Brief description of GSM standard

GSM is Short for Global System for Mobile Communications, one of the leading digital cellular systems. GSM uses narrowband TDMA, which allows eight simultaneous calls on the same radio frequency. GSM was first introduced in 1991. As of the end of 1997, GSM service was available in more than 100 countries and has become the de facto standard in Europe and Asia.

Considered the most advanced digital cellular technology, GSM networks are leaders in many typically "digital" services including the Short Message Service (SMS), Over the air (OTA) configuration and GSM positioning. Considering its technology and presence both in Americas and the rest of the world, GSM is in a good position for global roaming and many new GSM phones are called "global phones", since they can be used in virtually any country. The SIM card ("Subscriber Identification Module") is also a unique and essential component of GSM phones. Technically, GSM was built based on the TDMA protocol.