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full Contents for  TS 23.502  Word version:   16.4.0

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1…   4.2.2.2.2   4.2.2.2.3…   4.2.3…   4.2.3.3   4.2.4…   4.2.6   4.2.7…   4.2.9…   4.3…   4.3.2.2…   4.3.2.2.2   4.3.2.2.3…   4.3.3   4.3.4   4.3.5…   4.3.5.2…   4.3.5.4…   4.3.5.6…   4.3.6…   4.4…   4.5…   4.9…   4.9.1.3…   4.9.2…   4.11…   4.11.1.2.2…   4.11.1.3…   4.11.1.4…   4.11.1.5…   4.11.2   4.11.3…   4.12…   4.12.6…   4.12a   4.12b   4.13…   4.13.4…   4.13.6…   4.14…   4.15…   4.15.4…   4.16…   4.16.4…   4.16.8…   4.17…   4.17.9…   4.18…   4.19…   4.23…   4.23.7…   4.23.9…   4.23.11…   4.24   4.25   4.26…   5…   5.2.3…   5.2.5…   5.2.6…   5.2.7…   5.2.8…   5.2.9…   5.2.12…   A…   E…   F…

 

4.5  User Profile management proceduresWord-p. 154
4.5.1  Subscriber Data Update Notification to AMF
Whenever the user profile is changed for a user in the UDM/UDR, and the changes affect the user profile in the AMF, the UDM shall notify these changes to the affected AMF by the means of invoking Nudm_SDM_Notification service operation. Then the AMF adds or modifies the user profile.
The Nudm_SDM_Notification service operation specified in clause 5.2.3.3 is used by the UDM to update subscriber data stored in the AMF.
The AMF takes appropriate action according to the changed subscriber data as follows, e.g.:
  • initiating an AMF initiated Deregistration procedure if the updated subscription data indicates the UE is not allowed to roam in this network; and
  • updating UE context stored at AN to modify the subscribed UE-AMBR.
  • initiating UE Configuration Update procedure as defined in clause 4.2.4.2.
  • initiating UE Parameters Update via UDM Control Plane Procedure as defined in clause 4.20.
UDM can also use the Nudm_SDM_Notification service operation to update the Steering of Roaming information stored in the UE via the AMF (i.e. a list of preferred PLMN/access technology combinations or HPLMN indication that 'no change of the "Operator Controlled PLMN Selector with Access Technology" list stored in the UE is needed). UDM can include an indication for the UE to send an acknowledgement of the reception of this information. The AMF provides the acknowledgement sent from the UE to UDM using the Nudm_SDM_Info service operation. For more details regarding the handling of Steering of Roaming information refer to TS 23.122.
When the subscribed S-NSSAIs change, UDM provides a Network Slicing Subscription Change Indication to the UE via the AMF. Once the AMF updates the UE and obtains an acknowledgment from the UE, the AMF informs the UDM that the UE received the Network Slicing Subscription Change Indication using the Nudm_SDM_Info service operation.
When the CAG information in the subscription data changes, or when the SUPI and PEI association changes, UDM provides a CAG information Subscription Change Indication to the AMF. Once the AMF updates the UE and obtains an acknowledgment from the UE, the AMF informs the UDM that the UE received the CAG information using the Nudm_SDM_Info service operation.
If the AMF received a changed Service Gap Time parameter in the updated subscription data, and if the UE has indicated Service Gap Control capability the AMF shall provide the new Service Gap Time value to the UE in the next Registration Accept message, or, if the UE does not send any Registration Request within a certain time period that shall be longer than any MICO mode or eDRX interval used by the UE, the AMF may initiate a UE Configuration Update procedure.
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4.5.2  Session Management Subscriber Data Update Notification to SMFWord-p. 155
Whenever the session management subscriber data is changed for a user in the UDM/UDR, and if the SMF subscribed for the update of the session management subscriber data to be notified, the UDM shall notify these changes to the affected SMF by the means of invoking Nudm_SDM_Notification service operation. Then the SMF modifies the session management subscriber data in the UE SM context.
