Section: 5.5.1.2.7 Abnormal cases in the UE
Content: The following abnormal cases can be identified: a) Timer T3346 is running. The UE shall not start the registration procedure for initial registration unless: 1) the UE is a UE configured for high priority access in selected PLMN or SNPN; 2) the UE needs to perform the registration procedure for initial registration for emergency services; 3) the UE receives a DEREGISTRATION REQUEST message with the "re-registration required" indication; 4) 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[ Non-Access Stratum (NAS) configuration Management Object (MO) ]  [17] or the USIM file EFNASCONFIG in 3GPP TS 31.102[ Characteristics of the Universal Subscriber Identity Module (USIM) application ]  [22]); and - timer T3346 was not started when N1 NAS signalling connection was established with RRC establishment cause set to "mo-ExceptionData"; or 5) the UE needs to perform the registration procedure with 5GS registration type IE set to "initial registration" for initiating of an emergency PDU session, upon request of the upper layers to establish the emergency PDU session. The UE stays in the current serving cell and applies the normal cell reselection process. NOTE 1: It is considered an abnormal case if the UE needs to initiate a registration procedure for initial registration while timer T3346 is running independent on whether timer T3346 was started due to an abnormal case or a non-successful case. b) The lower layers indicate that the access attempt is barred. The UE shall not start the initial registration 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 initial registration 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. ba) The lower layers indicate that: 1) 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 2) 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 REGISTRATION REQUEST message has not been sent, the UE shall proceed as specified for case b. If the REGISTRATION REQUEST message has been sent, the UE shall proceed as specified for case e and, additionally, the registration procedure for initial registration 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. c) T3510 timeout. The UE shall abort the registration procedure for initial registration and the NAS signalling connection, if any, shall be released locally if the initial registration request is neither for emergency services nor for initiating a PDU session for emergency services with request type set to "existing emergency PDU session". The UE shall proceed as described below. d) REGISTRATION REJECT message, other 5GMM cause values than those treated in subclause 5.5.1.2.5, and cases of 5GMM cause values #10, #11, #15, #22, #31, #72, #73, #74, #75, #76, #77 and #78, if considered as abnormal cases according to subclause 5.5.1.2.5. If the registration request is neither an initial registration request for emergency services nor an initial registration request for initiating a PDU session for emergency services with request type set to "existing emergency PDU session", upon reception of the 5GMM causes #95, #96, #97, #99 and #111 the UE should set the registration attempt counter to 5. The UE shall proceed as described below. e) Lower layer failure or release of the NAS signalling connection received from lower layers before the REGISTRATION ACCEPT or REGISTRATION REJECT message is received. The UE shall abort the registration procedure for initial registration and proceed as described below. f) UE initiated de-registration required. The registration procedure for initial registration shall be aborted, and the UE initiated de-registration procedure shall be performed. g) De-registration procedure collision. If the UE receives a DEREGISTRATION REQUEST message from the network in state 5GMM-REGISTERED-INITIATED the de-registration procedure shall be aborted and the initial registration procedure shall be progressed. NOTE 2: The above collision case is valid if the DEREGISTRATION REQUEST message indicates the access type over which the initial registration procedure is attempted otherwise both the procedures are progressed. h) Change in the current TAI. If the current TAI is changed before the registration procedure for initial registration is completed, the registration procedure for initial registration shall be aborted and re-initiated immediately. If the REGISTRATION COMPLETE message needs to be sent and a tracking area border is crossed when the REGISTRATION ACCEPT message has been received but before a REGISTRATION COMPLETE message is sent and: 1) if the current TAI is in the TAI list, the UE sends the REGISTRATION COMPLETE message to the network; and 2) otherwise, the registration procedure for initial registration shall be aborted and the registration procedure for mobility registration update shall be initiated. If a 5G-GUTI was allocated during the registration procedure, this 5G-GUTI shall be used in the registration procedure. i) Transmission failure of REGISTRATION