Mobile Apps Testing, Tele communication

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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.

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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
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 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

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•Cluster
•Frequencyreusepattern

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

9. UplinkandDownlink

10. CircuitswitchedVs PacketSwitched

11. GSMIntroduction
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MS BTS BSC MSC
GSMInterfaces

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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
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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
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SignalingProtocolsbetweenGSMEntities

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GSMIntroduction
GPRSArchitecture

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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.