22.5.20 NB-IoT/ UE in NB-S1 mode supporting control plane data back-off timer/ Service reject with extended wait time CP data/ Release with extended wait time CP data/ Attach accept with extended wait time CP data

36.523-13GPPEvolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Packet Core (EPC)Part 1: Protocol conformance specificationRelease 16TSUser Equipment (UE) conformance specification

22.5.20.1 Test Purpose (TP)

(1)

with { UE has sent a CONTROL PLANE SERVICE REQUEST message with ESM DATA TRANSPORT piggybacked }

ensure that {

when { UE receives a SERVICE REJECT message with EMM cause value set to #22 "congestion" and a value for control plane data back-off timer T3448}

then { the UE starts timer T3448 with the received value and performs control plane data transmission on the expiry of timers T3448 }

}

(2)

with { UE has sent a TRACKING AREA UPDATE REQUEST message with indication supporting of Control Plane data back-off timer }

ensure that {

when { UE receives an RRC Connection Release message with extendedWaitTime-CPdata }

then { the UE starts timer T3448 with the "Extended wait time CP data" value and performs normal cell reselection process }

}

(3)

with { UE has sent a TRACKING AREA UPDATE REQUEST message with indication supporting of Control Plane data back-off timer }

ensure that {

when { UE receives an TRACKING AREA UPDATE ACCEPT message without T3448 }

then { the UE stops CP back-off timer and performs control plane data transmission }

}

(4)

with { UE has received a ATTACH ACCEPT message with T3448 }

ensure that {

when { UE receives an ESM DATA TRANSPORT message before T3448 expiry }

then { the UE performs control plane data transmission after expiry of T3448 }

}

22.5.20.2 Conformance requirements

References: The conformance requirements covered in the current TC are specified in: TS 23.401, clauses 4.3.7.4.2.7, and TS 24.301, clauses 5.5.1.2.6, 5.5.3.2.6, 5.6.1.5, and 5.6.1.6.

[TS 23.401, clause 4.3.7.4.2.7]

Under overload conditions the MME may restrict requests from UEs for data transmission via Control Plane CIoT EPS Optimisation. A Control Plane data back-off timer may be returned by the MME (e.g.in Attach/TAU/RAU Accept messages, Service Reject message or Service Accept message). While the Control Plane data back-off timer is running, the UE shall not initiate any data transfer via Control Plane CIoT EPS Optimisation, i.e. the UE shall not send any Control Plane Service Request with ESM Data Transport message as defined in TS 24.301 [46]. The MME shall store the Control Plane data back-off timer per UE and shall reject any further request (other than exception reporting and a response to paging) for data transmission via Control Plane Service Request from that UE while the Control Plane data back-off timer is still running.

NOTE 1: The Control Plane data back-off timer does not affect any other mobility management or session management procedure.

NOTE 2: The Control Plane data back-off timer does not apply to user plane data communication.

If the UE is allowed to send exception reporting, the UE may initiate Control Plane Service Request for exception reporting even if Control Plane data back-off timer is running.

The UE may respond with Control Plane Service Request without ESM Data Transport to a paging even if the Control Plane data back-off timer is running.

If the MME receives a Control Plane Service Request in response to a paging, and the MME has a Control Plane data back-off timer running for the UE, and the MME is not overloaded, and MME decides to accept the Control Plane Service Request, then the MME shall respond with Service Accept message without the Control Plane data back-off timer and stop the Control Plane data back-off timer. If the UE receives a Service Accept message without the Control Plane data back-off timer from the MME while the Control Plane data back-off timer is running, the UE shall stop the Control Plane data back-off timer. The Control Plane data back-off timer in the UE and the MME is stopped at PLMN change.

If the MME receives a Control Plane Service Request with ESM Data Transport message, and decides to send the UE a Control Plane data back-off timer, the MME may decide to process the Control Plane Service Request with ESM Data Transport message, i.e. decrypt and forward the data payload, or not based on the following:

– If the UE has additionally indicated in a Release Assistance Information in the NAS PDU that no further Uplink or Downlink Data transmissions are expected, then the MME may process (integrity check/decipher/forward) the received Control Plane data packet, and send SERVICE ACCEPT to the UE with Control Plane data back-off timer. The UE interprets this as successful transmission of the Control Plane data packet, starts the Control Plane data back-off timer and proceeds as described in clause 6.8.1.4.

