5.2 Behaviour of the UE in state 5GMM-DEREGISTERED and state 5GMM-REGISTERED

24.5013GPPNon-Access-Stratum (NAS) protocol for 5G System (5GS)Release 17Stage 3TS

5.2.1 General

In this subclause, the detailed behaviour of the UE in the states 5GMM-DEREGISTERED and 5GMM-REGISTERED is described.

5.2.2 UE behaviour in state 5GMM-DEREGISTERED

5.2.2.1 General

The state 5GMM-DEREGISTERED is entered in the UE, when:

a) the de-registration is performed either by the UE or by the network (see subclause 5.5.2);

b) the registration request is rejected by the AMF (see subclause 5.5.1.2.5 and 5.5.1.3.5);

c) the service request is rejected by the AMF (see subclause 5.6.1);

d) the UE is switched on; or

e) the UE registered for emergency services is in 5GMM-IDLE mode and its periodic registration update timer expires (see subclause 5.3.7).

In state 5GMM-DEREGISTERED, the UE shall behave according to the substate as explained in subclause 5.2.2.3.

5.2.2.2 Primary substate selection

5.2.2.2.1 Selection of the substate after power on

For a UE configured for eCall only mode as specified in 3GPP TS 31.102 [22], timers T3444 and T3445 are considered to have expired at power on. When the UE is switched on, the substate shall be PLMN-SEARCH if the USIM is available and valid or there are valid entries in the "list of subscriber data". See 3GPP TS 23.122 [5] for further details.

The substate chosen after PLMN-SEARCH, following power on is:

a) if no cell can be selected, the substate shall be NO-CELL-AVAILABLE;

b) if no USIM is present or no valid entry in the "list of subscriber data" exists, the substate shall be NO-SUPI;

c) if a suitable cell has been found, the PLMN or SNPN identity of the cell is not in one of the forbidden PLMN lists, the "permanently forbidden SNPNs" list or the "temporarily forbidden SNPNs" list which are, if the MS supports access to an SNPN using credentials from a credentials holder, associated with the selected entry of the "list of subscriber data" or the selected PLMN subscription, and the tracking area is not in one of the lists of 5GS forbidden tracking areas, then the substate shall be NORMAL-SERVICE;

d) if the selected cell is known not to be able to provide normal service, then the UE shall enter the substate LIMITED-SERVICE;

e) if the UE is in manual network selection mode and no cell of the selected PLMN or SNPN has been found, the UE shall enter the substate NO-CELL-AVAILABLE; and

f) if the UE is configured for eCall only mode as specified in 3GPP TS 31.102 [22], the substate shall be eCALL-INACTIVE.

5.2.2.3 Detailed description of UE behaviour in state 5GMM-DEREGISTERED

5.2.2.3.1 NORMAL-SERVICE

The UE shall initiate an initial registration procedure if the timer T3346 is not running. If timer T3346 is running, the UE shall initiate an initial registration procedure on the expiry of timer T3346.

The UE may initiate an initial registration procedure for emergency services even if timer T3346 is running.

5.2.2.3.2 LIMITED-SERVICE

The UE shall initiate an initial registration procedure when entering a cell which provides normal service.

The UE may initiate initial registration for emergency services.

5.2.2.3.3 ATTEMPTING-REGISTRATION

The UE in 3GPP access:

a) shall initiate an initial registration procedure on the expiry of timers T3502, T3511 or T3346;

b) may initiate an initial registration procedure for emergency services even if timers T3502, T3511 or T3346 are running;

b1) may initiate an initial registration procedure even if timer T3346 is running, if the UE is a UE configured for high priority access in selected PLMN;

c) shall initiate an initial registration procedure when entering a new PLMN or SNPN, except

i) if timer T3346 is running and the new PLMN is equivalent to the PLMN where the UE started timer T3346;

ii) if the PLMN identity of the new cell is in the forbidden PLMN lists or the SNPN identity of the new cell is in the "permanently forbidden SNPNs" list or the "temporarily forbidden SNPNs" list which are, if the MS supports access to an SNPN using credentials from a credentials holder, associated with the selected entry of the "list of subscriber data" or the selected PLMN subscription; or

iii) if the tracking area is in one of the lists of 5GS forbidden tracking areas;

