Global System for Mobile Communications The Global Systems for
Mobile Communications (GSM), is a radio-based technology that
allows mobile phones to communicate. GSM is considered to be the
world's most ubiquitous radio-based cellular technology, with
1.7 billion users as of March 2006. In the United States,
carriers such as T-Mobile and Cingular utilize GSM technology
for their cellular networks. GSM Cell Phone Providers GSM is
considered to be 2G and uses digital data for both signaling and
voice purposes. GSM uses a time division multiple access (TDMA)
protocol to transmit information. Aside from voice, GPRS and
EDGE allow for data transmissions across a GSM network. In terms
of frequencies used, GSM networks often use the 900MHz and
1800MHz bands, but carriers in the United States use 850MHz and
1900MHz bands. As a result, "dual-band" phones, which only
support two of the four major bands, can only be used in certain
parts of the world. More common are "tri-band" phones, which
usually operate on 900/1800M