– For all other cases, the MME may decide to not process the received control plane data packet and sends SERVICE REJECT to the UE with Control Plane data back-off timer. The UE interprets this indication as unsuccessful delivery of the control plane data packet, starts the Control Plane data back-off timer and proceeds as described in clause 6.8.1.4. Then MME may take into consideration whether the PDN Connection is set to Control Plane only to make the decision whether to reject the packet and send SERVICE REJECT or move the PDN connection to user plane and process the data packet.

– Alternatively, if UE has not provided in the in Control Plane service request the release assistance information, and the EPS bearer belongs to a PDN connection not set to Control Plane only, and UE supports user plane EPS CIoT optimisation (or legacy S1-U), then the MME may initiate establishment of S1-U bearer during Data Transport in Control Plane CIoT EPS optimisation (according to the procedure defined in clause 5.3.4B.4). In this case MME may also return a Control Plane data back-off timer within the NAS message.

The MME only includes the Control Plane data back-off timer if the UE has indicated support for Control Plane data back-off timer in the Attach/TAU/RAU request.

NOTE 3: If the MME is overloaded or close to overload, but the UE has not indicated support for Control Plane data back-off timer, the MME can use other overload control mechanisms, e.g. mobility management back-off timer or use user plane data communication.

[TS 24.301, clause 5.5.1.2.6]

la) "Extended wait time CP data" from the lower layers

If the UE is operating in NB-S1 mode, the UE shall start the timer T3346 with the "Extended wait time CP data" value and reset the attach attempt counter.

In other cases the UE shall ignore the "Extended wait time CP data".

The UE shall abort the attach procedure, stay in the current serving cell, change the state to EMM-DEREGISTERED.ATTEMPTING-TO-ATTACH and apply the normal cell reselection process.

The UE shall proceed as described below.

[TS 24.301, clause 5.5.3.2.6]

ka) "Extended wait time CP data" from the lower layers

If the UE is operating in NB-S1 mode and supports the timer T3448, the UE shall start the timer T3448 with the "Extended wait time CP data" value. If the UE is operating in NB-S1 mode and does not support the timer T3448, the UE shall start the timer T3346 with the "Extended wait time CP data" value and reset the tracking area updating attempt counter.

In other cases the UE shall ignore the "Extended wait time CP data".

The UE shall abort the tracking area updating procedure, stay in the current serving cell, set the EPS update status to EU2 NOT UPDATED, change the state to EMM-REGISTERED.ATTEMPTING-TO-UPDATE and apply the normal cell reselection process.

If the UE had used eDRX before initiating tracking area updating procedure, then the UE shall continue to use the eDRX with the extended DRX parameters IE received during the last attach or tracking area updating procedure.

The UE shall proceed as described below.

l) Timer T3346 is running

The UE shall not start the tracking area updating procedure unless:

– the UE is in EMM-CONNECTED mode;

– the UE received a paging;

– the UE is a UE configured to use AC11 – 15 in selected PLMN;

– the UE has a PDN connection for emergency bearer services established or is establishing a PDN connection for emergency bearer services;

– the UE is requested by the upper layer for a CS fallback for emergency call or a 1xCS fallback for emergency call;

– the UE in NB-S1 mode is requested by the upper layer to transmit user data related to an exceptional event and

i) the UE is allowed to use exception data reporting (see the ExceptionDataReportingAllowed leaf of the NAS configuration MO in 3GPP TS 24.368 [15A] or the USIM file EFNASCONFIG in 3GPP TS 31.102 [17]); and

ii) timer T3346 was not started when NAS signalling connection was established with RRC establishment cause set to "MO exception data"; or

– the UE has a PDN connection established without the NAS signalling low priority indication or is establishing a PDN connection without the NAS signalling low priority indication, the timer T3402 and the timer T3411 are not running and the timer T3346 was started due to rejection of a NAS request message (e.g. ATTACH REQUEST, TRACKING AREA UPDATE REQUEST or EXTENDED SERVICE REQUEST) which contained the low priority indicator set to "MS is configured for NAS signalling low priority".

The UE stays in the current serving cell and applies the normal cell reselection process.

NOTE 4: It is considered an abnormal case if the UE needs to initiate a tracking area updating procedure while timer T3346 is running independent on whether timer T3346 was started due to an abnormal case or a non successful case.

