What does GSM mean in a cell phone?

The GSM system uses TDMA to split a frequency into time slots.
Probably the most useful thing to know about the Global System for Mobile communications (GSM) is that it is an
international standard. If you travel in Europe and many other parts of the world, GSM is the only type of cellular service
available. Originally, the acronym GSM stood for Groupe Spécial Mobile, a group formed by the Conference of
European Posts and Telegraphs (CEPT) in 1982 to research the merits of a European standard for mobile
telecommunications. Commercial service using the GSM system did not actually start until 1991. Instead of using analog
service, GSM was developed as a digital system using TDMA technology.
Using TDMA, a narrow band that is 30 kHz wide and 6.7 milliseconds long is split time-wise into three time slots. Narrow
band means channels in the traditional sense. Each conversation gets the radio for one-third of the time. This is possible
because voice data that has been converted to digital information is compressed so that it takes up significantly less
transmission space. Therefore, TDMA has three times the capacity of an analog system using the same number of
channels.
TDMA is the access method used by GSM, as well as the Electronics Industry Alliance and the Telecommunications
Industry Association for Interim Standard 54 (IS-54) and Interim Standard 136 (IS-136). GSM implements TDMA in a
somewhat different and incompatible way from IS-136. Think of GSM and IS-136 as two different operating systems that
work on the same processor , like Windows and Linux both working on an Intel Pentium III. GSM systems provide a
number of useful features:
Uses encryption to make phone calls more secure
Data networking
Group III facsimile services
Short Message Service (SMS) for text messages and paging
Call forwarding
Caller ID
Call waiting
Multi-party conferencing
What does GSM mean in a cell phone

GSM operates in the 900 MHz band (890 MHz - 960 MHz) in Europe and Asia and in the 1900 MHz (sometimes referred
to as 1.9 GHz) band in the United States. It is used in digital cellular and PCS-based systems. GSM is also the basis for
Integrated Digital Enhanced Network (iDEN), a popular system introduced by Motorola and used by Nextel. The
incredible growth of GSM is a big part of why the acronym is now commonly thought of as standing for the Global System
for Mobile communications!
If you were on a cell phone in Europe, you'd be using the GSM service.
What does GSM mean in a cell phone