This paper addresses the problem of multicast wavelength assignment for sparse wavelength conversion in wavelength-routed WDM networks. It aims to optimally allocate the available wavelength for each link of the multicast tree, given a sparse wavelength conversion network and a multicast request. To our knowledge, little research work has been done to address this problem in literature. In this paper, we propose a new technique called MWA-SWC algorithm to solve the problem. The algorithm first maps the multicast tree from the sparse conversion case to the full conversion case, by making use of a novel virtual link method. The method provides a forward mapping to generate an auxiliary tree as well as a reverse mapping to recover the original tree. Applying the auxiliary tree, we propose a dynamic programming algorithm for the wavelength assignment aiming to minimize the number of wavelength converters required. Simulation results show that our new algorithm outperforms both random and greedy algorithms with regards to minimizing the number of wavelength converters. Testing on various scenarios by varying the number of wavelength conversion nodes in the tree has confirmed the consistency of the performance. The primary use of the MWA-SWC algorithm is for static traffic. However, it can also serve as a baseline for dynamic heuristic algorithms. Typically, the MWA-SWC algorithm will provide great benefit when the number of available wavelengths on each link of the multicast tree is relatively large and the performance advantage is significant.
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