The document provides an overview of the evolution of telecommunication technologies and the GSM network architecture. It discusses early telegraph and telephone inventions in the 1800s and the development of wired networks. It then summarizes the key components of the GSM network including mobile stations, base station subsystems, network switching subsystems, and the GPRS architecture. The GSM network uses various interfaces and protocols to connect its components and enable wireless communication.

1. www.h2kinfosys.com Email: training@h2kinfosys.com USA: 770-777-1269 UK: 020 33717615
Introductionto telecommunication
Telecommunication -Communicationatdistance through signalsofvariednaturecoming fromatransmitted
toreceiver
Signals:
Lights,Sounds,butnotin secured,nofastinformation
Electromagneticenergy,isable totransportinformation inanextremelyfast way
In1809,ThomasS.Sommeringproposedatelegraphicsystemcomposedofabattery,35wires(onefor
eachletterandnumber) andagroupofsensorsmadeofgold,whichweresubmergedin awatertank:whena
signalwas passingfromoneofthosewires,electricalcurrent would splitwatermolecules,and smalloxygen
bubbleswould bevisiblenearthatsensor
1843,the yearin which SamuelMorseproposedawaytoassigneachletterandnumbertoaternary code
(point,line, and space).Thiswayturnedouttobeextremelyconvenientandmoreaffordable than
Sommering’sidea,especially intermsofreducedcircuitry(you wouldn’tneedanymoreawireforeach
symbol).Meanwhile, technologybecameadvancedenough tofindawaytoconvertthosesignalsinaudible
(orsometimesgraphic)signals.Thecombination ofthese twofactorsquicklydeterminedthesuccessof
Morse’ssymbolcode,which wecanstillfindusedtoday
Sevenyears later,AntonioMeucciandGrahamBellindependentlymanagedtobuilda prototype ofan early
telephone(’soundatdistance’)machine.SinceMeuccididn’thavethemoneytopatenthisinvention (thecost
was$250atthetime),Bellmanagedtoregisteritfirst.
Bothwith telegraphsandtelephones,theneed fora distributedandreliablecommunicationnetworksoon
becameevident.Routingissueswerefirstsolved by meansofhuman operatorsandcircuit commutation:the
PSTN(PublicSwitchedTelephoneNetwork)wasborn. However,thissystemdidn’tguaranteetheprivacy and
secrecyofconversations,andeffortstowardsthedevelopmentofan automaticcircuit commutationwere
made.

2. www.h2kinfosys.com Email: training@h2kinfosys.com USA: 770-777-1269 UK: 020 33717615
EvolutionofGSM:(GlobalSystemfor Mobilecommunication)
GSM(2G)
GPRS(GeneralPacketRadioService)(2.5G)-dataspeedsofupto 171.2Kbps
EDGE(EnhancedDataratefor GSMEvolution)(2.5G)-dataratesto384 Kbps
if/whendeployed
HighSpeed CircuitSwitchedData(HSCSD)(2.5G)-speedsof upto64 Kbps. However,HSCSDperpetuatestheinefficientuseof
spectrumandtransmissionthatis relegatedby any circuitswitchedmechanism
3G(CDMA2000)-provideupto 2 Mbps
LongTermEvolution(4G)

3. GSMhistory
In1982,theEuropeanConferenceofPostalandTelecommunicationsAdministrations(CEPT)createdtheGroupeSpécia
lMobile(GSM)todevelopastandardforamobile telephonesystemthatcouldbe usedacrossEurope.[6]I
n1987,amemorandumofunderstandingwas signedby13countriestodevelopacommon
cellulartelephonesystemacrossEurope.
n1989,GSMresponsibilitywas transferredtotheEuropeanTelecommunicationsStandards
Institute(ETSI) andphaseI oftheGSMspecificationswerepublishedin1990.
ThefirstGSM networkwaslaunchedin1991byRadiolinjainFinlandwithjointtechnical
infrastructuremaintenancefromEricsson.
Bytheendof1993,overamillionsubscriberswereusingGSMphonenetworksbeing
operatedby70carriersacross48countries.
GSMStandards
ETSI
3GPP
Reference:
http://www.mobilein.com/gsm_standards.htm
http://www.etsi.org/WebSite/homepage.aspx
www.3gpp.org/

