The GSM standard. Стандарт gsm теле2
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GSM Frequencies | GSM Channels & Frequency Bands
- a tabular summary of the frequencies and frequency bands allocations and spectrum used by the GSM cellular telecommunications system.
Although it is possible for the GSM cellular system to work on a variety of frequencies, the GSM standard defines GSM frequency bands and frequencies for the different spectrum allocations that are in use around the globe. For most applications the GSM frequency allocations fall into three or four bands, and therefore it is possible for phones to be used for global roaming.
While the majority of GSM activity falls into just a few bands, for some specialist applications, or in countries where spectrum allocation requirements mean that the standard bands cannot be used, different allocations may be required. Accordingly for most global roaming dual band, tri-band or quad-band phones will operate in most countries, although in some instances phones using other frequencies may be required.
GSM band allocations
There is a total of fourteen different recognised GSM frequency bands. These are defined in 3GPP TS 45.005.
|380||380.2 - 389.8||390.2 - 399.8|
|410||410.2 - 419.8||420.2 - 429.8|
|450||450.4 - 457.6||460.4 - 467.6|
|480||478.8 - 486.0||488.8 - 496.0|
|710||698.0 - 716.0||728.0 - 746.0|
|750||747.0 - 762.0||777.0 - 792.0|
|810||806.0 - 821.0||851.0 - 866.0|
|850||824.0 - 849.0||869.0 - 894.0|
|900||890.0 - 915.0||935.0 - 960.0||P-GSM, i.e. Primary or standard GSM allocation|
|900||880.0 - 915.0||925.0 - 960.0||E-GSM, i.e. Extended GSM allocation|
|900||876.0 - 915||921.0 - 960.0||R-GSM, i.e. Railway GSM allocation|
|900||870.4 - 876.0||915.4 - 921.0||T-GSM|
|1800||1710.0 - 1785.0||1805.0 - 1880.0|
|1900||1850.0 - 1910.0||1930.0 - 1990.0|
GSM frequency band usage
The usage of the different frequency bands varies around the globe although there is a large degree of standardisation. The GSM frequencies available depend upon the regulatory requirements for the particular country and the ITU (International Telecommunications Union) region in which the country is located.
As a rough guide Europe tends to use the GSM 900 and 1800 bands as standard. These bands are also generally used in the Middle East, Africa, Asia and Oceania.
For North America the USA uses both 850 and 1900 MHz bands, the actual band used is determined by the regulatory authorities and is dependent upon the area. For Canada the 1900 MHz band is the primary one used, particularly for urban areas with 850 MHz used as a backup in rural areas.
For Central and South America, the GSM 850 and 1900 MHz frequency bands are the most widely used although there are some areas where other frequencies are used.
GSM multiband phones
In order that cell phone users are able to take advantage of the roaming facilities offered by GSM, it is necessary that the cellphones are able to cover the bands of the countries which are visited.
Today most phones support operation on multiple bands and are known as multi-band phones. Typically most standard phones are dual-band phones. For Europe, Middle east, Asia and Oceania these would operate on GSM 900 and 1800 bands and for North America, etc dual band phones would operate on GSM 850 and 1900 frequency bands.
To provide better roaming coverage, tri-band and quad-band phones are also available. European triband phones typically cover the GSM 900, 1800 and 1900 bands giving good coverage in Europe as well as moderate coverage in North America. Similarly North America tri-band phones use the 900, 1800 and 1900 GSM frequencies. Quad band phones are also available covering the 850, 900, 1800 and 1900 MHz GSM frequency bands, i.e. the four major bands and thereby allowing global use.
By Ian Poole
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More cellular telecommunications tutorials
The GSM standard
Introduction to the GSM standard
The GSM (Global System for Mobile communications) network is, at the start of the 21st century, the most commonly used mobile telephony standard in Europe. It is a so-called "second generation" (2G) standard because, unlike the first generation of portable telephones, communications occur in an entirely digital mode.
Called "Groupe Spécial Mobile" when first standardized in 1982, it became an international standard called "Global System for Mobile communications" in 1991.
In Europe, the GSM standard uses the 900 MHz and 1800 MHz frequency bands. In the United States, however, the frequency band used is the 1900 MHz band. For this reason, portable telephones that are able to operate in both Europe and the United States are called tri-band while those that operate only in Europe are called bi-band.
The GSM standard allows a maximum throughput of 9.6 kbps, which allows transmission of voice and low-volume digital data, for example text messages (SMS, for Short Message Service) or multimedia messages (MMS, for Multimedia Message Service).
The concept of cellular network
Mobile telephone networks are based on the concept of cells, circular zones that overlap to cover a geographical area.
Cellular networks are based on the use of a central transmitter-receiver in each cell, called a "base station" (or Base Transceiver Station, written BTS).
The smaller the radius of a cell, the higher the available bandwidth. So, in highly populated urban areas, there are cells with a radius of a few hundred metres, while huge cells of up to thirty kilometres provide coverage in rural areas.
In a cellular network, each cell is surrounded by 6 neighboring cells (which is why a cell is generally drawn as a hexagon). To avoid interference, adjacent cells cannot use the same frequency. In practice, two cells using the same frequency range must be separated by a distance of two to three times the diameter of the cell.
Architecture of the GSM network
In a GSM network, the user terminal is called a mobile station. A mobile station is made up of a SIM (Subscriber Identity Module) card allowing the user to be uniquely identified, and a mobile terminal, in other words the user device (normally a portable telephone).
