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Content for  TS 24.501  Word version:  17.5.0

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5  Elementary procedures for 5GS mobility managementWord‑p. 121

5.1  OverviewWord‑p. 121

5.1.1  GeneralWord‑p. 121

The main function of the 5GS mobility management (5GMM) sublayer is to support the identification, security, mobility of a UE as well as generic message transport.
A further function of the 5GMM sublayer is to provide connection management services to the other sublayer(s).

5.1.2  Types of 5GMM proceduresWord‑p. 121

Depending on how they can be initiated, three types of 5GMM procedures can be distinguished:
  1. 5GMM common procedures:
    5GMM common procedure can always be initiated when the UE is in 5GMM-CONNECTED mode. The procedures belonging to this type are:
    1. Initiated by the network:
      1. network-initiated NAS transport;
      2. primary authentication and key agreement;
      3. security mode control;
      4. generic UE configuration update;
      5. identification; and
      6. network slice-specific authentication and authorization;
    2. Initiated by the UE:
      UE-initiated NAS transport.
    3. Initiated by the UE or the network and used to report certain error conditions detected upon receipt of 5GMM protocol data:
      5GMM status.
  2. 5GMM specific procedures:
    At any time only one UE initiated 5GMM specific procedure can be running for each of the access network(s) that the UE is camping in. The procedures belonging to this type are:
    1. Initiated by the UE and used e.g. to register to the network for 5GS services and establish a 5GMM context, to update the location/parameter(s) of the UE:
      registration.
    2. Initiated by the UE or the network and used to deregister from the network for 5GS services and to release a 5GMM context:
      de-registration.
    3. Initiated by the UE and used to deregister from the network for 5GS services and to release a 5GMM context:
      eCall inactivity procedure.
  3. 5GMM connection management procedures:
    1. Initiated by the UE and used to establish a secure connection to the network or to request the resource reservation for sending data, or both:
      service request.
      The service request procedure can only be initiated if no UE initiated 5GMM specific procedure is ongoing for each of the access network(s) that the UE is camping in.
    2. Initiated by the network and used to request the establishment of an N1 NAS signalling connection or to request re-establishment of user-plane resources for the PDU session(s) associated with 3GPP access or to request re-establishment of user-plane resources of the PDU session(s) associated with non-3GPP access over 3GPP access; not applicable for the non-3GPP access network:
      paging.
    3. Initiated by the network and used to request re-establishment of user-plane resources of the PDU session(s) associated with non-3GPP access over 3GPP access or to deliver 5GSM downlink signalling messages associated with non-3GPP access over 3GPP access, when the UE is in 5GMM-CONNECTED mode over 3GPP access and in 5GMM-IDLE mode over non-3GPP access; or
      Initiated by the network and used to request re-establishment of user-plane resources of the PDU session(s) associated with 3GPP access over 3GPP access or to deliver downlink signalling associated with 3GPP access over 3GPP access, when the UE is in 5GMM-CONNECTED mode over non-3GPP access, and when the UE is in 5GMM-IDLE mode over 3GPP access and not in MICO mode:
      notification.
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5.1.3  5GMM sublayer statesWord‑p. 122

5.1.3.1  GeneralWord‑p. 122

In the following subclauses, the 5GS mobility management (5GMM) sublayer of the UE and the network is described by means of different state machines. The 5GMM sublayer states is managed per access type independently, i.e. 3GPP access or non-3GPP access. In subclause 5.1.3.2, the states of the 5GMM sublayer are introduced.

