A Computation Method for Scenario Studies in WDM Network Planning

Purpose – The problem of Wavelength Division Multiplexing (WDM) network planning for a given set of lightpath demands in a mesh topology network is to select lightpath routes and then allocate wavelength channels to the lightpaths. In WDM network planning, a scenario study is to find out the network performance under different lightpath demands and/or different network resource configurations. Approach – A scenario study must solve a series of related static WDM network planning problems. Each static WDM network planning problem is an optimization problem, and may be formulated as an integer linear programming problem, which can be solved by our proposed Lagrangian relaxation and subgradient methods. We use the Lagrange multipliers that are obtained from previous scenarios as initial Lagrange multiplier values for other related scenarios. Findings – Our approach dramatically reduces the computation time for related scenarios. For small to medium variations of scenarios, our method reduces the computation time by several folds. Practical implications – Our method improves the efficiency of a scenario study in WDM network planning. By using our method, many “what-if” type of scenario study questions can be answered quickly. Originality – Unlike other existing methods that treat each scenario individually, our method effectively use the information of the relation between different scenarios to improve the overall computation efficiency.