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The Global System for Mobile Communications (GSM) is a standard developed by the European Telecommunications Standards Institute (ETSI) to describe the protocols for second-generation ( 2G) digital
cellular network A cellular network or mobile network is a communication network where the link to and from end nodes is wireless. The network is distributed over land areas called "cells", each served by at least one fixed-location transceiver (typically thre ...
s used by mobile devices such as mobile phones and tablets. GSM is also a trade mark owned by the GSM Association. GSM may also refer to the Full Rate voice codec. It was first implemented in Finland in December 1991. By the mid-2010s, it became a global standard for mobile communications achieving over 90% market share, and operating in over 193 countries and territories. 2G networks developed as a replacement for first generation ( 1G) analog cellular networks. The GSM standard originally described a digital, circuit-switched network optimized for full duplex voice telephony. This expanded over time to include data communications, first by circuit-switched transport, then by packet data transport via
General Packet Radio Service General Packet Radio Service (GPRS) is a packet oriented mobile data standard on the 2G and 3G cellular communication network's global system for mobile communications (GSM). GPRS was established by European Telecommunications Standards Inst ...
(GPRS), and Enhanced Data Rates for GSM Evolution (EDGE). Subsequently, the 3GPP developed third-generation ( 3G) UMTS standards, followed by the fourth-generation ( 4G) LTE Advanced and the fifth-generation 5G standards, which do not form part of the ETSI GSM standard. As a result of the network's widespread use across Europe, the acronym "GSM" was briefly used as a generic term for mobile phones in France, the Netherlands, Bulgaria and in Belgium. A great number of people in Belgium still use it to date. Beginning in the late 2010s, various carriers worldwide started to shut down their GSM networks.


History


Initial European development

In 1983, work began to develop a European standard for digital cellular voice telecommunications when the European Conference of Postal and Telecommunications Administrations (CEPT) set up the ''Groupe Spécial Mobile'' (GSM) committee and later provided a permanent technical-support group based in Paris. Five years later, in 1987, 15 representatives from 13 European countries signed a memorandum of understanding in Copenhagen to develop and deploy a common cellular telephone system across Europe, and EU rules were passed to make GSM a mandatory standard. The decision to develop a continental standard eventually resulted in a unified, open, standard-based network which was larger than that in the United States. In February 1987 Europe produced the first agreed GSM Technical Specification. Ministers from the four big EU countries cemented their political support for GSM with the Bonn Declaration on Global Information Networks in May and the GSM MoU was tabled for signature in September. The MoU drew in mobile operators from across Europe to pledge to invest in new GSM networks to an ambitious common date. In this short 38-week period the whole of Europe (countries and industries) had been brought behind GSM in a rare unity and speed guided by four public officials: Armin Silberhorn (Germany), Stephen Temple (UK),
Philippe Dupuis Philippe Dupuis (; born April 24, 1985) is a Canadian former professional ice hockey player who played in the National Hockey League (NHL) with the Colorado Avalanche and the Toronto Maple Leafs. Playing career Dupuis was drafted 104th overall ...
(France), and Renzo Failli (Italy). In 1989 the Groupe Spécial Mobile committee was transferred from CEPT to the European Telecommunications Standards Institute (ETSI). The IEEE/RSE awarded to Thomas Haug and
Philippe Dupuis Philippe Dupuis (; born April 24, 1985) is a Canadian former professional ice hockey player who played in the National Hockey League (NHL) with the Colorado Avalanche and the Toronto Maple Leafs. Playing career Dupuis was drafted 104th overall ...
the 2018 James Clerk Maxwell medal for their "leadership in the development of the first international mobile communications standard with subsequent evolution into worldwide smartphone data communication". The GSM (2G) has evolved into 3G, 4G and 5G.


