Overview

GSM networks consist of cell site radio towers, communication links, switching center(s) and network databases and link to public telephone and data networks.

The main switching system in the GSM wireless network is the mobile switching center (MSC). The MSC coordinates the overall allocation and routing of calls throughout the wireless system. Inter-system connections can link different wireless network systems to allow wireless telephones to move from cell site to cell site and system to system. The GSM system defines inter-system connections in detail to allow universal and uniform service availability GSM wireless devices.

The GSM system can be divided into a base station subsystem (BSS), a network and switching system (NSS), and an operation and maintenance sub-system (OMS). The radio parts of the GSM network are contained in the BSS. The switching, databases, and interconnection parts are contained in the NSS. The OMS contains the necessary system to monitor and diagnose system operation.

Figure 1.26 shows a simplified functional diagram of a GSM network. This diagram shows that the GSM system provides for packet data, circuit data, and voice services. Medium-speed circuit data services (up to 56 kbps) are provided by combining multiple coded channels on a single GSM radio channel. This diagram shows that the Base Station (BTS) contains a radio transceiver (radio and transmitter) that converts the radio signal into a data signal (data and digital voice) that can transfer through the network. The BTS is connected to a base station controller (BSC) that coordinates the...