11.2.12 LIMITED-SERVICE / Inter-system mobility / E-UTRA to GSM CS / SRVCC Emergency Call Handover to GERAN

36.523-13GPPEvolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Packet Core (EPC)Part 1: Protocol conformance specificationRelease 17TSUser Equipment (UE) conformance specification

11.2.12.1 Test Purpose (TP)

(1)

with { UE in E-UTRA RRC_CONNECTED state }

ensure that {

when { UE receives a MobilityFromEUTRACommand message and an IMS emergency call is ongoing and an GERAN Speech Traffic channel is configured for an GSM cell}

then { UE transmits a HANDOVER COMPLETE message on the GSM cell}

}

11.2.12.2 Conformance requirements

References: The conformance requirements covered in the present TC are specified in: TS 36.331, clause 5.4.3.3, TS 23.216, clause 6.2.2.1 and TS 23.216, clause 6.2.2.1A.

[TS 36.331, clause 5.4.3.3]

The UE shall be able to receive a MobilityFromEUTRACommand message and perform a cell change order to GERAN, even if no prior UE measurements have been performed on the target cell.

The UE shall:

1> stop timer T310, if running;

1> if the MobilityFromEUTRACommand message includes the purpose set to ‘handover‘:

2> if the targetRAT-Type is set to ‘utra‘ or ‘geran‘:

3> consider inter-RAT mobility as initiated towards the RAT indicated by the targetRAT-Type included in the MobilityFromEUTRACommand message;

3> forward the nas-SecurityParamFromEUTRA to the upper layers;

3> access the target cell indicated in the inter-RAT message in accordance with the specifications of the target RAT;

[TS 23.216, clause 6.2.2.1]

Depicted in figure 6.2.2.1-1 is a call flow for SRVCC from E-UTRAN to GERAN without DTM support. The flow requires that eNB can determine that the target is GERAN without DTM support or that the UE is without DTM support.

Figure 6.2.2.1-1: SRVCC from E-UTRAN to GERAN without DTM support

1. UE sends measurement reports to E-UTRAN.

2. Based on UE measurement reports the source E‑UTRAN decides to trigger an SRVCC handover to GERAN.

3. Source E‑UTRAN sends Handover Required (Target ID, generic Source to Target Transparent Container, SRVCC HO Indication) message to the source MME. The E‑UTRAN places the "old BSS to new BSS information IE" for the CS domain in the generic Source to Target Transparent Container. The SRVCC HO indication indicates to the MME that target is only CS capable; hence this is a SRVCC handover operation only towards the CS domain. The message includes an indication that the UE is not available for the PS service in the target cell.

4. Based on the QCI associated with the voice bearer (QCI 1) and the SRVCC HO indication, the source MME splits the voice bearer from the non voice bearers and initiates the PS-CS handover procedure for the voice bearer only towards MSC Server.

5. The MME sends a SRVCC PS to CS Request (IMSI, Target ID, STN-SR, C‑MSISDN, generic Source to Target Transparent Container, MM Context, and Emergency Indication) message to the MSC Server. The Emergency Indication and the equipment identifier are included if the ongoing session is emergency session. Authenticated IMSI and C‑MSISDN shall also be included, if available. The MME received STN-SR and C‑MSISDN from the HSS as part of the subscription profile downloaded during the E‑UTRAN attach procedure. The MM Context contains security related information. CS security key is derived by the MME from the E‑UTRAN/EPS domain key as defined in TS 33.401 [22]. The CS Security key is sent in the MM Context.

6. The MSC Server interworks the PS-CS handover request with a CS inter‑MSC handover request by sending a Prepare Handover Request message to the target MSC. The MSC Server assigns a default SAI as Source ID on the interface to the target BSS and uses BSSMAP encapsulated for the Prepare Handover Request.

NOTE 1: The value of the default SAI is configured in the MSC and allows a release 8 and later BSC to identify that the source for the SRVCC Handover is E-UTRAN. To ensure correct statistics in the target BSS the default SAI should be different from the SAIs used in UTRAN.

7. Target MSC performs resource allocation with the target BSS by exchanging Handover Request/ Acknowledge messages.

8. Target MSC sends a Prepare Handover Response message to the MSC Server.

9. Establishment of circuit connection between the target MSC and the MGW associated with the MSC Server e.g. using ISUP IAM and ACM messages.

