2 Background Information 2.1 GSM-Network in general The GSM Network (Global System for Mobile Communications) is a standard for all-digital mobile phone networks. GSM has been created to provide a mobile telephone system offering the users europewide mobility and voice services compatible with ISDN or analog services. Originally GSM has been designed for voice calls, the tramsmission of text messages (SMS) and the transmission of data with a constant data speed. With the success of the internet an evolution of GSM startet. The GSM network was expanded to offer packet oriented data transmission (e.g. via GPRS) while keeping all other features and being fully downwards compatible.
2.2 GPRS GPRS (General Packet Radio Service) is a packet oriented transmission service which is used in the mobile networks and which is supported by almost all network providers. With GPRS you only have a virtually existing permanent connection to the other party. Only when you really transmit data will the channel will be used, otherwise it is free for other users. This means that no channel will be reserved permanently for a user (as it is with a GSM voice call). Therefore the GPRS-bills depend more on the actual data volume transmitted than on the connect time. If the device is booked into the GPRS-Net it will automatically be assigned an IP-Address and can exchange data with any server accessible via the internet, 51