TD-LTE CSFB to GSM  Configuratons and Analysis on eNB side

1.   Network Structure

2.   CSFB SIGNAL FLOW

2.1 The combined EPS/IMSI Attach

2.2 MO Call CSFB

2.3 MT Call CSFB

2.4 Returning back to E-UTRAN No PS HO

2.5 RIM (RAN IFORMATION MANAGEMENT)

1. The eNodeB initiates the RIM transfer procedure by sending an eNB

Direct Information Transfer message with the RIM information and the

RIM Routing Address IE to the MME.

2. The MME determines the SGSN which serves the BSC from the RIM

Routing Address IE, and then sends a RAN Information Relay message

with the RIM Routing Address IE to the SGSN. If the message is sent over

the Gn interface, it includes the RAN Transparent Container into which

the RIM PDU is mapped. If the message is sent over the S3 interface, it

includes the BSS Container into which the RIM PDU is mapped.

3. The SGSN sends the RIM PDU with the RIM information to the BSC.

4. The BSC sends a RIM PDU with the requested RIM information and the

eNodeB address to the SGSN.

5. The SGSN sends a RAN Information Relay message with the RIM Routing

Address IE to the MME. If the message is sent over the Gn interface,

it includes the RAN Transparent Container into which the RIM PDU is

mapped. If the message is sent over the S3 interface, it includes the BSS

Container into which the RIM PDU is mapped.

6. The MME sends the MME Direct Information Transfer message with the

RIM information to the eNodeB.

2.6 SMS MO

2.7 SMS MT

3.   Signaling analysis at LTE eNB side

R8

MO call

A Normal MO procedure

3.1 NAS: extendedServiceRequest (UE:301992109)

NAS {

    securityProtectedNASMessage {

      securityHeaderType Integrity (1),

      protocolDiscriminator 7,

      messageAuthenticationCode '00 00 00 00'H,

      sequenceNumber 2,

      extendedServiceRequest {

        securityHeaderType Not security protected (0),

        protocolDiscriminator 7,

        messageType 76,

        NASKeySetIdentifier {

          TSC 0,

          NASKeySetIdentifier 0

        },

        serviceType Mobile originating CS fallback or 1xCS fallback (0),

        M-TMSI 'F4 D0 00 E0 19'H,

        EPSBearerContextStatus '20 00'H

3.2 RRC Release

R8

RRC: rrcConnectionRelease (UE:301992109)
rCause:other redirCarInfo:geran

RRC {

  pdu value DL-DCCH-Message ::= {

    message c1 : rrcConnectionRelease : {

      rrc-TransactionIdentifier 0,

      criticalExtensions c1 : rrcConnectionRelease-r8 : {

        releaseCause other,

          redirectedCarrierInfo geran : {

          startingARFCN 80,

          bandIndicator dcs1800,

          followingARFCNs explicitListOfARFCNs : {}

R9

message c1 : rrcConnectionRelease :

          {

          rrc-TransactionIdentifier 0,

          criticalExtensions c1 : rrcConnectionRelease-r8 :

            {

              releaseCause other,

              redirectedCarrierInfo geran :

                {

                  startingARFCN 593,

                  bandIndicator dcs1800,

                  followingARFCNs explicitListOfARFCNs :

                    {

                    }

                },

              nonCriticalExtension

              {

                nonCriticalExtension

                {

                  cellInfoList-r9 geran-r9 :

                    {

                      {

                        physCellId-r9

                        {

                          networkColourCode '110'B,

                          baseStationColourCode '000'B

                        },

                        carrierFreq-r9

                        {

                          arfcn 593,                                     //GSM frequency

                          bandIndicator dcs1800

                        },

                        systemInformation-r9                    //RIM

                        {

                          '198F288000000000000000000000000000BD00002B'H,

                          '1B005D64F0990002880028034000BD00008000029B'H,

                          '00C0005887EB4A93F56A198A162B2B2B2B2B2B2B2B'H

Each OCTET STRING contains one System Information (SI) message as defined in TS 44.018 [45, table 9.1.1] excluding

1. the L2 Pseudo Length,

2. the RR management Protocol Discriminator and

3. the Skip Indicator or a complete Packet System Information (PSI) message as defined   in TS 44.060 [36, table 11.2.1].

