EPS专有承载建立流程.doc

EPS 专有承载建立流程
与缺省的EPS承载不同，专有EPS承载的建立，是为了满足用户特定QoS的需求。EPS专有承载建立之前，必须存在相应的缺省EPS承载。
EPS专有承载的建立，可以由网络侧来发起，也可以由终端侧来发起。在网络侧发起的专有承载建立过程中，专有承载建立的信令流程由网络侧发起，不要求UE上的应用层了解EPS承载层QoS的具体信息，UE上的应用层可以通过应用层的信令与网络协商QoS的相关信息，如SIP/SDP, RTSP等，但这种应用层的QoS协商并不包含承载层QoS的内容。在UE侧发起的EPS专有承载的建立中（也称为承载资源分配过程），UE上的应用层直接向网络侧提出承载层QoS（包括QCI， GBR等）的申请，如果网络侧接受UE的请求，就会与UE进一步信令交互，建立专有的EPS Bearer。
在网络侧发起的EPS专有承载的建立过程中，触发网络侧建立专有承载的条件可以是来自网络的应用层信令，也可以是来自UE的应用层信令。例如，UE发起基于IMS的VoIP呼叫或者UE需要接收基于IMS的VoIP呼叫。

下图是在基于GTP的S5接口下，网络侧发起的EPS专有承载的建立流程。

首先，PCRF根据UE应用层所需要的QoS信息，生成相应的QoS准则，通过基于Diameter的RAR（Re－Authentication Request）命令发送给PGW。
PGW根据相应的QoS准则来配置EPS Bearer的QoS，并发送Create Bearer Request  消息给SGW， SGW将相应的消息转发给MME， SGW与MME之间的信息示例如下：
GPRS Tunneling Protocol V2
Create Bearer Request
    Flags: 72
        010. .... = Version: 2
        .... 1... = T: 1
    Message Type: Create Bearer Request (95)
    Message Length: 743
    Tunnel Endpoint Identifier: 3300033 (MME的GTP －C的TEID 值)
    Sequence Number: 0
    Spare: 256
    Linked EPS Bearer ID (LBI) :
        IE Type: EPS Bearer ID (EBI) (73)
        IE Length: 1
        000. .... = CR flag: 0
        .... 0000 = Instance: 0
        .... 0101 = EPS Bearer ID (EBI): 5
    Bearer Context : [Grouped IE]
        IE Type: Bearer Context (93)
        IE Length: 69
        000. .... = CR flag: 0
        .... 0000 = Instance: 0
        EPS Bearer ID (EBI) :
            IE Type: EPS Bearer ID (EBI) (73)
            IE Length: 1
            000 .... = CR flag: 0
            .... 0000 = Instance: 0
            .... 0000 = EPS Bearer ID (EBI): 0 （EBI是由MME分配的，由于此时并没有分配，所以设置为零）
        Fully Qualified Tunnel Endpoint Identifier (F-TEID) :
            IE Type: Fully Qualified Tunnel Endpoint Identifier (F-TEID) (87)
            IE Length 9
            000. .... = CR flag: 0
            .... 0000 = Instance: 0
            1... .... = V4 (True-IPV4 address field Exists,False-Doesn't Exist in F-TEID): True
            .0.. .... = V6 (True-IPV6 address field Exists,False-Doesn't Exist in F-TEID): False
            ...0 0001 = Interface Type: S1-U SGW GTP-U interface (1)
            TEID/GRE Key: 34
            F-TEID IPv4: 30.0.2.1 (30.0.2.1)
        Fully Qualified Tunnel Endpoint Identifier (F-TEID) :
            IE Type: Fully Qualified Tunnel Endpoint Identifier (F-TEID) (87)
            IE Length: 9
            000. .... = CR flag: 0
            .... 0001 = Instance: 1
            1... .... = V4 (True-IPV4 address field Exists,False-Doesn't Exist in F-TEID): True
            .0.. .... = V6 (True-IPV6 address field Exists,False-Doesn't Exist in F-TEID): False
            ...0 0101 = Interface Type: S5/S8 PGW GTP-U interface (5)
            TEID/GRE Key: 34
            F-TEID IPv4: 20.0.0.1 (20.0.0.1)
        EPS Bearer Level Traffic Flow Template (Bearer TFT) :  
            IE Type: EPS Bearer Level Traffic Flow Template (Bearer TFT) (84)
            IE Length: 8
            000. .... = CR flag: 0
            .... 0000 = Instance: 0
            001. .... = Operation Code: Create New TFT (1)
            .... 0001 = Number of Packet Filters: 1
            ...0 .... = Ebit: False
            Packet Filter 1
                .... 0000 = Packet Filter Identifier: 0
                ..11 .... = Direction: bidirectional (3) (上行和下行双向的Filter)
                Evaluation Precedence: 0
                Length of Packet Filter: 3
                Component Type: Single remote port type (80)
                Single remote port type: 80
        Bearer Level Quality of Service (Bearer QoS) :
            IE Type: Bearer Level Quality of Service (Bearer QoS) (80)
            IE Length: 22
            000. .... = CR flag: 0
            .... 0000 = Instance: 0
            .... ...1 = PVI (Pre-emption Vulnerability): True
            ..00 00.. = PL (Priority Level): 0
            0.. .... = PCI (Pre-emption Capability): False （PVI，PL，以及是ARP的属性，具体内容参见3GPP 23.401）
            Label (QCI): 9
            Maximum Bit Rate For Uplink: 65535000
            Maximum Bit Rate For Downlink: 65535000
            Guaranteed Bit Rate For Uplink: 65535000
            Guaranteed Bit Rate For Downlink: 65535000

