GSM
(Global System for Mobile Communications) A digital cellular phone technology based on TDMA that is the predominant system in Europe, but also used worldwide. Developed in the 1980s, GSM was first deployed in seven European countries in 1992. It operates in the 900 MHz and 1.8 GHz bands in Europe and the 1.9 GHz PCS band in the U.S. Based on a circuit-switched system that divides each 200 kHz channel into eight 25 kHz time slots, GSM defines the entire cellular system, not just the TDMA air interface.
A fast-growing communications technology, there were more than 250 million GSM users early in 2000. By mid-2004, the one billionth GSM customer was connected. In the U.S., AT&T (formerly Cingular) and T-Mobile offer GSM service.
The SIM Card
GSM phones use a Subscriber Identity Module (SIM) smart card that contains user account information. Any GSM phone becomes immediately programmed after plugging in the SIM card, thus allowing GSM phones to be easily rented or borrowed. SIM cards can be programmed to display custom menus for personalized services.
Text Messaging
GSM provides a short messaging service (SMS) that enables text messages up to 160 characters in length to be sent to and from a GSM phone. It also supports data transfer at 9.6 Kbps to packet networks, ISDN and POTS users. See GPRS, WCDMA, EDGE, HSCSD, GSM Association, GSA, TDMA, CDMA and PCS.
Vive la Cellphone!
Years ago, when GSM phones were introduced, they were reported to produce a deafening sound for hearing aid wearers and to interfere with electronic devices such as 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. |