First networks

In parallel France and Germany signed a joint development agreement in 1984 and were joined by Italy and the UK in 1986. In 1986, the European Commission proposed reserving the 900 MHz spectrum band for GSM. It was long believed that the former Finnish prime minister Harri Holkeri made the world's first GSM call on 1 July 1991, calling
Kaarina Suonio Kaarina Elisabeth Suonio ( Brusiin; born 7 February 1941) is a Finnish retired politician and psychologist. She represented Helsinki in the Parliament of Finland from 1975 to 1986 as a member of the Social Democratic Party. From 1982 to 1986, sh ...
(deputy mayor of the city of Tampere) using a network built by Nokia and Siemens and operated by
Radiolinja Radiolinja was a Finnish GSM operator founded on September 19, 1988. On March 27, 1991, the world's first GSM phone call was made on Radiolinja's network. The network was opened for commercial use on July 1, 1991. Radiolinja's slogan was ''So tha ...
. In 2021 a former Nokia engineer
Pekka Lonka Pekka is a Finnish male given name. It was most popular around the middle of the 20th century. As of 2013 there were more than 100,000 people registered with this name in Finland. The nameday is the 29th of June in the Finnish tradition and the 25th ...
revealed to
Helsingin Sanomat ''Helsingin Sanomat'', abbreviated ''HS'' and colloquially known as , is the largest subscription newspaper in Finland and the Nordic countries, owned by Sanoma. Except after certain holidays, it is published daily. Its name derives from that of ...
making a test call just a couple of hours earlier. "World's first GSM call was actually made by me. I called Marjo Jousinen, in Salo.", Lonka informed. The following year saw the sending of the first
short messaging service Short Message/Messaging Service, commonly abbreviated as SMS, is a text messaging service component of most telephone, Internet and mobile device systems. It uses standardized communication protocols that let mobile devices exchange short text ...
(SMS or "text message") message, and Vodafone UK and Telecom Finland signed the first international
roaming Roaming is a wireless telecommunication term typically used with mobile devices, such as mobile phones. It refers to a mobile phone being used outside the range of its native network and connecting to another available cell network. Technical ...
agreement.


Enhancements

Work began in 1991 to expand the GSM standard to the 1800 MHz frequency band and the first 1800 MHz network became operational in the UK by 1993, called and DCS 1800. Also that year, Telstra became the first network operator to deploy a GSM network outside Europe and the first practical hand-held GSM mobile phone became available. In 1995 fax, data and SMS messaging services were launched commercially, the first 1900 MHz GSM network became operational in the United States and GSM subscribers worldwide exceeded 10 million. In the same year, the GSM Association formed. Pre-paid GSM SIM cards were launched in 1996 and worldwide GSM subscribers passed 100 million in 1998. In 2000 the first commercial
General Packet Radio Service General Packet Radio Service (GPRS) is a packet oriented mobile data standard on the 2G and 3G cellular communication network's global system for mobile communications (GSM). GPRS was established by European Telecommunications Standards Inst ...
(GPRS) services were launched and the first GPRS-compatible handsets became available for sale. In 2001, the first UMTS (W-CDMA) network was launched, a 3G technology that is not part of GSM. Worldwide GSM subscribers exceeded 500 million. In 2002, the first
Multimedia Messaging Service Multimedia Messaging Service (MMS) is a standard way to send messages that include multimedia content to and from a mobile phone over a cellular network. Users and providers may refer to such a message as a PXT, a picture message, or a multimedia ...
(MMS) was introduced and the first GSM network in the 800 MHz frequency band became operational. Enhanced Data rates for GSM Evolution (EDGE) services first became operational in a network in 2003, and the number of worldwide GSM subscribers exceeded 1 billion in 2004. By 2005 GSM networks accounted for more than 75% of the worldwide cellular network market, serving 1.5 billion subscribers. In 2005, the first HSDPA-capable network also became operational. The first HSUPA network launched in 2007. ( High Speed Packet Access (HSPA) and its uplink and downlink versions are 3G technologies, not part of GSM.) Worldwide GSM subscribers exceeded three billion in 2008.