The Nudm_SDM_Notification service operation specified in clause 5.2.3.3 is used by the UDM to update session management subscriber data stored in the SMF.
The SMF initiates appropriate action according to the changed subscriber data, e.g. including:
  • initiating an SMF initiated PDU Session Modification procedure; or
  • initiating an SMF initiated PDU Session Release procedure.
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4.5.3  Purge of subscriber data in AMF
An AMF may, as an implementation option, purge the subscriber data and MM context of a UE after the implicit or explicit Deregistration of the UE. In this case, the AMF shall unsubscribe and deregister from the UDM, where UDM may further do corresponding operation from UDR, by the means of following "Purge of subscriber data in AMF" procedure.
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Step 1.
After purging the subscriber data and MM context of a deregistered UE, the AMF unsubscribes to changes to subscription data using Nudm_SDM_Unsubscribe request operation (see clause 5.2.3.3.4), for the data the AMF has previously subscribed (see clause 4.2.2.2.2, step 14b). The UDM unsubscribes the AMF from the data indicated.
The UDM may unsubscribe to changes to subscription data from UDR by using Nudr_DM_Unsubscribe for the data the UDM has previously subscribed (see clause 4.2.2.2.2, step 14b).
Step 2.
The UDM sends a response back using Nudm_SDM_Unsubscribe response operation.
Step 3.
The AMF deregisters from UDM using Nudm_UECM_Deregistration request (SUPI, NF ID, Access Type) operation (see clause 5.2.3.2.3). The UDM may update UE context in UDR by Nudr_DM_Update (SUPI, Subscription Data, UE context in AMF data).
Step 4.
The UDM sets the UE Purged flag associated with the Access Type and acknowledges with a Nudm_UECM_Deregistration response operation.
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4.6  Security proceduresWord-p. 156
Security procedures for the 5GS are specified in 33.501 [15].
4.7  ME Identity check procedure
The AMF initiates Mobile Equipment Identity Check procedure by invoking the N5g-eir_MEIdentityCheck_Get service operation as defined in clause 5.2.4.2.2.
4.8  RAN-CN interactions
4.8.1  Connection Inactive and Suspend procedure
4.8.1.1  Connection Inactive procedure [R16]
This procedure may be initiated by the serving NG-RAN node when the UE is in CM-CONNECTED with RRC Connected state and has received the "RRC Inactive Assistance Information" from the AMF as defined in TS 23.501, clause 5.3.3.2.5. NG-RAN initiates the transition to RRC Inactive state as defined in TS 38.300.
4.8.1.2  Connection Suspend procedure [R16]
This procedure may be initiated by the serving NG-RAN node when the UE is in CM-CONNECTED and has at least one PDU session with active user plane connection, and NG-eNB has received indication from the AMF that User Plane CIoT 5GS Optimisation, as defined in TS 23.501, clause 5.31.18, is supported for the UE.
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Step 1.
NG-RAN to AMF: The NG-RAN sends the N2 Suspend Request message to the AMF, see TS 38.413. The AMF enters CM-IDLE with Suspend indicator. Context information related to the NGAP UE association, UE Context and PDU session context, necessary to resume the connection is stored in the UE, NG-RAN node and in the AMF. The NG-RAN may include the Suspend cause, and the N2 SM information.
The NG-RAN may include the Information On Recommended Cells And NG-RAN For Paging in the N2 Suspend Request message. If available, the AMF shall store this information to be used when paging the UE.
The NG-RAN includes Information for Enhanced Coverage, if available, in the N2 Suspend Request message.
If Service Gap Control is being applied to the UE (see clause 4.3.17.9) and the Service Gap timer is not already running, the Service Gap timer shall be started in the AMF when entering CM-IDLE, unless the connection was initiated after a paging of an MT event, or after a mobility registration procedure without Follow-on Request indication.