d) shall initiate an initial registration procedure when the tracking area of the serving cell has changed, if timer T3346 is not running, the PLMN identity of the new cell is not in one of the forbidden PLMN lists or the SNPN identity of the new cell is in neither the "permanently forbidden SNPNs" list nor the "temporarily forbidden SNPNs" list which are, if the MS supports access to an SNPN using credentials from a credentials holder, associated with the selected entry of the "list of subscriber data" or the selected PLMN subscription, and the tracking area of the new cell is not in one of the lists of 5GS forbidden tracking areas;

e) shall initiate an initial registration procedure if the 5GS update status is set to 5U2 NOT UPDATED, and timers T3511, T3502 and T3346 are not running;

f) may initiate an initial registration procedure for UE in NB-N1 mode upon receiving a request from upper layers 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]) if timer T3346 is not already running for "MO exception data" and even if timer T3502 or timer T3511 is running; and

g) may initiate an initial 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 in non-3GPP access:

a) shall initiate an initial registration procedure on the expiry of timers T3502, T3511 or T3346;

b) may initiate an initial registration procedure for emergency services even if timers T3502, T3511 or T3346 are running;

b1) may initiate an initial registration procedure even if timer T3346 is running if the UE is a UE configured for high priority access in selected PLMN;

c) shall initiate an initial registration procedure when entering a new PLMN, except if timer T3346 is running and the new PLMN is equivalent to the PLMN where the UE started timer T3346;

d) shall initiate an initial registration procedure if the 5GS update status is set to 5U2 NOT UPDATED, and timers T3511, T3502 and T3346 are not running; and

e) may initiate an initial 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.

5.2.2.3.4 PLMN-SEARCH

The UE shall perform PLMN selection or SNPN selection. If a new PLMN or SNPN is selected, the UE shall reset the registration attempt counter and initiate the registration procedure for initial registration (see subclause 5.5.1.2.2).

If the selected cell in the new PLMN is known not to be able to provide normal service, the UE may initiate the registration procedure for initial registration for emergency services.

5.2.2.3.5 NO-SUPI

The UE may initiate the registration procedure for initial registration for emergency services.

5.2.2.3.6 NO-CELL-AVAILABLE

The UE shall perform cell selection and choose an appropriate substate when a cell is found.

5.2.2.3.7 eCALL-INACTIVE

The UE camps on a suitable cell or an acceptable cell in a PLMN selected as specified in 3GPP TS 23.122 [5] but initiates no 5GMM signalling with the network and ignores any paging requests.

The UE shall leave substate 5GMM-DEREGISTERED.eCALL-INACTIVE state only when one of the following events occur:

a) if the USIM is removed, the UE enters substate 5GMM-DEREGISTERED.NO-SUPI;

b) if coverage is lost, the UE enters substate 5GMM-DEREGISTERED.PLMN-SEARCH;

c) if the UE is deactivated (e.g. powered off) by the user, the UE enters state 5GMM-NULL;

d) if the UE receives a request from upper layers to establish an eCall over IMS, the UE enters state 5GMM-DEREGISTERED.ATTEMPTING-REGISTRATION. The UE then uses the relevant 5GMM and 5GSM procedures to establish the eCall over IMS at the earliest opportunity; or

e) if the UE receives a request from upper layers to establish a call to an HPLMN designated non-emergency MSISDN or URI for test or terminal reconfiguration service, the UE enters state 5GMM-DEREGISTERED.ATTEMPTING-REGISTRATION. Once the registration procedure is completed, the UE uses the relevant 5GMM and 5GSM procedures to establish the non-emergency call.

5.2.2.3.8 INITIAL-REGISTRATION-NEEDED

The UE shall initiate the initial registration procedure, if still needed, as soon as the access is allowed in the selected cell for the UE.

The UE may initiate registration procedure for emergency services.

5.2.2.4 Substate when back to state 5GMM-DEREGISTERED from another 5GMM state

When returning to state 5GMM-DEREGISTERED, the UE shall select a cell as specified in 3GPP TS 38.304 [28] or 3GPP TS 36.304 [25C].