If the TAI of the current serving cell is not included in the TAI list or the TIN indicates "P-TMSI", the UE shall set the EPS update status to EU2 NOT UPDATED and change to state EMM-REGISTERED.ATTEMPTING-TO-UPDATE.

The UE shall proceed as described below.

la) Timer T3448 is running

The UE shall not start the tracking area updating procedure with the "signalling active" flag unless:

– the UE is a UE configured to use AC11 – 15 in selected PLMN;

– the UE which is only using EPS services with control plane CIoT EPS optimization received a paging; or

– the UE in NB-S1 mode is requested by the upper layer to transmit user data related to an exceptional event and the UE is allowed to use exception data reporting (see the ExceptionDataReportingAllowed leaf of the NAS configuration MO in 3GPP TS 24.368 [15A] or the USIM file EFNASCONFIG in 3GPP TS 31.102 [17]).

The UE stays in the current serving cell and applies the normal cell reselection process.

The UE shall proceed as described below.

[TS 24.301, clause 5.6.1.5]

If the MME sends a SERVICE REJECT message upon receipt of the CONTROL PLANE SERVICE REQUEST message piggybacked with the ESM DATA TRANSPORT message:

– if the Release assistance indication IE is not set to "No further uplink or downlink data transmission subsequent to the uplink data transmission is expected" in the message;

– if the UE has indicated a support for the control plane data back-off timer; and

– if the MME decides to activate the congestion control for transport of user data via the control plane,

then the MME shall set the EMM cause value to #22 "congestion" and assign a value for control plane data back-off timer T3448.

On receipt of the SERVICE REJECT message, if the UE is in state EMM-SERVICE-REQUEST-INITIATED and the message is integrity protected or contains a reject cause other than EMM cause value #25, the UE shall reset the service request attempt counter, stop timer T3417, T3417ext or T3417ext-mt, if running.

[TS 24.301, clause 5.6.1.6]

la) "Extended wait time CP data" from the lower layers

– The UE shall abort the service request procedure for transfer of user data via the control plane, enter state EMM-REGISTERED, and stop timer T3417 if still running.

– If the UE is operating in NB-S1 mode and supports the timer T3448, the UE shall start the timer T3448 with the "Extended wait time CP data" value. If the UE is operating in NB-S1 mode and does not support the timer T3448, the UE shall start the timer T3346 with the "Extended wait time CP data" value.

– In other cases the UE shall ignore the "Extended wait time CP data".

– The UE stays in the current serving cell and applies normal cell reselection process. The service request procedure for transfer of user data via the control plane is started, if still necessary, when the timer T3448 expires or is stopped.

22.5.20.3 Test description

22.5.20.3.1 Pre-test conditions

System Simulator:

– Ncell 1, Ncell 23 are defined in clause 8.1.4.2 in TS 36.508[18].

– System information combination 3 as defined in TS 36.508[18] clause 8.1.4.3.1.1 is used in NB-IoT cells;

UE:

– None.

Preamble:

– The UE is in state NB-IoT UE Attach, Connected Mode, UE Test Loopback mode G Activated (State 2B-NB) on Ncell 1 according to [18].

22.5.20.3.2 Test procedure sequence

Table 22.5.20.3.2-1: Main behaviour

St

Procedure

Message Sequence

TP

Verdict

U – S

Message

1

The SS transmits one IP packet to the UE embedded in a ESM DATA TRANSPORT and DLInformationTransfer-NB

<–

NAS: ESM DATA TRANSPORT

2

Wait for 1 s after the IP packet has been transmitted. (Note 1)

2A

The SS transmits an RRCConnectionRelease-NB message.

<–

RRCConnectionRelease-NB

3

Check: does the UE transmit an RRCConnectionRequest-NB message?

–>

RRC: RRCConnectionRequest-NB

4

SS transmits an RRCConnectionSetup-NB message.

<–

RRC: RRCConnectionSetup-NB

5

Check: does the UE transmit an RRCConnectionSetupComplete-NB message to confirm the successful completion of the connection establishment and to initiate the session management procedure by including the CONTROL PLANE SERVICE REQUEST message with ESM DATA TRANSPORT message? (Note 2)

–>

RRC: RRCConnectionSetupComplete-NB

NAS: CONTROL PLANE SERVICE REQUEST

6

The SS transmits a SERVICE REJECT message with the EMM cause set to ‘Congestion’ and assign a value for control plane data back-off timer T3448.

