11.2 5G-SRVCC

38.523-13GPP5GSPart 1: ProtocolRelease 17TSUser Equipment (UE) conformance specification

11.2.1 5G-SRVCC from NG-RAN to 3GPP UTRAN

11.2.1.1 Test Purpose (TP)

(1)

with { the UE is in NR RRC_CONNECTED state }

ensure that {

when { UE receives a MobilityFromNRCommand message and an IMS voice call is ongoing and an UTRA Speech RAB combination is configured for an UTRA cell }

then { UE transmits a HANDOVER TO UTRAN COMPLETE message on the utra cell }

}

(2)

with { the UE has performed 5G-SRVCC from NG-RAN to UTRAN }

ensure that {

when { UE in 5GMM-DEREGISTERED state moves from a UTRAN to NG-RAN coverage }

then { UE starts the Initial registration procedure on the NR cell }

}

11.2.1.2 Conformance requirements

References: The conformance requirements covered in the present test case are specified in TS 23.216, clause 6.5.4, TS 38.331, clause 5.4.3.3 and TS 24.501, clause 5.5.1.2.2. Unless otherwise stated these are Rel-16 requirements.

[TS 23.216, clause 6.5.4]

Depicted in Figure 6.5.4-1 is a call flow for 5G-SRVCC from NG-RAN to 3GPP UTRAN.

Figure 6.5.4-1: 5G-SRVCC from NG-RAN to 3GPP UTRAN call flow

1. UE establishes the PDU session for IMS.

2. 5G-SRVCC HO is triggered by NG-RAN.

3. NG-RAN sends a Handover Required (Target ID, generic Source to Target Transparent Container, 5G-SRVCC HO indication) message to the source AMF. The Target ID is the UTRAN RNC-ID. 5G-SRVCC HO Indication indicates to AMF that this if for 5G-SRVCC. The Generic Source to Target Transparent Container is the Source RNC to Target RNC Transparent container.

4. AMF determines the HO is used for 5G-SRVCC by the 5G-SRVCC HO Indication. AMF selects an MME_SRVCC that can have Sv connection to the MSC SERVER/MSC according to the target RNC ID which is included in the Target ID.

NOTE: The MME_SRVCC selection can be realised through operator’s configuration.

5. AMF sends the forward relocation request (IMSI, Target ID, STN-SR, C-MSISDN, MM Context, Generic Source to Target Transparent Container, 5G-SRVCC HO Indication, Supported Codec IE, MS ClassMark 2, Emergency Indication, Equipment Identifier) to MME_SRVCC. The Emergency Indication and the equipment identifier are included if the ongoing session is emergency session. Authenticated IMSI and C MSISDN are also included in this case, if available.

6. MME_SRVCC initiates the PS-CS handover procedure towards MSC Server. Steps 5 to 13 as specified in Figure 6.2.2.1-1 (referenced by clause 6.2.2.1A SRVCC from E-UTRAN to UTRAN without PS HO) are performed for the PS-CS handover procedure.

7. MME_SRVCC receives the response message from MSC server after HO preparation is completed. MME_SRVCC sends the Forward Relocation Response message (Target to Source Transparent Container) to AMF.

8. AMF sends the HO command to NG-RAN.

9. NG-RAN sends a HO command to the UE. UE detects the 5G-SRVCC HO.

10. UE tunes to the target UTRAN cell.

11. Handover Detection at the target RNS occurs, then the target RNS sends Handover Detection message to the target MSC SERVER/MSC.

12. The UE sends a Handover Complete message via the target RNS to the target MSC SERVER. Steps 19 to 21as specified in Figure 6.2.2.1-1 (referenced by clause 6.2.2.1A SRVCC from E-UTRAN to UTRAN without PS HO) are performed for this handover complete procedure. At this stage, the target MSC SERVER/MSC can send/receive voice data.

13. MSC SERVER sends MME_SRVCC the SRVCC PS to CS completion.

14. MME_SRVCC forwards the Forward Relocation completion message which includes the information received in step 13 to AMF.

15. AMF forwards the Forward Relocation Complete ACK message to MME_SRVCC. AMF releases the UE context related to MME_SRVCC.

16. MME_SRVCC forwards the PS to CS Complete ACK message to MSC server. MME_SRVCC removes stored UE context. After receives the message, MSC server removes the UE context related to the MME_SRVCC.