4. ElectroMagneticSpectrum

5. GSMIntroduction
www.h2kinfosys.comEmail: training@h2kinfosys.com USA: 770-777-1269 UK: 020 33717615
 GSM 900
 GSM 1800
 GSM 1900
 GSM 450
 GSM 480
 GSM 850
GSMFrequencyBands

6. Cellularconcepts
ThebasicunitofGSMradio coverageisknownasacell.Cellistheareacoveredby singletransmitter
TypesofCells
•Macro cells
•<35KMS
•Antennaabovetheroofs
•Micro cells
•Antennabelowtheroofs
•Picocells
•Verysmallcoverage
•ExtendedCells
•Radiusof maximum120kms
•Coastalregion

7. www.h2kinfosys.comEmail: training@h2kinfosys.com USA: 770-777-1269 UK: 020 33717615
•Cluster
•Frequencyreusepattern

8. •Cell capacityexpansiontechniques
•Cellsplitting
•Cellsectoring
•Frequencyallocation
•Multipleaccesstechniques
•FDMA
•TDMA
•CDM
A

9. UplinkandDownlink

10. CircuitswitchedVs PacketSwitched

11. GSMIntroduction
www.h2kinfosys.comEmail: training@h2kinfosys.com USA: 770-777-1269 UK: 020 33717615
MS BTS BSC MSC
GSMInterfaces

12. www.h2kinfosys.comEmail: training@h2kinfosys.com USA: 770-777-1269 UK: 020 33717615
MS:
TheMSconsistsofthephysicalequipmentusedbythesubscriber toaccessaPLMNforoffered
telecommunicationservices.Functionally,theMSincludesaMobileTermination (MT)and,depending onthe servicesit
cansupport,variousTerminalEquipment(TE),andcombinationsofTE andTerminalAdaptor (TA)
functions(theTAactsasagatewaybetweentheTE and theMT)(see Figure5.4).VarioustypesofMS,such asthe
vehiclemountedstation,portablestation,orhandheldstation, areused.
AnMS hasanumberofidentities including theInternationalMobileEquipmentIdentity(IMEI),theInternational
MobileSubscriberIdentity(IMSI),andtheISDNnumber.TheIMSIis storedintheSIM.TheSIMcard containsallthe subscriber-
relatedinformationstored ontheuser’ssideoftheradiointerface.
IMSI.TheIMSI isassignedtoanMSat subscriptiontime.Ituniquelyidentifiesa givenMS.TheIMSIwillbe
transmittedovertheradio interfaceonlyif necessary.TheIMSI contains15digitsand includes
•MobileCountryCode(MCC)—3digits(homecountry)
•MobileNetworkCode(MNC)—2digits(homeGSMPLMN)
•Mobile SubscriberIdentification(MSIN)
•NationalMobileSubscriberIdentity(NMSI)
IMEI:
TheIMEIuniquelyidentifiestheMSequipment.Itisassignedbytheequipmentmanufacturer.TheIMEI
contains 15digitsand carries
•TheTypeApprovalCode(TAC)—6digits
•TheFinalAssemblyCode(FAC)—2digits
•Theserialnumber (SN)—6digits
•ASpare(SP)—1digit

13. BSS:
TheBSSisthephysicalequipment thatprovidesradiocoverageto prescribed geographicalareas,known as thecells.It
containsequipment required to communicatewiththeMS.Functionally,aBSS consistsofacontrol functioncarried out bytheBSC
and atransmitting functionperformed by
theBTS.TheBTSistheradio transmissionequipment andcoverseachcell.ABSScan serveseveralcells
becauseit canhavemultipleBTSs.
TheBTScontainstheTranscoderRateAdapterUnit (TRAU).InTRAU,theGSM-specificspeech encoding and
decodingiscarriedout, aswellastherateadaptationfunctionfordata.Incertain situationstheTRAUis locatedat theMSC to
gainan advantageofmorecompressed transmissionbetweentheBTS and theMSC.
NSS:
TheNSSincludesthemainswitchingfunctionsof GSM,databasesrequired forthe subscribers,and mobility
management.Itsmain role isto managethecommunicationsbetweenGSM and other networkusers.
WithintheNSS,the switchingfunctionsareperformed bytheMSC.Subscriberinformationrelevant to
provisioningofservicesiskeptintheHLR.
TheotherdatabaseintheNSS istheVLR.
TheMSCperformsthenecessaryswitchingfunctionsrequiredfortheMSslocatedinan associated
geographicalarea,calledanMSC area