Adoption

The GSM Association estimated in 2011 that technologies defined in the GSM standard served 80% of the mobile market, encompassing more than 5 billion people across more than 212 countries and territories, making GSM the most ubiquitous of the many standards for cellular networks. GSM is a second-generation (2G) standard employing time-division multiple-access (TDMA) spectrum-sharing, issued by the European Telecommunications Standards Institute (ETSI). The GSM standard does not include the 3G Universal Mobile Telecommunications System (UMTS), code-division multiple access (CDMA) technology, nor the 4G LTE
orthogonal frequency-division multiple access Orthogonal frequency-division multiple access (OFDMA) is a multi-user version of the popular orthogonal frequency-division multiplexing (OFDM) digital modulation scheme. Multiple access is achieved in OFDMA by assigning subsets of subcarriers to ...
(OFDMA) technology standards issued by the 3GPP. GSM, for the first time, set a common standard for Europe for wireless networks. It was also adopted by many countries outside Europe. This allowed subscribers to use other GSM networks that have roaming agreements with each other. The common standard reduced research and development costs, since hardware and software could be sold with only minor adaptations for the local market.


Discontinuation

Telstra in
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
shut down its 2G GSM network on 1 December 2016, the first mobile network operator to decommission a GSM network. The second mobile provider to shut down its GSM network (on 1 January 2017) was
AT&T Mobility AT&T Mobility LLC, also known as AT&T Wireless and marketed as simply AT&T, is an American telecommunications company. It is a wholly owned subsidiary of AT&T Inc. and provides wireless services in the United States. AT&T Mobility is the thi ...
from the United States. Optus in
Australia Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
completed the shut down of its 2G GSM network on 1 August 2017, part of the Optus GSM network covering Western Australia and the Northern Territory had earlier in the year been shut down in April 2017. Singapore shut down 2G services entirely in April 2017.


Technical details


Network structure

The network is structured into several discrete sections: * Base station subsystem – the base stations and their controllers * Network and Switching Subsystem – the part of the network most similar to a fixed network, sometimes just called the "core network" * GPRS Core Network – the optional part which allows packet-based Internet connections * Operations support system (OSS) – network maintenance


Base-station subsystem

GSM utilizes a
cellular network A cellular network or mobile network is a communication network where the link to and from end nodes is wireless. The network is distributed over land areas called "cells", each served by at least one fixed-location transceiver (typically thre ...
, meaning that
cell phone A mobile phone, cellular phone, cell phone, cellphone, handphone, hand phone or pocket phone, sometimes shortened to simply mobile, cell, or just phone, is a portable telephone that can make and receive calls over a radio frequency link whil ...
s connect to it by searching for cells in the immediate vicinity. There are five different cell sizes in a GSM network: *
macro Macro (or MACRO) may refer to: Science and technology * Macroscopic, subjects visible to the eye * Macro photography, a type of close-up photography * Image macro, a picture with text superimposed * Monopole, Astrophysics and Cosmic Ray Observat ...
*
micro Micro may refer to: Measurement * micro- (μ), a metric prefix denoting a factor of 10−6 Places * Micro, North Carolina, town in U.S. People * DJ Micro, (born Michael Marsicano) an American trance DJ and producer *Chii Tomiya (都宮 ちい ...
*
pico Pico may refer to: Places The Moon * Mons Pico, a lunar mountain in the northern part of the Mare Imbrium basin Portugal * Pico, a civil parish in the municipality of Vila Verde * Pico da Pedra, a civil parish in the municipality of Ribei ...
* femto, and * umbrella cells The coverage area of each cell varies according to the implementation environment. Macro cells can be regarded as cells where the base-station
antenna Antenna ( antennas or antennae) may refer to: Science and engineering * Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves * Antennae Galaxies, the name of two collid ...
is installed on a mast or a building above average rooftop level. Micro cells are cells whose antenna height is under average rooftop level; they are typically deployed in urban areas. Picocells are small cells whose coverage diameter is a few dozen meters; they are mainly used indoors. Femtocells are cells designed for use in residential or small-business environments and connect to a telecommunications service provider's network via a broadband-internet connection. Umbrella cells are used to cover shadowed regions of smaller cells and to fill in gaps in coverage between those cells. Cell horizontal radius varies – depending on antenna height,
antenna gain In electromagnetics, an antenna's gain is a key performance parameter which combines the antenna's directivity and radiation efficiency. The term ''power gain'' has been deprecated by IEEE. In a transmitting antenna, the gain describes how ...
, and propagation conditions – from a couple of hundred meters to several tens of kilometers. The longest distance the GSM specification supports in practical use is . There are also several implementations of the concept of an extended cell, where the cell radius could be double or even more, depending on the antenna system, the type of terrain, and the
timing advance In the GSM cellular mobile phone standard, timing advance (TA) value corresponds to the length of time a signal takes to reach the base station from a mobile phone. GSM uses TDMA technology in the radio interface to share a single frequency betwee ...
. GSM supports indoor coverage – achievable by using an indoor picocell base station, or an indoor repeater with distributed indoor antennas fed through power splitters – to deliver the radio signals from an antenna outdoors to the separate indoor distributed antenna system. Picocells are typically deployed when significant call capacity is needed indoors, as in shopping centers or airports. However, this is not a prerequisite, since indoor coverage is also provided by in-building penetration of radio signals from any nearby cell.


