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GSM Tutoriali

GLOBAL SYSTEM FOR MOBILE COMMUNICATIONS (GSM)TUTORIALSimply Easy Learning by tutorialspoint.comtutorialspoint.coii

ABOUT THE TUTORIALGSM TutorialGSM is a globally accepted standard for digital cellular communications.GSM uses narrowband Time Division Multiple Access (TDMA) for providing voice and text basedservices over mobile phone networks.AudienceThis tutorial has been designed for readers who want to understand the basics of GSM in verysimple terms. This tutorial provides just about enough material to have a solid foundation on GSMfrom where you can move on to higher levels of expertise.PrerequisitesA general awareness of some basics of telecommunications is sufficient to understand the conceptsexplained in this tutorial.1

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Table of ContentsOverview . 5What is GSM? . 5Why GSM? . 6GSM History: . 6GSM Architecture . 8GSM network areas: . 9GSM Specification. 10Modulation: . 10Access Methods: . 10Transmission Rate: . 10Frequency Band: . 11Channel Spacing: . 11Speech Coding: . 11Duplex Distance: . 11Misc: . 11GSM Addressing and Identifiers . 12International Mobile Station Equipment Identity (IMEI): . 12International Mobile Subscriber Identity ( IMSI): . 12Mobile Subscriber ISDN Number ( MSISDN): . 13Mobile Station Roaming Number ( MSRN): . 13Location Area Identity (LAI): . 13Temporary Mobile Subscriber Identity (TMSI): . 15Local Mobile Subscriber Identity (LMSI): . Error! Bookmark not defined.Cell Identifier (CI): . Error! Bookmark not defined.GSM Operations .Error! Bookmark not defined.Call from Mobile Phone to Public Switched Telephone Network (PSTN): . Error! Bookmarknot defined.Call from PSTN to Mobile Phone: . Error! Bookmark not defined.GSM Protocol Stack. 17MS Protocols: . 17The Mobile Station (MS) to Base Tranceiver Station (BTS) Protocols: . Error! Bookmark notdefined.3

BSC Protocols: . 18MSC Protocols:. Error! Bookmark not defined.GSM User Services .Error! Bookmark not defined.1.Teleservices or Telephony Services: . Error! Bookmark not defined. VOICE CALLS: . Error! Bookmark not defined. VIDEOTEXT AND FACSMILE: . Error! Bookmark not defined. SHORT TEXT MESSAGES: . Error! Bookmark not defined.2.Bearer Services or Data Services . Error! Bookmark not defined.3.Supplementary Services . Error! Bookmark not defined.GSM Security and Encryption .Error! Bookmark not defined.Mobile Station Authentication: . Error! Bookmark not defined.Signaling and Data Confidentiality: . Error! Bookmark not defined.Subscriber Identity Confidentiality: . Error! Bookmark not defined.GSM Billing.Error! Bookmark not defined.Telephony Service: . Error! Bookmark not defined.SMS Service: . Error! Bookmark not defined.GPRS Services . Error! Bookmark not defined.Supplementary Services . Error! Bookmark not defined.GSM Mobile Phones .Error! Bookmark not defined.GSM Enabled Phones . Error! Bookmark not defined.4

CHAPTER1OverviewWhat is GSM?If you are in Europe or Asia and using a mobile phone, then most probably you are using GSMtechnology in your mobile phone. GSM stands for Global System for Mobile Communication. It is a digital cellular technology usedfor transmitting mobile voice and data services.The concept of GSM emerged from a cell-based mobile radio system at Bell Laboratories in theearly 1970s.GSM is the name of a standardization group established in 1982 to create a common Europeanmobile telephone standard.GSM is the most widely accepted standard in telecommunications and it is implementedglobally.GSM is a circuit-switched system that divides each 200 kHz channel into eight 25 kHz timeslots. GSM operates on the mobile communication bands 900 MHz and 1800 MHz in most partsof the world. In the US, GSM operates in the bands 850 MHz and 1900 MHz.GSM owns a market share of more than 70 percent of the world's digital cellular subscribers.GSM makes use of narrowband Time Division Multiple Access (TDMA) technique fortransmitting signals.GSM was developed using digital technology. It has an ability to carry 64 kbps to 120 Mbps ofdata rates.Presently GSM supports more than one billion mobile subscribers in more than 210 countriesthroughout the world.GSM provides basic to advanced voice and data services including roaming service. Roaming isthe ability to use your GSM phone number in another GSM network.GSM digitizes and compresses data, then sends it down through a channel with two other streamsof user data, each in its own timeslot.5

Why GSM?Listed below are the features of GSM that account for its popularity and wide accepatance. Improved spectrum efficiencyInternational roamingLow-cost mobile sets and base stations (BSs)High-quality speechCompatibility with Integrated Services Digital Network (ISDN) and other telephone companyservices Support for new servicesGSM HistoryThe following table shows some of the important events in the rollout of the GSM system.Years Events1982Conference of European Posts and Telegraph (CEPT) establishes a GSM group towiden the standards for a pan-European cellular mobile system.1985A list of recommendations to be generated by the group is accepted.1986Executed field tests to check the different radio techniques recommended forthe air interface.1987Time Division Multiple Access (TDMA) is chosen as the access method (withFrequency Division Multiple Access [FDMA]). The initial Memorandum ofUnderstanding (MoU) is signed by telecommunication operators representing12 countries.1988GSM system is validated.1989The European Telecommunications Standards Institute (ETSI) was given theresponsibility of the GSM specifications.1990Phase 1 of the GSM specifications is delivered.1991Commercial launch of the GSM service occurs. The DCS1800 specifications arefinalized.1992The addition of the countries that signed the GSM MoU takes place. Coveragespreads to larger cities and airports.1993Coverage of main roads' GSM services starts outside Europe.6

1994Data transmission capabilities launched. The number of networks rises to 69 in43 countries by the end of 1994.1995Phase 2 of the GSM specifications occurs. Coverage is extended to rural areas.1996June: 133 networks in 81 countries operational.1997July: 200 networks in 109 countries operational, around 44 million subscribersworldwide.1999Wireless Application Protocol (WAP) came into existence and becameoperational in 130 countries with 260 million subscribers.2000General Packet Radio Service (GPRS) came into existence.2001As of May 2001, over 550 million people were subscribers to mobiletelecommunications.7

CHAPTER2GSM ArchitectureA GSM network comprises of many functional units. These functions and interfaces are explained inthis chapter. The GSM network can be broadly divided into: The Mobile Station (MS)The Base Station Subsystem (BSS)The Network Switching Subsystem (NSS)The Operation Support Subsystem (OSS)Given below is a simple pictorial view of the GSM architecture.8

The additional components of the GSM architecture comprise of databases and messaging systems’functions: Home Location Register (HLR)Visitor Location Register (VLR)Equipment Identity Register (EIR)Authentication Center (AuC)SMS Serving Center (SMS SC)Gateway MSC (GMSC)Chargeback Center (CBC)Transcoder and Adaptation Unit (TRAU)The following diagram shows the GSM netwrok along with the added elements:The MS and the BSS communicate across the Um interface. It is also known as the air interface orthe radio link. The BSS communicates with the Network Service Switching (NSS) center across the Ainterface.GSM Network AreasIn a GSM network, the following areas are defined: Cell: Cell is the basic service area; one BTS covers one cell. Each cell is given a Cell Global Identity(CGI), a number that uniquely identifies the cell. Location Area: A group of cells form a Location Area (LA). This is the area that is paged when asubscriber gets an incoming call. Each LA is assigned a Location Area Identity (LAI). Each LA isserved by one or more BSCs. MSC/VLR