GSM was first implemented inFinland in December 1991.[5] It became the global standard for mobile cellular communications, with over 2 billion GSM subscribers globally in 2006, far above its competing standard,CDMA.[6] Its share reached over 90% market share by the mid-2010s, and operating in over 219 countries and territories.[2] The specifications and maintenance of GSM passed over to the3GPP body in 2000,[7] which at the time developed third-generation (3G)UMTS standards, followed by the fourth-generation (4G) LTE Advanced and the fifth-generation5G standards, which do not form part of the GSM standard. Beginning in the late 2010s, various carriers worldwidestarted to shut down their GSM networks; nevertheless, as a result of the network's widespread use, the acronym "GSM" is still used as a generic term for the plethora ofG mobile phone technologies evolved from it or mobile phones itself.
Thomas Haug (first GSM president) and Philippe Dupuis (second GSM president) during a GSM meeting in Belgium, April 1992
In 1983, work began to develop a European standard for digital cellular voice telecommunications when theEuropean Conference of Postal and Telecommunications Administrations (CEPT) set up theGroupe Spécial Mobile (GSM) committee and later provided a permanent technical-support group based inParis. Five years later, in 1987, 15 representatives from 13 European countries signed amemorandum of understanding inCopenhagen to develop and deploy a common cellular telephone system across Europe, and EU rules were passed to make GSM a mandatory standard.[8] 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.[9][10][11][12]
In February 1987 Europe produced the first agreed GSM Technical Specification. Ministers from theEU Big Four (France, West Germany, United Kingdom and Italy) cemented their political support for GSM with the Bonn Declaration on Global Information Networks in May and the GSMMoU 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 (France), and Renzo Failli (Italy).[13] In 1989 the Groupe Spécial Mobile committee was transferred from CEPT to theEuropean Telecommunications Standards Institute (ETSI).[10][11][12]The IEEE/RSE awarded toThomas Haug andPhilippe Dupuis the 2018James Clerk Maxwell medal for their "leadership in the development of the first international mobile communications standard with subsequent evolution into worldwide smartphone data communication".[14] The GSM (2G) has evolved into 3G, 4G and 5G.
In parallelFrance andGermany signed a joint development agreement in 1984 and were joined byItaly and theUK in 1986. In 1986, theEuropean Commission proposed reserving the 900 MHz spectrum band for GSM. It was long believed that the formerFinnish prime ministerHarri Holkeri made the world's first GSM call on 1 July 1991, callingKaarina Suonio (deputy mayor of the city ofTampere) using a network built byNokia and Siemens andoperated byRadiolinja.[15] In 2021 a former Nokia engineerPekka Lonka revealed toHelsingin Sanomat 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.[16] The following year saw the sending of the firstshort messaging service (SMS or "text message") message, andVodafone UK and Telecom Finland signed the first internationalroaming agreement.
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 the DCS 1800. Also that year,Telstra became the first network operator to deploy a GSM network outside Europe and the first practical hand-held GSMmobile 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, theGSM Association formed. Pre-paid GSM SIM cards were launched in 1996 and worldwide GSM subscribers passed 100 million in 1998.[11]
In 2000 the first commercialGeneral Packet Radio Service (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 firstMultimedia Messaging Service (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.[11]
By 2005 GSM networks accounted for more than 75% of the worldwide cellular network market, serving 1.5 billion subscribers. In 2005, the firstHSDPA-capable network also became operational. The firstHSUPA 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.[11]
GSM logo icon shown on the face of a Siemens GSM mobile phone from 1996
TheGSM 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.[17]
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.[19]
Telstra inAustralia shut down its 2G GSM network on 1 December 2016, the first mobile network operator to decommission a GSM network.[20] The second mobile provider to shut down its GSM network (on 1 January 2017) wasAT&T Mobility from theUnited States.[21]Optus inAustralia completed the shut down of its 2G GSM network on 1 August 2017, part of the Optus GSM network coveringWestern Australia and theNorthern Territory had earlier in the year been shut down in April 2017.[22]Singapore shut down 2G services entirely in April 2017.[23]
GSM utilizes acellular network, meaning thatcell phones connect to it by searching for cells in the immediate vicinity. There are five different cell sizes in a GSM network:
The coverage area of each cell varies according to the implementation environment. Macro cells can be regarded as cells where thebase-stationantenna 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 orsmall-business environments and connect to atelecommunications service provider's network via abroadband-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, andpropagation conditions – from a couple of hundred meters to several tens of kilometers. The longest distance the GSM specification supports in practical use is 35 kilometres (22 mi). There are also several implementations of the concept of an extended cell,[24] where the cell radius could be double or even more, depending on the antenna system, the type of terrain, and thetiming advance.