GSM carrier frequencies

GSM networks operate in a number of different carrier frequency ranges (separated into
GSM frequency ranges GSM frequency bands or frequency ranges are the cellular frequencies designated by the ITU for the operation of GSM mobile phones and other mobile devices. Frequency bands GSM frequency usage around the world A dual-band 900/1800 device i ...
for 2G and UMTS frequency bands for 3G), with most 2G GSM networks operating in the 900 MHz or 1800 MHz bands. Where these bands were already allocated, the 850 MHz and 1900 MHz bands were used instead (for example in Canada and the United States). In rare cases the 400 and 450 MHz frequency bands are assigned in some countries because they were previously used for first-generation systems. For comparison, most 3G networks in Europe operate in the 2100 MHz frequency band. For more information on worldwide GSM frequency usage, see GSM frequency bands. Regardless of the frequency selected by an operator, it is divided into timeslots for individual phones. This allows eight full-rate or sixteen half-rate speech channels per radio frequency. These eight radio timeslots (or
burst Burst may refer to: *Burst mode (disambiguation), a mode of operation where events occur in rapid succession **Burst transmission, a term in telecommunications **Burst switching, a feature of some packet-switched networks ** Bursting, a signaling m ...
periods) are grouped into a TDMA frame. Half-rate channels use alternate frames in the same timeslot. The channel data rate for all is and the frame duration is The transmission power in the handset is limited to a maximum of 2 watts in and in .


Voice codecs

GSM has used a variety of voice codecs to squeeze 3.1 kHz audio into between 7 and 13 kbit/s. Originally, two codecs, named after the types of data channel they were allocated, were used, called Half Rate (6.5 kbit/s) and Full Rate (13 kbit/s). These used a system based on linear predictive coding (LPC). In addition to being efficient with bitrates, these codecs also made it easier to identify more important parts of the audio, allowing the air interface layer to prioritize and better protect these parts of the signal. GSM was further enhanced in 1997 with the enhanced full rate (EFR) codec, a 12.2 kbit/s codec that uses a full-rate channel. Finally, with the development of UMTS, EFR was refactored into a variable-rate codec called AMR-Narrowband, which is high quality and robust against interference when used on full-rate channels, or less robust but still relatively high quality when used in good radio conditions on half-rate channel.