MME为每个EPS Bearer分配相应的EBI （EPS Bearer ID），构造相应的 Activate Dedicated EPS Bear消息，将其作为NAS PDU，包含在发送到eNodeB的Bear Setup Request 消息中。

eNodeB将EPS Bearer的QoS映射到空口上的QoS，然后通过向UE发送RRCConnectionReconfiguration消息来建立相应的DRB，并对DRB进行PDCP层，逻辑层，以及RLC层等进行配置。在消息中还作为NAS PDU传输来自MME的Activate Dedicated EPS Bear。在NAS PDU中，LBI （Linked EPS Bear ID）给出了与Dedicated EPS Bearer对应的Default EPS Bear的标识， TFT表示应用到UE的上行TFT，其中的Precedence指出了Packet Filter的优先级，数值越低，表示优先级越高。UE在发送上行数据包的时候，按照Packet Filter的优先级对数据包进行匹配，如果匹配成功， UE就会在相应的EPS Bearer（Radio Bearer）上发送数据，否则的话， UE会在缺省的EPS Bearer上发送数据。

+-Rrc
  | \-Dcch [Union]
  |   +-message_
  |     \-c1 [Union]
  |       \-rrcConnectionReconfiguration [Union]
  |         +-rrc_TransactionIdentifier=0 [INTEGER]
  |         +-criticalExtensions
  |           \-c1 [Union]
  |             \-rrcConnectionReconfiguration_r8 [Union]
  |               +-measConfig=omit
  |               +-mobilityControlInfo=omit
  |               +-dedicatedInfoNASList=omit
  |               +-radioResourceConfigDedicated
  |               | +-srb_ToAddModList=omit
  |               | +-drb_ToAddModList [RecordOf]
  |               | | [0]
  |               | |    +-eps_BearerIdentity=6 [INTEGER]
  |               | |    +-drb_Identity=2 [INTEGER]
  |               | |    +-pdcp_Config
  |               | |    | +-discardTimer=infinity_ [ENUM]
  |               | |    | +-rlc_AM
  |               | |    | | +-statusReportRequired=true [BOOLEAN]
  |               | |    | +-rlc_UM=omit
  |               | |    | +-headerCompression
  |               | |    |   \-notUsed [Union]=NULL
  |               | |    +-rlc_Config
  |               | |    | \-am [Union]
  |               | |    |   +-ul_AM_RLC
  |               | |    |   | +t_PollRetransmit=ms80 [ENUM]
  |               | |    |   | +-pollPDU=p128 [ENUM]
  |               | |    |   | +-pollByte=kB125 [ENUM]
  |               | |    |   | +-maxRetxThreshold=t4 [ENUM]
  |               | |    |   +-dl_AM_RLC
  |               | |    |     +-t_Reordering=ms80 [ENUM]
  |               | |    |     +-t_StatusProhibit=ms60 [ENUM]
  |               | |    +-logicalChannelIdentity=4 [INTEGER]
  |               | |    +-logicalChannelConfig
  |               | |      +-ul_SpecificParameters
  |               | |        +-priority=13 [INTEGER]
  |               | |        +-prioritisedBitRate=infinity_ [ENUM]
  |               | |        +-bucketSizeDuration=ms100 [ENUM]
  |               | |        +-logicalChannelGroup=2 [INTEGER]
  |               | +-drb_ToReleaseList=omit
  |               | +-mac_MainConfig=omit
  |               | +-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] 表示创建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] IPV4 remote Address type (具体内容参见10.5.162/3GPP 24.008)
         |   | | |  +-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=omit

