As GSM has grown worldwide, it has expanded to operate at three frequency bands: 900, 1800 and 1900.
GSM 900
The original frequency band specified for GSM was 900 MHz. Most GSM networks worldwide use this band. In some countries and extended version of GSM 900 can be used, which provides extra network capacity. This extended version of GSM is called E-GSM, while the primary version is called P-GSM.
GSM 1800
In 1990, in order to increase competition between operators, the United Kingdom requested the start of a new version of GSM adapted to the 1800 MHz frequency band. Licenses have been issued in several countries and networks are in full operation. By granting licenses for GSM 1800 in addition to GSM 900, a country can increase the number of operators. In this way, due to increased competition, the service to subscribers is improved.
GSM 1900
In 1995, the Personal Communications Services (PCS) concept was specified in the United States. The basic idea is to enable "person-to-person" communication rather than "station-tostation". PCS does not require that such services be implemented using cellular technology, but this has proven to be
the most effective method. The frequencies available for PCS are around 1900 MHz. As GSM 900 could not be used in North America due to prior allocation of the 900 MHz frequencies, GSM 1900 MHz is seen as an opportunity to bridge this gap. The main differences between the American GSM 1900 standard and GSM 900 is that it supports ANSI signaling.
GSM 400
Ericsson and Nokia support the work of ETSI on a global standard for GSM on the 450 MHz frequency band. Ericsson and Nokia are aiming to make GSM 450 products available for the market during 2001. The believe is that the introduction of GSM in the 450 MHz frequency band will further leverage the
success of global GSM. GSM 400 also provides NMT system operators a logical way to introduce quality digital services and seamless international roaming possibilities.
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