicast sessions in WDM ring networks

In this paper, we address the problem of routing and wavelength assignment of multicast sessions with subwavelength traffic demands. We consider this problem in the scenario of WDM ring networks. In order to support multicasting, individual nodes need to have the capability to duplicate traffic. We consider two different node architectures which perform the duplication in optical and electronic domain, respectively. As traffic duplication at the electronic level is much more expensive than the optical alternative, we study the problem of assigning routes and wavelengths to the multicast sessions so as to minimize electronic copying. The solution to this problem can be divided into three phases -- (1) routing of multicast sessions, (2) construction of circles by grouping non-overlapping arcs and (3) grouping these circles onto wavelengths. We propose a heuristic algorithm which implements the routing as well as circle construction phases simultaneously and then groups the circles. We present extensive simulation results to show that our approach leads to much lesser equipment cost than that obtained by routing each multicast session along its minimum spanning tree and then using the best known heuristic for circle construction.