5.6.1.7 Abnormal cases in the UE

The following abnormal cases can be identified:

• T3517 expired.

The UE shall enter the state 5GMM-REGISTERED.

If the UE triggered the service request procedure in 5GMM-IDLE mode sending a:

• SERVICE REQUEST message and the service type of the SERVICE REQUEST message was not set to "emergency services fallback"; or
• CONTROL PLANE SERVICE REQUEST message and the control plane service type of the CONTROL PLANE SERVICE REQUEST message was not set to "emergency services fallback";

then the 5GMM sublayer shall increment the service request attempt counter, abort the procedure and release locally any resources allocated for the service request procedure. The service request attempt counter shall not be incremented, if:

• the service request procedure is initiated to establish an emergency PDU session;
• the UE has an emergency PDU session established;
• the UE is a UE configured for high priority access in selected PLMN or SNPN;
• the service request procedure is initiated in response to paging or notification from the network; or
• the UE in NB-N1 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 [17] or the USIM file EFNASCONFIG in 3GPP TS 31.102 [22]).

If the service request attempt counter is greater than or equal to 5, the UE shall start timer T3525. Additionally,

if the service request procedure was initiated for an MO MMTEL voice call, for an MO MMTEL video call or for an MO IMS registration related signalling, a notification that the service request was not initiated due to the UE having started timer T3525 shall be provided to the upper layers; and

NOTE 1: This can result in the upper layers requesting implementation specific mechanisms, e.g. the MMTEL voice call being attempted to another IP-CAN, or establishment of a CS voice call (if supported and not already attempted in the CS domain).

if the service request procedure was initiated for other than an MO MMTEL voice call, an MO MMTEL video call and an MO IMS registration related signalling, then upon an upper layer request, the UE as an implementation option may attempt to select E-UTRA cell connected to EPC or any other suitable cell of other RAT.

The UE shall not attempt service request until expiry of timer T3525 unless:

• the service request procedure is initiated in response to paging or notification from the network;
• the UE is a UE configured for high priority access in selected PLMN or SNPN;
• the service request procedure is initiated to establish an emergency PDU session;
• the UE has an emergency PDU session established;
• the service request procedure is initiated for emergency services fallback;
• the UE is registered in a new PLMN or SNPN;

NOTE 2: According to Table 10.2.1, when "UE camped on a new PLMN other than the PLMN on which timer started", timer T3525 is stopped, hence this check may be skipped.

• the UE in NB-N1 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 [17] or the USIM file EFNASCONFIG in 3GPP TS 31.102 [22]); or
• the UE supports the reconnection to the network due to RAN timing synchronization status change and receives an indication of a change in the RAN timing synchronization status.

NOTE 3: The NAS signalling connection can also be released if the UE deems that the network has failed the authentication check as specified in clause 5.4.1.3.7.

If the UE triggered the service request procedure in 5GMM-CONNECTED mode sending a:

• SERVICE REQUEST message and the service type of the SERVICE REQUEST message was not set to "emergency services fallback"; or
• CONTROL PLANE SERVICE REQUEST message and the control plane service type of the CONTROL PLANE SERVICE REQUEST message was not set to "emergency services fallback",

the 5GMM sublayer shall abort the procedure, and stay in 5GMM-CONNECTED mode.

If the service type of the SERVICE REQUEST message was set to "emergency services fallback" or the control plane service type of the CONTROL PLANE SERVICE REQUEST message was set to "emergency services fallback" and:

• the service request procedure was triggered in 5GMM-IDLE mode, the 5GMM sublayer shall abort the procedure, release locally any resources allocated for the service request procedure; or
• the service request procedure was triggered in 5GMM-CONNECTED mode, the 5GMM sublayer shall abort the procedure, stay in 5GMM-CONNECTED mode.
• The lower layers indicate that the access attempt is barred.

The UE shall not start the service request procedure. The UE stays in the current serving cell and applies the normal cell reselection process. Receipt of the access barred indication shall not trigger the selection of a different core network type (EPC or 5GCN).

The service request procedure is started, if still needed, when the lower layers indicate that the barring is alleviated for the access category with which the access attempt was associated.

