(A) study on channel assignment policies in cellular mobile telephone systems

Abstract

A channel assignment problem is to develop efficient channel assignment policies that can maximize the number of calls served in cellular mobile systems. This problem is one of the most important problems in the design and operation of cellular mobile systems. In the future, the number of subscribers will increase more rapidly and hence the number of cells will also increase more rapidly. Thus this problem will be much more important. Channel assignment policies can be roughly classified into two categories: fixed channel assignment (FCA) and dynamic channel assignment (DCA). FCA is to assign a fixed channel to a call appearing in each cell, where the fixed channel is one of channels allocated to the cell in advance. In FCA, it counts how channels are allocated to each cell in advance. On the other hand, DCA is to assign a fixed or dynamic channel to a call, where the dynamic channel is one of channels allocated to common pools and used in several cells. In DCA, it is interesting how dynamic channels are assigned to calls in each cell. In this thesis, we have dealt with a minimum span problem for FCA, and a hybrid channel assignment (HCA) problem and a borrowing channel assignment (BCA) problem for DCA. MSP is to minimize the span, i.e., the number of channels which are required to satisfy a given grade of service for a cellular system, subject to the channel separation constraints. To solve the problem, we have suggested how to reduce a considered system to a smaller system by using a clustering concept, and how to partition the reduced system into several parts, and then a heuristic algorithm based on these two methods. A basic idea of solving a partitioned problem is to maximize the separation between channels assigned to any two nearest cells. We have compared the computational results of our algorithm with those of existing algorithms. In HCA, each cell has more than two types of channel sets, where one type of channel set consists of fixed channels and...