Optimization of wavelength assignment for QoS multicast in WDM networks

This paper discusses quality-of-service (QoS) multicast in wavelength-divis ion multiplexing (WDM) networks. Given a set of QoS multicast requests, we are to find a set of cost suboptimal QoS routing trees and assign wavelengt hs to them. The objective is to minimize the number of wavelengths in the s ystem. This is a challenging issue. It involves not only optimal QoS multic ast routing, but also the optimal wavelength assignment. Existing methods c onsider channel setup in WDM networks in two separate steps: routing and wa velength assignment, which has limited power in minimizing the number of wa velengths. In this paper, we propose a new optimization method, which integ rates routing and wavelength assignment in optimization of wavelengths. Two optimization algorithms are also proposed in minimizing the number of wave lengths. One algorithm minimizes the number of wavelengths through reducing the maximal link load in the system; while the other does it by trying to free out the least used wavelengths. Simulation results demonstrate that th e proposed algorithms can produce suboptimal QoS routing trees and substant ially save the number of wavelengths.