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Keywords:

  • Heuristics;
  • Equipment selection;
  • Frequency assignment

Abstract

Microwave fixed links use highly standardized radio equipment and, in the radio equipment standard referenced in this paper, there is a choice between exactly two radio systems when the assigner wishes to resolve a specific data rate exactly: one using a relatively lower-order modulation scheme and one a relatively higher-order scheme. Although the higher-order equipment requires less bandwidth for an isolated link, these systems radiate at higher powers and require larger protection ratios in the radio interference environment which lead to well-established trade-offs between modulation, bandwidth, equivalent isotropic radiated power, and frequency assignment criteria. Our earlier research showed that by extending the Frequency Assignment Problem to include equipment selection and using lower-order modulation equipment on selected links, we can actually reduce the overall span of frequencies required for a network frequency assignment. This work focused on the development of integer programming formulations and analyzed the exact solutions obtained. Exact solutions are impractical for real world problems; hence, here we focus on the development of heuristics for equipment selection. We can model the fixed link network as a complete graph where the vertices represent fixed link frequency assignment requests and the edges represent interference between pairs of vertices. Using a graph theoretic analysis of the interference problem, we propose heuristic techniques and discuss the relative success of our approach in this article.