14. GSMIntroduction
www.h2kinfosys.comEmail: training@h2kinfosys.com USA: 770-777-1269 UK: 020 33717615
GSMInterfaces
TheRadioInterface(MS toBTS)
TheUmradio interface(betweenMSand basetransceiverstations[BTS])isthemost importantin anymobile
radiosystem, inthat it addressesthedemandingcharacteristicsoftheradio environment.
AbisInterface(BTStoBSC)
TheinterconnectionbetweentheBTS and theBSC isthroughastandard
interface,Abis(mostAbisinterfacesarevendorspecific).Theprimaryfunctions
carriedoverthisinterfacearetrafficchanneltransmission,terrestrialchannel management,and
radio channelmanagement.
AInterface(BSCtoMSC)
TheAinterfaceallowsinterconnectionbetweentheBSSradio basesubsystem
andtheMSC.ThephysicallayeroftheAinterfaceisa2-Mbps standard Consultative
CommitteeonTelephoneandTelegraph (CCITT)digitalconnection.

15. GSMIntroduction
www.h2kinfosys.comEmail: training@h2kinfosys.com USA: 770-777-1269 UK: 020 33717615
SignalingProtocolsbetweenGSMEntities

16. www.h2kinfosys.comEmail: training@h2kinfosys.com USA: 770-777-1269 UK: 020 33717615
GSMIntroduction
GPRSArchitecture

17. www.h2kinfosys.comEmail: training@h2kinfosys.com USA: 770-777-1269 UK: 020 33717615
GSMIntroduction
ComponentsinGPRS
GPRSMobileStations:
NewMobileStationarerequiredtouse GPRSservices
becauseexistingGSMphonesdonothandletheenhancedairinterfaceorpacket
data.Avarietyof MScanexist,includingahigh-speedversionof currentphonesto
supporthigh-speed dataaccess,anewPDAdevice withanembedded GSMphone,and PC
cardsforlaptop computers.Thesemobilestationsarebackward
compatibleformakingvoicecalls usingGSM.
GPRSBaseStationSubsystem:
EachBSCrequires theinstallationof oneormorePacketControlUnits(PCUs) and
asoftwareupgrade.The PCU providesaphysicaland logicaldatainterfaceto the
basestationsubsystem(BSS)forpacketdata
traffic.TheBTScanalsorequireasoftwareupgradebut
typicallydoesnotrequirehardwareenhancements.
Wheneithervoiceor data trafficisoriginatedat thesubscribermobile,it
istransportedovertheairinterface to the BTS,andfromthe
BTStotheBSCinthesamewayasastandard GSMcall.However,attheoutputof
theBSC,thetrafficisseparated;voiceissentto the
mobileswitchingcenter(MSC)perstandardGSM,and dataissentto
anewdevicecalledtheSGSN viathe PCU overaFrame Relay interface.
GPRSSupportNodes:
Followingtwo new components,calledGPRSsupportnodes (GSNs),areadded:
GatewayGPRSsupport node(GGSN):
TheGateway GPRSSupport Nodeactsasaninterfaceandarouterto
externalnetworks.The GGSNcontainsroutinginformationforGPRS mobiles,
whichisusedtotunnelpacketsthroughthe IPbasedinternalbackbonetothe
correctServing GPRSSupportNode. TheGGSN
alsocollectscharginginformationconnectedtotheuseof
theexternaldatanetworksandcanactasapacketfilterforincomingtraffic.
ServingGPRSsupportnode(SGSN):
TheServing GPRSSupport Nodeisresponsibleforauthenticationof
GPRSmobiles,registrationofmobilesin thenetwork,mobility
management,and collectinginformationforchargingfortheuseoftheair interface.
InternalBackbone:
Theinternal backboneisanIP based networkused tocarrypacketsbetween
differentGSNs.Tunnelingisused betweenSGSNsand
GGSNs,sotheinternal backbone doesnotneed anyinformationaboutdomainsoutsidethe
GPRSnetwork.SignalingfromaGSNtoaMSC, HLRorEIRisdoneusingSS7.