Exploring core based tree (CBT) in WDM networks

In this paper, we explore the routing and wavelength assignment problem for the CBT service in a WDM network where k sources need to send data to a common core node. We formally model the problem as a problem of finding k shortest lightpaths from sources to the core subject to the constraint of wavelength collision free. We define and study several subproblems, each addressing a different objective. For the feasibility and the minimum total cost problems of k shortest lightpaths, we show how the classical network flow algorithms can be modified and applied efficiently on the network flow model constructed on the transformed wavelength graph. For the minimum max-cost problem, we prove its NP-completeness and propose two efficient heuristic algorithms. Simulation results show that the proposed heuristic algorithms perform very close to the calculated lower bounds.