The Global System

The Global System for Mobile Communications (GSM) is the most popular standard for mobile phones in the world. GSM service is used by over 1.5 billion people across more than 210 countries and territories [1]. The ubiquity of the GSM standard makes international roaming very common between mobile phone operators, enabling subscribers to use their phones in many parts of the world. GSM differs significantly from its predecessors in that both signaling and speech channels are digital, which means that it is considered a second generation (2G) mobile phone system. This fact has also meant that data communication was built into the system from very early on. GSM is an open standard which is currently developed by the 3GPP.

From the point of view of the consumer, the key advantage of GSM systems has been higher digital voice quality and low cost alternatives to making calls such as text messaging. The advantage for network operators has been the ability to deploy equipment from different vendors because the open standard allows easy inter-operability. Also, the standards have allowed network operators to offer roaming services which mean subscribers can use their phone all over the world.

GSM retained backward-compatibility with the original GSM phones as the GSM standard continued to develop, for example packet data capabilities were added in the Release '97 version of the standard, by means of GPRS. Higher speed data transmission has also been introduced with EDGE in the Release '99 version of the standard.

Contents[hide]* 1 History * 2 Market situation * 3 Radio interface * 4 Network structure o 4.1 Subscriber Identity Module o 4.2 GSM security o 4.3 Patent issues o 4.4 Satellite issues * 5 See also * 6 External links

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History

Throughout the evolution of cellular telecommunications, various systems were developed without the benefit of standardized specifications. This presented many problems directly related to compatibility, especially with the development of digital radio technology. In 1982, The GSM group ("Groupe Spйcial Mobile" (French) 1, 2, 3 and 4) was formed to address these problems. The name of the system comes from the name of this group, though later the decision was made to keep the initials but to change what they stood for. Originally the group was hosted by CEPT.

From 1982 to 1985 discussions were held to decide between building an analog or digital system. After multiple field tests, a digital system was adopted for GSM. The next task was to decide between a narrow or broadband solution. In May 1987, the narrowband time division multiple access (TDMA) solution was chosen.

The technical fundamentals of the GSM system were defined in 1987. In 1989, ETSI took over control and by 1990 the first GSM specification was completed, amounting to over 6,000 pages of text. Commercial operation began in 1991 with Radiolinja in Finland.

In 1998, the 3rd Generation Partnership Project (3GPP) was formed. Originally it was intended only to produce the specifications of the next (third, 3G) generation of mobile networks. However, 3GPP also took over the maintenance and development of the GSM specification. ETSI is a partner in 3GPP.

GSM provides recommendations, not requirements. The GSM specifications define the functions and interface requirements in detail but do not address the hardware. The reason for this is to not limit the designers yet still make it possible for the operators to buy equipment from different suppliers.

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Market situation

GSM base station in Walbrzych, Poland

More than 1.6 billion people use GSM phones as of 2005, making GSM the dominant mobile phone system worldwide with about 70% of the world's market. The countries of the European Union passed legislation mandating the use of the European-originated GSM (and its 3G successors) as the single mobile phone system in their countries in order to maximize interoperability. This gave the system a solid base for expansion to other countries, as users in other countries who wish to roam in Europe have to use GSM. GSM dominates across Europe, Russia, Africa, and the Middle East, and has a presence in nearly every country. GSM's main competitor, cdmaOne, is used primarily in North America, South America, and Asia. [2] [3]. cdmaOne also benefited from increased radio spectrum efficiencies as compared to the more common GSM networks. Roaming with GSM phones is a major advantage over the competing technology as roaming across CDMA networks from different operators can be difficult or impossible, if the operators lack a roaming agreement or work on different frequency bands.

Another major reason for the growth in GSM usage, particularly between 1998 to 2002, was the availability of prepaid calling from mobile phone operators. This allows people who are either unable or unwilling to enter into a contract with an operator to have mobile phones. For example, students and teenagers can get a prepaid account which they can manage themselves without needing a parent to manage and sign for a contracted account. It also allows some operators to offer solutions for low-frequency users who are likely to choose prepaid accounts rather than the cheapest non-prepaid accounts since the latter still costs more. Prepaid also enabled the rapid expansion of GSM in many developing countries where large sections of the population do not have access to banks or bank accounts and countries where there are no effective credit rating agencies. (In many developed countries, starting a non-prepaid contract with a cellular phone operator is almost always subject to credit verification through personal information provided by credit rating agencies).

GSM was also the first to have SMS text messaging which proved extremely popular with the teenage market.

The largest North American GSM carrier (also the largest North American phone operator) is Cingular Wireless, which acquired AT&T Wireless in the fall of 2004. Other North American GSM carriers include T-Mobile USA, Cincinnati Bell Wireless and Rogers Wireless.

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Radio interface

GSM is a cellular network, which means that mobile phones connect to it by searching for cells in the immediate vicinity. GSM networks operate at various different radio frequencies. Most GSM networks operate in the 900 MHz or 1800 MHz bands. The exceptions to the rule are networks in parts of the Americas (including the USA and Canada) that operate in the 850 MHz or 1900 MHz bands.

In