Browsing by Author "Mahey, Philippe"

Now showing 1 - 4 of 4
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    Geração de colunas para o problema de roteamento e atribuição de comprimentos de onda.
    (2012) Martins, Alexandre Xavier; Duhamel, Christophe; Mahey, Philippe; Souza, Maurício Cardoso de; Saldanha, Rodney Rezende
    Neste trabalho, apresenta-se um estudo sobre o Problema de Roteamento e Atribuição de Comprimentos de Onda em redes ópticas WDM independentemente da topologia física subjacente. Por se tratar de um problema NP difícil muitos métodos exatos e heurísticos vem sendo estudados para a sua resolução. Apresentamos o estudo da versão do problema onde o objetivo é maximizar o número de requisições atendidas. Inicialmente é feita uma revisão da literatura apresentando alguns modelos matemáticos formulados para a resolução do problema. Depois apresentamos uma estratégia baseada em geração de colunas que combina métodos já existentes. Os resultados computacionais sobre instâncias consagradas da literatura comprovam a eficiencia do método
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    Heuristique VND-ILS pour le problème de routage et d’affectation de longueur d’onde.
    (2011) Martins, Alexandre Xavier; Duhamel, Christophe; Mahey, Philippe; Souza, Maurício Cardoso de; Saldanha, Rodney Rezende
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    Model-hierarchical column generation and heuristic for the routing and wavelength assignment problem.
    (2016) Duhamel, Christophe; Mahey, Philippe; Martins, Alexandre Xavier; Saldanha, Rodney Rezende; Souza, Maurício Cardoso de
    The routing and wavelength assignment (RWA) problem typically occurs in wavelength division multiplexing optical networks. Given a number of available wavelengths, we consider here the problem of maximising the number of accepted connections with respect to the clash and continuity constraints. We first propose a new strategy which combines two existing models. This leads to an improved column generation scheme. We also present two heuristics to compute feasible solutions: a hybrid heuristic and the integer solution at the root node of the column generation. Our approaches are compared with the best existing results on a set of classic RWA instances.
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    Variable neighborhood descent with iterated local search for routing and wavelength assignment.
    (2012) Martins, Alexandre Xavier; Duhamel, Christophe; Mahey, Philippe; Saldanha, Rodney Rezende; Souza, Maurício Cardoso de
    In this work we treat the Routing and Wavelength Assignment (RWA) with focus on minimizing the number of wavelengths to route demand requests. Lightpaths are used to carry the traffic optically between origin-destination pairs. The RWA is subjected to wavelength continuity constraints, and a particular wavelength cannot be assigned to two different lightpaths sharing a common physical link. We develop a Variable Neighborhood Descent (VND) with Iterated Local Search (ILS) for the problem. In a VND phase we try to rearrange requests between subgraphs associated to subsets of a partition of the set of lightpath requests. In a feasible solution, lightpaths belonging to a subset can be routed with the same wavelength. Thus, the purpose is to eliminate one subset of the partition. When VND fails, we perform a ILS phase to disturb the requests distribution among the subsets of the partition. An iteration of the algorithm alternates between a VND phase and a ILS phase. We report computational experiments that show VND-ILS was able to improve results upon powerful methods proposed in the literature.