【VOLTE】【SRVCC】【1】 VOLTE SRVCC(SRVCC TO 3GPP)

        SRVCC 过程有很多，例如从 E-UTRAN->GERAN(with DTM) 、 E-UTRAN->GERAN(without DTM) 、 E-UTRAN->CDMA1X ， E-UTRAN->WCDMA 、 UTRAN(HSPA)->GERAN 等诸多情形，本文主要介绍从 E-UTRAN 到 23G/CDMA1X 网络的接续

一、SRVCCATTACH过程

如果终端支持SRVCC功能，则终端在ATTACH REQEUST / TAU等消息中的MS Network Capability 信元中携带是否支持SRVCC，并上报CLASSMARK2/CLASSMARK3的能力（如果终端支持）

如果网络MME支持SRVCC，则在S1上下文建立过程中的S1 AP Initial Context Setup Request 中指明SRVCC operation possible

二、SRVCC TO 3GPP

2.1 SRVCC TO3GPP的网路架构

2.2  SRVCC TO 3GPP流程图(简略)

         当终端在 LTE 环境下，不满足 VOLTE 承载时，终端根据测量控制进行测量、并向网络发送测量报告 MR （例如 A2 、 B2 事件），由 E-UTRAN 决定是否进行切换

2.3 SRVCC TO3GPP流程图(详细)

无DTM SRVCC过程

 

带DTM的SRVCC过程

WithDTM和without DTM流程的区别在于，无DTM流程的切换，切换后GPRS需要挂起GPRS suspend

 

三、 SRVCC to3GPP LOG

2013 Jul  8  11:51:08.078  [00]  0xB0C0  LTE RRC OTA Packet  --  DL_DCCH / MobilityFromEUTRACommand

value DL-DCCH-Message ::= 

{

  message c1 : mobilityFromEUTRACommand : 

      {

        rrc-TransactionIdentifier 0,

        criticalExtensions c1 : mobilityFromEUTRACommand-r8 : 

            {

              cs-FallbackIndicator FALSE,

              purpose handover : 

                {

                 targetRAT-Type utra, //目标网络类型

                  targetRAT-MessageContainer '102D2B7C600883C35B202D8A28113F94'H,

                  nas-SecurityParamFromEUTRA '06'H

                }

            }

      }

}

=======================================================

Further Decode WCDMA RRC IEs:

=======================================================

Interpreted PDU:

value HandoverToUTRANCommand ::= r3 : 

  {

    handoverToUTRANCommand-r3 

    {

      new-U-RNTI 

      {

        srnc-Identity '00000010 1101'B,

        s-RNTI-2 '00101011 01'B

      },

      cipheringAlgorithm uea1,

      specificationMode preconfiguration : 

        {

          preConfigMode defaultConfig : 

            {

              defaultConfigMode fdd,

              defaultConfigIdentity 3

            },

          rab-Info 

          {

            rab-Identity gsm-MAP-RAB-Identity : '00000001'B,

            cn-DomainIdentity cs-domain

          },

          modeSpecificInfo fdd : 

            {

              ul-DPCH-Info 

              {

                ul-DPCH-PowerControlInfo 

                {

                  dpcch-PowerOffset -24,

                  pc-Preamble 0,

                  sRB-delay 7

                },

                scramblingCodeType longSC,

                reducedScramblingCodeNumber 429,

                spreadingFactor sf64

              },

              dl-CommonInformationPost 

              {

                dl-DPCH-InfoCommon 

                {

                  dl-DPCH-PowerControlInfo 

                  {

                    modeSpecificInfo fdd : 

                      {

                        dpc-Mode singleTPC

                      }

                  }

                }

              },

              dl-InformationPerRL-List 

              {

                {

                  primaryCPICH-Info 

                  {

                    primaryScramblingCode 91

                  },

                  dl-DPCH-InfoPerRL 

                  {

                    pCPICH-UsageForChannelEst mayBeUsed,

                    dl-ChannelisationCode 

                    {

                      sf-AndCodeNumber sf128 : 10

                    },

                    tpc-CombinationIndex 0

                  }

                }

              },

              frequencyInfo 

              {

               uarfcn-DL 4415  //需要切换的网络类型和频点

              }

            }

        },

      maxAllowedUL-TX-Power 24

    }

  }