10. For non-emergency session, the MSC Server initiates the Session Transfer by using the STN-SR e.g. by sending an ISUP IAM (STN-SR) message towards the IMS. For emergency session, the MSC Server initiates the Session Transfer by using the locally configured E-STN-SR and by including the equipment identifier. Standard IMS Service Continuity or Emergency IMS Service Continuity procedures are applied for execution of the Session Transfer; see TS 23.237 [14].

NOTE 2: This step can be started after step 8.

NOTE 3: If the MSC Server is using an ISUP interface, then the initiation of the session transfer for non-emergency session may fail if the subscriber profile including CAMEL triggers is not available prior handover (see clause 7.3.2.1.3 in TS 23.292 [13]).

11. During the execution of the Session Transfer procedure the remote end is updated with the SDP of the CS access leg. The downlink flow of VoIP packets is switched towards the CS access leg at this point.

12. Source IMS access leg is released as per TS 23.237 [14].

NOTE 4: Steps 11 and 12 are independent of step 13.

13. MSC Server sends a SRVCC PS to CS Response (Target to Source Transparent Container) message to the source MME.

14. Source MME sends a Handover Command (Target to Source Transparent Container) message to the source E-UTRAN. The message includes information about the voice component only.

15. Source E-UTRAN sends a Handover from E-UTRAN Command message to the UE.

16. UE tunes to GERAN.

17. Handover Detection at the target BSS occurs. The UE sends a Handover Complete message via the target BSS to the target MSC. If the target MSC is not the MSC Server, then the Target MSC sends an SES (Handover Complete) message to the MSC Server.

18. The UE starts the Suspend procedure specified in TS 23.060 [10], clause 16.2.1.1.2. The TLLI and RAI pair are derived from the GUTI as described in TS 23.003 [27]. This triggers the Target SGSN to send a Suspend Notification message to the Source MME. The MME returns a Suspend Acknowledge to the Target SGSN.

NOTE 5: The MME might not be able to derive the GUTI from the received P-TMSI and RAI pair and therefore it might not be able to identify which UE context is associated with the Suspend Notification message. Also in this case the bearers are deactivated and/or suspended as in step 22a.

19. Target BSS sends a Handover Complete message to the target MSC.

20. Target MSC sends an SES (Handover Complete) message to the MSC Server. The speech circuit is through connected in the MSC Server/MGW according to TS 23.009 [18].

21. Completion of the establishment procedure with ISUP Answer message to the MSC Server according to TS 23.009 [18].

22. MSC Server sends a SRVCC PS to CS Complete Notification message to the source MME, informing it that the UE has arrived on the target side. Source MME acknowledges the information by sending a SRVCC PS to CS Complete Acknowledge message to the MSC Server.

22a. The MME deactivates bearers used for voice and other GBR bearers. All GBR bearers are deactivated towards S-GW and P-GW by initiating MME-initiated Dedicated Bearer Deactivation procedure as specified in TS 23.401 [2]. The MME does not send deactivation request toward the eNodeB on receiving PS-to-CS Complete Notification in step 22. PS-to-CS handover indicator is notified to P-GW for voice bearer during the bearer deactivation procedure. For GTP-based S5/S8, the S-GW requests the P-GW to delete all GBR bearer contexts by sending a Delete Bearer Command message. If dynamic PCC is deployed, the P‑GW may interact with PCRF as defined in TS 23.203 [31]. For PMIP-based S5/S8, S-GW interacts with the PCRF which in turn updates PCC rules for GBR traffic in the P-GW.

The MME starts preservation and suspension of non-GBR bearers by sending Suspend Notification message towards S-GW. For these non-GBR bearers, the S-GW releases S1-U bearers for the UE and sends Suspend Notification message to the P-GW(s). The MME stores in the UE context that UE is in suspended status. All the preserved non-GBR bearers are marked as suspended status in the S-GW and P-GW. The P-GW should discard packets if received for the suspended UE.

