Introduction to GSM (Global System for Mobile Communication)

Along with the mobility of the world population and increasing international trade developed, the necessary telecommunications facilities which can be brought on the way (Mobile).

In the early 80s in several European countries began to be tested to try the technology provider, namely the use of radio communication can be carried in a particular region called cells (cells). Among others the NMT system developed Ericsson in the Nordic countries, the developed system Cnet Siemens in Germany and TACS or AMPS system developed in the UK.
To overcome the various non-standard system was then in 1982 the countries of Europe formed an organization called the Group Special Mobile (GSM). This organization pioneered mobile technology is known as the GSM (Global System for Mobile Communication). Later in the year 1991 of the cellular system was still using analogue technology replaced entirely with digital technology. While the standard used is called ETSI (European Telecommunications Standards Institute).

In accordance with the rules of ITU (International Telecommunication Union) frequencies used by GSM network is in range of 900 MHz, which is the uplink frequency: 890-915 MHz and downlink frequency: 935-960 MHz. Bandwidth / bandwidth used is 25 MHz and the channel width of 200 Khz. Thus the number of channels will be obtained as many as 125 channels, in which 124 channels are used as voice channels and 1 channel for signaling.

With a limited number of channels so that can not follow the development of the growing conversation, the ITU decided to increase the frequency allocation for mobile is at 1800MHz frequency, called DCS (Digital Cellular System) or GSM1800. The division is the uplink frequency: 1710-1785 MHz and downlink frequency: 1805-1880 MHz. The available bandwidth of 75 MHz with the same channel width of 200 Khz, then the GSM will be available in 1800 as many as 375 channels