The substate depends on the result of the cell selection procedure, the outcome of the previously performed 5GMM specific procedures, on the 5GS update status of the UE, on the tracking area data stored in the UE, on the presence of the USIM, on the UE configuration and on the reason for moving to 5GMM-DEREGISTERED:

a) If no cell has been found, the substate is NO-CELL-AVAILABLE, until a cell is found;

b) If no USIM is present or if the inserted USIM is considered invalid by the UE, the substate shall be NO-SUPI;

c) If a suitable cell has been found and the PLMN or tracking area is not in one of the forbidden lists, the substate shall be NORMAL-SERVICE;

d) If an initial registration shall be performed (e.g. network-requested re-registration), the substate shall be ATTEMPTING-REGISTRATION;

e) If a PLMN reselection or SNPN reselection (according to 3GPP TS 23.122 [5]) is needed, the substate shall be PLMN-SEARCH;

f) If the selected cell is known not to be able to provide normal service, the substate shall be LIMITED-SERVICE; and

g) If the UE is configured for eCall only mode as specified in 3GPP TS 31.102 [22], T3444 and T3445 have expired or are not running, and substate PLMN-SEARCH is not required, the substate shall be eCALL-INACTIVE.

5.2.3 UE behaviour in state 5GMM-REGISTERED

5.2.3.1 General

The state 5GMM-REGISTERED is entered at the UE, when the initial registration procedure is performed by the UE (see subclause 5.5.1.2.2).

In state 5GMM-REGISTERED, the UE shall behave according to the substate as explained in subclause 5.2.3.2.

5.2.3.2 Detailed description of UE behaviour in state 5GMM-REGISTERED

5.2.3.2.1 NORMAL-SERVICE

The UE:

a) shall initiate the mobility or the periodic registration update procedure (according to conditions given in subclause 5.5.1.3.2), except that the periodic registration update procedure shall not be initiated over non-3GPP access;

b) shall initiate the service request procedure (according to conditions given in subclause 5.6.1);

c) shall respond to paging;

d) if configured for eCall only mode as specified in 3GPP TS 31.102 [22], shall perform the eCall inactivity procedure at expiry of timer T3444 or timer T3445 (see subclause 5.5.3); and

e) shall initiate a registration procedure for mobility and periodic registration update on the expiry of timer T3511.

NOTE 1: Paging is not supported over non-3GPP access.

NOTE 2: As an implementation option, the MUSIM capable UE is allowed to not respond to paging based on the information available in the paging message, e.g. voice service indication.

5.2.3.2.2 NON-ALLOWED-SERVICE

The UE shall behave as specified in subclause 5.3.5.

5.2.3.2.3 ATTEMPTING-REGISTRATION-UPDATE

The UE in 3GPP access:

a) shall not send any user data;

b) shall initiate a registration procedure for mobility and periodic registration update on the expiry of timers T3502, T3511 or T3346;

c) shall initiate a registration procedure for mobility and periodic registration update when entering a new PLMN, if timer T3346 is running and the new PLMN is not equivalent to the PLMN where the UE started timer T3346, the PLMN identity of the new cell is not in the forbidden PLMN lists, and the tracking area is not in one of the lists of 5GS forbidden tracking areas;

d) shall initiate a registration procedure for mobility and periodic registration update when the tracking area of the serving cell has changed, if timer T3346 is not running, the PLMN identity of the new cell is not in one of the forbidden PLMN lists or the SNPN identity of the new cell is in neither the "permanently forbidden SNPNs" list nor the "temporarily forbidden SNPNs" list which are, if the MS supports access to an SNPN using credentials from a credentials holder, associated with the selected entry of the "list of subscriber data" or the selected PLMN subscription, and the tracking area is not in one of the lists of 5GS forbidden tracking areas;

e) may initiate a registration procedure for mobility and periodic registration update upon request of the upper layers to establish an emergency PDU session;

e1) may initiate a registration procedure for mobility and periodic registration update upon request of the upper layers to establish a PDU session, if the UE is a UE configured for high priority access in selected PLMN;

f) may perform de-registration locally and initiate a registration procedure for initial registration for emergency services even if timer T3346 is running;

g) shall initiate registration procedure for mobility and periodic registration update upon reception of paging, or upon reception of NOTIFICATION message with access type indicating 3GPP access;