Step 2.
AMF to SMF: For each of the PDU Sessions in the N2 Suspend Request, the AMF invokes Nsmf_PDUSession_UpdateSMContext Request (PDU Session ID, Cause, Operation type, User Location Information, Age of Location Information, N2 SM Information (Secondary RAT usage data)). The Operation Type is set to "UP Suspend" to indicate suspend of user plane resources for the PDU Session.
Step 3.
SMF to UPF: N4 Session Modification Request (AN Tunnel Info to be suspended, Buffering on/off).
The SMF initiates an N4 Session Modification procedure indicating the need to release the tunnel info of AN terminating N3 between AN and UPF. Buffering on/off indicates whether the UPF shall buffer incoming DL PDU or not.
The UPF sends N4 Session Modification Response to acknowledge the SMF request.
The SMF shall maintain the N3 tunnel info (including both AN Tunnel Info and the CN Tunnel Info).
NOTE:
The UPF maintains the CN tunnel info as it may receive uplink packets from the AN.
Step 4.
SMF to AMF: The SMF sends Nsmf_PDUSession_UpdateSMContext response to the AMF.
Step 5.
AMF to NG-RAN: After response for each PDU session in step 4, the AMF sends N2 Suspend Response to NG-RAN to successfully terminate the Connection Suspend procedure initiated by the NG-RAN, see TS 38.413.
Step 6.
The NG-RAN sends RRC message to suspend the RRC Connection towards the UE including UE Resume ID, see TS 36.300).
If Service Gap Control is applied for the UE (see TS 23.501, clause 5.31.16) and the Service Gap timer is not already running, the Service Gap timer shall be started in the UE when entering CM-IDLE, unless the connection was initiated as a response to paging of an MT event, or after a mobility registration procedure without Follow-on Request Indication set.
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4.8.2  Connection Resume procedureWord-p. 157
4.8.2.1  General [R16]
The Connection Resume procedure is used by a UE to request the establishment of a secure connection between a UE and the network when the UE is in CM-CONNECTED with RRC Inactive state, or in CM-IDLE with Suspend indicator for the UE supporting User Plane CIoT 5GS Optimisation. The UE initiates the procedure when upper layers or the AS (when responding to RAN paging or upon triggering RNA updates) requests the resumption of a suspended RRC connection. NG-RAN details are specified in TS 38.300 and TS 38.331 for NR, and in TS 36.300 and TS 36.331 for E-UTRA.
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4.8.2.2  Connection Resume in RRC Inactive procedure [R16]
The Connection Resume procedure is used by the UE to perform RRC Inactive to RRC Connected state transition. Triggers for the UE to initiate this procedure are defined in TS 23.501, clause 5.3.3.2.5.
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Step 1.
UE to NG-RAN: RRC message (Resume ID).
The UE initiates the transition from RRC Inactive state to RRC Connected state, see TS 38.300. The UE provides its Resume ID needed by the NG-RAN to access the UE's stored Context.
Step 2.
[Conditional] NG-RAN performs UE Context Retrieval.
UE Context Retrieval is performed when the UE Context associated with the UE attempting to resume its connection is not locally available at the accessed NG-RAN. The UE Context Retrieval procedure via radio access network is specified in TS 38.300.
Step 3.
[Conditional] N2 Path switch procedure.
If the accessed NG-RAN is able to retrieve the UE Context, the accessed NG-RAN node initiates N2 Path Switch procedure, i.e. steps 1 to 8 of clause 4.9.1.2.2 and including Xn data forwarding.
If the Connection Resume procedure is a response to RAN paging which is triggered by 5GC due to an N2 interface procedure, NG-RAN and 5GC handle the N2 interface procedure as a collision described in clause 4.9.1.2.
The NG-RAN sends UE Notification message to report that UE is in RRC Connected if an AMF requested N2 Notification (see clause 4.8.3) to NG-RAN.
