Wireless Personal Communications (2005) 34: 411–439 DOI: 10.1007/s11277-005-6496-0 C  Springer 2005 A Novel Approach to Cell Coverage Area Determination for FDMA–CDMA Systems F. HENDESSI 1 , KH. GHASSEMI 1 , A. GHAYOORI 1 and T. A. GULLIVER 2 1 Department of Electrical & Computer Engineering, Isfahan University of Technology, Iran 2 Department of Electrical & Computer Engineering, University of Victoria, Victoria, BC Canada E-mail: agullive@ece.uvic.ca Abstract. There is no theoretical time or frequency restrictions on capacity in DS-CDMA systems. In these systems, the signal to interference ratio (SIR) has a major effect on capacity. Since an increase in the user SIR at the base station (BS) leads to higher capacity, transmission power control is employed. The nonuniform distribution of users in the network causes different quality of service (QOS) in distinct regions, therefore network resources may not be utilized properly. A dynamic distribution algorithm can be employed to balance the QOS delivered in different regions of the network. In this paper, a novel dynamic distribution algorithm is introduced. The proposed algorithm deactivates certain users when the network encounters an overload. By applying this policy, the required SIR can be maintained for the remaining users. Keywords: Capacity, CDMA, FDMA, Power Control, Quality of Service 1. Introduction In cellular systems, the transmitted signal passes through a multipath fading channel. As a consequence, the signal power is adjusted at the transmitter in order to achieve acceptable performance. The capacity of TDMA and FDMA systems has a predetermined value. Therefore power control has no effect on the capacity of these systems, it is only employed to decrease the cochannel interference (CCI). In code division multiple access (CDMA) systems, signals are transmitted in the same frequency band simultaneously. There are no time or frequency restrictions in these systems and the capacity is defined by the number of users that can be accommodated without losing acceptable quality of service (QOS). The signal to interference ratio (SIR) of all users should not fall below a given threshold, so power control in CDMA systems has a great impact on capacity. It is shown in [1] that a 60% improvement in outage probability is obtained by controlling the transmission power. In [2], it is observed that improper power control reduces the capacity by 50% or more. Wideband CDMA has been proposed to utilize additional bandwidth to deliver services to more users. However, in some cases the available bandwidth is not sufficient for WCDMA to be implemented. In these situations multiband CDMA can be employed. Multiband CDMA systems use different frequency bands in different cells resulting in decreased cochannel interference [3]. These CDMA systems are backward compatible with IS-95 systems and are easy to implement [4], but are more vulnerable to channel frequency selective fading. Also in each cell, a portion of the bandwidth is not utilized which leads to fewer users that can be serviced. The performance of multiband CDMA depends on the band alloca- tion algorithm used. In [4], frequency bands were assigned according to the measured path