Hierarchical Ring Network Design Using Branch-and-Price

Abstract. We consider the problem of designing hierarchical two layer ring networks. The top layer consists of a federal-ring which establishes connection between a number of node disjoint metro-rings in a bottom layer. The objective is to minimize the costs of links in the network, taking both the fixed link establishment costs and the link capacity costs into account. Hierarchical ring network design problems combines the following optimization problems: Clustering, hub selection, metro ring design, federal ring design and routing problems. In this paper a branch-and-price algorithm is presented for jointly solving the clustering problem, the metro ring design problem and the routing problem. Computational results are given for networks with up to 36 nodes

Design of local networks using USHRs

We consider the problem of designing a local network in a two-level telecommunication network. Given one or two hub nodes, central offices (COs) and conduits, the problem is to find a set of unidirectional self-healing rings (USHRs) which covers all COs and satisfies all demands at minimum cost. The solution approach used is the decomposition and column generation. Master problem and subproblem are modeled as integer programming models. After the optimal solution to linear programming relaxation of the master problem is obtained, a branch-and-bound algorithm is used to get an integer solution. A set of valid inequalities for a subproblem is given and a branch-and-cut algorithm is used to find an optimal solution to the subproblem. Computational results using real data are reported