GSM supports indoor coverage – achievable by using an indoor picocell base station, or anindoor 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 networks operate in a number of differentcarrier frequency ranges (separated intoGSM frequency ranges for 2G andUMTS frequency bands for 3G), with most2G 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, most3G networks in Europe operate in the 2100 MHz frequency band. For more information on worldwide GSM frequency usage, seeGSM frequency bands.
Regardless of the frequency selected by an operator, it is divided intotimeslots for individual phones. This allows eight full-rate or sixteen half-rate speech channels perradio frequency. These eight radio timeslots (orburst periods) are grouped into aTDMA frame. Half-rate channels use alternate frames in the same timeslot. The channel data rate for all8 channels is270.833 kbit/s, and the frame duration is4.615 ms.[25] TDMA noise is interference that can be heard on speakers near a GSM phone using TDMA, audible as a buzzing sound.[26]
The transmission power in the handset is limited to a maximum of 2 watts inGSM 850/900 and1 watt inGSM 1800/1900.
GSM has used a variety of voicecodecs 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, calledHalf Rate (6.5 kbit/s) andFull Rate (13 kbit/s). These used a system based onlinear predictive coding (LPC). In addition to being efficient withbitrates, 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[27]with theenhanced full rate (EFR) codec, a 12.2 kbit/s codec that uses a full-rate channel. Finally, with the development ofUMTS, EFR was refactored into a variable-rate codec calledAMR-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.
One of the key features of GSM is theSubscriber Identity Module, commonly known as aSIM card. The SIM is a detachablesmart card[3] 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.
Sometimesmobile network operators restrict handsets that they sell for exclusive use in their own network. This is calledSIM 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 andGermany) all phones are sold unlocked due to the abundance of dual-SIM handsets and operators.[28]
GSM was intended to be a secure wireless system. It has considered the user authentication using apre-shared key andchallenge–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.[29]
Research findings indicate that GSM faces susceptibility to hacking byscript kiddies, a term referring to inexperienced individuals utilizing readily available hardware and software. The vulnerability arises from the accessibility of tools such as a DVB-T TV tuner, posing a threat to both mobile and network users. Despite the term "script kiddies" implying a lack of sophisticated skills, the consequences of their attacks on GSM can be severe, impacting the functionality ofcellular networks. Given that GSM continues to be the main source of cellular technology in numerous countries, its susceptibility to potential threats from malicious attacks is one that needs to be addressed.[30]
The development ofUMTS introduced an optionalUniversal 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 nonon-repudiation.
GSM uses several cryptographic algorithms for security. TheA5/1,A5/2, andA5/3stream ciphers 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 aciphertext-only attack, and in January 2007, The Hacker's Choice started the A5/1 cracking project with plans to useFPGAs that allow A5/1 to be broken with arainbow table attack.[31] 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 theircryptanalysis has been revealed in the literature. As an example,Karsten Nohl developed a number ofrainbow tables (static values which reduce the time needed to carry out an attack) and have found new sources forknown plaintext attacks.[32] 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.[33] Nohl claimed that he was able to intercept voice and text conversations by impersonating another user to listen tovoicemail, make calls, or send text messages using a seven-year-oldMotorola cellphone and decryption software available for free online.[34]
GSM usesGeneral Packet Radio Service (GPRS) for data transmissions like browsing the web. The most commonly deployed GPRS ciphers were publicly broken in 2011.[35]
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 forsniffing 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 withUSIM to prevent connections to fake base stations anddowngrade attacks, 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 was not intentional. This may have been done in order to satisfy European controls on export of cryptographic programs.[36][37][38]
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.[citation needed]
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 whetherOpenBTS 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. As of 2011[update], there have been no lawsuits against users of OpenBTS over GSM use.[citation needed]
^Sauter, Martin (21 November 2013)."The GSM Logo: The Mystery of the 4 Dots Solved". Archived fromthe original on 4 March 2016. Retrieved23 November 2013.[...] here's what [Yngve Zetterstrom, rapporteur of the Marketing and Planning (MP) group of the MoU (Memorandum of Understanding group, later to become the GSM Association (GSMA)) in 1989] had to say to solve the mystery: '[The dots symbolize] three [clients] in the home network and one roaming client.' There you go, an answer from the prime source!
