ependent on C/I ratios. With the GPRS network using the resources of the GSM network, interference will be high, thus degrading the C/I ratio. Degradation of the C/I ratio in turn means a reduction in coverage areas. Moreover, addition of the GPRS network will decrease the voice quality of the network. In urban areas, there is always a problem with frequencies. Channel allocation to a GPRS network in the initial phase is always based on the GSM channel allocation, with voice (CS) subscribers taking priority. Thus, capacity plans and channel allocations have to be studied and optimised again during this process. Another aspect is the speed of the data services. Though the theoretical speed of a GPRS network should be about 171 kbps, in practice values are still around 40-60 kbps. The higher speed is possible only when all the eight time slots are utilised, which is not the case as usually five TS can be used for data. Moreover, the C/I requirements may not be satisfied for coding schemes beyond CS-1, thus reducing the data processing scheme. All the above factors coverage, capacity and quality - are also affected by the parameter settings. As seen in Chapter 2, parameter settings (or readjustments) again have an important role in the GPRS network optimisation process. NETWORK OPTIMISATION The optimisation process starts with the collection of required data. This can be radio network planning data from the design phase, and performance data. Radio Planning Data The existing network data includes site information such as the location of base stations, antenna locations and heights, antenna azimuths and inclinations (tilts), etc. Planning data also includes parameter settings. The configuration data includes base station numbers and identity codes (e.g. BSIC), cell configuration, frequency plans, power budget calculations (both uplink and downlink), etc. This information is similar to that required in GSM radio network optimisation. Additional information needed includes the radio time-slot usage for signalling, voic