Cost-minimizing construction of a unidirectional SHR with diverse protection

The widespread use of SONET technology makes the self-healing ring (SHR) architecture the most basic building-block in designing a large fiber-optic network which is not only survivable but also cost-effective. We address the design problem of placing a single SONET unidirectional ring with a single gateway hub in a region administered by a community of interest. Introduced for the purpose of further cost-saving in our problem setting is the flexibility that some offices, instead of being included in the ring, can be homed to the ring via two arc-disjoint paths. Given the set of offices and potential arcs, the objective is then to determine at the minimum total cost both the ring location and the homing to the ring of its nonmember nodes. We formulate the problem as a mixed integer programming model and develop an efficient solution procedure by devising six improvement heuristics. Extensive computational experiments are conducted with input data instances selected from the data ranges of the real-world environments. The practical value of the solution procedure for network planners is well evidenced by its excellent and consistent performance of quickly generated good-quality solutions over various input data instances