Subscriber Identity Module (SIM)

One of the key features of GSM is the Subscriber Identity Module, commonly known as a SIM card. The SIM is a detachable
smart card A smart card, chip card, or integrated circuit card (ICC or IC card) is a physical electronic authentication device, used to control access to a resource. It is typically a plastic credit card-sized card with an embedded integrated circuit (IC) c ...
containing a user's subscription information and phone book. This allows users to retain their information after switching handsets. Alternatively, users can change networks or network identities without switching handsets - simply by changing the SIM.


Phone locking

Sometimes
mobile network operator A mobile network operator (MNO), also known as a wireless service provider, wireless carrier, cellular company, or mobile network carrier, is a provider of wireless communications services that owns or controls all the elements necessary to sell ...
s restrict handsets that they sell for exclusive use in their own network. This is called SIM locking and is implemented by a software feature of the phone. A subscriber may usually contact the provider to remove the lock for a fee, utilize private services to remove the lock, or use software and websites to unlock the handset themselves. It is possible to hack past a phone locked by a network operator. In some countries and regions (e.g. Brazil and Germany) all phones are sold unlocked due to the abundance of dual-SIM handsets and operators.


GSM security

GSM was intended to be a secure wireless system. It has considered the user authentication using a
pre-shared key In cryptography, a pre-shared key (PSK) is a shared secret which was previously shared between the two parties using some secure channel before it needs to be used. Key To build a key from shared secret, the key derivation function is typically us ...
and challenge–response, and over-the-air encryption. However, GSM is vulnerable to different types of attack, each of them aimed at a different part of the network. The development of UMTS introduced an optional Universal Subscriber Identity Module (USIM), that uses a longer authentication key to give greater security, as well as mutually authenticating the network and the user, whereas GSM only authenticates the user to the network (and not vice versa). The security model therefore offers confidentiality and authentication, but limited authorization capabilities, and no non-repudiation. GSM uses several cryptographic algorithms for security. The
A5/1 A5/1 is a stream cipher used to provide over-the-air communication privacy in the GSM cellular telephone standard. It is one of several implementations of the A5 security protocol. It was initially kept secret, but became public knowledge through l ...
,
A5/2 A5/2 is a stream cipher used to provide voice privacy in the GSM cellular telephone protocol. It was designed in 1992-1993 (finished March 1993) as a replacement for the relatively stronger (but still weak) A5/1, to allow the GSM standard to b ...
, and A5/3
stream cipher stream cipher is a symmetric key cipher where plaintext digits are combined with a pseudorandom cipher digit stream (keystream). In a stream cipher, each plaintext digit is encrypted one at a time with the corresponding digit of the keystream ...
s are used for ensuring over-the-air voice privacy. A5/1 was developed first and is a stronger algorithm used within Europe and the United States; A5/2 is weaker and used in other countries. Serious weaknesses have been found in both algorithms: it is possible to break A5/2 in real-time with a ciphertext-only attack, and in January 2007, The Hacker's Choice started the A5/1 cracking project with plans to use
FPGA A field-programmable gate array (FPGA) is an integrated circuit designed to be configured by a customer or a designer after manufacturinghence the term '' field-programmable''. The FPGA configuration is generally specified using a hardware de ...
s that allow A5/1 to be broken with a
rainbow table A rainbow table is an efficient way to store data that has been computed in advance to facilitate cracking passwords. To protect stored passwords from compromise in case of a data breach, organizations avoid storing them directly, instead transfo ...
attack. The system supports multiple algorithms so operators may replace that cipher with a stronger one. Since 2000, different efforts have been made in order to crack the A5 encryption algorithms. Both A5/1 and A5/2 algorithms have been broken, and their cryptanalysis has been revealed in the literature. As an example, Karsten Nohl developed a number of
rainbow table A rainbow table is an efficient way to store data that has been computed in advance to facilitate cracking passwords. To protect stored passwords from compromise in case of a data breach, organizations avoid storing them directly, instead transfo ...
s (static values which reduce the time needed to carry out an attack) and have found new sources for
known plaintext attack The known-plaintext attack (KPA) is an attack model for cryptanalysis where the attacker has access to both the plaintext (called a crib), and its encrypted version (ciphertext). These can be used to reveal further secret information such as secre ...
s. He said that it is possible to build "a full GSM interceptor...from open-source components" but that they had not done so because of legal concerns. Nohl claimed that he was able to intercept voice and text conversations by impersonating another user to listen to voicemail, make calls, or send text messages using a seven-year-old Motorola cellphone and decryption software available for free online. GSM uses
General Packet Radio Service General Packet Radio Service (GPRS) is a packet oriented mobile data standard on the 2G and 3G cellular communication network's global system for mobile communications (GSM). GPRS was established by European Telecommunications Standards Inst ...
(GPRS) for data transmissions like browsing the web. The most commonly deployed GPRS ciphers were publicly broken in 2011. The researchers revealed flaws in the commonly used GEA/1 and GEA/2 (standing for GPRS Encryption Algorithms 1 and 2) ciphers and published the open-source "gprsdecode" software for sniffing GPRS networks. They also noted that some carriers do not encrypt the data (i.e., using GEA/0) in order to detect the use of traffic or protocols they do not like (e.g., Skype), leaving customers unprotected. GEA/3 seems to remain relatively hard to break and is said to be in use on some more modern networks. If used with USIM to prevent connections to fake base stations and
downgrade attack A downgrade attack, also called a bidding-down attack or version rollback attack, is a form of cryptographic attack on a computer system or communications protocol that makes it abandon a high-quality mode of operation (e.g. an encrypted connec ...
s, users will be protected in the medium term, though migration to 128-bit GEA/4 is still recommended. The first public cryptanalysis of GEA/1 and GEA/2 (also written GEA-1 and GEA-2) was done in 2021. It concluded that although using a 64-bit key, the GEA-1 algorithm actually provides only 40 bits of security, due to a relationship between two parts of the algorithm. The researchers found that this relationship was very unlikely to have happened if it wasn't intentional. This may have been done in order to satisfy European controls on export of cryptographic programs.