The terminals (devices) are identified by a unique 15-digit identification number called IMEI (International Mobile Equipment Identity). Each SIM card also has a unique (and secret) identification number called IMSI (International Mobile Subscriber Identity). This code can be protected using a 4-digit key called a PIN code.
The SIM card therefore allows each user to be identified independently of the terminal used during communication with a base station. Communications between a mobile station and a base station occur via a radio link, generally called an air interface (or more rarely Um interface).
All the base stations of a cellular network are connected to a base station controller (written BSC), which is responsible for managing distribution of the resources. The system consisting of the base station controller and its connected base stations is called the Base Station Subsystem (BSS).
Finally, the base station controllers are themselves physically connected to the Mobile Switching Centre (MSC), managed by the telephone network operator, which connects them to the public telephone network and the Internet. The MSC belongs to a Network Station Subsystem (NSS), which is responsible for managing user identities, their location and establishment of communications with other subscribers.
The MSC is generally connected to databases that provide additional functions:
- The Home Location Register (written HLR): a database containing information (geographic position, administrative information, etc.) on the subscribers registered in the area of the switch (MSC).
- The Visitor Location Register (written VLR): a database containing information on users other than the local subscribers. The VLR retrieves the data on a new user from the HLR of the user's subscriber zone. The data are maintained as long as the user is in the zone and are deleted when the user leaves or after a long period of inactivity (terminal off).
- The Equipment Identify Register (written EIR): a database listing the mobile terminals.
- The Authentication Centre (AUC): responsible for verifying user identities.
The cellular network formed in this way is designed to support mobility via management of handovers (movements from one cell to another).
Finally, GSM networks support the concept of roaming: movement from one operator network to another.
A SIM card contains the following information:
- Subscriber telephone number (MSISDN)
- International subscriber number (IMSI, international mobile subscriber identity)
- State of the SIM card
- Service code (operator)
- Authentication key
- PIN (Personal Identification Code)
- PUK (Personal Unlock Code)
Latest update on October 16, 2008 at 09:43 AM by Jeff.
GSM - Overview
What is GSM?
If you are in Europe or Asia and using a mobile phone, then most probably you are using GSM technology in your mobile phone.
GSM stands for Global System for Mobile Communication. It is a digital cellular technology used for transmitting mobile voice and data services.
The concept of GSM emerged from a cell-based mobile radio system at Bell Laboratories in the early 1970s.
GSM is the name of a standardization group established in 1982 to create a common European mobile telephone standard.
GSM is the most widely accepted standard in telecommunications and it is implemented globally.
GSM is a circuit-switched system that divides each 200 kHz channel into eight 25 kHz time-slots. GSM operates on the mobile communication bands 900 MHz and 1800 MHz in most parts of the world. In the US, GSM operates in the bands 850 MHz and 1900 MHz.
GSM owns a market share of more than 70 percent of the world's digital cellular subscribers.
GSM makes use of narrowband Time Division Multiple Access (TDMA) technique for transmitting signals.
GSM was developed using digital technology. It has an ability to carry 64 kbps to 120 Mbps of data rates.
Presently GSM supports more than one billion mobile subscribers in more than 210 countries throughout the world.
GSM provides basic to advanced voice and data services including roaming service. Roaming is the ability to use your GSM phone number in another GSM network.
GSM digitizes and compresses data, then sends it down through a channel with two other streams of user data, each in its own timeslot.
Listed below are the features of GSM that account for its popularity and wide acceptance.
Improved spectrum efficiency
Low-cost mobile sets and base stations (BSs)
Compatibility with Integrated Services Digital Network (ISDN) and other telephone company services
Support for new services
The following table shows some of the important events in the rollout of the GSM system.
|1982||Conference of European Posts and Telegraph (CEPT) establishes a GSM group to widen the standards for a pan-European cellular mobile system.|
|1985||A list of recommendations to be generated by the group is accepted.|
|1986||Executed field tests to check the different radio techniques recommended for the air interface.|
|1987||Time Division Multiple Access (TDMA) is chosen as the access method (with Frequency Division Multiple Access [FDMA]). The initial Memorandum of Understanding (MoU) is signed by telecommunication operators representing 12 countries.|
|1988||GSM system is validated.|
|1989||The European Telecommunications Standards Institute (ETSI) was given the responsibility of the GSM specifications.|
|1990||Phase 1 of the GSM specifications is delivered.|
|1991||Commercial launch of the GSM service occurs. The DCS1800 specifications are finalized.|
|1992||The addition of the countries that signed the GSM MoU takes place. Coverage spreads to larger cities and airports.|
|1993||Coverage of main roads GSM services starts outside Europe.|
|1994||Data transmission capabilities launched. The number of networks rises to 69 in 43 countries by the end of 1994.|
|1995||Phase 2 of the GSM specifications occurs. Coverage is extended to rural areas.|
|1996||June: 133 network in 81 countries operational.|
|1997||July: 200 network in 109 countries operational, around 44 million subscribers worldwide.|
|1999||Wireless Application Protocol (WAP) came into existence and became operational in 130 countries with 260 million subscribers.|
|2000||General Packet Radio Service(GPRS) came into existence.|
|2001||As of May 2001, over 550 million people were subscribers to mobile telecommunications.|