5.1.3.2  5GMM sublayer statesWord‑p. 122

5.1.3.2.1  5GMM sublayer states in the UEWord‑p. 122
5.1.3.2.1.1  GeneralWord‑p. 122
In the following subclauses, the possible 5GMM sublayer states of the UE are described and shown in Figure 5.1.3.2.1.1.1.
Reproduction of 3GPP TS 24.501, Fig. 5.1.3.2.1.1.1: 5GMM main states in the UE
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5.1.3.2.1.2  Main statesWord‑p. 123
5.1.3.2.1.2.1  5GMM-NULLWord‑p. 123
5GS services are disabled in the UE. No 5GS mobility management function shall be performed in this state.
5.1.3.2.1.2.2  5GMM-DEREGISTEREDWord‑p. 123
In the state 5GMM-DEREGISTERED, no 5GMM context has been established and the UE location is unknown to the network and hence it is unreachable by a network. In order to establish a 5GMM context, the UE shall start the initial registration procedure.
5.1.3.2.1.2.3  5GMM-REGISTERED-INITIATEDWord‑p. 123
A UE enters the state 5GMM-REGISTERED-INITIATED after it has started the initial registration procedure or the non-initial registration procedure, and is waiting for a response from the network.
5.1.3.2.1.2.4  5GMM-REGISTEREDWord‑p. 123
In the state 5GMM-REGISTERED, a 5GMM context has been established. Additionally, one or more PDU session(s) may be established at the UE. The UE may initiate the non-initial registration procedure (including the normal registration update and periodic registration update) and the service request procedure. The UE in the state 5GMM-REGISTERED over non-3GPP access shall not initiate the periodic registration update procedure.
5.1.3.2.1.2.5  5GMM-DEREGISTERED-INITIATEDWord‑p. 123
A UE enters the state 5GMM-DEREGISTERED-INITIATED after it has requested release of the 5GMM context by starting the de-registration procedure and is waiting for a response from the network.
5.1.3.2.1.2.6  5GMM-SERVICE-REQUEST-INITIATEDWord‑p. 123
A UE enters the state 5GMM-SERVICE-REQUEST-INITIATED after it has started the service request procedure and is waiting for a response from the network.
5.1.3.2.1.3  Substates of state 5GMM-DEREGISTEREDWord‑p. 124
5.1.3.2.1.3.1  GeneralWord‑p. 124
The state 5GMM-DEREGISTERED is subdivided into a number of substates as described in this subclause. The following substates are not applicable to non-3GPP access:
  1. 5GMM-DEREGISTERED.PLMN-SEARCH:
  2. 5GMM-DEREGISTERED.NO-CELL-AVAILABLE; and
  3. 5GMM-DEREGISTERED.eCALL-INACTIVE.
Valid subscriber data are available for the UE before it enters the substates, except for the substate 5GMM-DEREGISTERED.NO-SUPI.
5.1.3.2.1.3.2  5GMM-DEREGISTERED.NORMAL-SERVICEWord‑p. 124
The substate 5GMM-DEREGISTERED.NORMAL-SERVICE is chosen in the UE when a suitable cell has been found and the PLMN, SNPN, or tracking area is not in the forbidden list.
5.1.3.2.1.3.3  5GMM-DEREGISTERED.LIMITED-SERVICEWord‑p. 124
The substate 5GMM-DEREGISTERED.LIMITED-SERVICE is chosen in the UE, when it is known that a selected cell for 3GPP access or TA for non-3GPP access is unable to provide normal service (e.g. the selected cell over 3GPP access is in a forbidden PLMN or SNPN or is in a forbidden tracking area or TA for non-3GPP access is forbidden) or the selected cell is a CAG cell whose CAG ID is not included in the "Allowed CAG list" in the entry of the "CAG information list" for the PLMN, or the selected cell is a non-CAG cell in a PLMN for which there exists an "indication that the UE is only allowed to access 5GS via CAG cells" in the entry of the "CAG information list" for the PLMN.
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5.1.3.2.1.3.4  5GMM-DEREGISTERED.ATTEMPTING-REGISTRATIONWord‑p. 124
The substate 5GMM-DEREGISTERED.ATTEMPTING-REGISTRATION is chosen in the UE if the initial registration procedure failed due to a missing response from the network or due to the circumstances described in subclauses 5.5.1.2.4, 5.5.1.2.5, 5.5.1.2.7 and 5.5.1.3.4.
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5.1.3.2.1.3.5  5GMM-DEREGISTERED.PLMN-SEARCHWord‑p. 124
The substate 5GMM-DEREGISTERED.PLMN-SEARCH is chosen in the UE, if the UE is searching for PLMNs or SNPNs. This substate is left either when a cell has been selected (the new substate is NORMAL-SERVICE or LIMITED-SERVICE) or when it has been concluded that no cell is available at the moment (the new substate is NO-CELL-AVAILABLE).