4.   How to configure in LTE eNB

4.1 Feature needed:

Licensing=1,OptionalFeatures=1,GsmSessionContinuity=1   featureStateGsmSessionContinuity 1

Licensing=1,OptionalFeatures=1,CsfbToGeranUtran=1       featureStateCsfbToGeranUtran 1

Licensing=1,OptionalFeatures=1,EcsCsfb=1 featureStateEcsCsfb 1

4.2 Create Frequency Relation and Cell Relation

cr ENodeBFunction=1,GeraNetwork=1,GeranFreqGroup=1

    526

cr ENodeBFunction=1,GeraNetwork=1,GeranFreqGroup=1,GeranFrequency=1

    512

cr ENodeBFunction=1,GeraNetwork=1,GeranFreqGroup=1,GeranFrequency=1,ExternalGeranCell=1

    plmnidentity:

    mcc=460,mnc=00,mncLength=2

    lac: 10354

    rac:1

    cellIdentity:6666

    bcc:0

    ncc:7

cr ENodeBFunction=1,EUtranCellTDD=1,GeranFreqGroupRelation=1

    Enter mo LDN: ENodeBFunction=1,GeraNetwork=1,GeranFreqGroup=1

cr ENodeBFunction=1,EUtranCellTDD=1,GeranFreqGroupRelation=1,GeranCellRelation=1

Enter mo LDN: ENodeBFunction=1,GeraNetwork=1,GeranFreqGroup=1,GeranFrequency=1,ExternalGeranCell=1

ENodeBFunction=1,EUtranCellTDD=1,GeranFreqGroupRelation=1,GeranCellRelation=1

csFallbackPrio

If there are several cells which can csfb to, we should define the csFallbackPrio to decide which cell to csfb

set system constant cmccFtEnabled (332) to 1

set system constant cmccFtGeranDtmSupport (480) to 0  to indicate target GERAN doesn’t support DTM

·         R8

ENodeBFunction=1,EUtranCellTDD=1,GeranFreqGroupRelation=1,GeranCellRelation=1 mobilityAction 0

ENodeBFunction=1,EUtranCellTDD=1,GeranFreqGroupRelation=1,GeranCellRelation=1 mobilityActionCsfb 0

·         R9

Licensing=1,OptionalFeatures=1,RedirectWithNacc=1       featureStateRedirectWithNacc 1

ENodeBFunction=1,GeraNetwork=1,GeranFreqGroup=1,GeranFrequency=1,ExternalGeranCell=1  rimCapable  0

ENodeBFunction=1,EUtranCellTDD=1,GeranFreqGroupRelation=1,GeranCellRelation=1 mobilityAction 1

ENodeBFunction=1,EUtranCellTDD=1,GeranFreqGroupRelation=1,GeranCellRelation=1 mobilityActionCsfb 1

4.3 RIM

rimAssociationRetryTimer:

This parameter contains the time in minutes until the eNB will retry setting up the association. The value -1 means that the timer is inactive.

rimAssociationRetryValue:

This parameter holds the value for the next time-out value.  The value -1 means that there is no set Retry Value.

rimSIUpdateTimeOut:

This parameter holds the time in minutes until the next SI needs to have arrived. If an update has not arrived when this value reaches 0 the eNB will assume there are some problems with the RIM transmission and try to restart the association.  The value -1 means that there is no time out.

5.   eNB Side Trace:

5.1 MO CALL(R8)

5.2 Returning back to E-UTRAN NO PS HO

5.3 RIM

When RIM procedure is successful

You can check from MO

6     Reference

[1] TS23272 Circuit Switched (CS) fallback in Evolved Packet System (EPS);

[2] TS36413 Evolved Universal Terrestrial Radio Access Network (E-UTRAN)S1 Application Protocol (S1AP)

[3] TS 48.018 V9.8.0 (2012-09) General Packet Radio Service (GPRS) Base Station System (BSS) -Serving GPRS Support Node (SGSN) BSS GPRS Protocol (BSSGP) (Release 9)