• The lower layers indicate that:
• access barring is applicable for all access categories except categories 0 and 2 and the access category with which the access attempt was associated is other than 0 and 2; or
• access barring is applicable for all access categories except category 0 and the access category with which the access attempt was associated is other than 0.

If the SERVICE REQUEST message or CONTROL PLANE SERVICE REQUEST has not been sent, the UE shall proceed as specified for case b.

If the SERVICE REQUEST message or CONTROL PLANE SERVICE REQUEST has been sent:

• the UE shall abort the service request procedure and stop timer T3517. The UE stays in the current serving cell and applies the normal cell reselection process; and
• the service request procedure is started, if still needed, when the lower layers indicate that the barring is alleviated for the access category with which the access attempt was associated.

For additional UE requirements for both cases see clause 4.5.5.

• Timer T3346 is running.

The UE shall not start the service request procedure unless:

• the UE receives a paging;
• the UE receives a NOTIFICATION message over non-3GPP access when the UE is in 5GMM-CONNECTED mode over non-3GPP access and in 5GMM-IDLE mode over 3GPP access;
• the UE receives a NOTIFICATION message over 3GPP access when the UE is in 5GMM-CONNECTED mode over 3GPP access and in 5GMM-IDLE mode over non-3GPP access;
• the UE is a UE configured for high priority access in selected PLMN or SNPN;
• the UE has an emergency PDU session established or is establishing an emergency PDU session;
• the service request procedure is initiated for emergency services fallback;
• the service request procedure is initiated for elevated signalling;
• the UE in NB-N1 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 [17] or the USIM file EFNASCONFIG in 3GPP TS 31.102 [22]); and
• timer T3346 was not started when N1 NAS signalling connection was established with RRC establishment cause set to "mo-ExceptionData"; or
• the MUSIM UE is in 5GMM-CONNECTED mode and requests the network to release the NAS signalling connection (see case o in clause 5.6.1.1).

If the UE is in 5GMM-IDLE mode, the UE stays in the current serving cell and applies normal cell reselection process. The service request procedure is started, if still necessary, when timer T3346 expires or is stopped.

If the service request procedure was triggered for an MO MMTEL voice call (i.e. access category 4), or for an MO MMTEL video call (i.e. access category 5) or for an MO IMS registration related signalling (i.e. access category 9), a notification that the service request procedure was not initiated due to congestion shall be provided to the upper layers.

If the UE receives a paging with access type set to "Non-3GPP access" and the non-3GPP access is available and UE is in 5GMM-REGISTERED.NORMAL SERVICE over non-3GPP access, the UE shall stop timer T3346 and send the SERVICE REQUEST message over non-3GPP access.

• Registration procedure for mobility and periodic registration update is triggered.

The UE shall abort the service request procedure, stop timer T3517, if running and perform the registration procedure for mobility and periodic registration update. The Follow-on request indicator in the REGISTRATION REQUEST message shall be handled as specified in clause 5.5.1.3.2.

• Switch off.

If the UE is in state 5GMM-SERVICE-REQUEST-INITIATED at switch off, the de-registration procedure shall be performed.

• De-registration procedure collision.

If the UE receives a DEREGISTRATION REQUEST message from the network in state 5GMM-SERVICE-REQUEST-INITIATED, the UE shall progress the DEREGISTRATION REQUEST message and the service request procedure shall be aborted.

NOTE 4: The above collision case is valid if the DEREGISTRATION REQUEST message indicates the access type over which the service request procedure is attempted otherwise both the procedures are progressed.

• Transmission failure of SERVICE REQUEST or CONTROL PLANE SERVICE REQUEST message indication with change in the current TAI.

If the current TAI is not in the TAI list, UE shall abort the service request procedure to perform the registration procedure for mobility and periodic registration update as specified in clause 5.5.1.3.2.

If the current TAI is part of the TAI list, the UE shall restart the service request procedure unless the service request procedure is initiated for case o) or p) in clause 5.6.1.1. For case o) and p) in clause 5.6.1.1 the UE shall abort the service request procedure, enters state 5GMM-REGISTERED, locally release the N1 NAS signalling connection, stop timer T3517 and locally release any resources allocated for the service request procedure.