17. AMF performs the PDU session release procedure for all the PDU session(s) which is described in TS 23.502 [45] indicating that the release is due to PS to CS handover for 5G SRVCC.

18. For an emergency services session after handover is complete, the source AMF or the MSC Server may respectively invoke the Namf_Location_EventNotify service operation or send a Subscriber Location Report, towards a GMLC associated with the source or target side, respectively, carrying the identity of the MSC Server, as defined respectively in TS 23.273 [50] or TS 23.271 [29], to support location continuity.

The IMS service control is described in TS 23.292 [13] when UE accesses in UTRAN cell due to 5G-SRVCC.

[TS 38.331, clause 5.4.3.3]

Reception of the MobilityFromNRCommand by the UE

The UE shall:

1> stop timer T310, if running;

1> stop timer T312, if running;

1> if T316 is running:

2> stop timer T316;

2> clear the information included in VarRLF-Report, if any;

1> if T390 is running:

2> stop timer T390 for all access categories;

2> perform the actions as specified in 5.3.14.4;

1> if the targetRAT-Type is set to eutra:

2> consider inter-RAT mobility as initiated towards E-UTRA;

2> forward the nas-SecurityParamFromNR to the upper layers, if included;

1> else if the targetRAT-Type is set to utra-fdd:

2> consider inter-RAT mobility as initiated towards UTRA-FDD;

2> forward the nas-SecurityParamFromNR to the upper layers, if included;

1> access the target cell indicated in the inter-RAT message in accordance with the specifications of the target RAT.

[TS 24.501, clause 5.5.1.2.2]

The UE in state 5GMM-DEREGISTERED shall initiate the registration procedure for initial registration by sending a REGISTRATION REQUEST message to the AMF,

a) when the UE performs initial registration for 5GS services;

b) when the UE performs initial registration for emergency services;

c) when the UE performs initial registration for SMS over NAS; and

d) when the UE moves from GERAN to NG-RAN coverage or the UE moves from a UTRAN to NG-RAN coverage and the following applies:

1) the UE initiated a GPRS attach or routing area updating procedure while in A/Gb mode or Iu mode; or

2) the UE has performed 5G-SRVCC from NG-RAN to UTRAN as specified in 3GPP TS 23.216 [6A],

and since then the UE did not perform a successful EPS attach or tracking area updating procedure in S1 mode or registration procedure in N1 mode,

…

11.2.1.3 Test Description

11.2.1.3.1 Pre-test conditions

System Simulator:

– NR Cell 1 with system information combination NR-1 as defined in TS 38.508-1 [4].

– UTRA Cell 5 as defined in TS 36.508 [7].

UE:

None.

Preamble:

– The UE is in test state 0N-B according to TS 38.508-1.

11.2.1.3.2 Test procedure sequence

Table 11.2.1.3.2-1/2 illustrate the downlink power levels and other changing parameters to be applied for the cell at various time instants of the test execution. The exact instants on which these values shall be applied are described in the texts in this clause. The configuration T0 indicates the initial conditions for preamble. Configurations marked "T1" and “T2” are applied at the points indicated in the Main behaviour description in Table 11.2.1.3.2-3.

Table 11.2.1.3.2-1: Time instances of cell power level and parameter changes for FR1

Parameter

Unit

NR Cell 1

UTRA Cell 5

Remark

T0

SS/PBCH

SSS EPRE

dBm/

SCS

-88

–

CPICH_Ec (UTRA FDD)

dBm/3.84 MHz

–

Off

T1

SS/PBCH

SSS EPRE

dBm/

SCS

-88

–

CPICH_Ec (UTRA FDD)

dBm/3.84 MHz

–

-60

T2

SS/PBCH

SSS EPRE

dBm/

SCS

-88

–

CPICH_Ec (UTRA FDD)

dBm/3.84 MHz

–

Off

Table 11.2.1.3.2-2: Time instances of cell power level and parameter changes for FR2

Parameter

Unit

NR Cell 1

UTRA Cell 5

Remark

T0

SS/PBCH

SSS EPRE

dBm/

SCS

-82

–

CPICH_Ec (UTRA FDD)

dBm/3.84 MHz

–

Off

T1

SS/PBCH

SSS EPRE

dBm/

SCS

-82

–

CPICH_Ec (UTRA FDD)

dBm/3.84 MHz

–

-60

T2

SS/PBCH

SSS EPRE

dBm/

SCS

-82

–

CPICH_Ec (UTRA FDD)

dBm/3.84 MHz

–

Off

Table 11.2.1.3.2-3: Main behaviour

St

Procedure

Message Sequence

TP

Verdict

U – S

Message

1

The UE is switched on.

