5G原理和协议重点解读英文版.docx

5G原理和协议重点解读英文版.docx

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5G原理和协议重点解读英文版

5GMasterInformationBlock（NR-MIB）

OverallstructureofMIBandSIBinNRisalmostsimilartoLTEandotherlegacytechnologies.HoweverthereisamajordifferencerelatedtotheperiodicaltransmissionofSIBs.InLTEandotherlegacytechnologiestheSIBsarebroadcastedpriodicallyregardlessofwhetherUEwantsitornot.But,inNewRadio（NR）therearetwoversionsofSIBs.OneisbeingtransmittedperiodicallylikeLTEandotherisbeingtransmittedonlyon-Demandi.e.whenrequestedbyUE.

NRMIBcharacteristics 

∙MIBistransmittedoverBCHtransportchannelandPBCHphysicalchannel

∙ItisQPSKmodulated

∙ItincludedthenecessaryparametersrequiredtodecodeSystemInformationBlockType1（SIB1）

∙Itspriodicityisabout80msandwithinthis80msrepetitivetransmissionhappens

∙ItistransmittedonOFDMsymbol1,2,3.

∙Ituses0to239subcarriernumberonsymbol1&3,whereasonsymbol2itusessubcarriednumber0to47and192to239asperTS38.211.

MIB/SIBsignallingcallflow:

∙Signallingradiobearer:

N/A

∙RLC-SAP:

TM

∙Logicalchannel:

BCCH

∙Direction:

NetworktoUE

RRCParametersforMasterInformationBlock:

MIB:

:

=SEQUENCE{

∙systemFrameNumber                       BITSTRING（SIZE（6））,

∙subCarrierSpacingCommon             ENUMERATED{scs15or60,scs30or120},

∙ssb-SubcarrierOffset              INTEGER（0…15）,

∙dmrs-TypeA-Position             ENUMERATED{pos2,pos3},

∙pdcch-ConfigSIB1                 INTEGER（0…255）,

∙cellBarred                        ENUMERATED{barred,notBarred},

∙intraFreqReselection              ENUMERATED{allowed,notAllowed},

∙spare                            BITSTRING（SIZE

（1））

}

ParametersDescription:

∙systemFrameNumber :

SimilartoLTE,NRdoeshavea10bitSystemFrameNumberstartfrom0to1023.MIBcarries6mostsignificantbit（MSB）ofthe10bitsandremaining4LSBoftheSFNareconveyedinthePBCHtransportblockaspartofchannelcoding（i.e.outsidetheMIBencoding）.

∙subCarrierSpacingCommon:

IndicatestheSubcarrierspacingforSIB1,Message2/4forinitialaccessandSystemInformation-messages.Itcanhaveavalues15and30kHzvalidforcarrierfrequencies<6GHz;Values60and120kHzareapplicableforcarrierfrequencies>6GHz

∙ssb-subcarrierOffsetindicatesthefrequencydomainoffsetbetweenSSBandtheoverallresourceblockgridinnumberofsubcarriers.ThisfieldmayindicatethatthiscelldoesnotprovideSIB1andthatthereishencenocommonCORESET.Inthiscase,thefieldpdcch-ConfigSIB1mayindicatethefrequencypositionswheretheUEmay（not）findaSS/PBCHwithacontrolresourcesetandsearchspaceforSIB1

∙dmrs-TypeA-Position:

IndicatesPositionof（first）DLDM-RS.ItcorrespondstoL1parameter‘DL-DMRS-typeA-pos’

∙pdcchConfigSIB1:

ItiscorrespondstoRMSI-PDCCH-ConfiginTS38.213[13],section4.1.DeterminesabandwidthforPDCCH/SIB,acommonControlResourceSet（CORESET）acommonsearchspaceandnecessaryPDCCHparameters.Ifthefieldssb-SubcarrierOffset indicatesthatSIB1isnotpresent,thefieldpdcch-ConfigSIB1indicatethefrequencypositionswheretheUEmayfindSS/PBCHblockwithSIB1orthefrequencyrangewherethenetworkdoesnotprovideSS/PBCHblockwithSIB1（seeTS38.213[13],section13）.

∙cellBarred indicateswhetherthecellallowsUEstocamponthiscellasperspecificationTS38.304

∙intraFreqReselection indicatesifIntrafrequencycellreselectionisAllowedornotAllowed.Itcontrolscellreselectiontointra-frequencycellswhenthehighestrankedcellisbarred,ortreatedasbarredbytheUEasspecifiedinTS38.304

MIBAcquiring  and Processing 

MIB/SIBacquisitionprocess varycasetocase.HerewewilldicsussoverallMIB/SIBacquisitionprocessasdefinedinTS38.331NR-RRCspecification.

Case1:

NoOn-DemandSystemInformation,NopreviouslystoredSIBandUEjustpoweredON

∙UEPoweredON

∙CellSearch（PSSandSSS）andPBCHdecodetogetMIB

∙DecodeandstoretheMIB

∙checkifcellBarred=barred, stophere  cellBarred!

=barred,movetonexttoprocessfurtherinformation

∙DecodeSIB1usingparametersprovidedbyMIBandstoretheresults

∙AsSIB1indicatenodemandSI,decodeotherSystemInformation（SIBs）

Case2:

On-DemandSystemInformationIndication,NopreviouslystoredSIBandUEjustpoweredON

∙UEPoweredON

∙CellSearch（PSSandSSS）andPBCHdecodetogetMIB

∙DecodeandstoretheMIB

∙checkifcellBarred=barred, stophere  cellBarred!

=barred,movetonexttoprocessfurtherinformation

∙DecodeSIB1usingparametersprovidedbyMIBandstoretheresults

∙AsSIB1 indicateondemandSI,checkRRCstatus

IfUERRCstatusisinRRC-IDLEorRRC-INACTIVEstate

∙TriggerUElowerlayerstoinitateRACHprocedure

∙Acquiretheon-DemandSImessageswhenAckn