EPS 專有承載建立流程

與缺省的EPS承載不同，專有EPS承載的建立，是為了滿足用戶特定QoS的需求。EPS專有承載建立之前，必須存在相應(yīng)的缺省EPS承載。EPS專有承載的建立，可以由網(wǎng)絡(luò)側(cè)來發(fā)起，也可以由終端側(cè)來發(fā)起。在網(wǎng)絡(luò)側(cè)發(fā)起的專有承載建立過程中，專有承載建立的信令流程由網(wǎng)絡(luò)側(cè)發(fā)起，不要求UE上的應(yīng)用層了解EPS承載層QoS的具體信息，UE上的應(yīng)用層可以通過應(yīng)用層的信令與網(wǎng)絡(luò)協(xié)商QoS的相關(guān)信息，如SIP/SDPRTSP等，但這種應(yīng)用層的QoS協(xié)商并不包含承載層QoS的內(nèi)容。在UE側(cè)發(fā)起的EPS專有承載的建立中（也稱為承載資源分配過程），UE上的應(yīng)用層直接向網(wǎng)絡(luò)側(cè)提出承載層QoS（包括QCI，GBR等）的申請，如果網(wǎng)絡(luò)側(cè)接受UE的請求，就會與UE進一步信令交互，建立專有的EPSBearer。在網(wǎng)絡(luò)側(cè)發(fā)起的EPS專有承載的建立過程中，觸發(fā)網(wǎng)絡(luò)側(cè)建立專有承載的條件可以是來自網(wǎng)絡(luò)的應(yīng)用層信令，也可以是來自UE的應(yīng)用層信令。例如，UE發(fā)起基于IMS的VoIP呼叫或者UE需要接收基于IMS的VoIP呼叫。下圖是在基于GTP的S5接口下，網(wǎng)絡(luò)側(cè)發(fā)起的EPS專有承載的建立流程。UELIEUn5T1SGW制fffiCCMnecL FUe噸uruBearersmrp.CYe—bcSe&tcf—Cre-satEBearer二Ryu瑚口日曲購「成叩日HSfiI^QEl^anEQ!Imno虱廈M叩Ra&pDnscRRCGonnMnien?UL船陽FHfifiUoHiT1如出世LILA 首先，PCRF根據(jù)UE應(yīng)用層所需要的QoS信息，生成相應(yīng)的QoS準(zhǔn)則，通過基于Diameter的RAR（Re—AuthenticationRequest）命令發(fā)送給PGW。PGW根據(jù)相應(yīng)的QoS準(zhǔn)則來配置EPSBearer的QoS，并發(fā)送CreateBearerRequest消息給SGW，SGW將相應(yīng)的消息轉(zhuǎn)發(fā)給MME，SGW與MME之間的信息示例如下：GPRSTunnelingProtocolV2CreateBearerRequestFlags:72010 = Version:2....1...=T:1MessageType:CreateBearerRequest(95)MessageLength:743TunnelEndpointIdentifier:3300033(MME的GTP—C的TEID值)SequenceNumber:0Spare:256LinkedEPSBearerID(LBI):IEType:EPSBearerID(EBI)(73)IELength:1000 =CRflag:0....0000=Instance:0....0101=EPSBearerID(EBI):5BearerContext:[GroupedIE]IEType:BearerContext(93)IELength:69000 =CRflag:0 0000=Instance:0EPSBearerID(EBI):IEType:EPSBearerID(EBI)(73)IELength:1000 =CRflag:0 0000=Instance:0....0000=EPSBearerID(EBI):0(EBI是由MME分配的，由于此時并沒有分配，所以設(shè)置為零)FullyQualifiedTunnelEndpointIdentifier(F-TEID):IEType:FullyQualifiedTunnelEndpointIdentifier(F-TEID)(87)IELength:9000.....=CRflag:0 0000=Instance:01 =V4(True-IPV4addressfieldExists,False-Doesn'tExistinF-TEID):True.0 =V6(True-IPV6addressfieldExists,False-Doesn'tExistinF-TEID):False...00001=InterfaceType:S1-USGWGTP-Uinterface(1)TEID/GREKey:34F-TEIDIPv4:30.0.2.1(30.0.2.1)FullyQualifiedTunnelEndpointIdentifier(F-TEID):IEType:FullyQualifiedTunnelEndpointIdentifier(F-TEID)(87)IELength:9000.....=CRflag:0 0001=Instance:11 =V4(True-IPV4addressfieldExists,False-Doesn'tExistinF-TEID):True.0 =V6(True-IPV6addressfieldExists,False-Doesn'tExistinF-TEID):False...00101=InterfaceType:S5/S8PGWGTP-Uinterface(5)TEID/GREKey:34F-TEIDIPv4:20.0.0.1(20.0.0.1)EPSBearerLevelTrafficFlowTemplate(BearerTFT):IEType:EPSBearerLevelTrafficFlowTemplate(BearerTFT)(84)IELength:8000 =CRflag:0....0000=Instance:0001 =OperationCode:CreateNewTFT(1)....0001=NumberofPacketFilters:1...0....