The design of survivable all-optical networks based on self-healing WDM rings (SHR/WDM) to provide 100% protection from any single link failure requires the joint solution of three sub-problems. These are the ring cover of the mesh topology (the RC sub-problem), the routing of working lightpaths between node pairs to support traffic demands (the WL sub-problem) and the selection of the SHR/WDM spare wavelengths for the protection of every link traffic (the SW subproblem). This paper presents an integer linear programming (ILP) formulation of the problem of minimizing the total wavelength mileage (λ-miles) required to support a set of given traffic demands in a given network topology using SHR/WDM employing 1:N line protection mechanism (the WRL problem). This formulation allows to jointly and optimally solve the three subproblems, and yields up to 15% reduction of the total λ-miles required by existing solutions that separately resolve the sub-problems. A simplified sub-optimal solution of the WRL problem is also provided, that yields results few percent worse than the optimal solution and that is tractable for networks whose size is on the order of the pan-European network, i.e., 19 nodes
A fundamental task of the optical layer in modern telecommunication systems consists of providing a fast protection mechanism against possible faults in the network. A particularly attractive protection technique in the optical layer is the so called shared line protection, in which network lines are protected using shared resources. A previous work of the authors formally describes the problem of minimizing the total wavelength mileage, or A-mileage, necessary in a Wavelength Routing network with arbitrary topology to provide shared line protection. This paper presents an efficient approach to solving the above wavelength mileage problem based on: 1) an algorithm that identifies a feasible solution with the minimal, possibly null, violation of the design constraints, 2) an intelligent pruning technique of the search space that highly reduces the complexity of the optimization problem. Using the proposed approach, a study on the total wavelength mileage is carried out for the European network (19 nodes) and the PanAmerican network (79 nodes) to assess the influence of design constraints on the cost function.
Abstract:Designing arbitrary topologies based on Wavelength Division MUltiplexing (WDM) rings yields a number of advantages, including fast restoration mechanisms, simple network management and control. The optimal design of such networks is however a rather complex task, with multiple objectives being optimized that can often be in conflict one with another. The paper presents a modular methodology that encompasses three fundamental steps in designing an arbitrary topology organized as a set of interconnected WDM rings. These are the selection of the Ring Cover, the Routing of the inter-ring traffic and the Traffic Balancing with Wavelength Assignment (TBW A) of the traffic locally on individual rings. After a description of the overall methodology, a detailed formulation of the TBWA problem in presence of both symmetric and asymmetric traffic demands is given. An efficient algorithm that yields sub-optimal solution of the TBW A problem is then proposed. Numerical results show that the algorithm finds an optimum solution in a number of experiments.
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