Lower bounding techniques for frequency assignment

The frequency assignment problem is an NP complete problem of great importance to the radiocommunications industry. Most current solution techniques for Peal frequency assignment problems use heuristic algorithms to obtain suboptimal solutions in an acceptable time. By formulating the problems in terms of graph colourings, lower bounds can be obtained to assess the quality of these heuristic solutions. Bounds based on the travelling salesman problem have proved to be successful, in some cases giving tight bounds when applied to a suitable subproblem. However, for general problems these bounds may be difficult to calculate or are far from optimal. The choice of subproblem is critical in evaluating these bounds and can also be of use in the application of the heuristic algorithms. In this paper we present a number of new and improved techniques for determining lower bounds. (C) 1999 Elsevier Science B.V. All rights reserved.