GSMBSSGP Layer DescriptionWord文件下载.docx
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GSMBSSGP Layer DescriptionWord文件下载.docx
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∙NM.ThisconcernsthefunctionsassociatedwiththemanagementofthevirtualconnectionsbetweentheSGSNandBSSandthecontroloftheBSSorSGSNnodessuchasflowcontrol.
∙Relay(RL).ThislayeractsasrelaybetweentheGbinterfaceandtheradiointerface.ItcontrolsthetransferofLLCframesbetweentheRLC/MACandBSSGPlayers.
∙PFM.ThishandlesthemanagementofBSSpacketflowcontextsbetweentheSGSNandtheBSS.
Figure6.20:
BSSGPservicemodel.
6.5.2UserProceduresBetweenLLCandRELAYSAPs
Figure6.21describestheproceduresusedforthetransferofLLCPDUsbetweentheSGSNandtheBSS.
Figure6.21:
DataPDUstransfer.
6.5.2.1TransferofLLCPDUsinDownlink
ThetransferofLLCPDUsindownlinkisperformedinunacknowledgedmode.TheLLCPDUistransportedwithintheDL-UNITDATAmessage.ThismessageissentontheBVCofthecellinwhichislocatedtheaddressedmobile.
TheSGSNprovidestheBSSwithMS-specificinformation,enablingtheRLC/MACentityintheBSStotransmittheLLCPDUtotheMSinauser-specificmanner.TheinformationgiventotheRLC/MACentityinclude:
∙MSradioaccesscapability.Thisdefinestheradiocapabilityofthemobile(multislotclass,powercapability,frequencybandsupported).
∙PFI.Thisparameteridentifiesthepacketflowcontext(whenexisting),containingtheQoSparametersforthetransferoftheLLCPDU.
∙QoSprofile.Thisdefinesthepeakbitrate,thetypeofBSSGPSDU(signalingordata),thetypeofLLCframe,theprecedenceclass,andthetransmissionmode(ACKNACK,seeChapter5).
∙PDUlifetime.ThisdefinestheremainingtimeperiodthatthePDUisconsideredasvalidwithintheBSS.IfthePDUisheldforaperiodexceedingthePDUlifetimetimeperiod,thePDUisdiscardedbytheBSS.
∙DRXparameters.TheseparametersareusedbytheBSStodeterminewhenthemobileoperatesinDRXornon-DRXmode.
TheDL-UNITDATAmessagecontainsthecurrentTLLIidentifyingtheMS,theIMSI,theQoSprofile,thePDUlifetime,andoptionallythePFI,theMSradioaccesscapability,andtheDRXparameters.IftheSGSNhasvalidDRXparameters(seeChapter3)foraTLLI,itincludestheminthePDU.
NotethatduringGMMattachprocedure,itmayhappenthattheSGSNdoesnothaveavalidIMSI,inwhichcasetheDL-UNITDATAPDUissentwithouttheIMSI.
TheTLLIallowstheBSStoidentifytheDLtransfer.Itcouldhappenthatduringanuplinktransferontheairinterface,theBSSreceivesadownlinkLLCPDUthatisaddressedtothemobileperformingtheuplinktransfer.TheTLLIisusedbytheBSStocorrelatetheuplinkanddownlinktransfersothatitallocatesdownlinkresourcesthatwhentakenincombinationwiththeallocateduplinkresourcesremainwithinthemultislotclassconstraintofthemobile.
NotethattheNSEIandtheBVCIarenotcontainedintheDL-UNITDATAmessage.TheNSlayerprovidesthemtogetherwiththeDL-UNITDATAmessagewhenitisreceived.
6.5.2.2TransferofLLCPDUsinUplink
ThetransferofLLCPDUsinuplinkisperformedinunacknowledgedmode.OneLLCPDUisencapsulatedinoneUL-UNIDATAPDU.ThisPDUissentontheBVCofthecellinwhichithasbeenreceived.
TheUL-UNITDATAmessagecontains:
∙TheTLLIidentifyingthemobilethathassenttheLLCPDU;
∙TheQoSprofilethathasbeenusedforthetransferoftheLLCPDUontheairinterface;
∙TheLLCPDU;
∙ThePFIidentifyingthepacketflowcontextassociatedwiththetransfer(optional).
NotethattheNSEIandBVCIarenotpartoftheUL-UNIDATAmessage.TheNSlayerprovidesthemtogetherwiththeDL-UNITDATAmessagewhenitisreceived.
6.5.3SignalingProceduresBetweenGMMSAPs
6.5.3.1Paging
TwokindsofpagingprocedurescanbeinitiatedbytheSGSN:
1.PagingprocedureforGPRSservices,inwhichcasetheSGSNcansendoneormorePAGING-PSPDUtotheBSS;
2.Pagingprocedurefornon-GPRSservicesrequestedbytheMSC/VLR,inwhichcasetheSGSNcansendoneormorePAGING-CSPDUstotheBSS.
ThesepagingPDUscontaininformationthatisnecessaryfortheBSStoinitiatethepagingforanMSwithinagroupofcells.Thelevelofresolutionofthisgroupofcellscanbe:
∙AllcellswithintheBSS;
∙AllcellswithinoneLA;
∙AllcellswithinoneRA;
∙Onecell(oneBVCI).