<–

SERVICE REJECT

1

7

The SS releases the RRC connection.

8

The SS waits for T3448 to elapse

8A1-8A3

Repeat Steps 3 to 5 above

8B

The SS transmits a SERVICE REJECT message with the EMM cause set to ‘Congestion’ and assign a value for control plane data back-off timer T3448.

<–

SERVICE REJECT

8C

The SS transmits an RRCConnectionRelease-NB message.

<–

RRCConnectionRelease-NB

9

The SS configures:

– NCell 1 as the "Non-Suitable cell".

– NCell 23 as a "Serving cell".

The following messages are to be observed on Ncell 23 unless explicitly stated otherwise.

10

Check: Does the UE transmit a TRACKING AREA UPDATE REQUEST?

–>

TRACKING AREA UPDATE REQUEST

1

P

11

SS transmits an RRCConnectionRelease-NB message with extendedWaitTime-CPdata.

<–

RRC: RRCConnectionRelease-NB

12

The SS configures:

– NCell 23 as the "Non-Suitable cell".

– NCell 1 as a "Serving cell".

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

13

Check: Does the UE transmit a TRACKING AREA UPDATE REQUEST?

–>

TRACKING AREA UPDATE REQUEST

2

P

14

The SS transmits a TRACKING AREA UPDATE ACCEPT message without T3448.

<–

TRACKING AREA UPDATE ACCEPT

15

The UE transmits a TRACKING AREA UPDATE COMPLETE message.

–>

TRACKING AREA UPDATE COMPLETE

16

The SS starts timer Timer_1 = 5s

EXCEPTION: Steps 17a1 to 17b6 describe a behaviour that depend on UE implementation

17a1

The UE sends an ESM Data Transport Message containing the same user data sent by the SS in Step 1

–>

RRC: ULInformationTransfer-NB

TC: ESM DATA TRANSPORT

17b1

The SS waits for Timer_1 expiry

17b2

The SS transmits an RRCConnectionRelease-NB message.

<–

RRCConnectionRelease-NB

17b3

The UE transmit an RRCConnectionRequest-NB message?

–>

RRC: RRCConnectionRequest-NB

17b4

SS transmits an RRCConnectionSetup-NB message.

<–

RRC: RRCConnectionSetup-NB

17b5

Check: does the UE transmits an RRCConnectionSetupComplete-NB message to confirm the successful completion of the connection establishment and to initiate the session management procedure by including the CONTROL PLANE SERVICE REQUEST message and an ESM DATA TRANSPORT message containing the same user data sent by the SS in step 1?

–>

RRC: RRCConnectionSetupComplete-NB

NAS: CONTROL PLANE SERVICE REQUEST
NAS: ESM DATA TRANSPORT

2,3

P

17b6

The SS transmits a SERVICE ACCEPT message.

<–

RRC: DLInformationTransfer-NB

NAS: SERVICE ACCEPT

18-20

Void

21

If possible (see ICS) switch off is performed or the USIM is removed.

Otherwise the power is removed.

21A

If pc_SwitchOnOff or pc_USIM_Removal then the UE sends DETACH REQUEST message.

–>

DETACH REQUEST

22

The UE is brought back to operation or the USIM is inserted.

23

Steps 2-14 from generic procedure ‘ NB-IoT UE Attach, Connected mode, UE Test Mode Activated (State 2A-NB)’ specified in TS 36.508 [18], clause 8.1.5.2A takes place.

24

The SS sends an ATTACH ACCEPT message allocating T3448 of 1 minute.

IF px_DoAttachWithoutPDN THEN the ESM DUMMY MESSAGE is piggybacked in ATTACH ACCEPT OTHERWISE the ACTIVATE DEFAULT EPS BEARER CONTEXT REQUEST message is piggybacked in ATTACH ACCEPT

<–

ATTACH ACCEPT

25

The UE transmits an ATTACH COMPLETE message including an ACTIVATE DEFAULT EPS BEARER CONTEXT ACCEPT or ESM DUMMY MESSAGE message.

–>

ATTACH COMPLETE

26

Generic test procedure in TS 36.508 [18] clause 8.1.5.2B is performed.

NOTE: The UE enters the UE test loop mode G.

27

The SS delays 5s. NOTE: Ensure that the T3448 is running on UE side.

