Minimization of SONET ADMs in ring networks revisited

We design improved approximation algorithms for two variants of the ADM minimization problem. SONET add-drop multiplexers (ADMs) are the dominant cost factor in SONET/WDM rings. The number of SONET ADMs required by a set of traffic streams (lightpaths) in a ring is determined by the routing and the wavelength assignment of the traffic streams. We consider both the arc version where the route of each traffic stream is given as input, and the chord version, where the routing is to be decided by the algorithm. The goal in both cases is to assign wavelengths so as to minimize the total number of used SONET ADMs.