This substate is not applicable to non-3GPP access.
5.1.3.2.1.3.6  5GMM-DEREGISTERED.NO-SUPIWord‑p. 124
The substate 5GMM-DEREGISTERED.NO-SUPI is chosen in the UE, if the N1 mode is enabled and the UE has no valid subscriber data available (USIM not available, the USIM is considered invalid by the UE or an entry of the "list of subscriber data" with the SNPN identity of the SNPN is considered invalid by the UE).
5.1.3.2.1.3.7  5GMM-DEREGISTERED.NO-CELL-AVAILABLEWord‑p. 124
No 5G cell can be selected. This substate is entered after a first intensive search failed when in substate 5GMM-DEREGISTERED.PLMN-SEARCH. Cells are searched for at a low rhythm. No 5GS services are offered.
This substate is not applicable to non-3GPP access.
5.1.3.2.1.3.8  5GMM-DEREGISTERED.eCALL-INACTIVEWord‑p. 124
The substate 5GMM-DEREGISTERED.eCALL-INACTIVE is chosen in the UE when:
  1. the UE is configured for eCall only mode as specified in TS 31.102;
  2. timer T3444 and timer T3445 have expired or are not running;
  3. a PLMN has been selected as specified in TS 23.122;
  4. the UE does not need to perform an eCall over IMS; and
  5. the UE does not need to perform a call to a non-emergency MSISDN or URI for test or terminal reconfiguration service.
In this substate, the UE shall not initiate any signalling towards the network, except to originate an eCall over IMS, or a call to a non-emergency MSISDN or URI for test or terminal reconfiguration service.
This substate is not applicable to non-3GPP access.
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5.1.3.2.1.3.9  5GMM-DEREGISTERED.INITIAL-REGISTRATION-NEEDEDWord‑p. 125
Valid subscriber data are available for the UE and for some reason a registration procedure for initial registration has to be performed as soon as possible. This substate can be entered if the access is barred due to unified access control, (see subclause 4.5.4) or if the network rejects the N1 NAS signalling connection establishment.
5.1.3.2.1.4  Substates of state 5GMM-REGISTEREDWord‑p. 125
5.1.3.2.1.4.1  GeneralWord‑p. 125
The state 5GMM-REGISTERED is subdivided into a number of substates as described in this subclause. The following substates are not applicable to non-3GPP access:
  1. 5GMM-REGISTERED.PLMN-SEARCH:
  2. 5GMM-REGISTERED.NON-ALLOWED-SERVICE; and
  3. 5GMM-REGISTERED.NO-CELL-AVAILABLE.
5.1.3.2.1.4.2  5GMM-REGISTERED.NORMAL-SERVICEWord‑p. 125
The substate 5GMM-REGISTERED.NORMAL-SERVICE is chosen by the UE as the primary substate when the UE enters the state 5GMM-REGISTERED, and:
  • for 3GPP access, the cell the UE selected is known to be in an allowed area (see subclause 5.3.5.2); or
  • for wireline access, the wireline access service area restrictions are not enforced.
5.1.3.2.1.4.3  5GMM-REGISTERED.NON-ALLOWED-SERVICEWord‑p. 125
The substate 5GMM-REGISTERED.NON-ALLOWED-SERVICE is chosen in the UE, if:
  • for 3GPP access, the cell the UE selected is known to be in a non-allowed area (see subclause 5.3.5.2); or
  • for wireline access, the wireline access service area restrictions are enforced.
This substate is applicable only to 3GPP access and to wireline access.
5.1.3.2.1.4.4  5GMM-REGISTERED.ATTEMPTING-REGISTRATION-UPDATEWord‑p. 125
The substate 5GMM-REGISTERED.ATTEMPTING-REGISTRATION-UPDATE is chosen by the UE if the registration procedure for mobility and periodic registration update failed due to a missing response from the network, or due to the circumstances described in subclauses 5.3.9, 5.5.1.3.5 and 5.5.1.3.7. No 5GMM procedure except registration procedure for mobility and periodic registration update (i.e. the 5GS registration type IE set to "mobility registration updating" or "periodic registration updating" in the REGISTRATION REQUEST message) shall be initiated by the UE in this substate. No data shall be sent or received.
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5.1.3.2.1.4.5  5GMM-REGISTERED.LIMITED-SERVICEWord‑p. 126
The substate 5GMM-REGISTERED.LIMITED-SERVICE is chosen in the UE, if the cell the UE selected is known not to be able to provide normal service.
5.1.3.2.1.4.6  5GMM-REGISTERED.PLMN-SEARCHWord‑p. 126
The substate 5GMM-REGISTERED.PLMN-SEARCH is chosen in the UE, while the UE is searching for PLMNs or SNPNs.
