Otimization models for frequency channel management in a cellular system

Abstract

This thesis is concerned with some optimization models for frequency resource management in a cellular system. Frequency resource management includes frequency channel assignment and operation. First, we consider the Frequency Assignment Problem (FAP) for a system with nonhomogeneous traffic distribution and the interference-related constraints. Most of the heuristic algorithms for the FAP have adopted sequential assignment algorithms developed for the Graph Coloring Problem (GCP). In this study, we consider two representative frequency assignment strategies, the frequency exhaustive strategy (FES) and the requirement exhaustive strategy (RES), which are adopted by most of such heuristic algorithms for the FAP. We first show that there always exists an order of the requirement list which provides an optimal assignment with the FES, while the RES doesn``t always have such an order. We will also present two polynomial time heuristic algorithms, one for each strategy. Our second model deals with the so-called Perturbation-Minimizing Frequency Assignment Problem (PMFAP), the objective of which is to assign the available frequency channels for newly generated channel requirements at the minimum reassignment of the preassigned frequencies while meeting the compatibility constraints. For developing the heuristic algorithm for the PMFAP, we adopt the rearrangement technique, which rearranges some of the already assigned frequencies in order to assign frequencies into some more of the new requirements. Generally, subscriber mobility in cellular mobile system is controlled through location updating based on the so-called location area (LA), the basic area unit for paging which consists of a number of cells. There is a tradeoff relation between the two kinds of signalling traffic: paging and location updating. As LAs become bigger consisting of a larger number of cells, the traffic volume for paging increases while that for location updating decreases. This realization...