Optimizing Frequency Hopping in GSM Cellular Phone Networks

Abstract

The mobile telephony market has been undergoing a dramatic increase in the volume of demand as well as in the quality requirements. The limiting resource in this highly competitive market is the available frequency spectrum. In GSM networks, frequency reuse has been the basic tool for optimizing the spectrum management. This method is sometimes insufficient, however, for the most congested networks. Frequency Hopping (FH) is a method that allows one to expand the available capacity of mobile networks or to improve the quality of service through interference averaging and frequency diversity. Current implementations of FH are based on Random or Cyclic Hopping patterns. In this paper, we propose to optimize FH. We describe a simple heuristic algorithm for allocating frequencies to cells and scheduling the frequency hopping for each mobile. The performance of the proposed approach in a synchronized network is compared to Random and Cyclic FH and to the optimized static frequency reuse implementations. We show that hopping algorithms that use some form of controlled optimization beyond random and cyclic hopping could significantly improve the quality of service and achieve interference averaging, should the telecommunications equipment manufacturers decide to implement such a feature or to allow the operators to control frequency hopping by using their own algorithms.