UE存贮得到的相应QoS信息， 并作相应的处理， 然后向eNodeB回应RRCConnectionReconfiguration Complete消息。eNodeB接收到UE的回应后， 回复给MME Bear Setup Response消息。
UE NAS层同时会构造Activate Dedicated EPS Bearer Context Complete消息，并将其作为NAS PDU通过UL Info Transfer发送给eNodeB， eNodeB将此NAS PDU 透传给MME。MME接收到后，生成 Create Bearer Response 消息， 发送给SGW和PGW。

GPRS Tunneling Protocol V2
Create Bearer Response
    Flags: 72
        010. .... = Version: 2
        .... 1... = T: 1
    Message Type: Create Bearer Response (96)
    Message Length: 424
    Tunnel Endpoint Identifier: 1
    Sequence Number: 0
    Spare: 256
    Cause :
        IE Type: Cause (2)
        IE Length: 2
        000. .... = CR flag: 0
        .... 0000 = Instance: 0
        Cause: Request accepted (16)
        .... ...0 = Cause Source (CS: True-Error originated by remote node, False-Error originated by Node sending the Message): False
    Bearer Context : [Grouped IE]
        IE Type: Bearer Context (93)
        IE Length: 37
        000. .... = CR flag: 0
        .... 0000 = Instance: 0
        Cause :
            IE Type: Cause (2)
            IE Length: 2
            000. .... = CR flag: 0
            .... 0000 = Instance: 0
            Cause: Request accepted (16)
            .... ...0 = Cause Source (CS: True-Error originated by remote node, False-Error originated by Node sending the Message): False
        EPS Bearer ID (EBI) :
            IE Type: EPS Bearer ID (EBI) (73)
            IE Length: 1
            000. .... = CR flag: 0
            .... 0000 = Instance: 0
            .... 0110 = EPS Bearer ID (EBI): 6
        Fully Qualified Tunnel Endpoint Identifier (F-TEID) :
            IE Type: Fully Qualified Tunnel Endpoint Identifier (F-TEID) (87)
            IE Length: 9
            000. .... = CR flag: 0
            .... 0000 = Instance: 0
            1... .... = V4 (True-IPV4 address field Exists,False-Doesn't Exist in F-TEID): True
            .0.. .... = V6 (True-IPV6 address field Exists,False-Doesn't Exist in F-TEID): False
            ...0 0000 = Interface Type: S1-U eNodeB GTP-U interface (0)
            TEID/GRE Key: 34
            F-TEID IPv4: 30.0.0.1 (30.0.0.1)
        Fully Qualified Tunnel Endpoint Identifier (F-TEID) :
            IE Type: Fully Qualified Tunnel Endpoint Identifier (F-TEID) (87)
            IE Length: 9
            000. .... = CR flag: 0
            .... 0001 = Instance: 1
            1... .... = V4 (True-IPV4 address field Exists,False-Doesn't Exist in F-TEID): True
            .0.. .... = V6 (True-IPV6 address field Exists,False-Doesn't Exist in F-TEID): False
            ...0 0001 = Interface Type: S1-U SGW GTP-U interface (1)
            TEID/GRE Key: 34
            F-TEID IPv4: 30.0.2.1 (30.0.2.1)