COMPLETE message indication with change in the current TAI. 1) If the current TAI is still part of the TAI list, the UE resends the REGISTRATION COMPLETE message to the network; and 2) otherwise, the registration procedure for initial registration shall be aborted and the registration procedure for mobility registration update shall be initiated. j) Transmission failure of REGISTRATION COMPLETE message indication without change in the current TAI from lower layers. It is up to the UE implementation how to re-run the ongoing procedure. k) Transmission failure of REGISTRATION REQUEST message indication from the lower layers. The registration procedure for initial registration shall be aborted and re-initiated immediately. l) Timer T3447 is running. The UE shall not start the registration procedure for initial registration with Follow-on request indicator set to "Follow-on request pending" unless: 1) the UE is a UE configured for high priority access in selected PLMN; or 2) the UE needs to perform the registration procedure for initial registration for emergency services. The UE stays in the current serving cell and applies the normal cell reselection process. The registration procedure for initial registration is started, if still necessary, when timer T3447 expires or timer T3447 is stopped. m) UE is not registered to the access other than the access the REGISTRATION ACCEPT message is received and the 5GS registration result value in the 5GS registration result IE value in the REGISTRATION ACCEPT message is set to "3GPP access and non-3GPP access". The UE shall consider itself as being registered to only the access where the REGISTRATION ACCEPT message is received. n) Access for localized services in current SNPN is no longer allowed. If the initial registration request is neither for emergency services nor for initiating a PDU session for emergency services with request type set to "existing emergency PDU session", the selected SNPN is an SNPN selected for localized services in SNPN as specified in 3GPP TS 23.122[ Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode ]  [5] and: 1) access for localized services in SNPN is disabled; or 2) the validity information for the selected SNPN is no longer met; the UE shall reset the registration attempt counter, stop T3510, abort the registration procedure for initial registration, locally release the NAS signalling connection, if any, and enter state 5GMM-DEREGISTERED.LIMITED-SERVICE or 5GMM-DEREGISTERED.PLMN-SEARCH in order to perform SNPN selection according to 3GPP TS 23.122[ Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode ]  [5]. For the cases c, d and e, the UE shall proceed as follows: Timer T3510 shall be stopped if still running. If the registration procedure is neither an initial registration for emergency services nor for establishing an emergency PDU session with registration type not set to "emergency registration", the registration attempt counter shall be incremented, unless it was already set to 5. If the registration attempt counter is less than 5: - if the initial registration request is not for emergency services, timer T3511 is started and the state is changed to 5GMM-DEREGISTERED.ATTEMPTING-REGISTRATION. When timer T3511 expires the registration procedure for initial registration shall be restarted, if still required. If the registration attempt counter is equal to 5 - the UE shall delete TAI list and last visited registered TAI, start timer T3502 if the value of the timer as indicated by the network is not zero and shall set the 5GS update status to 5U2 NOT UPDATED. If the UE is not registering or has not registered to the same PLMN over both 3GPP access and non-3GPP access, the UE shall additionally delete 5G-GUTI, ngKSI and list of equivalent PLMNs (if any) or list of equivalent SNPNs (if any). The state is changed to 5GMM-DEREGISTERED.ATTEMPTING-REGISTRATION or optionally to 5GMM-DEREGISTERED.PLMN-SEARCH in order to perform a PLMN selection, SNPN selection or SNPN selection for onboarding services according to 3GPP TS 23.122[ Non-Access-Stratum (NAS) functions related to Mobile Station (MS) in idle mode ]  [5]. - if the value of T3502 as indicated by the network is zero, the UE shall perform the actions defined for the expiry of the timer T3502. - if the procedure is performed via 3GPP access and the UE is operating in single-registration mode: - the UE shall in addition handle the EMM parameters EPS update status, EMM state, 4G-GUTI, TAI list, last visited registered TAI, list of equivalent PLMNs and eKSI as specified in 3GPP TS 24.301[ Non-Access-Stratum (NAS) protocol for Evolved Packet System (EPS); Stage 3 ]  [15] for the abnormal cases when an EPS attach procedure fails and the attach attempt counter is equal to 5; and - the UE shall attempt to select E-UTRAN radio access technology and proceed with appropriate EMM specific procedures. Additionally, The UE may disable the N1 mode capability as specified in subclause 4.9.