gsm

Table Mobile phone standards The Global System for Mobile Communications (GSM) is the most popular standard for mobile phones in the world. GSM phones are used by over a billion people across more than 200 countries. The ubiquity of the GSM standard makes international roaming very common between mobile phone operators with "roaming agreements". GSM differs significantly from its predecessors in that both signalling and speech channels are digital, which means that it is seen as 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 have also been introduced with EDGE in the Release '99 version of the standard.

History - In spite of its current popularity, the history of mobile phones began long before GSM was conceived. 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. The GSM standard was intended to address these problems.The GSM group (''"Groupe Spécial Mobile"'' (French languageFrench) 1, 2, 3 and 4) was founded in 1982. 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 European Conference of Postal and Telecommunications AdministrationsCEPT. 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.

Market situation - , Poland]]More than one billion people use GSM phones as of 2005, making GSM the dominant mobile phone system worldwide with about 70% of the world's market. GSM's main competitor, CDMA2000, is used primarily in North America and eurotechnology.com - Asia . CDMA2000 was seeing increased worldwide adoption when WCDMA did not appear to be commercially available. CDMA2000also benefited from increased radio techno-preneur.net - spectrum efficiencies as compared to the more common GSM networks and the not quite available WCDMA.RoamingRoaming with GSM phones is a major advantage over the competing technology as roaming across CDMA networks from different operators is difficult or impossible, depending on the handset and operators concerned. Another major reason for the growth in GSM usage, particularly between 1998 to 2002, was the availability of prepaid telephone callsprepaid 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. 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 ratingcredit rating agencies. (In the USA, 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).

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 GSM frequency rangesradio frequencies. Most GSM networks operate at 900MHz and/or 1800MHz. The exception to the rule are networks in the USA and Canada which operate at 850MHz and/or 1900MHz.There are four different cell sizes in a GSM network - macro, micro, pico and umbrella cells. The coverage area of each cell is different in different environments. Macro cells can be regarded as cells where the base station antenna (electronics)antenna is installed in a mast or a building above average roof top level. Micro cells are cells whose antenna height is under average roof top level; they are typically used in urban areas. Picocells are small cells whose diameter is a few dozen metres; they are mainly used indoors. On the other hand, umbrella cells are used to cover shadowed regions of smaller cells and fill in gaps in coverage between those cells. Cell radius varies depending on antenna height, antenna gain and propagation conditions from a couple of hundred meters to several tens of kilometres. The longest distance the GSM specification supports in practical use is 35 kilometerkm. There is also a concept of an extended cell, where the cell radius could be double or even more.Indoor coverage is also supported by GSM and is achieved by using power splitters to deliver the radio signal from the antenna outdoors to a separate indoor antenna distribution system. This is typically deployed when a lot of call capacity is needed indoors, for example in shopping centres or airports. However, this is not a pre-requisite, since indoor coverage is also provided by in-building penetration of the radio signal. The modulation used in GSM is Gaussian minimum shift keying (GMSK), a kind of continuous-phase frequency shift keying. In GMSK, the signal being modulated is smoothened with a gaussian functionGaussian low-pass filter prior to being fed to a frequency modulationfrequency modulator, which greatly reduces the interference (communications)interference to neighboring channels.

Network structure - The network behind the GSM system seen by the customer is large and complicated in order to provide all of the services which are required. It is divided into a number of sections and these are each covered in separate articles.

the Base Station Subsystem (the base stations and their controllers).

the Network and Switching Subsystem (the part of the network most similar to a fixed network). This is sometimes also just called the core network.

the GPRS Core Network (the optional part which allows packet based Internet connections).

all of the elements in the system combine to produce many GSM services such as voice calls and SMS.

