connections are made on a circuit switched basis; i.e. the network establishes an air interface connection. A radio channel is then assigned to a mobile station and the data are transferred via this channel. The MS occupies this radio channel for the entire duration of the transfer process and the user must therefore pay for the full duration of the connection. With the new packet switching transfer system, a data packet is only transferred when there is actually data ready for transfer. This means that several MSs can use a single radio channel simultaneously. The MS is able to use a maximum of eight radio timeslots simultaneously. Whenever the MS sends a data packet, the network forwards the packet to the recipient through the first free radio channel. Since data transfer frequently consists of transfer 'bursts', this system makes efficient use of the radio channels. Preplanning in a GSM Radio Network Coding Schemes in GPRS ETSI has specified four coding schemes in the GPRS network: CS-1, CS-2, CS-3 and CS-4. These coding schemes have been developed based on a compromise between the amount of user data carried and error protection. Coding scheme CS-1 has the lowest data rate and the highest protection while CS-4 has the highest data rate but the lowest protection. When introducing GPRS to the network the operator has certain requirements for the coverage and capacity for the GPRS service and at the same time it is also required that the existing GSM service is not degraded by the introduction of the GPRS service. The planning aspects of introducing GPRS can be considered as two separate approaches, a high level plan and a detailed plan. The high level plan considers the strategy of the GPRS service, whereas the detailed plan places the strategy requirements in the network on a cell-by-cell basis. To meet these requirements the operator needs to consider the following tasks: Select the area in which GPRS will be offered. Identify the cell groups that will offer the GPRS service: - macro cells, micro cells, pico 