23a. If the HLR is to be updated, i.e. if the IMSI is authenticated but unknown in the VLR, the MSC Server performs a TMSI reallocation towards the UE using its own non-broadcast LAI and, if the MSC Server and other MSC/VLRs serve the same (target) LAI, with its own Network Resource Identifier (NRI).

NOTE 5: The TMSI reallocation is performed by the MSC Server towards the UE via target MSC.

23b. If the MSC Server performed a TMSI reallocation in step 23a, and if this TMSI reallocation was completed successfully, the MSC Server performs a MAP Update Location to the HSS/HLR.

NOTE 6: This Update Location is not initiated by the UE.

24. For an emergency services session after handover is complete, the source MME or the MSC Server may send a Subscriber Location Report carrying the identity of the MSC Server to a GMLC associated with the source or target side, respectively, as defined in TS 23.271 [29] to support location continuity.

NOTE 7: Any configuration of the choice between a source MME versus MSC Server update to a GMLC needs to ensure that a single update occurs from one of these entities when the control plane location solution is used on the source and/or target sides.

After the CS voice call is terminated and if the UE is still in GERAN (or for any other reason specified in TS 24.008), then the UE shall resume PS services as specified in TS 23.060 [10]. A Gn SGSN will follow TS 23.060 [10] to resume the PDP Context(s). An S4 SGSN will follow TS 23.060 [10] to resume the bearers, and will in addition inform S-GW and P-GW(s) to resume the suspended bearers. If the UE has returned to E-UTRAN after the CS voice call was terminated, then the UE shall resume PS service by sending TAU to MME. The MME will in addition inform S-GW and P-GW(s) to resume the suspended bearers. Resuming the suspended bearers in the S-GW and in the P-GW should be done by implicit resume using the Modify Bearer request message if it is triggered by the procedure in operation, e.g. RAU, TAU or Service Request. The S-GW is aware of the suspend state of the bearers and will forward the Modify Bearer request to the P-GW. Explicit resume using the Resume Notification message should be used in cases when Modify Bearer Request is not triggered by the procedure in operation.

[TS 23.216, clause 6.2.2.1A]

The call flow for this scenario is similar to the call flow depicted in figure 6.2.2.1‑1, with the exceptions that the Suspend procedure (step 18 and step 22a in figure 6.2.2.1-1) is not performed and that the MME only deactivates bearers used for voice (step 22a in figure 6.2.2.1-1) and sets the PS-to-CS handover indicator. The scenario requires that eNB can determine that the target is either GERAN with DTM but without DTM HO support and that the UE is supporting DTM or that the target is UTRAN (HSPA) without PS HO support. The message in step 3 in figure 6.2.2.1-1 includes an indication to the MME that the UE is available for PS service in the target cell. Furthermore, if the target is GERAN, the E‑UTRAN places in the generic Source to Target Transparent Container the "old BSS to new BSS information IE", while if the target is UTRAN, the generic Source to Target Transparent container is encoded according to the Source RNC to Target RNC Transparent Container IE definition. At the end of the procedure described in figure 6.2.2.1‑1, the remaining PS resources are re-established when the UE performs the Routeing Area update procedure. Triggers for performing Routeing Area update procedure are described in TS 23.060 [10]. The target SGSN may deactivate the PDP contexts that cannot be established as described in TS 23.060 [10].

11.2.12.3 Test description

11.2.12.3.1 Pre-test conditions

System Simulator:

– Cell A and Cell 24.

– System information combination 5 as defined in TS 36.508 [18] clause 4.4.3.1 is used in E-UTRA cells.

– The PLMN is defined in Table 11.2.12.3.1-1.

Table 11.2.12.3.1–1: PLMN identifier

Cell

PLMN name

A

PLMN4

24

PLMN1

UE:

– The UE is equipped with either ISIM and USIM applications or only a USIM application on UICC. The USIM containing default values except for those listed in Table 11.2.12.3.1-2.

Table 11.2.12.3.1–2: USIM configuration

USIM field

Priority

Value

Access Technology Identifier

EFIMSI

–

The HPLMN (MCC+MNC) of the IMSI is set to PLMN1.

–

EFFPLMN

–

PLMN4

–

EFPLMNwAcT

1

Default

E-UTRAN

EFOPLMNwACT

1

PLMN1

E-UTRAN

EFHPLMNwAcT

1

PLMN1

E-UTRAN

Preamble:

– The UE is Switched OFF (State 1) according to [18].

