Abstract. This paper describes a system, FASoft, for discrete channel frequency assignment. In practice, the assignment of frequencies in a network of compatible equipment is often done manually or by the use of a single computational technique. FASoft incorporates state-of-the-art heuristics, sequential assignment algorithms, and a maximal clique algorithm to aid in the assignment process. Lower bounding procedures are included into the system to assess the performance of the assignment techniques and to provide an assessment of how close a particular assignment is to the optimal. The results show that FASoft produces optimal solutions to several practical examples. IntroductionThe radio spectrum is an important natural resource. Many services, both civil and military, require access to the spectrum in order to function, and the demand for frequencies is increasing year by year. Consequently, efficient management of the spectrum requires that frequencies be assigned, for a particular service, in an optimum or near-optimum manner. In practice, this assignment of frequencies is often done using greedy heuristics, which mimic the way the process may be done manually. These methods produce assignments quickly (even for large problems) but inevitably use more spectrum than is necessary. Exact methods based on graph theory give the optimum solution but are computationally unrealistic for problems involving •>50 transmitters. The purpose of this paper is to show how the so-called metaheuristic techniques (simulated annealing, genetic algorithms, and tabu search) can be used to produce optimum solutions to frequency assignment problems. This paper is concerned with the assignment of discrete channels to the transmitters of a system of compatible equipment. In some applications, such as cellular radio networks, the coverage area is divided into a number of cells, typically hexagonal, with each cell assigned a set of frequencies. We refer to such A software system FASoft will be described which produces a frequency assignment for any problem described by a constraint matrix, not necessarily a cellular system. FASoft can handle constraints with transmitters external to the system under consideration. However, it does not handle issues such as intermodulation products or required bandwidth for different modulation schemes such as digital code division multiple access (CDMA), nor does it address problems such as spread spectrum systems and discrete narrowband systems operating in the same 1921
A tabu search algorithm with a dynamic tabu list for the fixed-spectrum frequency-assignment problem is presented. For cellular problems, the algorithm can be combined with an efficient cell reoptimization step. The algorithm is tested on several sets of test problems and compared with existing algorithms of established performance. In particular, it is used to improve some of the best existing assignments for COST 259 benchmarks. These results add support to the claim that the algorithm is the most effective available, at least when solution quality is a more important criterion than solution speed. The algorithm is robust and easy to tune.
Permutation codes (or permutation arrays) have received considerable interest in recent years, partly motivated by a potential application to powerline communication. Powerline communication is the transmission of data over the electricity distribution system. This environment is rather hostile to communication and the requirements are such that permutation codes may be suitable. The problem addressed in this study is the construction of permutation codes with a specified length and minimum Hamming distance, and with as many codewords (permutations) as possible. A number of techniques are used including construction by automorphism group and several variations of clique search based on vertex degrees. Many significant improvements are obtained to the size of the best known codes.
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