Gsm Architecture

GSM(Global System For Mobile Communication)

Guided By:Mr. G.R. Beigh, Lecturer,

Department of Electronics & Communication,NIT Srinagar.

Presented by:Saksham Choudhary

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Brief History Before 1980,problems were being confronted in Mobile

Communication because of different standards adopted by different countries.

Conference of European Portal And Telecommunication(CEPT),in 1980,craeted Group Special Mobile with aim of developing Pan-European standard.

Project was named GSM and system implementing the corresponding standard, Global System For Mobile Communication(GSM).

The responsibility for development was transferred to European Telecommunication Standards Institute(ETSI) and MOU’S were signed by various network operators.

Field trials were carried out in 1980’s and system was finally put into operation in 1990’s.

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Frequency Bands GSM-900(Around 900 MHz) GSM-1800(Around 1.8 GHz) GSM-1900(Around 1.9 GHz) E-GSM

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System Reverse(MHz)

Forward(MHz)

ChannelWidth(KHz)

Max. No. Of Channels

GSM-900

890–915 935–960 200 125

E-GSM 880–915 925–960 200 175

GSM-1800

1710–1785

1805–1880

200 375

GSM-1900

1850–1910

1930–1990

200 300

GSM ServicesTeleservices TS cover, in essence, telephony e.g. Regular

telephony, emergency calls, voice messaging.Bearer Services BS encompass basically data transmission

e.g. call broadcast, Short messaging services.Supplementary Services These are value added services e.g.call

forwarding, call waiting, call hold etc.

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GSM ArchitectureThe Public Land Mobile Network System(PLMN) with GSM architecture consists of four major blocks:

Mobile Station Subsystem(MSS)Base Station Subsystem(BSS)Network And Switching Subsystem(NSS)Operation And Support Subsystem(OSS)

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Mobile Station Subsystem(MSS)It is basically a human-machine interface performing functions

to connect user and PLMN.

MSS Includes:

Mobile Station(MS)Subscriber Identity Module(SIM)

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Mobile station(MS) consists of:

Terminal Equipment(TE)-It may be a fax, a computer or another non specific GSM device. Mobile Termination(MT)-It realizes the standard GSM mobile terminal functions. Terminal Adapter(TA)-It works as interface between TE and MT.

Subscriber Identity Module(SIM)

SIM is a removable card containing all subscriber specific data, such as

identification numbers or contracted services, personal features as

chosen by subscriber.

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Identification Codes

IMSITMSIMS-ISDNMSRN IMEILAI

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Base Station Subsystem(BSS)It is responsible for radio coverage of given geographic

regionand for appropriate signal processing.

It consists of:Base Transceiving Centre(BTS)-A BTS is

responsible for the radio coverage itself and basically consists of the radio equipment.

Base Station Controller(BSC)-A BSC controls one or more (typically several) BTS’s. Its functions include radio resource management, signalling transmission, power control, handover control, frequency hopping control, and others.

Transcoder/Rate Adapter Unit(TRAU)-ATRAU is a device placed between two GSM elements—BTS, BSC, or mobile switching centre (MSC)—and is used to conserve transmission resources.

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Network And Switching Substation(NSS)

The network and switching subsystem (NSS) carries out the GSM switching procedures and the manipulation of the databases for mobility

management of the subscribers. Its functions include coordination of call setup, paging, resource allocation, location registration etc.

It Consists Of:MSCHLRVLRAuCEIR

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Operation And Support Subsystem(OSS)The operation and support subsystem (OSS) performs the

operation and maintenance functions through two entities, namely:

Operation And Maintenance Centre(OMC)

Network And Management Subsystem(NMC)

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Open Interfaces A-Interface Abis-Interface B-Interface C-Interface D-Interface E-Interface F-Interface G-Interface H-Interface Um-Interface

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Signal Processing

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Burst FormatsGSM specifies five different time slot formats (156.25 bits),

or burst formats, to comply with the various functions to be performed:

Normal BurstFrequency BurstSynchronization BurstAccess BurstDummy Burst

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ChannelsIn GSM there are two types Of Channels

Physical Channels: The physical channels constitute the physical medium through which information flows.

Logical Channels: The logical channels support the logical functions within the network.

CP2077 - Networking 18

Physical ChannelsThe absolute radiofrequency channel number (N) and the

correspondingcentre frequency, in MHz, for the uplink and for the downlink are

related to each other as:GSM 900-

f(uplink)=0.2N+890 f(downlink)=0.2N+935GSM 1800- f(uplink)=0.2N+1710 f(downlink)=0.2N+1805GSM 1900- f(uplink) =0.2N+1850 f(downlink)=0.2N+1930

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Logical Channels

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SummaryGSM has emerged as a digital solution to the incompatible analog air interfaces of the differing cellular networks operating in Europe. Among the set of ambitious targets to be pursued, full roaming was indeed a very important one. In addition, a large number of open interfaces have been specified within the GSM architecture. Open interfaces favour market competition with operators able to choose equipment from different vendors.GSMwas the first system to stimulate the incorporation of the personal communication services philosophy into a cellular network. These and other innovative features rendered GSM networks, either in the original GSM conception or as an evolution of it, a very successful project with worldwide acceptance. GSM systems are found operating in frequency bands around 900 MHz (GSM-900), 1.8 GHz (GSM-1800), or 1.9 GHz (GSM-1900).Anew revision of the GSM specifications define an E-GSM that extends the original GSM-900 operation band and stipulates lower power terminals and smaller serving areas.

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Thanks And Have A Great Day

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