Optimization of frequency assignment for reduction of cochannel interference

Abstract This paper describes the method of optimization of frequency assignment in satellite communication, aiming at reducing cochannel interference. The method is based on the formulation of the assignment problem, so‐called mathematical programming, and is widely applicable. The basic model is defined, and is composed of a pair of systems sharing the same frequency band. A discrete frequency assignment is made with the small segment as the unit, which is obtained by equi‐partitioning the common channel, and the model is formulated as an assignment problem. The lexicographical minimization is employed as the criterion of optimization, by which the interference is reduced for all carriers. A method is presented in which the optimum solution is obtained by the numerical conversion of the cost matrix and the Hungarian method for the assignment problem. To determine efficiently the optimum assignment for carriers with various bandwidths, an algorithm is presented which is based on the branch‐and‐bound method used frequently in the mathematical programming. By this method, the solution can be determined with a small amount of computation for a problem of practical size. Examples are shown which are the assignment of FM carriers by the basic model and the optimum frequency assignment for eight satellites. As a result, it is shown that the frequency assignment can be determined with sufficient accuracy, and the interference is reduced drastically by sufficiently fine segmentation.