Ef®cient Wavelength Assignment Algorithms for Light Paths

Ef®cient Wavelength Assignment Algorithms for Light Paths

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Photonic Network Communications, 2:4, 349–359, 2000 # 2000 Kluwer Academic Publishers. Manufactured in The Netherlands. Efficient Wavelength Assignment Algorithms for Light Paths in WDM Optical Networks With/Without Wavelength Conversion Gangxiang Shen, Sanjay K. Bose, Tee Hiang Cheng, Chao Lu, Teck Yoong Chai Network Technology Research Center, Nanyang Technological University, Nanyang Avenue, Singapore 639798 E-mail: egxshen, ESKBose, ethcheng, eclu@ntu.edu.sg Accepted June 19, 2000 Abstract. In order to reduce the overall wavelength number required in a wavelength division multiplexing (WDM) network with static traffic loading, new heuristic algorithms for wavelength assignment are proposed in this paper. A new parameter called ‘‘one-wavelength-decrease cost’’ is defined and used to compare the efficiency of these algorithms. Comparative simulation studies have been carried out for various network topologies to investigate the effectiveness of the proposed algorithms. Keywords: wavelength routing, non-wavelength continuous, wavelength continuous, NWC, WC, one-wavelength-decrease cost 1 Introduction Wavelength division multiplexing (WDM) [1–3] is expected to be a popular technique for constructing large optical networks interconnecting a large number of nodes. With suitable optical cross connects (OXC) [4] at the nodes, such a network will allow very flexible switching of the various wavelengths and light-paths between the active source-destination pairs. This flexibility in routing will make these networks easy to configure and operate and will also improve the reliability of the network by providing easy-to-set-up alternative paths in case of node and link failures. In a network with static traffic loading, the traffic requirements between different node pairs would be known a priori . From the viewpoint of the network’s optical complexity, it would be desirable to support all the static network traffic with as small a set of different wavelengths as possible. The size of this set, i.e., the number of different wavelengths required in the overall network, will be referred to as the wavelength number of the network [4]. This is usually directly related to the cost of the WDM optical network. Various algorithms have been proposed [4–10] for minimizing the wavelength number of a network. In Chlamtac et al. [4], a task scheduling method is used to carry out wavelength assignments; the author also subsequently shows that, in case of static traffic, the wavelength number in a wavelength continuous (WC) network will be virtually the same (or only slightly larger) as that in a non-wavelength continuous (NWC) network. A new method of computing the lower bound for the required wavelength number is proposed in Nagatsu et al. [5]; a new algorithm is also proposed to get a low cost network implementa- tion where the wavelength number of a link is taken to be the weight (or cost) of that link. In Chlamtac et al.
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Ef®cient Wavelength Assignment Algorithms for Light Paths

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