NOTE: As an implementation option, the MUSIM capable UE is allowed to not respond to paging based on the information available in the paging message, e.g. voice service indication.

h) may initiate a registration procedure for mobility and periodic registration update upon request for an MMTEL voice call, MMTEL video call, or an MO IMS registration related signalling from the upper layers, and none of the following conditions is met:

– timer T3346 is running;

– the UE has stored a list of "non-allowed tracking areas" and the UE is camped on a cell which is in the registered PLMN or a PLMN from the list of equivalent PLMNs whose TAI is in the list of "non-allowed tracking areas"; or

– the UE has stored a list of "allowed tracking areas" and the UE is not camped on a cell which is in the registered PLMN or a PLMN from the list of equivalent PLMNs whose TAI is in the list of "allowed tracking areas";

i) shall initiate a registration procedure for mobility and periodic registration update if the 5GS update status is set to 5U2 NOT UPDATED, and timers T3511, T3502 and T3346 are not running;

j) if configured for eCall only mode as specified in 3GPP TS 31.102 [22], shall perform the eCall inactivity procedure at expiry of timer T3444 or timer T3445 (see subclause 5.5.3);

k) may initiate a registration procedure for mobility and periodic registration update for UE in NB-N1 mode upon receiving a request from upper layers 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]) if timer T3346 is not already running for "MO exception data" and even if timer T3502 or timer T3511 is running; and

l) shall not initiate the de-registration signalling procedure unless the current TAI is part of the TAI list.

The UE in non-3GPP access:

a) shall not send any user data;

b) shall initiate the registration procedure for mobility and periodic registration update on the expiry of timers T3502, T3511 or T3346;

c) may initiate a registration procedure for mobility registration update upon request of the upper layers to establish an emergency PDU session;

c1) may initiate a registration procedure for mobility and periodic registration update upon request of the upper layers to establish a PDU session, if the UE is a UE configured for high priority access in selected PLMN;

d) may perform de-registration locally and initiate a registration procedure for initial registration for emergency services even if timer T3346 is running;

e) may initiate a registration procedure for mobility and periodic registration update upon request for an MMTEL voice call, MMTEL video call, or an MO IMS registration related signalling from the upper layers, if timer T3346 is not running;

f) shall initiate a registration procedure for mobility and periodic registration update if the 5GS update status is set to 5U2 NOT UPDATED, and timers T3511, T3502 and T3346 are not running; and

g) shall not initiate the de-registration signalling procedure unless timer T3346 is running.

5.2.3.2.4 LIMITED-SERVICE

The UE:

a) shall perform cell selection/reselection;

b) may perform de-registration locally and initiate an initial registration for emergency services; and

c) if configured for eCall only mode as specified in 3GPP TS 31.102 [22], shall perform the eCall inactivity procedure at expiry of timer T3444 or timer T3445 (see subclause 5.5.3).

5.2.3.2.5 PLMN-SEARCH

The UE shall perform PLMN selection or SNPN selection. If a new PLMN is selected, the UE shall reset the registration attempt counter and initiate a registration procedure for mobility and periodic registration update (see subclause 5.5.1.3). If a new SNPN is selected, the UE shall reset the registration attempt counter, may perform de-registration locally and shall initiate a registration procedure for initial registration (see subclause 5.5.1.2.2).

If the selected cell in the new PLMN is known not to be able to provide normal service, the UE may perform de-registration locally and initiate an initial registration for emergency services.

5.2.3.2.6 NO-CELL-AVAILABLE

The UE shall perform cell selection and choose an appropriate substate when a cell is found.

5.2.3.2.7 UPDATE-NEEDED

The UE:

a) shall not send any user data;

b) shall not send signalling information, unless it is a service request as a response to paging or to initiate signalling for emergency services or emergency services fallback;

c) shall perform cell selection/reselection;

d) shall enter the appropriate new substate as soon as the lower layers indicate that the barring is alleviated for the access category with which the access attempt for the registration procedure for mobility and periodic registration update was associated; and

e) if configured for eCall only mode as specified in 3GPP TS 31.102 [22], shall perform the eCall inactivity procedure at expiry of timer T3444 or T3445 (see subclause 5.5.3).