A. I. Zreikat, Khalid Al-Begain

Abstract

The coverage of a mobile system depends significantly on the geographical nature of the covered area. The signal propagation can be dramatically different in downtown area with many high buildings than in a building free area. This is particularly critical in third generation (3G) mobile systems based on Code-Division Multiple Access (CDMA) air interfaces where the power management is a core part of the call admission control of the system. Therefore, performance studies of such systems based on free space assumptions may lead to optimistic results. In this paper, the performance of a 3G UMTS mobile network covering an urban area and surrounding suburban areas is considered. For modelling the propagation, the COST-231 extended Hata model has been used which represents more realistic propagation models for urban-suburban environments. Based on this model, closed expressions have been derived for the capacity bounds in the existence of interference due to non-ideal orthogonality of codes in the used CDMA system and background noise. These expressions are used to develop a network level sophisticated call admission control (CAC) algorithm to achieve nearly equal blocking probability and balanced utilization over the whole network area. Detailed simulation is used to study the performance of the network under different traffic and interference conditions. The results show that the proposed CAC algorithm performs very well in achieving equal blocking probability by releasing the load on the heavily loaded central area and, thus, achieving better balanced load on the network under different interference conditions. Additionally, some design and environment parameters are studied like the height of the base station and the average height of the mobile.

International Journal on Simulation: Systems, Science and Technology, Special Issue by G. K. Theodoropoulos: Modeling and simulation of Computer Systems, Vol. 4, No. 3-4, September, 2003.