ortant to verify the subscriber forecast from time to time and keep it up to date. The coverage and quality targets need to be adjusted for the different network evolution phases. Interference probability becomes more important as the network capacity enlarges and has to be added as part of the quality targets. The network features that are used have an effect on the dimensioning phase. The capacity and quality requirements need to be adjusted according to the features in use. Some parameters that affect network planning cannot be controlled and therefore it is important to know what they are and then to take them into account in the planning. The topology and morphology is always area specific and due to this the area related planning parameters are case specific. An accurate digital map is needed in network planning. The map is used together with the propagation model to calculate the coverage areas in the planning phase. The propagation model is customised for the planning area with propagation measurements. Population data are needed when estimating subscriber numbers. Population data as a layer on the map are useful in the planning tasks in order to cover a dense population area and allocate needed capacity. The available bandwidth is a critical network planning parameter. Some basic decisions are dependent on the bandwidth, BTS configuration and frequency planning. The quality of the cellular network is highly dependent on the quality of the network plan. The network performance will be measured and analysed to prove that it is working according to the planning requirements. 2.2.2 Introducing GPRS in the GSM Network The GSM networks did not previously feature any efficient method for dealing with larger data quantities (packets). Excessive connecting times and signalling traffic did not allow the effective transfer of large quantities of data. The GPRS system, however, fulfills the requirements of future markets for mobile data communication in a far more innovative and effective manner. In the GSM system, 