GSM


The Global System for Mobile Communications is a family of standards to describe the protocols for second-generation digital cellular networks, as used by mobile devices such as mobile phones and mobile broadband modems. GSM is also a trademark owned by the GSM Association. "GSM" may also refer to the voice codec initially used in GSM.
2G networks were developed as a replacement for first generation analog cellular networks. The original GSM standard, which was developed by the European Telecommunications Standards Institute, originally described a digital, circuit-switched network optimized for full duplex voice telephony, employing time division multiple access between stations. This expanded over time to include data communications, first by circuit-switched transport, then by packet data transport via its upgraded standards, GPRS and then EDGE. GSM exists in various versions based on the frequency bands used.
GSM was first implemented in Finland in December 1991. It became the global standard for mobile cellular communications, with over 2 billion GSM subscribers globally in 2006, far above its competing standard, CDMA. Its share reached over 90% market share by the mid-2010s, and operating in over 219 countries and territories. The specifications and maintenance of GSM passed over to the 3GPP body in 2000, which at the time developed third-generation UMTS standards, followed by the fourth-generation LTE Advanced and the fifth-generation 5G standards, which do not form part of the GSM standard. Beginning in the late 2010s, various carriers worldwide [|started 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 of G mobile phone technologies evolved from it or mobile phones itself.

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 set up the Groupe Spécial Mobile 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 EU Big Four 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 had been brought behind GSM in a rare unity and speed guided by four public officials: Armin Silberhorn, Stephen Temple, Philippe Dupuis, and Renzo Failli. In 1989 the Groupe Spécial Mobile committee was transferred from CEPT to the European Telecommunications Standards Institute.
The IEEE/RSE awarded to Thomas Haug and Philippe Dupuis 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 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 using a network built by Nokia and Siemens and operated by Radiolinja. In 2021 a former Nokia engineer Pekka Lonka revealed to Helsingin 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. The following year saw the sending of the first short messaging service message, and Vodafone UK and Telecom Finland signed the first international roaming 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 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 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 services were launched and the first GPRS-compatible handsets became available for sale. In 2001, the first UMTS 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 was introduced and the first GSM network in the 800 MHz frequency band became operational. Enhanced Data rates for GSM Evolution 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. 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 standard employing time-division multiple-access spectrum-sharing, issued by the European Telecommunications Standards Institute. The GSM standard does not include the 3G Universal Mobile Telecommunications System, code-division multiple access technology, nor the 4G LTE orthogonal frequency-division multiple access 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

in Australia 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 was AT&T Mobility from the United States.
Optus in Australia 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:
GSM utilizes a cellular network, meaning that cell 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 the base-station antenna 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, 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.
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.