TOPOLOGICAL OPTIMIZATION OF A COMMUNICATION-NETWORK SUBJECT TO A RELIABILITY CONSTRAINT

This paper considers network topological optimization with a reliability constraint. The objective is to find the topological layout of links, at a minimal cost, under the constraint that the network reliability is not less than a given level of system reliability. A decomposition method, based on branch & bound, is used for solving the problem. In order to speed-up the procedure, an upper bound on system reliability in terms of node degrees is applied. A numerical example illustrates, and shows the effectiveness of the method. If a*, an important parameter, is close to the minimal number of links in a network which satisfy the reliability constraint, then a better starting solution can be obtained, and many searching steps can be saved. In our method, the lower bound a* is close to its actual value if the operational reliability of the link is close enough to 1. Also, if we can find the maximal increasing value of the reliability when a set of links is added to a specified topology, the efficiency of the branch & bound algorithm is improved.