^Leader (7 September 2007)."Happy 20th Birthday, GSM".zdnet.co.uk. CBS Interactive. Archived fromthe original on 5 May 2011. Retrieved5 May 2011.Before GSM, Europe had a disastrous mishmash of national analogue standards in phones and TV, designed to protect national industries but instead creating fragmented markets vulnerable to big guns from abroad.
^ab"GSM".etsi.org. European Telecommunications Standards Institute. 2011. Archived fromthe original on 11 February 2012. Retrieved5 May 2011.GSM was designed principally for voice telephony, but a range of bearer services was defined...allowing circuit-switched data connections at up to 9600 bits/s.
^abcde"History".gsmworld.com. GSM Association. 2001. Archived fromthe original on 19 May 2011. Retrieved5 May 2011.1982 Groupe Speciale Mobile (GSM) is formed by the Confederation of European Posts and Telecommunications (CEPT) to design a pan-European mobile technology.
^ab"Cellular History".etsi.org. European Telecommunications Standards Institute. 2011. Archived fromthe original on 17 February 2012. Retrieved5 May 2011.The task was entrusted to a committee known as Groupe Spécial Mobile (GSMTM), aided by a "permanent nucleus" of technical support personnel, based in Paris.
^"Who created GSM?". Stephen Temple. 7 January 2007. Retrieved7 April 2013.Before GSM, Europe had a disastrous mishmash of national analogue standards in phones and TV, designed to protect national industries but instead creating fragmented markets vulnerable to big guns from abroad.
^"Maailman ensimmäinen GSM-puhelu" [World's first GSM call].yle.fi. Yelisradio OY. 22 February 2008. Archived fromthe original on 6 July 2011. Retrieved5 May 2011.Harri Holkeri made the first call on the Radiolinja (Elisa's subsidiary) network, at the opening ceremony in Helsinki on 07.01.1991.
^"Ensimmäinen gsm-puhelu soitettiin 30 vuotta sitten" [World's first GSM call was made 30 years ago].hs.fi. Helsingin Sanomat. 1 July 2021. Retrieved11 October 2022.Tasan 30 vuotta sitten Esplanadin puistossa tehtiin historiaa. Kulisseissa vaikutti Nokian nykyinen toimitusjohtaja Pekka Lundmark. Hän uskoo, että seuraava murros kestää ainakin 10 vuotta.
^Martin Sauter (23 June 2014).From GSM to LTE-Advanced : An Introduction to Mobile Networks and Mobile Broadband (Second ed.). John Wiley & Sons, Incorporated.ISBN9781118861929.
^Solutions to the GSM Security Weaknesses, Proceedings of the 2nd IEEE International Conference on Next Generation Mobile Applications, Services, and Technologies (NGMAST2008), pp.576–581, Cardiff, UK, September 2008,arXiv:1002.3175
^Owano, Nancy (27 December 2011)."GSM phones -- call them unsafe, says security expert". Archived fromthe original on 3 January 2012. Retrieved27 December 2011.Nohl said that he was able to intercept voice and text conversations by impersonating another user to listen to their voice mails or make calls or send text messages. Even more troubling was that he was able to pull this off using a seven-year-old Motorola cellphone and decryption software available free off the Internet.
Redl, Siegmund M.; Weber, Matthias K.; Oliphant, Malcolm W (February 1995).An Introduction to GSM. Artech House.ISBN978-0-89006-785-7.
Redl, Siegmund M.; Weber, Matthias K.; Oliphant, Malcolm W (April 1998).GSM and Personal Communications Handbook. Artech House Mobile Communications Library. Artech House.ISBN978-0-89006-957-8.
Hillebrand, Friedhelm, ed. (December 2001).GSM and UMTS, The Creation of Global Mobile Communications. John Wiley & Sons.ISBN978-0-470-84322-2.
Mouly, Michel; Pautet, Marie-Bernardette (June 2002).The GSM System for Mobile Communications. Telecom Publishing.ISBN978-0-945592-15-0.
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