Standards information

The GSM systems and services are described in a set of standards governed by
ETSI The European Telecommunications Standards Institute (ETSI) is an independent, not-for-profit, standardization organization in the field of information and communications. ETSI supports the development and testing of global technical standard ...
, where a full list is maintained.


GSM open-source software

Several open-source software projects exist that provide certain GSM features: * gsmd daemon by Openmoko * OpenBTS develops a Base transceiver station * ''The GSM Software Project'' aims to build a GSM analyzer for less than $1,000 * '' OsmocomBB'' developers intend to replace the proprietary baseband GSM stack with a free software implementation * YateBTS develops a Base transceiver station


Issues with patents and open source

Patents remain a problem for any open-source GSM implementation, because it is not possible for GNU or any other free software distributor to guarantee immunity from all lawsuits by the patent holders against the users. Furthermore, new features are being added to the standard all the time which means they have patent protection for a number of years. The original GSM implementations from 1991 may now be entirely free of patent encumbrances, however patent freedom is not certain due to the United States' "first to invent" system that was in place until 2012. The "first to invent" system, coupled with "patent term adjustment" can extend the life of a U.S. patent far beyond 20 years from its priority date. It is unclear at this time whether OpenBTS will be able to implement features of that initial specification without limit. As patents subsequently expire, however, those features can be added into the open-source version. , there have been no lawsuits against users of OpenBTS over GSM use.