This substate is not applicable to non-3GPP access.
5.1.3.2.1.4.7  5GMM-REGISTERED.NO-CELL-AVAILABLEWord‑p. 126
5G coverage has been lost or MICO mode is active in the UE. If MICO mode is active, the UE can deactivate MICO mode at any time by activating the AS layer when the UE needs to send mobile originated signalling or user data. Otherwise, the UE shall not initiate any 5GMM procedure except for cell and PLMN reselection.
This substate is not applicable to non-3GPP access.
5.1.3.2.1.4.8  5GMM-REGISTERED.UPDATE-NEEDEDWord‑p. 126
This state can be entered if the UE has to perform a registration procedure for mobility and periodic registration update but:
  1. the access is barred due to unified access control when in 3GPP access;
  2. the network rejects the N1 NAS signalling connection establishment when in 3GPP access or in non-3GPP access; or
  3. the UE in 5GMM-CONNECTED mode with RRC inactive indication receives an indication from the lower layers that the resumption of the RRC connection has failed and for access is barred for all categories except categories '0' and '2' as specified in subclause 5.3.1.4.
No 5GMM procedure except:
  1. registration procedure for mobility and periodic registration update; and
  2. service request procedure as a response to paging or notification
shall be initiated by the UE in this substate.
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5.1.3.2.2  5GS update status in the UEWord‑p. 126
In order to describe the detailed UE behaviour, the 5GS update (5U) status pertaining to a specific subscriber is defined.
If the UE is not operating in SNPN access operation mode (see TS 23.501), the 5GS update status is stored in a non-volatile memory in the USIM if the corresponding file is present in the USIM, else in the non-volatile memory in the ME, as described in Annex C.
If the UE is operating in SNPN access operation mode, the 5GS update status for each SNPN whose SNPN identity is included in the "list of subscriber data" configured in the ME (see TS 23.122) is stored in the non-volatile memory in the ME as described in Annex C.
The 5GS update status value is changed only after the execution of a registration, network-initiated de-registration, 5GS based primary authentication and key agreement, service request, paging procedure or due to change in TAI which does not belong to the current registration area while T3346 is running.
5U1: UPDATED
The last registration attempt was successful.
5U2: NOT UPDATED
The last registration or service request attempt failed procedurally, e.g. no response or reject message was received from the AMF.
5U3: ROAMING NOT ALLOWED
The last registration, service request, or registration for mobility or periodic registration update attempt was correctly performed, but the answer from the AMF was negative (because of roaming or subscription restrictions).
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5.1.3.2.3  5GMM sublayer states in the network sideWord‑p. 127
5.1.3.2.3.1  GeneralWord‑p. 127
In the following subclauses, the possible 5GMM sublayer states of the network are described and shown in Figure 5.1.3.2.3.1.1.
Reproduction of 3GPP TS 24.501, Fig. 5.1.3.2.3.1.1: 5GMM main states in the network
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5.1.3.2.3.2  5GMM-DEREGISTEREDWord‑p. 127
In the state 5GMM-DEREGISTERED, no 5GMM context has been established or the 5GMM context is marked as deregistered. The UE is deregistered. The network may answer to an initial registration procedure initiated by the UE. The network may also answer to a de-registration procedure initiated by the UE.
5.1.3.2.3.3  5GMM-COMMON-PROCEDURE-INITIATEDWord‑p. 128
The network enters the state 5GMM-COMMON-PROCEDURE-INITIATED, after it has started a common 5GMM procedure and is waiting for a response from the UE.
5.1.3.2.3.4  5GMM-REGISTEREDWord‑p. 128
In the state 5GMM-REGISTERED, a 5GMM context has been established. Additionally, one or more PDU session(s) may be established at the network.
5.1.3.2.3.5  5GMM-DEREGISTERED-INITIATEDWord‑p. 128
The network enters the state 5GMM-DEREGISTERED-INITIATED after it has started a de-registration procedure and is waiting for a response from the UE.

