GSM refers to Global System for Mobile communication and it is a digital mobile telephony system which is widely used in Europe and almost all over the world. GSM had its origin when CEPT created the Groupe Special Mobile (GSM) and the main purpose for creating the GSM was to design a pan-European Mobile technology. Finland was the first country to launch the mobile services that are based on GSM technology. It is estimated that GSM reaches over 1 billion mobile subscribers by representing over 82% of the global mobile connectivity by forming its base in more than 210 countries all over the world.

When compared TDMA and CDMA digital wireless telephony technologies, GSM is the most widely used technology with a slighter variation of TDMA. T-Mobile and AT & T cell phone carriers are using GSM for cell phone networks but the other cell phone carriers like Verizon Wireless, Sprint and Virgin Mobile uses the competing CDMA technology.

As a circuit-switched system, GSM functions by dividing each and every 200kHz channel into eight 25kHz time slots. In most parts of the world, GSM functions on the mobile communication bands of 900MHz and 1800MHz. For transmitting the signals, GSM uses the narrowband TDMA technique. It has the capability to carry data rates ranging from 64 kbps to 120 Mbps.

Main features of GSM that account for its popularity and wide acceptance includes: High-quality speech, improved spectrum efficiency, compatibility with ISDN and other telephone company services, support for new services. GSM provides wider international roaming facilities for its users than the U.S based network technologies by making a mobile phone to be a “world phone”. GSM networks also have good agreements for roaming with the foreign operators and this helps the users to use their cell phones during their travel to foreign countries. If a user’s SIM card is having home network access, it can be configured to the local access with the help of GSM. This helps in reducing the roaming rates significantly without any reduction in service. With the help of GSM, your mobile phone will not be linked to the handset but to the mobile phone’s service carrier’s service network. This facilitates easy exchange from one mobile phone to the other phone without any need for new mobile phone service activation.

GSM belongs to the 2nd generation (2G) mobile phone system. GSM along with the other technologies such as HSCSD, GPRS, EDGE, and UMTS becomes a part of the evolution of wireless mobile telecommunications.