Subscriber Identity Module - One of the key features of GSM is the Subscriber Identity Module (SIM), commonly known as a ''SIM card''. The SIM is a detachable smartcard containing the user's subscription information and phonebook. This allows the user to retain his information after switching handsets. Alternatively, the user can also change operators while retaining the handset simply by changing the SIM. Some operators will block this by allowing the phone to use only a single SIM, or only a SIM issued by them; this practice is known as SIM lockSIM locking, and is illegal in some countries. In the USA and Europe, most operators lock the mobiles they sell. This is done because the price of the mobile phone is usually subsidised with revenue from subscriptions and operators want to try to avoid subsidising competitor's mobiles. A subscriber can usually contact the provider to remove the lock for a fee (which operators sometimes try to claim to be ignorant of), utilize private services to remove the lock, or make use of ample software and websites available on the Internet to unlock the handset themselves. Some providers in the USA, such as T-Mobile and Cingular, will unlock the phone for free if the customer has held an account for a certain period. Third party unlocking services exist that are often quicker and lower cost than that of the operator. In most countries removing the lock is legal.

GSM security - GSM was designed with a moderate level of security. The system was designed to authenticate the subscriber using shared-secret cryptography. Communications between the subscriber and the base station can be encrypted. The development of UMTS introduces an optional USIM, that uses a longer authentication key to give greater security, as well as mutually authenticating the network and the user - whereas GSM only authenticated 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 and A5/2 stream 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 countries that may not be able to support the infrastructure necessary for A5/1. A large security advantage of GSM is that the Ki, the crypto variable stored on the SIM card that is the key to any GSM ciphering algorithm, is never sent over the air interface. Serious weaknesses have been found in both algorithms, and it is possible to break A5/2 in real-time in a ciphertext-only attack. The system supports multiple algorithms so operators may replace that cipher with a stronger one.

Patent issues - In 2005, a number of companies (including Cisco Systems and Ericsson) were sued for infringement of U.S. Patent No. 5,561,706 for offering products alleged to be compliant with the GSM 3.60 standard.

Related topics -

Core technology: 2G — 2.5G — 3G

Architectural elements: Base Station ControllerBSC — Base Station SubsystemBSS — Home Location RegisterHLR — Mobile Switching CenterMSC — Subscriber Identity ModuleSIM — Visitors Location RegisterVLR

Radio: GSM frequency ranges

Cellular traffic

Services: GSM localization — GSM services — Multimedia Messaging SystemMMS — Short message serviceSMS — Wireless Application ProtocolWAP

Standards: ETSI — Intelligent networkIntelligent network (IN) — Parlay

Common terms: IMEI — IMSI — MSISDN — Handoff

Related technologies: Gsm-rGSM-R (GSM-Railroads)

External links -

corscience.de - GSM tracking-systems

3gpp.org - 3GPP The current standardisation body for GSM with free standards available.

openmobilealliance.org - OMA The current standardisation body for services aspects of mobile networks - some free standards available.

etsi.org - ETSI the original GSM standardisation body

gsmworld.com - GSM Association - the group representing GSM operators (official site) - includes coverage maps for all members

gsmworld.com - Number of GSM Subscribers

tele-servizi.com - List of acronyms of GSM network parameters

ccnga.uwaterloo.ca - Overview of GSM by John Scourias

bryte.net - Tutorial on GSM from Bryte.net

visualgsm.com - Visualtron's tutorial on GSM

radio-electronics.com - GSM technical overview / tutorial from Radio-Electronics.Com

telenor.com - GSM - ideas, origin and milestones - a Norwegian perspective from Telenor's journal of technology telektronikk.com - Telektronikk

gsm-security.net - GSM Security FAQ

gsmprofile.com - GSM PROFILE - its all about your cell phone

hellomobile.com - GSM Service and TriBand International Roaming FAQs

hellomobile.com - Cell Phone Safety and Wireless Facts

hellomobile.com - GSM Phone World Network List

eventhelix.com - GSM Call Flow Diagrams

lodgephoto.com - Article for Americans on using GSM cellphones in Europe and ROWCategory:Audio codecsCategory:GSM StandardCategory:Mobile telephony standardscs:Global System for Mobile Communicationsde:Global System for Mobile Communicationses:Global System for Mobile Communicationsfr:Global System for Mobile !Communicationsko:GSMid:GSMit:G lobal? System for Mobile !Communicationshe:GSMlt:GSMnl:G smja:GSMno:GSMpl:GSMpt:GSMru:G SMsk:Global? System for Mobile Communicationssr:ГСМ мрежаfi:GSMsv:Globalt system för mobil !kommunikationzh:全球移动� �信系统 DEBUG REDIRECT (global system for mobile communications)

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