Design of local networks using USHRs

We consider the problem of designing a local network in a two-level telecom munication network. Given one or two hub nodes, central offices (COs) and c onduits, 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. Computati onal results using real data are reported.