Step 4.
NG-RAN to UE: RRC message.
The NG-RAN confirms to the UE that the UE has entered RRC Connected state.
NOTE:
Steps 3 and 4 can be executed in parallel.
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4.8.2.3  Connection Resume in CM-IDLE with Suspend procedure [R16]Word-p. 158
For the UE supporting User Plane CIoT 5GS Optimisation, the Connection Resume procedure is used by the UE to perform RRC_IDLE with Suspend to RRC_CONNECTED state transition. Triggers for the UE to initiate this procedure are defined in TS 23.501, clause 5.31.18.
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Step 1.
UE to NG-RAN: RRC message (Resume ID).
The UE initiates the transition from CM-IDLE and RRC IDLE state with Suspend to CM-CONNECTED and RRC Connected state, see TS 36.300. The UE provides its Resume ID needed by the NG-RAN to access the UE's stored Context.
Step 2.
[Conditional] NG-RAN performs UE Context Retrieval.
UE Context Retrieval may be performed when the UE Context associated with the UE attempting to resume its connection is not locally available at the accessed NG-RAN. The UE Context Retrieval procedure via radio access network is specified in TS 38.300.
Step 3.
NG-RAN and UE continues the resume procedure and access stratum configuration synchronization is performed between the UE and the network. UE enters CM-CONNECTED and RRC_CONNECTED.
Step 4.
NG-RAN to AMF:
  1. If the NG-RAN is the same as the NG-RAN when UE is suspended, the NG-RAN sends N2 Resume Request to AMF including Resume cause, and N2 SM information which indicates the PDU sessions successfully resumed, and PDU sessions failed or partially failed to resume the user plane resource.
  2. If the NG-RAN is different from the NG-RAN when UE is suspended, and the new NG-RAN is able to retrieve the UE Context from the old NG-RAN, the new NG-RAN node initiates N2 Path Switch Request towards AMF, i.e. Steps 1b of clause 4.9.1.2.2.
Step 5.
AMF to SMF: For each of the PDU Sessions indicated in step 4, the AMF invokes Nsmf_PDUSession_UpdateSMContext Request (PDU Session ID, Cause, Operation type, User Location Information, Age of Location Information, N2 SM Information). The Operation Type is set to "UP Resume" to indicate resume of user plane resources for the PDU Session.
For PDU Session(s) to be switched to the new NG-RAN, upon receipt of the Nsmf_PDUSession_UpdateSMContext request, the SMF determines whether the existing UPF can continue to serve the UE. If the existing UPF cannot continue to serve the UE, steps 3 to 7 of clause 4.9.1.2.3 or clause 4.9.1.2.4 are performed depending on whether the existing UPF is a PDU Session Anchor and flow continues in step 7. Otherwise, step 6 is performed if the existing UPF can continue to serve the PDU Session.
If the RRC connection is resumed and the UE is accessing via the NB-IoT RAT with the RRC resume cause set to "MO exception data" or the RRC resume cause is set to non "MO exception data" for the first time after the previous "MO exception data", the AMF updates all (H-)SMFs which have PDU Sessions using Small Data Rate Control. If AMF indicates "MO exception data" then it includes the MO Exception Data Counter. The AMF maintains the MO Exception Data Counter for Small Data Rate Control purposes as described in clause 5.31.14.3 of TS 23.501. Each (H-)SMF should be updated for every RRC Connection which is triggered for "MO exception data" and for the first new RRC Connection afterwards without "MO exception data".
In the home-routed roaming case, if Small Data Rate Control applies, the V-SMF waits for H-SMF response before proceeding with the N3 establishment.
Step 6.
SMF to UPF: N4 Session Modification Request (AN Tunnel Info to be resumed, Buffering on/off).
The SMF initiates an N4 Session Modification procedure indicating the resume of AN tunnel. Buffering on/off indicates whether the UPF shall buffer incoming DL PDU or not.
