Optimizing a ring-based private line telecommunication network using tabu search

One of the private line network design problems in the telecommunications industry is to interconnect a set of customer locations through a ring of end offices so as to minimize the total tariff cost and provide reliability. We develop a Tabu Search method for the problem that incorporates long term memory, probabilistic move selections, hierarchical move evaluation, candidate list strategies and an elite solution recovery strategy. Computational results for test data show that the Tabu Search heuristic finds optimal solutions for all test problems that can be solved exactly by a branch-and-cut algorithm, while running about three orders of magnitude faster than the exact algorithm. In addition, for larger size problems that cannot be solved exactly, the tabu search algorithm outperforms the best local search heuristic currently available. The performance gap favoring Tabu Search increases significantly for more difficult problem instances.