A lagrangean decomposition approach for the routing and wavelength assignment in multifiber WDM networks

Mohamed E.M. Saad, Zhi Quan Luo

Research output: Chapter in Book/Report/Conference proceedingConference contribution

16 Scopus citations


This paper addresses the problem of routing and wavelength assignment (RWA) in multifiber WDM networks assuming neither a special topology nor wavelength converters. Given a set of connection requests, the number of fibers deployed on each link, and the number of wavelengths a fiber can support, we seek to maximize the number of lightpaths that can be established. We formulate the problem as an integer linear program (ILP), whose validity is proven by showing that the selected lightpaths can indeed be realized by properly configuring the optical switches. Furthermore, using a Lagrangean decomposition approach, the problem formulation is significantly simplified. The main advantage of our approach is that, independent of the number of wavelengths, provably optimal solutions to the problem can be obtained by considering only one wavelength in the formulation, leading to highly efficient and scalable algorithms. Although our formulation is path-flow based rather than link-flow based, we will prove that, even if all, possibly exponentially many, paths are considered, its linear programming (LP) relaxation can always be solved in polynomial time. We use the branch-and-bound algorithm in the CPLEX optimization package to solve the resulting ILP formulation. Computational results confirm the high efficiency of the Lagrangean decomposition approach.

Original languageEnglish (US)
Title of host publicationConference Record / IEEE Global Telecommunications Conference
Number of pages5
StatePublished - Dec 1 2002
EventGLOBECOM'02 - IEEE Global Telecommunications Conference - Taipei, Taiwan, Province of China
Duration: Nov 17 2002Nov 21 2002


OtherGLOBECOM'02 - IEEE Global Telecommunications Conference
CountryTaiwan, Province of China

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