If the first new "MO exception data" indication was received from the AMF in step 5 or if the first non "MO exception data" indication is received after the previous "MO exception data" indication, then the (H-)SMF, using N4 Session Modification Request, updates all UPFs and NEFs which have PDU Session(s) using Small Data Rate Control as to whether an RRC Connection was established for "MO exception data" for Small Data Rate Control purposes or not. Each UPF should be updated for the first new RRC Connection which is triggered for "MO exception data" and the first new RRC Connection afterwards without "MO exception data". If "MO exception data" is indicated in N4 Session Modification Request, the UPF shall consider all subsequent MO and MT data as "Exception Data".
NOTE:
The AMF Updates the SMFs for every "MO exception data" access so that the SMF gets the latest MO Exception Data Counter value, but the SMF only needs to update the UPFs and NEFs when changing from "MO exception data" to non "MO exception data" or vice versa.
If step 4a) is performed, the AN tunnel info is the one maintained by the SMF during Connection Suspend procedure, step 3 of clause 4.8.1.2. If step 4b) is performed, the AN tunnel info is part of the N2 SM information received by SMF in step 5.
The UPF sends N4 Session Modification Response to acknowledge the SMF request.
Step 7.
SMF to AMF: The SMF sends Nsmf_PDUSession_UpdateSMContext response to the AMF.
If new CN tunnel information is allocated for the PDU session, i.e. in the case of new AN tunnel is received in step 6, the SMF includes the new CN tunnel information as part of the N2 SM information.
If the resume for PDU session is unsuccessful, the SMF shall include the resume failure as part of the N2 SM information.
Step 8.
AMF to NG-RAN: After response for each PDU session in step 7, the AMF sends N2 Resume Response to NG-RAN and indicates success, including N2 SM information for PDU session received in step 7, if at least one PDU session is resumed successfully. If none of the PDU sessions is resumed successfully, AMF indicates failure to NG-RAN.
The AMF sends N2 Path Switch Acknowledge with PDU session resume information, if Path Switch Request is received in step 4.
The AMF may provide Extended Connected Time value to the NG-RAN. If the NG-RAN receives the Extended Connected Time value, the NG-RAN may take this information into account when determining user inactivity.
Step 9.
[Conditional] NG-RAN to UE: RRC message.
The NG-RAN may reconfigure the RRC connection based on resume result received from AMF.
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4.8.2.4  Connection Resume in CM-IDLE with Suspend and MO EDT procedure [R16]Word-p. 160
The Connection Resume with Early Data Transmission procedure is used by the UE to optimise sending user data in a single uplink packet and single uplink followed by single downlink packet cases for a UE in CM-IDLE with Suspend.
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Step 1.
UE to NG-eNB: RRC message (Resume ID, AS RAI) with UL EDT.
The UE initiates the transition from RRC IDLE with Suspend state to RRC Connected state, see TS 36.300.
The UE may include AS Release Assistance information indicating:
  • No further Uplink and Downlink Data transmission, or
  • Only a single Downlink Data transmission subsequent to the Uplink transmission.
Step 2.
The NG-eNB deciphers the EDT UL data received from the UE and forwards it to the UPF using the N3 UL TEID in the AS context.
Step 3.
The NG-eNB sends N2 Resume Request to AMF including Resume cause and N2 SM.
If the UE included AS Release Assistance information indicating No further Uplink and Downlink Data transmission in step 1, NG-eNB may request for immediate transition to RRC IDLE with Suspend.
Step 4.
[Conditional] The AMF interacts with SMF to establish the N3 tunnel, except for the case:
  • The AMF receives a request for immediate transition to RRC IDLE with Suspend in step 3; and
  • the AMF is not aware of any downlink data or signalling pending.
Step 5.
The AMF sends an N2 Resume Response to NG-eNB.
