bdivided into two parts: capacity planning for the radio interface and capacity planning for the Gb interface. In this section, we deal with capacity planning for the radio interface. The network has three kinds of traffic: voice, CS data and PS data. All these have to be considered when doing capacity planning for the radio interface. Circuit-switched traffic always has priority over PS traffic, but owing to the delay-sensitive nature of some PS services, some time slots are dedicated to carry the PS traffic only. CS traffic calculations, as with GSM, pre-dominantly involves the Erlang B tables, blocking and C/I thresholds. Assume the casè shown earlier in Figure 5.5. There is one cell that has two TRXs. In ideal conditions (i.e. without blocking), 14 (voice) users can use the time slots continuously, SO traffic of 14 Erl would be generated if there is no blocking. If the number of voice users is reduced to eight, then the remaining six time slots can be used for data. It should be noted, however, that data which are not delay-sensitive could still be sent through the gaps in the air interface. Only the data that are delay sensitive need uninterrupted availability of time slots. When an existing GSM network is upgraded to a GPRS network, the available ca- pacity falls short for the PS data. Increasing the number of TRXs and the time slots in GPRS territories (dedicated + default) would be one effective way to tackle the capacity problem. Quality of service (QoS) has a deep impact on capacity planning. An increased load would decrease the quality of a call. For critical applications, a minimum QoS should be met, which means that the loading can increase only up to a certain point. Thus, frequency planning takes an important place in achieving a desired QoS level in a GPRS radio network. GPRS NETWORK PLANNING Frequency Planning Coverage and capacity planning go hand-in-hand, and coverage planning is quite related to frequency planning. An effective frequency plan will increase coverage areas significantly and limi