WhenthemobileisinGMMREADYstate,thecellinwhichthemobileislocatedisprovidedinthepagingmessage.ThepagingmessageisthensentontheBVCassociatedwiththecell.
WhenthemobileisinGMMIDLEstate,thepagingmessagecontainsoneofthefollowinglocationsforthemobile:
LA,RA,orBSS.IftheLA,RA,orBSSinwhichthemobileislocatedismappedondifferentNSentitieswithintheSGSN,itmustsendonepagingmessagetoeachNSentityhavingcellsthatbelongtotheLA,RA,orBSS.Inthiscase,thepagingmessageissentoneachsignalingBVCoftheNSEs.
Figure6.22describesapagingPSprocedure.ThePAGING-PSPDUcontainsthefollowingparameters:
∙TheIMSIofthepagedmobile.ItisusedbytheBSStoderivethePAGINGGROUPofthemobile.
∙Thelocationofthemobile:
eithercell,RA,LAorBSS.
∙TheQoSprofile.
∙TheDRXparameterswhenavailableatSGSNside.TheyinformtheBSSofthenon-DRXandDRXperiodofthemobile.
∙ThePFIwhenavailable.Itindicatestheassociatedpacketflowcontext.
∙TheP-TMSIwhenavailableattheSGSNside.Whenitispresentinthemessage,itisusedtopagethemobileontheradiointerface.Otherwise,theIMSIisused.
Figure6.22:
PagingPSprocedure.
Inthecaseofpagingfornon-GPRSservices,theSGSNprovidestheIMSIofthemobile,itslocation,andtheDRXparameters.TheTLLIandTMSIcanalsobeprovidedbytheSGSN.Inthiscase,oneoftheparametersisusedtopagethemobileontheradiointerface.TheIMSIandDRXparametersareusedbytheBSStoderivethePAGINGGROUP.
APAGING-PSorPAGING-CSPDUisrelayedintheBSSbyaPACKETPAGINGREQUESTmessagewhenPCCCHispresentinthecell;
otherwisebyaPAGINGREQUESTmessagethatissentontheairinterface.
6.5.3.2RadioAccessCapabilityUpdate
TheBSStriggerstheRAcapabilityupdateproceduretorequestanMS'
scurrentRAcapability,itsIMSI,orboth.ThisisrequestedbysendinganRA-CAPABILITY-UPDATEPDU(seeFigure6.23).ThismessageincludestheTLLIoftheMS.ItissentontheBVCassociatedwiththecellwherethemobileislocated.
Figure6.23:
Radioaccesscapabilityupdateprocedure.
TheSGSNrespondsbysendinganRA-CAPABILITY-UPDATE-ACKincludingtheTLLI,theIMSI,andtheRAcapabilityifavailable.
6.5.3.3RadioStatus
ThisprocedureistriggeredbytheBSSwhenithasbeenrequestedtosenddownlinkLLCPDUsand,becauseofexceptionconditions,thetransferthroughtheairinterfaceofLLCPDUsisnolongerpossible.Exceptionconditionsareoccurrencesinwhich:
1.TheMSgoesoutofcoverageandislost;
2.Thelinkqualityistoopoortocontinuethetransferthroughtheairinterface;
3.TheBSShasorderedtheMStoperformacellreselection.
Conditions1and2indicatetotheSGSNthatitshouldstopsendingLLCPDUstothecellfortheconcernedMS.Condition3indicatestotheSGSNthatitshouldwaitforacellupdatebeforeresumingthetransmissionofLLCPDUs.
AsdescribedinFigure6.24,theBSSusestheRADIO-STATUSPDUtosignaltheseexceptionconditionstotheSGSN.TheRADIOSTATUSPDUincludestheidentificationoftheMS(eithertheTLLI,IMSI,orTMSI)andthecauseofthefailure.ItissentontheBVCassociatedwiththecellwherethemobilewaslocated.
Figure6.24:
RadioSTATUSprocedure.
6.5.4SignalingProceduresBetweenNMSAPs
6.5.4.1Flush
TheflushprocedureisinitiatedbytheSGSN.ThisprocedureistriggeredwhentheSGSNdetectsthatamobilehasperformedacellreselectionduringadownlinkpackettransfer.TheSGSNdetectsthecellreselectionafteracellupdateorRAupdateprocedure.Theprocedurecanbeinitiatedfortwopurposes:
1.ThecellreselectionoccursbetweentwocellsthatarenotinthesameRAorinthesameNSentity,inwhichcasetheflushprocedureensuresthatLLCPDUsthatarestoredintheBSSatcelllevel,fortheconcernedmobile,aredeleted.
2.ThecellreselectionoccursbetweentwocellsthatareinthesameRAandinthesameNSentity,inwhichcasetheflushprocedureindicatesthenewcell(BVCI)wheretheLLCPDUsaretobetransferred.Theinterruptionoftrafficduetothecellreselectionisthenreduced.
TheflushprocedureisdescribedinFigure6.25.TheSGSNinitiatestheflushprocedurebysendingaFLUSH-LLPDU
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