Wavelength assignment in WDM rings with splitable lightpaths

This paper presents a new practical approximation algorithm for wavelength assignment to splitable lightpaths over WDM (wavelength division multiplexing) rings, with the objective of minimizing the number of SONET ADMs (add-drop multiplexers). Allowing the splitting of traffic streams can significantly reduce the number of required ADMs. Moreover, while finding the best assignment is proved to be NP-hard, the problem seems easier to approximate than the variation when traffic streams cannot be split. In the worst case, the output of the new polynomial-time algorithm is at most 25% more than the optimum solution. This result is significantly better than the best known approximation ratio for non-splitable traffic streams.