• Transmission failure of SERVICE REQUEST or CONTROL PLANE SERVICE REQUEST message indication without change in the current TAI.

The UE shall restart the service request procedure unless the service request procedure is initiated for case o) or p) in clause 5.6.1.1. For case o) and p) in clause 5.6.1.1 the UE shall abort the service request procedure, enters state 5GMM-REGISTERED, locally release the N1 NAS signalling connection, stop timer T3517 and locally release any resources allocated for the service request procedure.

• SERVICE REJECT message received with other 5GMM cause values than those treated in clause 5.6.1.5, and cases of 5GMM cause values #11, #15, #22, #28, #31, #36, #72, #73, #74, #75, #76, #77 and #78 that are considered as abnormal cases according to clause 5.6.1.5.

The UE shall enter state 5GMM-REGISTERED.

The UE shall abort the service request procedure, stop timer T3517 and locally release any resources allocated for the service request procedure.

• The UE in 5GMM-CONNECTED mode with RRC inactive indication over the 3GPP access, and in 5GMM-CONNECTED mode over non-3GPP access, receives a NOTIFICATION message over the non-3GPP access with access type indicating 3GPP access.

The UE shall transition from 5GMM-CONNECTED mode with RRC inactive indication to 5GMM-IDLE mode over 3GPP access and initiate the service request procedure over the 3GPP access.

• Timer T3447 is running

The UE shall not start any service request procedure unless:

• the UE in 5GMM-IDLE receives a paging request;
• the UE is a UE configured for high priority access;
• the UE has a PDU session for emergency services established or is establishing a PDU session for emergency services;
• the service request procedure is initiated for emergency services fallback;
• the UE in 5GMM-CONNECTED mode receives mobile terminated signalling or downlink data over the user-plane;
• the service request procedure is initiated for elevated signalling;
• the MUSIM UE requests the network to release the NAS signalling connection (see case o in clause 5.6.1.1); or
• the UE in NB-N1 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 [17] or the USIM file EFNASCONFIG in 3GPP TS 31.102 [22]).

The UE stays in the current serving cell and applies the normal cell reselection process. The service request procedure is started, if still necessary, when timer T3447 expires or timer T3447 is stopped.

• Lower layer failure, release of the N1 signalling connection received from lower layers or the lower layers indicate that the RRC connection has been suspended before the service request procedure is completed or SERVICE REJECT message is received.

The UE shall abort the service request procedure, stop timer T3517, locally release any resources allocated for the service request procedure and enters state 5GMM-REGISTERED. For case m) in clause 5.6.1.1 the UE may retry the service request procedure a certain number of times (maximum re-attempts 5).

• Timer T3448 is running

The UE in 5GMM-IDLE mode shall not initiate the service request procedure for transport of user data via the control plane unless:

• the UE is a UE configured for high priority access in selected PLMN;
• the UE which is only using 5GS services with control plane CIoT 5GS optimization received a paging request;
• the UE in NB-N1 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 [17] or the USIM file EFNASCONFIG in 3GPP TS 31.102 [22]); or
• the UE is initiating the service request procedure to request emergency services or emergency services fallback.

The UE stays in the current serving cell and applies the normal cell reselection process. The service request procedure is started, if still necessary, when timer T3448 expires.

• Access for localized services in current SNPN is no longer allowed.

If the service request procedure is not to request emergency services and there is no PDU session for emergency services, the registered SNPN is an SNPN selected for localized services in SNPN (see 3GPP TS 23.122 [5]) and:

• access for localized services in SNPN is disabled; or
• the validity information for the selected SNPN is no longer met;

then the UE shall reset the service request attempt counter, stop T3517, abort the service request procedure, locally release the NAS signalling connection, if any, and enter state 5GMM-REGISTERED.LIMITED-SERVICE or 5GMM-REGISTERED.PLMN-SEARCH in order to perform SNPN selection according to 3GPP TS 23.122 [5].