=Ebit:FalsePacketFilter1....0000=PacketFilterIdentifier:0..11....=Direction:bidirectional(3)(上行和下行雙向的Filter)EvaluationPrecedence:0LengthofPacketFilter:3ComponentType:Singleremoteporttype(80)Singleremoteporttype:80BearerLevelQualityofService(BearerQoS):IEType:BearerLevelQualityofService(BearerQoS)(80)IELength:22000 =CRflag:0 0000=Instance:0 1=PVI(Pre-emptionVulnerability):True..0000..=PL(PriorityLevel):0.0 = PCI(Pre-emptionCapability):False(PVI,PL,以及是ARP的屬性，具體內(nèi)容參見3GPP23.401)Label(QCI):9MaximumBitRateForUplink:65535000MaximumBitRateForDownlink:65535000GuaranteedBitRateForUplink:65535000GuaranteedBitRateForDownlink:65535000MME為每個EPSBearer分配相應(yīng)的EBI(EPSBearerID)，構(gòu)造相應(yīng)的ActivateDedicatedEPSBear消息，將其作為NASPDU，包含在發(fā)送到eNodeB的BearSetupRequest消息中。eNodeB將EPSBearer的QoS映射到空口上的QoS，然后通過向UE發(fā)送RRCConnectionReconfiguration消息來建立相應(yīng)的DRB，并對DRB進行PDCP層，邏輯層，以及RLC層等進行配置。在消息中還作為NASPDU傳輸來自MME的ActivateDedicatedEPSBear。在NASPDU中，LBI(LinkedEPSBearID)給出了與DedicatedEPSBearer對應(yīng)的DefaultEPSBear的標(biāo)識，TFT表示應(yīng)用到UE的上行TFT，其中的Precedence指出了PacketFilter的優(yōu)先級，數(shù)值越低，表示優(yōu)先級越高。UE在發(fā)送上行數(shù)據(jù)包的時候，按照PacketFilter的優(yōu)先級對數(shù)據(jù)包進行匹配，如果匹配成功，UE就會在相應(yīng)的EPSBearer(RadioBearer)上發(fā)送數(shù)據(jù)，否則的話，UE會在缺省的EPSBearer上發(fā)送數(shù)據(jù)。+-Rrc|\-Dcch[Union]|+-message_|\-cl[Union]| \-rrcConnectionReconfiguration[Union]| +-rrc_Transactionldentifier=0[INTEGER]|+-criticalExtensions|\-cl[Union]|\-rrcConnectionReconfiguration_r8[Union]| 4-measConfig=omit| 4-mobilityControllnfo=omit| 4-dedicatedlnfoNASList=omit| 4--radioResourceConfigDedicated| |4--srb_ToAddModList=omit| |+-drb_ToAddModList[RecordOf]I I I[0]| | | +-eps_Bearerldentity=6[INTEGER]| | | +-drb_ldentity=2[INTEGER]| | | +-pdcp_Config| | | | +-discardTimer=infinity_[ENUM]| | | | +-rlc_AM| || ||+-statusReportRequired=true [BOOLEAN]| | | | +-rlc_UM=omit| | | | +-headerCompression| | | |\-notllsed[Union]=NULL| | | +-rlc_Config| | | |\-am[Union]| | | |+-ul_AM_RLC| || ||+-t_PollRetransmit=ms80[ENUM]| | | ||+-pollPDU=pl28[ENUM]| || ||+-pollByte=kB125[ENUM]| || ||+-maxRetxThreshold=t4[ENIIM]| | | |+-dl_AM_RLC| | | |+-t_Reordering=ms80[ENIIM]| | | |+-t_StatusProhibit=ms60[ENIIM]| | | +-logicalChannelldentity=4[INTEGER]| | | +-logicalChannelConfig| | |+-ul_SpecificParameters| | | +-priority=13[INTEGER]| | | +-prioritisedBitRate=infinity_[ENIIM]| | | +-bucketSizeDuration=mslOO[ENIIM]| | | +-logicalChannelGroup=2[INTEGER]| | 4--drb_ToReleaseList=omit| | 4-mac_MainConfig=omit| | 