See also

*
Cellular network A cellular network or mobile network is a communication network where the link to and from end nodes is wireless. The network is distributed over land areas called "cells", each served by at least one fixed-location transceiver (typically thre ...
* Enhanced Data Rates for GSM Evolution (EDGE) *
Enhanced Network Selection Enhanced Network Selection (sometimes referred to as Enhanced Network Service, or simply ENS) extends GSM by making it possible for a GSM cellular device (e.g., handset) to be "homed" OTA (over the air) to different networks. This made it possible ...
(ENS) * GSM forwarding standard features codes – list of call forward codes working with all operators and phones * GSM frequency bands *
GSM modem A GSM modem or GSM module is a device that uses GSM mobile telephone technology to provide a wireless data link to a network. GSM modems are used in mobile telephones and other equipment that communicates with mobile telephone networks. They use ...
* GSM services **
Cell Broadcast Cell Broadcast (CB) is a method of sending messages to multiple mobile telephone users in a defined area at the same time. It is defined by the ETSI’s GSM committee and 3GPP and is part of the 2G, 3G, 4G LTE (telecommunication) and 5G s ...
**
GSM localization The Global System for Mobile Communications (GSM) is a standard developed by the European Telecommunications Standards Institute (ETSI) to describe the protocols for second-generation (2G) digital cellular networks used by mobile devices such as ...
**
Multimedia Messaging Service Multimedia Messaging Service (MMS) is a standard way to send messages that include multimedia content to and from a mobile phone over a cellular network. Users and providers may refer to such a message as a PXT, a picture message, or a multimedia ...
(MMS) ** NITZ Network Identity and Time Zone ** Wireless Application Protocol (WAP) * GSM-R (GSM-Railway) * GSM USSD codes – Unstructured Supplementary Service Data: list of all standard GSM codes for network and SIM related functions * Handoff * High-Speed Downlink Packet Access (HSDPA) * International Mobile Equipment Identity (IMEI) * International Mobile Subscriber Identity (IMSI) * Long Term Evolution (LTE) * MSISDN Mobile Subscriber ISDN Number * Nordic Mobile Telephone (NMT) *
ORFS ORFS stands for ''Output RF Spectrum'', where 'RF' stands for Radio Frequency. The acronym ORFS is used in the context of mobile communication systems, e.g., GSM. It stands for the relationship between (a) the frequency offset from the carrier a ...
*
Personal communications network Personal communications network (PCN) is the European digital cellular mobile telephone network, developed in accordance with GSM standards. The PCN system was first initiated by Lord Young, UK Secretary of State for Trade and Industry, in 1988. ...
(PCN) * RTP audio video profile * Simulation of GSM networks * Standards ** Comparison of mobile phone standards **
GEO-Mobile Radio Interface GEO-Mobile Radio Interface (GEO stands for Geostationary Earth Orbit), better known as GMR, is an ETSI standard for satellite phones. The GMR standard is derived from the 3GPP-family terrestrial digital cellular standards and supports access to ...
**
GSM 02.07 The SMG GSM 02.07 Technical Specification (Version 7.1.0 Release 1998) called Digital cellular telecommunications system (Phase 2+); Mobile Stations (MS) features defines Mobile Station (MS) features and to classifies them according to their type ...
– Cellphone features **
GSM 03.48 GSM 03.48 is a protocol used to exchange secured packets between an entity in a GSM PLMN and an entity in the SIM card. Secured packets contain application messages to which certain mechanisms according to GSM 03.48 have been applied. Application ...
– Security mechanisms for the SIM application toolkit **
Intelligent Network The Intelligent Network (IN) is the standard network architecture specified in the ITU-T Q.1200 series recommendations. It is intended for fixed as well as Global System for Mobile Communications, mobile telecommunication, telecom networks. It al ...
** Parlay X ** RRLP – Radio Resource Location Protocol * Um interface * Visitors Location Register (VLR)


References


Further reading

* * * * *


External links


GSM Association
Official industry trade group representing GSM network operators worldwide
3GPP
3G GSM standards development group
LTE-3GPP.info: online GSM messages decoder fully supporting all 3GPP releases from early GSM to latest 5G
{{DEFAULTSORT:Gsm Telecommunications-related introductions in 1991 GSM standard