Global System for Mobile communication
GSM (Global System for Mobile communication) is a digital
mobile telephony system that is widely used in Europe
and other parts of the world. GSM uses a variation of time division multiple
access (TDMA) and is the most widely used of the three digital wireless telephony
technologies (TDMA, GSM, and CDMA). GSM digitizes and compresses data, then
sends it down a channel with two other streams of user data, each in its own
time slot. It operates at either the 900 MHz or 1800 MHz frequency band.
Mobile services based on GSM technology were first launched
in Finland
in 1991. Today, more than 690 mobile networks provide GSM services across 213
countries and GSM represents 82.4% of all global mobile connections. According
to GSM World, there are now more than 2 billion GSM mobile phone users
worldwide. GSM World references China
as "the largest single GSM market, with more than 370 million users,
followed by Russia with 145
million, India with 83
million and the USA
with 78 million users."
Since many GSM network operators have roaming agreements
with foreign operators, users can often continue to use their mobile phones
when they travel to other countries. SIM cards (Subscriber Identity Module)
holding home network access configurations may be switched to those will
metered local access, significantly reducing roaming costs while experiencing
no reductions in service.
GSM, together with other technologies, is part of the
evolution of wireless mobile telemmunications that includes High-Speed
Circuit-Switched Data (HSCSD), General Packet Radio System (GPRS), Enhanced
Data GSM Environment (EDGE), and Universal Mobile Telecommunications Service
(UMTS).
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