4--sps_Config=omit| |+-physicalConfigDedicated=omit| +-securityConfigHO=omit| +-nonCriticalExtension=omit+-Nas[RecordOf][0]+-SecurityProtection|+-Status='0010'B[BITSTRING]+-Pdu+-Msg|\-aCTIVATE_DEDICATED_EPS_BEARER_CONTEXT_REQUEST[Union]|+-epsBearerId='6'H[HEXSTRING]|+-protocolDiscriminator='0010'B[BITSTRING]|+-procedureTransactionIdentifier='00'O[OCTETSTRING]|+-messageType='11000101'B[BITSTRING]|+-spareHalfOctet='0'H[HEXSTRING]|+-linkedEpsBearerId||+-idValue='0101'B[BITSTRING]|+-epsQos||+-iei=omit||+-iel='09'O[OCTETSTRING]||+-qci='00000100'B[BITSTRING]||+-maxBitRateUl='01101000'B[BITSTRING]||+-maxBitRateDl='01101000'B[BITSTRING]||+-guaranteedBitRateUl='01001000'B[BITSTRING]||+-guaranteedBitRateDl='01001000'B[BITSTRING]||+-maxBitRateUlExt='00000000'B[BITSTRING]||+-maxBitRateDlExt='00000000'B[BITSTRING]||+-guaranteedBitRateUlExt='00000000'B[BITSTRING]||+-guaranteedBitRateDlExt='00000000'B[BITSTRING]|+-tft||+-iei=omit||+-iel='23'O[OCTETSTRING]||+-tftOperationCode='001'B[BITSTRING]表示創(chuàng)建TFT||+-eBit='0'B[BITSTRING]||+-noOfPktFilter='0010'B[BITSTRING]||+-packetFilterList[RecordOf]|||[0]||||+-iei='10'O[OCTETSTRING]其中可以表示Filter的方向。||||+-precendence='00000000'B[BITSTRING]| |||+-iel='0E'O[OCTETSTRING]IPV4remoteAddresstype（具體內(nèi)容參見10.5.162/3GPP24.008）| | | |+-contents='10C0A80101FFFFFFFF5079B83011'O [OCTETSTRING]| | | [1]| | | +-iei='20'O[OCTETSTRING]| | | +-precendence='00000001'B[BITSTRING]| | | +-iel='0E'O[OCTETSTRING]| | | +-contents='10C0A80101FFFFFFFF50EE483011'O [OCTETSTRING]||+-parameterList=omit|+-transactionIdentifier=omit|+-negotiatedQos=omit|+-negotiatedLlcSapi=omit|+-radioPriority=omit|+-packetFlowIdentifier=omit|+-protocolConfigurationOptions=omit+-PiggybackedPduList=omitUE存貯得到的相應(yīng)QoS信息，并作相應(yīng)的處理，然后向eNodeB回應(yīng)RRCConnectionReconfigurationComplete消息。eNodeB接收到UE的回應(yīng)后，回復(fù)給MMEBearSetupResponse消息。UENAS層同時會構(gòu)造ActivateDedicatedEPSBearerContextComplete消息，并將其作為NASPDU通過ULInfoTransfer發(fā)送給eNodeB，eNodeB將此NASPDU透傳給MME。MME接收到后，生成CreateBearerResponse消息，發(fā)送給SGW和PGW。GPRSTunnelingProtocolV2CreateBearerResponseFlags:72010 =Version:2....1...=T:1MessageType:CreateBearerResponse(96)MessageLength:424TunnelEndpointIdentifier:1SequenceNumber:0Spare:256Cause:IEType:Cause(2)IELength:2000.....=CRflag:0 0000=Instance:0Cause:Requestaccepted(16) 0=CauseSource(CS:True-Errororiginatedbyremotenode,False-ErrororiginatedbyNodesendingtheMessage):FalseBearerContext:[GroupedIE]IEType:BearerContext(93)IELength:37000.....=CRflag:0 0000=Instance:0Cause:IEType:Cause(2)IELength:2000.....=CRflag:0....0000=Instance:0Cause:Requestaccepted(16) 0=CauseSource(CS:True-Errororiginatedbyremotenode,False-ErrororiginatedbyNodesendingtheMessage):FalseEPSBearerID(EBI):IEType:EPSBearerID(EBI)(73)IELength:1000.....=CRfl