GSM
From Halbeeg, the open encyclopedia · Af-Soomaali
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GSM (Global System for Mobile Communications) is a standard for managing mobile telephone networks. It is known as the second generation (2G) of mobile technology, because voice and data are transmitted digitally rather than using the analog method of the earlier generation.
GSM became widespread because many networks in different countries adopted the same standard and operated together. This allowed a user to use his telephone in another country (roaming), using the same SIM card and the same authentication method.
Brief history
Work on the standard began in Europe in the 1980s, when European telecommunications bodies sought a common system to replace the different national networks. GSM commercial service began in the early 1990s and then spread to other continents. Management of the standard was later transferred to international standardization bodies, particularly 3GPP.
How it works
GSM divides the radio spectrum into small portions called channels, and then divides time into slots. This method, known as TDMA (time division multiple access), allows several users to share a single channel, each taking his time slot. Voice is encoded before it is transmitted over the air.
SIM card
One of the important features that GSM introduced is the SIM card—a small smart card that holds the user's identity and security keys. The identity is tied to the card, not to the handset, so the user can change phones while keeping the same number.
Data and later generations
Later, data services were added to GSM, such as GPRS and EDGE, sometimes called 2.5G. These enabled internet access for users, but with limited speeds. Later generations—UMTS/3G, LTE/4G, and 5G—use different methods of dividing the radio spectrum, but many elements of the GSM network architecture and SIM card remained.
Current status
Many networks around the world have begun shutting down GSM networks to free up radio spectrum for newer technologies. However, in some places, particularly where machine-to-machine (M2M) devices and basic phones are used, GSM remains active.