11.2.12.3.2 Test procedure sequence

Table 11.2.12.3.2-1 illustrates the downlink power levels and other changing parameters to be applied for the cells at various time instants of the test execution. Row marked "T0" denotes the initial conditions after preamble, while columns marked "T1" is to be applied subsequently. The exact instants on which these values shall be applied are described in the texts in this clause.

Table 11.2.12.3.2-1: Time instances of cell power level and parameter changes

Parameter

Unit

Cell A

Cell 24

Remark

T0

Cell-specific RS EPRE

dBm/15kHz

-85

–

The power level values are such that entering conditions for event B2 are not satisfied.

RSSI

dBm

–

”Switched Off”

T1

Cell-specific RS EPRE

dBm/15kHz

-85

–

The power level values are such that entering conditions for event B2 are satisfied.

RSSI

dBm

–

-65

Table 11.2.12.3.2-2: Main behaviour

St

Procedure

Message Sequence

TP

Verdict

U – S

Message

1

The SS configures GERAN Cell 24 to reference configuration according 36.508 Table 4.8.4-1, condition GERAN Speech.

–

–

–

–

2

Power on the UE.

–

–

–

–

3

Wait 60s for the UE to camp on Cell A as an acceptable cell.

–

–

–

–

4-6

Steps 1 to 3 of the generic test procedure for IMS Emergency call establishment in EUTRA: Limited Service (TS 36.508 subclause 4.5A.5.3-1).

–

–

–

–

7

The UE transmits an RRCConnectionSetupComplete message.

–>

RRC: RRCConnectionSetupComplete

NAS: ATTACH REQUEST

NAS: PDN CONNECTIVITY REQUEST

–

–

8-22

Steps 5 to 19 of the generic test procedure for IMS Emergency call establishment in EUTRA: Limited Service (TS 36.508 subclause 4.5A.5.3-1).

–

–

–

–

23

The SS transmits an RRCConnectionReconfiguration message on Cell A to setup inter RAT measurement and reporting for event B2.

<–

RRCConnectionReconfiguration

–

–

24

The UE transmits an RRCConnectionReconfigurationComplete message on Cell A.

–>

RRCConnectionReconfigurationComplete

–

–

25

The SS changes the power level for Cell A and Cell 24 according to the row "T1" in table 11.2.12.3.2-1

–

–

–

–

26

The UE transmits a MeasurementReport message on Cell A to report event B2 for Cell 24.

–>

MeasurementReport

–

–

27

The SS transmits a MobilityFromEUTRACommand message on Cell A. (Note)

<–

MobilityFromEUTRACommand

–

–

28

Check: Does the UE transmit a HANDOVER COMPLETE message on cell 24?

–>

HANDOVER COMPLETE

1

P

Note: Ciphering is not used in GERAN.

11.2.12.3.3 Specific message contents

Table 11.2.12.3.3-1: ATTACH REQUEST (Step 7, Table 11.2.12.3.2-2)

Derivation path: 36.508 table 4.7.2-4

Information Element

Value/remark

Comment

Condition

EPS attach type

‘0110’B

EPS emergency attach

ESM message container

PDN CONNECTIVITY REQUEST message to request PDN connectivity to an emergency PDN

MS network capability

SRVCC from UTRAN HSPA or E-UTRAN to GERAN/UTRAN supported

Mobile station classmark 2

Any allowed value

Supported Codecs

Any allowed value

Table 11.2.12.3.3-2: RRCConnectionReconfiguration (step 23, Table 11.2.12.3.2-2)

Derivation Path: 36.508 clause 4.6.1 table 4.6.1-8 with condition MEAS

Table 11.2.12.3.3-3: MeasConfig (step 23, Table 11.2.12.3.2-2)

Derivation path: 36.508 clause 4.6.6 table 4.6.6-1 with condition GERAN

Information Element

Value/Remark

Comment

Condition

measurementConfiguration ::= SEQUENCE {

measObjectToAddModifyList SEQUENCE (SIZE (1..maxObjectId)) OF SEQUENCE {

2 entries

measObjectId[1]

