5.4.5.2.6 Abnormal cases in the UE

The following abnormal cases can be identified:

• The lower layers indicate that the access attempt is barred.

The UE shall not start the UE-initiated NAS transport procedure. The UE stays in the current serving cell and applies the normal cell reselection process.

If the access category for the access attempt is 6 due to a request from upper layers to send a mobile originated SMS over NAS and the UE is registered to the network via both 3GPP access and non-3GPP access, the UE may transmit the UL NAS TRANSPORT message via non-3GPP access, if available.

Otherwise, the UE-initiated NAS transport 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.

The UE shall proceed as specified for case a. For additional UE requirements see clause 4.5.5.

• If the Payload container type IE is set to "N1 SM information", the Request type IE is set to "initial request" or "MA PDU request" and registration procedure for mobility and periodic registration update is pending due to receipt by the UE of new network slicing information via the generic UE configuration update procedure with re-registration request; and an emergency PDU session exists then:
• The UE shall not send the UL NAS TRANSPORT message; and
• The UL NAS TRANSPORT message can be sent, if still necessary, after a successful procedure for mobility and periodic registration update.
• Transmission failure of the UL NAS TRANSPORT message with change in the current TAI.

If the current TAI is not in the TAI list, the UE-initiated NAS transport procedure shall be aborted and a registration procedure for mobility and periodic registration update shall be initiated. The UL NAS TRANSPORT message can be sent, if still necessary, after a successful procedure for mobility and periodic registration update.

If:

• the current TAI is still part of the TAI list;
• the UL NAS TRANSPORT message is sent to transport a 5GSM message associated with an S-NSSAI included in the partially allowed NSSAI; and
• the current TAI is not in the list of TAs where the S-NSSAI is allowed,

then the UE-initiated NAS transport procedure shall be aborted.

Otherwise, it is up to the UE implementation how to re-run the ongoing procedure that triggered the UE-initiated NAS transport procedure.

• Transmission failure of the UL NAS TRANSPORT message indication without change in the current TAI.

It is up to the UE implementation how to re-run the ongoing procedure that triggered the UE-initiated NAS transport procedure.

• Void.
• Timer T3447 is running.

The UE shall not send the UL NAS TRANSPORT message unless:

• the Payload container type IE is set to "N1 SM information" and:
• the Request type IE is set to:

A) "initial emergency request";

B) "existing emergency PDU session"; or

C) "modification request" and the PDU session being modified is an emergency PDU session (see error cases described in clause 6.4.1.3 and clause 6.3.2.3); or

• the Request type IE is not included and the PDU session modification procedure is used to indicate a change of 3GPP PS data off UE status for a PDU session;
• the UE is a UE configured for high priority access in selected PLMN;
• a paging request triggered the establishment of the current NAS signalling connection;
• the UE in 5GMM-CONNECTED mode receives mobile terminated signalling or downlink data over the user-plane; 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 UL NAS TRANSPORT message can be sent, if still necessary, when timer T3447 expires or timer T3447 is stopped.

• The lower layers indicate that the RRC connection has been suspended.

The UE shall abort the UE-initiated NAS transport procedure.

• Timer T3346 is running.

The UE shall not send the UL NAS TRANSPORT message unless:

• the Payload container type IE is set to "N1 SM information" and:
• the Request type IE is set to:

A) "initial emergency request";

B) "existing emergency PDU session"; or

C) "modification request" and the PDU session being modified is an emergency PDU session; or

• the Request type IE is not included and the PDU session modification procedure is used to indicate a change of 3GPP PS data off UE status for a PDU session; or
• the UE is a UE configured for high priority access in selected PLMN or SNPN.

The UL NAS TRANSPORT message can be sent, if still necessary, when timer T3346 expires.

• NAS MAC calculation indication from lower layers.

If lower layers indicate to calculate an NAS MAC, the UE shall calculate an NAS MAC as specified in 3GPP TS 33.501 [24] and then provide the calculated NAS MAC and 5 least significant bits of the uplink NAS COUNT used to calculate the NAS MAC to lower layers (see 3GPP TS 36.331 [25A]). The UE shall increase the uplink NAS COUNT by one after the calculation of the NAS MAC.