Routing and wavelength assignment for WDM multicast networks

The multicast routing and wavelength assignment (MC-RWA) problem is generally studied with the objective to maximize the number of multicast groups admitted, or equivalently, to minimize the call (or session) blocking probability given a certain number of wavelengths. While this approach is sound, a better objective is to maximize the total number of users served (i.e., minimizing the user blocking probability) by allowing part of a multicast group to be admitted. We present for the first time a formulation of the MC-RWA problem with such an objective. The formulation is a nonlinear integer program, which in general is complex to solve. We hence propose a heuristic algorithm based on linear programming (LP). We further develop a simpler MAX-FIRST algorithm, which achieves almost the same performance as the LP algorithm. These algorithms are for static MC-RWA, where the multicast trees are predetermined and cannot be changed during the wavelength assignment. We extend the algorithms to dynamic MC-RWA, where new multicast trees can be built for unserved groups. We finally present upper and lower bounds on the user blocking probability for the static MC-RWA.