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GSM phone

A cellphone or smartphone that uses the GSM cellular system and TDMA air interface. In the U.S., AT&T and T-Mobile are GSM carriers. Contrast with CDMA phone. See GSM.



GSM

(Global System for Mobile Communications) A digital cellular phone technology that started in Europe. The GSM Association (GSMA) defines the entire cellular system for GSM as well as LTE phones. GSM uses the TDMA air interface, while LTE uses OFDM (see LTE).

In the early 1990s, GSM enabled roaming across European nations for the first time. Eventually more than three billion customers worldwide could phone each other via roaming agreements between the carriers. AT&T and T-Mobile offered GSM service in the U.S., while Rogers Wireless deployed GSM in Canada.

GSM operates in several frequency bands, including 900 MHz and 1.8 GHz in Europe and 850 MHz and 1.9 GHz in the U.S. and Canada. GSM's TDMA technology is based on a circuit-switched system that divides each 200 kHz channel into eight 25 kHz time slots.

The SIM Smart Card
GSM phones use a Subscriber Identity Module (SIM) card that contains user account information. Every GSM phone becomes immediately programmed after inserting the SIM card, thus allowing GSM phones to be easily rented or borrowed. See SIM card.

Text and Data
Text messaging (SMS) and data transfer were built into GSM, and data rates have continually increased over the years. See GPRS, WCDMA, EDGE, HSCSD, GSM Association, GSA, TDMA, CDMA and PCS.

Vive la Cellphone!
When GSM phones were introduced, they were reported to produce a deafening sound for hearing aid wearers and interfere with pacemakers. Swedish hospitals banned them. An Australian newspaper claimed a motorist set off his airbag with one, and most curious, in Paris, they were said to occasionally reset taxi meters to zero.




The SIM Card
The back of a GSM phone opens, and the tiny SIM card is inserted, as in this example from Europe's Amena cellphone service. The bottom view is the card outside the socket showing contact points.






Evolution of 3G Technologies
This chart shows the evolution of carrier technologies throughout the world as they move from standard cellphone services to high-speed data capabilities.






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