t interference (as will power control). The principles and methods of frequency re-use (the same as used in GSM radio net- works, e.g. frequency hopping) are used extensively so that the spectrum is used effectively. Power control is more necessary in the downlink direction. Using the BCCH layer does this. The BCCH layer has an important characteristic, namely that burst transmission in the DL is constant and with full power. This means that variation in throughput is due to user multiplexing over the same time slot, thereby making the time slot capacity con- stant (and independent of the GPRS traffic load). Time slot capacity is also interference- limited. With an increase of traffic, the number of users per time slot decreases because of interference. Thus, in a GPRS network, interference reduction becomes quite an important aspect of the whole network-planning scenario. Parameter Planning Parameter planning in a GPRS network can be considered to be an extension of GSM parameter planning. Signalling, RRM, power control, handover, etc., are still relevant, and extra parameters related to packet data are added. The major enhancements are in the signalling parameters. As seen earlier in Table 5.1, there is whole list of parameters associated with the signalling of packet data transfer. One important parameter to decide is whether or not the GPRS traffic goes on the BCCH time slot. Then there are parameters that are related to defining the GPRS territory. Lastly, there are parameters related to routing and location area codes, to ensure enough capacity is available for paging. 5.5.3 Transmission Network Planning The fundamental concepts remain the same as for a GSM network, as described in Chapter 3. However, one extra aspect that transmission planning engineers have to deal with is PCU dimensioning. The packet control unit is located in the BSC, as shown in Figure 5.6. It is responsible for management of the GPRS (or packet) traffic. The main aspect of dimensioning of the PCU is its capacity with respect to: the m