Minimizing Wavelength Conversions in WDM Path Establishment

This paper studies algorithms for connection establishment in wavelength division multiplexing networks. Although wavelength conversion capabilities are assumed at each node in the network, the goal of this research is to minimize or impose an upper bound on the number of wavelength conversions on the established path. Two types of schemes are investigated and compared. In the first scheme, the wavelengths are selected adaptively during path establishment on a given route, and in the second scheme, both the route and the wavelength assignment are selected optimally based on global information about path costs and wavelength availability in the network. We present two efficient algorithms for globally selecting routes and wavelengths, one finds the least cost route for a maximum number of wavelength conversions, and the other selects from among the shortest routes, the one with a minimum number of wavelength conversions. The results of comparing the two path establishment schemes show that, for dynamically changing traffic, the adaptive selection of wavelengths on a fixed route during path establishment is more beneficial than the optimal selection of the route and wavelengths prior to path establishment.