5.1.4  Coordination between 5GMM and EMMWord‑p. 128

5.1.4.1  GeneralWord‑p. 128

If both 5GMM and EMM are enabled, a UE, operating in single-registration mode, shall maintain one common registration for 5GMM for 3GPP access and EMM.
Coordination between 5GMM for 3GPP access and EMM for a UE, which is capable of N1 mode and S1 mode and operates in dual-registration mode, is not needed, except as specified in subclause 4.8.3.
The coordination between 5GMM for 3GPP access and EMM in subclauses 5.1.4.2 and 5.1.4.3 only applies to the UEs operating in single-registration mode.
Regarding the coordination of "SIM/USIM considered invalid" and "USIM considered invalid for 5GS services" between the various mobility management entities see subclause 5.1.5.
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5.1.4.2  Coordination between 5GMM for 3GPP access and EMM with N26 interfaceWord‑p. 128

A UE that is not registered shall be in state EMM-DEREGISTERED and state 5GMM-DEREGISTERED for 3GPP access.
In N1 mode, upon successful completion of a registration procedure over 3GPP access, the UE operating in single-registration mode shall enter substates 5GMM-REGISTERED.NORMAL-SERVICE or 5GMM-REGISTERED.NON-ALLOWED-SERVICE as described in subclause 5.3.5.2 for 3GPP access and EMM-REGISTERED.NO-CELL-AVAILABLE. The UE shall reset the registration attempt counter for 3GPP access and the attach attempt counter (see TS 24.301).
At inter-system change from S1 mode to N1 mode, the UE shall enter substates 5GMM-REGISTERED.NORMAL-SERVICE or 5GMM-REGISTERED.NON-ALLOWED-SERVICE as described in subclause 5.3.5.2 for 3GPP accessand EMM-REGISTERED.NO-CELL-AVAILABLE and initiate a registration procedure for mobility and periodic registration update over 3GPP access indicating "mobility registration updating" in the 5GS registration type IE of the REGISTRATION REQUEST message (see subclause 5.5.1.3).
In S1 mode, upon successful completion of an attach or tracking area updating procedure, the UE operating in single-registration mode shall enter substates 5GMM-REGISTERED.NO-CELL-AVAILABLE for 3GPP access and EMM-REGISTERED.NORMAL-SERVICE. The UE shall reset the registration attempt counter for 3GPP access and the attach attempt counter (see TS 24.301).
At inter-system change from N1 mode to S1 mode when there is no active PDU session for which interworking with EPS is supported as specified in subclause 6.1.4.1, and EMM-REGISTERED without PDN connection is not supported by the UE or the MME, the UE shall enter state 5GMM-DEREGISTERED for 3GPP access and state EMM-DEREGISTERED and then initiate the EPS attach procedure. If EMM-REGISTERED without PDN connection is supported by the UE and the MME, the UE shall enter substates EMM-REGISTERED.NORMAL-SERVICE and 5GMM-REGISTERED.NO-CELL-AVAILABLE for 3GPP access and initiate a tracking area updating procedure.
At inter-system change from N1 mode to S1 mode when there is at least one active PDU session for which interworking with EPS is supported as specified in subclause 6.1.4.1, the UE shall enter substates EMM-REGISTERED.NORMAL-SERVICE and 5GMM-REGISTERED.NO-CELL-AVAILABLE for 3GPP access and initiate a tracking area updating procedure (see TS 24.301).
At inter-system change from N1 mode to S1 mode, if the UE has any PDU sessions associated with one or more MBS multicast sessions, the UE shall locally leave the associated MBS multicast sessions and the network shall consider the UE as removed from the associated MBS sessions.
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5.1.4.3  Coordination between 5GMM for 3GPP access and EMM without N26 interfaceWord‑p. 129

A UE operating in the single-registration mode that is not registered over 3GPP access shall be in state EMM-DEREGISTERED and in state 5GMM-DEREGISTERED for 3GPP access.
In N1 mode, upon successful completion of a registration procedure over 3GPP access, the UE operating in the single-registration mode shall enter substates 5GMM-REGISTERED.NORMAL-SERVICE or 5GMM-REGISTERED.NON-ALLOWED-SERVICE as described in subclause 5.3.5.2 for 3GPP access and EMM-REGISTERED.NO-CELL-AVAILABLE.
At inter-system change from N1 mode to S1 mode in 5GMM-IDLE mode, the UE shall behave as specified in subclause 4.8.2.3.
At inter-system change from N1 mode to S1 mode, if the UE has any PDU sessions associated with one or more MBS multicast sessions, the UE shall locally leave the associated MBS multicast sessions and the network shall consider the UE as removed from the associated MBS sessions.
In S1 mode, upon successful completion of an attach or tracking area updating procedure, the UE operating in the single-registration mode shall enter substates 5GMM-REGISTERED.NO-CELL-AVAILABLE for 3GPP access and EMM-REGISTERED.NORMAL-SERVICE.
At inter-system change from S1 mode to N1 mode in 5GMM-IDLE mode, the UE operating in the single-registration mode shall enter substates EMM-REGISTERED.NO-CELL-AVAILABLE and 5GMM- REGISTERED.NORMAL-SERVICE for 3GPP access and then initiate the registration procedure for mobility and periodic registration update over 3GPP access indicating "mobility registration updating" in the 5GS registration type IE of the REGISTRATION REQUEST message (see subclause 5.5.1.3).
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5.1.5  Coordination between 5GMM and GMM |R16|Word‑p. 129

Coordination between 5GMM and GMM states is not required.
Regardless whether the UE is operating in single-registration mode or dual-registration mode,
  1. if the UE considers the SIM/USIM invalid for any of: 3GPP access in N1 mode, S1 mode, A/Gb mode or Iu mode, then it considers the SIM/USIM invalid for all of them; and
  2. if the UE considers the USIM invalid for 5GS services for any of: 3GPP access in N1 mode, S1 mode, A/Gb mode or Iu mode, then it considers the USIM invalid for 5GS services for all of them.
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