If the AMF received a request for immediate transition to RRC IDLE with Suspend in step 3 and there is no downlink data or signalling pending, the AMF includes a Suspend indication, keeps the UE in CM-IDLE with Suspend and restarts the Periodic Registration Timer unless the Strictly Periodic Registration Timer Indication has been provided to the UE during the previous registration procedure.
Otherwise the AMF sends an N2 Resume Response to NG-eNB after the N3 Connectivity has been established, and moves the UE to CM-CONNECTED. If the AMF knows of mobile terminating data or signalling pending, the AMF may include the Extended Connected Time value to the RAN
Step 6.
[Conditional] RRC procedure:
Step 6a.
If the AMF included the Suspend indication, the NG-eNB releases the RRC Connection with Suspend. The procedure is complete and following steps are skipped.
Step 6b.
If the AMF did not include the Suspend indication, and:
  • The UE did not include AS Release Assistance Indication; or
  • The AMF included the Extended Connected Time value.
the NG-eNB sends an RRC Resume message to the UE and the UE moves to CM-CONNECTED and RRC Connected. The procedure is complete, and the following steps are skipped.
Step 6c.
Otherwise, if the AMF did not include Extended Connected Time value, and the UE included AS Release Assistance information with only a single Downlink Data transmission subsequent to the Uplink transmission, the NG-eNB waits for the DL data to arrive, and proceeds to steps 7-10.
Step 7-9.
The NG-eNB releases the N3 connectivity by sending an N2 Suspend Request to AMF including Suspend cause and N2 SM. Steps 2-4 of Connection Suspend procedure in clause 4.8.1.2 is executed.
Step 10.
[Conditional] NG-eNB to UE: RRC message (with DL data).
The NG-eNB ciphers received DL data.
The NG-eNB releases the RRC Connection with Suspend including the DL EDT data.
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4.8.3  N2 Notification procedureWord-p. 162
This procedure is used by an AMF to request the NG-RAN to report RRC state information, when the target UE is in CM-CONNECTED state. When AMF has requested reporting of subsequent state changes, the need for the NG-RAN to continue reporting ceases when the UE transitions to CM-IDLE or the AMF sends a cancel indication. This procedure may be used for services that require RRC state information (e.g. 5GC MT control and paging assistance, O&M and collection of statistics), or for subscription to the service by other NFs. See TS 38.413 for details of the procedure.
Reporting of RRC state transitions can be requested per UE by AMF. Continuous reporting of all RRC state transitions can be enabled by operator local configuration.
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Step 1.
The AMF sends a UE State Transition Notification Request to the NG-RAN as described in TS 38.413. The UE State Transition Notification Request message shall identify the UE for which notification(s) are requested, and may contain a reporting type. The reporting type either indicates subsequent state transitions shall be notified at every RRC state transition (i.e. from RRC Connected state to RRC Inactive state, or from RRC Inactive to RRC Connected state), or it indicates Single RRC-Connected state notification.
Step 2.
The NG-RAN sends the UE Notification message to report the current RRC state for the UE (i.e. RRC Inactive state or RRC Connected state). The current UE location information (i.e. TAI + Cell Identity) is always included when RRC state information is reported.
2b. When the AMF has requested reporting about subsequent state transitions, the NG-RAN sends subsequent UE Notification messages to the AMF at every RRC state transition until the UE transitions to CM-IDLE or NG-RAN receives a Cancel UE State Notification message from the AMF.
When the AMF has requested reporting for Single RRC-Connected state notification and UE is in RRC-Connected state, the NG-RAN sends one UE Notification message but no subsequent messages. If UE is in RRC-Inactive state, the NG-RAN sends one UE Notification message plus one subsequent UE Notification message when RRC state transits to RRC-Connected.
Step 3.
The AMF can send a Cancel UE State Notification message to inform the NG-RAN that it should terminate notifications for a given UE. This message should only be used when notification(s) about subsequent state transitions was requested at every RRC state transition.
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