IdMeasObject-f11

measObject[1]

MeasObjectGERAN-GENERIC(f11)

measObjectId[2]

IdMeasObject-f1

measObject[2]

MeasObjectEUTRA-GENERIC(f1)

measObject[2]

MeasObjectEUTRA-GENERIC(maxEARFCN)

Band > 64

}

reportConfigToAddModifyList SEQUENCE (SIZE (1..maxReportConfigId)) OF SEQUENCE {

1 entry

reportConfigId[1]

IdReportConfigInterRAT-B2-GERAN

reportConfig[1]

ReportConfigInterRAT-B2-GERAN (-69, -75)

}

measIdToAddModifyList SEQUENCE (SIZE (1..maxMeasId)) OF SEQUENCE {

1 entry

measId[1]

1

measObjectId[1]

IdMeasObject-f11

reportConfigId[1]

IdReportConfigInterRAT-B2-GERAN

}

measObjectToAddModList-v9e0 ::= SEQUENCE (SIZE (1..maxObjectId)) OF SEQUENCE {

2 entries

Band > 64

measObjectEUTRA-v9e0[1] SEQUENCE {}

measObjectEUTRA-v9e0[2] SEQUENCE {

carrierFreq-v9e0

Same downlink EARFCN as used for f1

}

}

}

Condition

Explanation

Band > 64

If band > 64 is selected

Table 11.2.12.3.3-4: MeasurementReport (step 26, Table 11.2.12.3.2-2)

Derivation Path: 36.508, table 4.6.1-5

Information Element

Value/remark

Comment

Condition

MeasurementReport ::= SEQUENCE {

criticalExtensions CHOICE {

c1 CHOICE{

measurementReport-r8 SEQUENCE {

measResults SEQUENCE {

measId

1

measResultServCell SEQUENCE {

rsrpResult

(0..97)

rsrqResult

(0..34)

}

measResultNeighCells CHOICE {

measResultListGERAN SEQUENCE (SIZE (1..maxCellReport)) OF SEQUENCE {

1 entry

physCellId

PhysicalCellIdentity of Cell 24

cgi-Info[1]

Not present

measResult[1] SEQUENCE {

rssi

The value of rssi is present but contents not checked

}

}

}

}

}

}

}

}

Table 11.2.12.3.3-5: MobilityFromEUTRACommand (step 27, Table 11.2.12.3.2-2)

Derivation Path: 36.508, Table 4.6.1-6

Information Element

Value/remark

Comment

Condition

MobilityFromEUTRACommand ::= SEQUENCE {

criticalExtensions CHOICE {

c1 CHOICE{

mobilityFromEUTRACommand-r8 SEQUENCE {

cs-FallbackIndicator

False

purpose CHOICE{

handover SEQUENCE {

targetRAT-Type

geran

targetRAT-MessageContainer

HANDOVER COMMAND(GERAN RRC message), see Table 11.2.12.3.3-6

nas-SecurityParamFromEUTRA

The 4 least significant bits of the NAS downlink COUNT value

systemInformation

Not present

}

}

nonCriticalExtension SEQUENCE {

lateNonCriticalExtension

Not present

nonCriticalExtension SEQUENCE {

bandIndicator

Set according to the band used for Cell 24

nonCriticalExtension SEQUENCE {}

Not present

}

}

}

}

}

}

Table 11.2.12.3.3-6: HANDOVER COMMAND (Table 11.2.12.3.3-5)

Derivation Path: 51.010, Table 40.2.4.33

Information Element

Value/remark

Comment

Condition

Cell Description

Network Colour Code

1

Base Station Colour Code

5

BCCH Carrier Number

The BCCH Carrier ARFCN as per table in clause 40.1.1 of 51.010-1.

Description of the First Channel, after time

Channel Description

Channel Type and TDMA offset

TCH/F + ACCH’s

Timeslot Number

Chosen arbitrarily, but not Zero.

Training Sequence Code

Same as the BCCH

Hopping channel

Single RF channel

ARFCN

The first ARFCN in the cell allocation as per table in clause 40.2.1.1.1 of 51.010-1

Cipher Mode Setting

1001xxx0

See TS 44.018 §9.1.15.10

xxx – px_GSM_CipherAlg