Approximation Algorithms for Traffic Grooming in WDM Rings

This paper addresses the problem of traffic grooming in WDM rings in which all traffic emanates from a single node and all other nodes are destination nodes. This "one-to-many" scenario arises in metropolitan access networks in which one node serves as a "hub" connecting the ring to a larger network as well as in video-on-demand and other multimedia services where a single source node serves a collection of subscriber nodes. The ring comprises a given number of wavelengths of uniform capacity and a variable number of tunable add-drop multiplexers (ADMs) at each node. Given a set of requests at the destination nodes, where each request comprises a bandwidth demand and a profit for fulfilling the request, our objective is to select a subset of the requests and pack ("groom") them onto the wavelengths such that no wavelength\´s capacity is exceeded and the total profit of the selected requests is maximized. Although this problem is NP-complete, we give polynomial time approximation algorithms with excellent theoretical performance validated with experimental results.