28

The SS transmits one IP packet to the UE embedded in an ESM DATA TRANSPORT and DLInformationTransfer-NB.

<–

RRC: DLInformationTransfer-NB

NAS: ESM DATA TRANSPORT

29

Void

29A

The SS transmits an RRCConnectionRelease-NB message.

<–

RRC: RRCConnectionRelease-NB

29B

Check : does the UE transmit an RRCConnectionRequest-NB message within 45s

RRC: RRCConnectionRequest-NB

4

F

29C

The UE transmit an RRCConnectionRequest-NB message

–>

RRC: RRCConnectionRequest-NB

29D

SS transmits an RRCConnectionSetup-NB message.

<–

RRC: RRCConnectionSetup-NB

29E

Check: does the UE transmits an RRCConnectionSetupComplete-NB message to confirm the successful completion of the connection establishment and to initiate the session management procedure by including the CONTROL PLANE SERVICE REQUEST message and an ESM DATA TRANSPORT message containing the same user data sent by the SS in step 28?

–>

RRC: RRCConnectionSetupComplete-NB

NAS: CONTROL PLANE SERVICE REQUEST
NAS: ESM DATA TRANSPORT

4

P

29F

The SS transmits a SERVICE ACCEPT message.

<–

RRC: DLInformationTransfer-NB

NAS: SERVICE ACCEPT

30

Void

31

The SS transmits an RRCConnectionRelease-NB message.

RRCConnectionRelease-NB

Note 1: The 1 second delay is used to secure that the UE have received and forwarded the IP Packet transmitted by the SS to the UE test loop function before the RRCConnectionRelease-NB message is sent by the SS.

Note 2: UE may include an ESM DATA TRANSPORT message containing the same user data sent by the SS in step 1

22.5.20.3.3 Specific message contents

Table 22.5.20.3.3-1: Message ESM DATA TRANSPORT (step 1 and step 28, Table 22.5.20.3.2-1)

Derivation path: TS 36.508 table 4.7.3-12A.

Information Element

Value/Remark

Comment

Condition

Protocol discriminator

EPS bearer identity

Procedure transaction identity

ESM data transport message identity

User data container

‘11110000 11110000 11110000’B

3 Octets of user data

– The value is arbitrary chosen

Release assistance indication

Not present

Table 22.5.20.3.3-2: Message SERVICE REJECT (Step 6, Table 22.5.20.3.2-1)

Derivation Path: TS 36.508 table 4.7.2.22

Information Element

Value/remark

Comment

Condition

EMM Cause

‘0001 0110’B

Congestion

T3448

30 seconds

Timer value

‘01111’B

Unit

‘000’B

Table 22.5.20.3.3-3: Message RRCConnectionRelease-NB (step 11, Table 22.5.20.3.2-1)

Derivation Path:TS 36.508 table 8.1.6.1-9

Information Element

Value/remark

Comment

Condition

RRCConnectionRelease-NB ::= SEQUENCE {

criticalExtensions CHOICE {

c1 CHOICE {

rrcConnectionRelease-r13 SEQUENCE {

redirectedCarrierInfo-r13 SEQUENCE {

carrierFreq-r13

Downlink ARFCN of Ncell 1

}

nonCriticalExtension SEQUENCE {

extendedWaitTime-CPdata-r14

30

}

}

}

}

}

Table 22.5.20.3.3-4: Message TRACKING AREA UPDATE REQUEST (step 10 and step 13, Table 22.5.20.3.2-1)

Derivation path: 36.508 table 4.7.2-27

Information Element

Value/Remark

Comment

Condition

UE network capability

the bit that indicates the support of back-off timer for transport of user data via the control plane is 1

Control Plane data back-off timer

Table 22.5.20.3.3-5: Message ATTACH ACCEPT (step 24, Table 22.5.20.3.2-1)

Derivation path: TS 36.508 table 4.7.3-1

Information Element

Value/Remark

Comment

Condition

T3448

1 minute

Timer value

‘00001’B

Unit

‘001’B

Table 22.5.20.3.3-5: Message SERVICE REJECT (Step 8B, Table 22.5.20.3.2-1)

Derivation Path: TS 36.508 table 4.7.2.22

Information Element

Value/remark

Comment

Condition

EMM Cause

‘0001 0110’B

Congestion

T3448

1 minute

Timer value

‘00001’B

Unit

‘001’B