On the routing and wavelength assignment in multifiber WDM networks

Mohamed Saad, Zhi Quan Luo

Research output: Contribution to journalArticlepeer-review

31 Scopus citations


This paper addresses the problem of routing and wavelength assignment (RWA) in multifiber WDM networks with limited resources. Given a traffic matrix, the number of fibers per link, and the number of wavelengths a fiber can support, we seek to maximize the carried traffic of connections. We formulate the problem as an integer linear program (ILP), and show that the lightpaths selected by this formulation can indeed be established by properly configuring the optical switches. An upper bound on the carried traffic can be computed by solving the linear programming (LP)-relaxation of the ILP formulation. It is shown that this bound can be also computed exactly, and in polynomial-time, by solving a significantly simplified LP which considers only one wavelength. The bound can, thus, easily scale to an arbitrarily large number of wavelengths. Furthermore, we demonstrate that any instance of the RWA problem is also an instance of the more general maximum coverage problem. This allows us to take a greedy algorithm for maximum coverage and obtain an algorithm which provides solutions for the RWA problem that are guaranteed to be within a factor of (1 - (1/e)) of the optimal solution. Each iteration of the greedy algorithm selects a set of lightpaths that realizes, using one wavelength, the maximum number of connection requests not previously realized. Computational results confirm the high efficiency of our proposed algorithm.

Original languageEnglish (US)
Pages (from-to)1708-1717
Number of pages10
JournalIEEE Journal on Selected Areas in Communications
Issue number9
StatePublished - Nov 2004

Bibliographical note

Funding Information:
Manuscript received June 10, 2003; revised January 26, 2004. This paper was supported in part by a grant from the Natural Sciences and Engineering Research Council of Canada (NSERC), in part by a grant from Communications and Information Technology Ontario (CITO), in part by the Canada Research Chair Program, and in part by the National Science Foundation (NSF) under Grant DMS-0312416.


  • Greedy algorithms
  • Integer linear programming (ILP)
  • Multifiber networks
  • Routing
  • Wavelength assignment


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