Parallel hyperheuristics for the frequency assignment problem

This work presents a set of approaches used to deal with the frequency assignment problem (FAP), which is one of the key issues in the design of GSM networks. The used formulation of FAP is focused on aspects which are relevant for real-world GSM networks. A memetic algorithm, together with the specifically designed local search and variation operators, are presented. The memetic algorithm obtains good quality solutions but it must be adapted for each instance to be solved. A parallel hyperheuristic-based model was used to parallelize the approach and to avoid the requirement of the adaptation step of the memetic algorithm. The model is a hybrid algorithm which combines a parallel island-based scheme with a hyperheuristic approach. The main operation of the island-based model is kept, but the configurations of the memetic algorithms executed on each island are dynamically mapped. The model grants more computational resources to those configurations that show a more promising behavior. For this purpose two different criteria have been used in order to select the configurations. The first one is based on the improvements that each configuration is able to achieve along the executions. The second one tries to detect synergies among the configurations, i.e., detect which configurations obtain better solutions when they are cooperating. Computational results obtained for two different real-world instances of the FAP demonstrate the validity of the proposed model. The new designed schemes have made possible to improve the previously known best frequency plans for a real-world network.