Global System for Mobile Communications(GSM)

When I purchased my new mobile, I was totally unaware about GSM (Global System for Mobile Communication). I had knowledge of mobile features i.e., SMS, MMS, Emails but unaware of GSM features like measuring the speed of data transmission and security. Then I searched on net to get the knowledge of GSM technology and what I got information about GSM technology is sharing with you.

GSM is a cellular network, which means that mobile phones connect to it by searching for cells in the immediate vicinity.

 There are five different cell sizes in a GSM network—macro, micro, pico, femto and umbrella cells. The coverage area of each cell varies according to the implementation environment. Macro cells can be regarded as cells where the base station antenna is installed on a mast or a building above average roof top level. Micro cells are cells whose antenna height is under average roof top level; they are typically used in urban areas. Pico cells are small cells whose coverage diameter is a few dozen metres; they are mainly used indoors. Femto cells are cells designed for use in residential or small business environments and connect to the service provider’s network via a broadband internet connection. Umbrella cells are used to cover shadowed regions of smaller cells and fill in gaps in coverage between those cells.

GSM networks operate in a number of different carrier frequency ranges (separated into GSM frequency ranges for 2G and UMTS frequency bands for 3G), with most 2G GSM networks operating in the 900 MHz or 1800 MHz bands. Most 3G networks in Europe operate in the 2100 MHz frequency band. The transmission power in the handset is limited to a maximum of 2 watts in GSM850/900 and 1 watt in GSM1800/1900.

One of the key features of GSM is the Subscriber Identity Module, commonly known as a SIM card. The SIM is a detachable smart card containing the user's subscription information, phone book and calendar information in most cases. This allows the user to retain his or her information after switching handsets. Alternatively, the user can also change operators while retaining the handset simply by changing the SIM. Some operators will block this by allowing the phone to use only a single SIM, or only a SIM issued by them; this practice is known as   SIM locking

There is lot of information about it when I searched on it, this helps you to understand some basics about GSM technology what we are using in daily practice.