12 September 2008
GSM (Global System for Mobile communications: originally from Groupe Spécial Mobile) is the most popular standard for mobile phones in the world.GSM is a cellular network, which means that mobile phones connect to it by searching for cells in the immediate vicinity. GSM networks operate in four different frequency ranges. Most GSM networks operate in the 900 MHz or 1800 MHz bands. Some countries in the Americas (including Canada and the United States) use the 850 MHz and 1900 MHz bands because the 900 and 1800 MHz frequency bands were already allocated.
Network structure
The structure of a GSM networkThe network behind the GSM system seen by the customer is large and complicated in order to provide all of the services which are required. It is divided into a number of sections and these are each covered in separate articles.
the Base Station Subsystem (the base stations and their controllers). the Network and Switching Subsystem (the part of the network most similar to a fixed network). This is sometimes also just called the core network. the GPRS Core Network (the optional part which allows packet based Internet connections). all of the elements in the system combine to produce many GSM services such as voice calls and SMS.
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