Abstract :
SONET rings remain the dominant optical transport architecture in the metropolitan area. To support traffic growth on these rings, WDM technology is used to provide multiple SONET rings on the same fiber, each SONET ring running on a separate wavelength. Traffic grooming refers to intelligently arranging low speed traffic streams onto different SONET rings and selecting the proper line speed for each wavelength so as to minimize certain cost objective, such as the total cost of electronic Add-Drop Multiplexer (ADM) equipments used. The problem can be formulated as an Integer Linear Programming (ILP) problem by generalizing the formulation in [1] [2] to support multiple line speeds. Unfortunately, solving the ILP directly could be very computation intensive. In this paper, we propose a non-linear formulation instead, and then solve it by decomposing it into several smaller ILP subproblems, each can be solved separately by an ILP solver. Decomposition allows us to exploit the symmetry in the problem structure, and cut down the solution space dramatically, therefore, reducing the computation time to solve a problem. Even if we may have to terminate the computation early for large size problems, decomposition allows us to explore a larger portion of the solution space in a given amount of time, therefore, obtain better results.