–

–

–

–

–

The following messages are to be observed on NR Cell 1 unless explicitly stated otherwise.

–

–

–

–

2-3

The UE establishes RRC connection by executing steps 2-3 of Table 4.5.2.2-2 in TS 38.508-1 [4].

–

–

–

–

4

The UE transmits an RRCSetupComplete message and a REGISTRATION REQUEST message indicating 5G-SRVCC from NG-RAN to UTRAN supported.

–>

NR RRC: RRCSetupComplete

5GMM: REGISTRATION REQUEST

–

–

5-19

Steps 5-19a1 of Table 4.5.2.2-2 of the generic procedure in TS 38.508-1 [4] are performed.

–

–

–

–

20

The SS transmits a UECapabilityEnquiry message to request UE radio access capability information for NR and UTRA.

<–

NR RRC: UECapabilityEnquiry

–

–

21

The UE transmits a UECapabilityInformation message.

NOTE: The start-CS values received, should be used to configure ciphering on cell 5.

–>

NR RRC: UECapabilityInformation

–

–

22

The SS releases the RRC Connection.

<–

NR RRC: RRCRelease

–

–

23

Perform Generic Test Procedure for IMS MO speech call establishment as specified in TS 38.508-1 [4], subclause 4.9.15.

–

–

–

–

24

Set the power levels according to “T1” as per Table 11.2.1.3.2-1/2.

–

–

–

–

25

The SS transmits a MobilityFromNRCommand message.

<–

NR RRC: MobilityFromNRCommand

–

–

–

The following messages are to be observed on UTRA Cell 5 unless explicitly stated otherwise.

–

–

–

–

26

Check: Does the UE transmit a HANDOVER TO UTRAN COMPLETE message on cell 5?

–>

HANDOVER TO UTRAN COMPLETE

1

P

–

EXCEPTION: In parallel to the events described in step 27 to 32 the steps specified in table 11.2.1.3.2-4 takes place.

–

–

–

–

27

The SS transmits a SECURITY MODE COMMAND message for the CS domain.

<–

SECURITY MODE COMMAND

–

–

28

The UE transmits a SECURITY MODE COMPLETE message.

–>

SECURITY MODE COMPLETE

–

–

29

The SS transmits an UTRAN MOBILITY INFORMATION message to notify CN information.

<–

UTRAN MOBILITY INFORMATION

–

–

30

The UE transmits an UTRAN MOBILITY INFORMATION CONFIRM message.

–>

UTRAN MOBILITY INFORMATION CONFIRM

–

–

31

The SS transmits a TMSI REALLOCATION COMMAND message.

<–

TMSI REALLOCATION COMMAND

–

–

32

The UE transmits a TMSI REALLOCATION COMPLETE message.

–>

TMSI REALLOCATION COMPLETE

–

–

33

Make the UE release the CS call.

–

–

–

–

33A

The UE transmits a DISCONNECT message.

–>

DISCONNECT

33B

The SS transmits a RELEASE message.

<–

RELEASE

–

–

33C

The UE transmits a RELEASE COMPLETE message.

–>

RELEASE COMPLETE

–

–

33D

The SS releases the RRC connection.

–

–

–

–

34

Set the power levels according to “T2” as per Table 11.2.1.3.2-1/2.

–

–

–

–

35-52

Check: Does the UE perform initial registration procedure on NR Cell 1 as steps 2-19a1 of Table 4.5.2.2-2 NR RRC_IDLE in TS 38.508-1 [4]?

–

–

2

P

Table 11.2.1.3.2-4: Parallel behaviour

St

Procedure

Message Sequence

TP

Verdict

U – S

Message

1

Check: Does the UE transmit an ATTACH REQUEST message?

–>

ATTACH REQUEST

–

–

1AA

The SS transmits an AUTHENTICATION AND CIPHERING REQUEST message.

<–

AUTHENTICATION AND CIPHERING REQUEST

–

–

1AB

The UE transmits an AUTHENTICATION AND CIPHERING RESPONSE message.

–>

AUTHENTICATION AND CIPHERING RESPONSE

–

–

1A

The SS transmits a SECURITY MODE COMMAND message for the PS domain.

<–

SECURITY MODE COMMAND

–

–

1B

The UE transmits a SECURITY MODE COMPLETE message.

–>

SECURITY MODE COMPLETE

–

–

2

The SS transmits an ATTACH ACCEPT message.

<–

ATTACH ACCEPT

–

–

3

The UE transmits an ATTACH COMPLETE message.

–>

ATTACH COMPLETE

–

–

11.2.1.3.3 Specific message contents

Table 11.2.1.3.3-1: Message REGISTRATION REQUEST (step 4, Table 11.2.1.3.2-3)

Derivation path: TS 38.508-1 [4], table 4.7.1-6

Information Element

Value/Remark

Comment

Condition

5GMM capability

5GSRVCC (octet 4, bit 1)

‘1’B

5G-SRVCC from NG-RAN to UTRAN supported

Table 11.2.1.3.3-2: UECapabilityEnquiry (step 20, Table 11.2.1.3.2-3)

Derivation Path: TS 38.508-1 [4], Table 4.6.1-31

Information Element

Value/remark

Comment

Condition

UECapabilityEnquiry ::= SEQUENCE {

rrc-TransactionIdentifier

RRC-TransactionIdentifier

criticalExtensions CHOICE {

ueCapabilityEnquiry SEQUENCE {

ue-CapabilityRAT-RequestList SEQUENCE (SIZE (1.. maxRAT-CapabilityContainers)) OF CapabilityRAT-Request {

2 entries

UE-CapabilityRAT-Request[1] SEQUENCE {

entry 1

rat-Type

nr

}

UE-CapabilityRAT-Request[2] SEQUENCE {

entry 2

rat-Type

utra-fdd-v1610

}

}

lateNonCriticalExtension

Not present

nonCriticalExtension

Not present

}

criticalExtensionsFuture

}

}

Table 11.2.1.3.3-3: UECapabilityInformation (step 21, Table 11.2.1.3.2-3)

Derivation Path: TS 38.508-1 [4], Table 4.6.1-32

Information Element

Value/remark

Comment

Condition

UECapabilityInformation ::= SEQUENCE {

rrc-TransactionIdentifier

RRC-TransactionIdentifier

criticalExtensions CHOICE {

ueCapabilityInformation SEQUENCE {

ue-CapabilityRAT-ContainerList SEQUENCE (SIZE (0..maxRAT-CapabilityContainers)) OF CapabilityRAT- Container{

2 entries

UE-CapabilityRAT- Container[1] SEQUENCE {

entry 1

rat-Type

nr

ueCapabilityRAT-Container

Not checked

}

UE-CapabilityRAT- Container[2] SEQUENCE {

entry 2

rat-Type

utra-fdd-v1610

ueCapabilityRAT-Container

Octet string

INTER RAT HANDOVER INFO

}

}

lateNonCriticalExtension

Not checked

nonCriticalExtension

Not checked

}

criticalExtensionsFuture

Not checked

}

}

Table 11.2.1.3.3-4: MobilityFromNRCommand (step 25, Table 11.2.1.3.2-3)

Derivation Path: TS 38.508-1 [4] Table 4.6.1-8

Information Element

Value/remark

Comment

Condition

MobilityFromNRCommand::= SEQUENCE {

rrc-TransactionIdentifier

RRC-TransactionIdentifier

criticalExtensions CHOICE {

mobilityFromNRCommand ::= SEQUENCE {

targetRAT-Type

utra-fdd-v1610

targetRAT-MessageContainer

HANDOVER TO UTRAN COMMAND(UTRA RRC message)

nas-SecurityParamFromNR

4 LSB of the downlink NAS COUNT

}

}

}

Table 11.2.1.3.3-5: HANDOVER TO UTRAN COMMAND (Table 11.2.1.3.3-4)

Derivation Path: TS 36.508 [7], Table 4.7B.1-1, condition UTRA Speech

Table 11.2.1.3.3-6: SECURITY MODE COMMAND (step 27, Table 11.2.1.3.2-3)

Derivation Path: TS 36.508 [7], Table 4.7B.1-n

Information Element

Condition

Value/remark

Ciphering mode info

Not Present

Table 11.2.1.3.3-7: Void

Table 11.2.1.3.3-8: SECURITY MODE COMMAND (step 1A, 11.2.1.3.2-4)

Derivation Path: TS 36.508 [7], Table 4.7B.1-n

Information Element

Condition

Value/remark

Ciphering mode info

StartRestart

Integrity protection mode info

modify

CN Domain Identity

ps-domain