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fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 4.4.6.1 User plane architecture to support 5G LAN-type service | The general User Plane architectures described in clause 4.2.3 and clause 4.2.4 apply to 5G LAN-type services, with the additional options described in this clause.
Figure 4.4.6.1-1 depicts the non-roaming user plane architecture to support 5G LAN-type service using local switch.
Figure 4.4.6.1-1: Local-switch based user plane architecture in non-roaming scenario
Figure 4.4.6.1-2 depicts the non-roaming user plane architecture to support 5G LAN-type service using N19 tunnel.
Figure 4.4.6.1-2: N19-based user plane architecture in non-roaming scenario
NOTE: As described in clause 5.29.3, the PSA UPFs can be controlled by a dedicated SMF, a dedicated SMF Set or multiple SMF Sets. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 4.4.6.2 Reference points to support 5G LAN-type service | N19: Reference point between two UPFs for direct routing of traffic between different PDU Sessions without using N6. It has a per 5G VN group granularity. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 4.4.7 MSISDN-less MO SMS Service | MSISDN-less MO SMS via T4 is subscription based. The subscription provides the information whether a UE is allowed to originate MSISDN-less MO SMS.
The UE is pre-configured with the Service Centre address that points to SMS-SC that performs this MO SMS delivery via NEF delivery procedure. The recipient of this short message is set to the pre-configured address of the AF (i.e. Address of the destination SME). If UE has multiple GPSIs associated to the same IMSI, the GPSI that is associated with an SMS may be determined from the UE's IMSI and the Application Port ID value in the TP-User-Data field (see TS 23.040 [5]). The NEF may obtain the GPSI by querying the UDM with the IMSI and application port ID.
UE is aware whether the MO SMS delivery status (success or fail) based on the SMS delivery report from SMS-SC. The network does not perform any storing and forwarding functionality for MO SMS.
See clause 5.2.6 of TS 23.502 [3] for a description of NEF Services and Service Operations. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 4.4.8 Architecture to enable Time Sensitive Communication, Time Synchronization and Deterministic Networking | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 4.4.8.1 General | The 5G System can be extended to support the following:
a) Integration of 5GS into a TSN data network (DN): Integration as a bridge in an IEEE 802.1 Time Sensitive Networking (TSN). The 5GS bridge supports the Time sensitive communication as defined in IEEE 802.1 Time Sensitive Networking (TSN) standards. The architecture is described in clause 4.4.8.2.
This Release supports of the specification, integration of the 5G System with IEEE 802.1 TSN networks that apply the fully centralized configuration model as defined in IEEE Std 802.1Q [98]. IEEE TSN is a set of standards to define mechanisms for the time-sensitive (i.e. deterministic) transmission of data over Ethernet networks.
b) Enablers for AF requested support of Time Synchronization and/or some aspects of Time Sensitive Communication. The architecture is described in clause 4.4.8.3.
c) Support for TSN enabled transport network (TN): Enablers for interworking with TSN network deployed in the transport network. This option can be used simultaneously with either option a) or b). The architecture is described in clause 5.28a. The interworking is applicable when the transport network deploys the fully centralized configuration model as defined in IEEE Std 802.1Q [98]. In this scenario, a TSN TN is deployed to realize the N3 interface between (R)AN and UPF. From the perspective of the TSN TN, (R)AN and UPF act as End Stations of the TSN TN.
d) Integration as a router in a Deterministic Network as defined in IETF RFC 8655 [150]. The architecture is described in clause 4.4.8.4. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 4.4.8.2 Architecture to support IEEE Time Sensitive Networking | The 5G System is integrated with the external network as a TSN bridge. This "logical" TSN bridge (see Figure 4.4.8.2-1) includes TSN Translator functionality for interoperation between TSN Systems and 5G System both for user plane and control plane. 5GS TSN translator functionality consists of Device-side TSN translator (DS-TT) and Network-side TSN translator (NW-TT). The TSN AF is part of 5GC and provides the control plane translator functionality for the integration of the 5GS with a TSN network, e.g. the interactions with the CNC. 5G System specific procedures in 5GC and RAN, wireless communication links, etc. remain hidden from the TSN network. To achieve such transparency to the TSN network and the 5GS to appear as any other TSN Bridge, the 5GS provides TSN ingress and egress ports via DS-TT and NW-TT. DS-TT and NW-TT optionally support:
- hold and forward functionality for the purpose of de-jittering;
- per-stream filtering and policing as defined in clause 8.6.5.2.1 of IEEE Std 802.1Q [98].
DS-TT optionally supports link layer connectivity discovery and reporting as defined in IEEE Std 802.1AB [97] for discovery of Ethernet devices attached to DS-TT. NW-TT supports link layer connectivity discovery and reporting as defined in IEEE Std 802.1AB [97] for discovery of Ethernet devices attached to NW-TT. If a DS-TT does not support link layer connectivity discovery and reporting, then NW-TT performs link layer connectivity discovery and reporting as defined in IEEE Std 802.1AB [97] for discovery of Ethernet devices attached to DS-TT on behalf of DS-TT.
NOTE 1: If NW-TT performs link layer connectivity discovery and reporting on behalf of DS-TT, it is assumed that LLDP frames are transmitted between NW-TT and UE on the QoS Flow with the default QoS rule as defined in the clause 5.7.1.1. Alternatively, SMF can establish a dedicated QoS Flow matching on the Ethertype defined for LLDP (IEEE Std 802.1AB [97]).
There are three TSN configuration models defined in IEEE Std 802.1Q [98]. Amongst the three models:
- fully centralized model is supported in this Release of the specification;
- fully distributed model is not supported in this Release of the specification;
- centralized network/distributed user model is not supported in this Release of the specification.
NOTE 2: This Release supports interworking with TSN using clause 8.6.8.4 of IEEE Std 802.1Q [98] scheduled traffic and clause 8.6.5.2.1 of IEEE Std 802.1Q [98] per-stream filtering and policy.
Figure 4.4.8.2-1: System architecture view with 5GS appearing as TSN bridge
NOTE 3: Whether DS-TT and UE are combined or are separate is up to implementation.
NOTE 4: TSN AF does not need to support N33 in this release of the specification. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 4.4.8.3 Architecture for AF requested support of Time Sensitive Communication and Time Synchronization | This clause describes the architecture to enable Time Sensitive Communication AF requested time sensitive communication and time synchronization services. The Time Sensitive Communication and Time Synchronization related features that are supported based on AF request are described in clauses 5.27.1 and 5.27.2, respectively. Figure 4.4.8.3-1 shows the architecture to support Time Sensitive Communication and Time Synchronization services.
As shown in Figure 4.4.8.3-1, to support Time Synchronization service based on IEEE Std 802.1AS [104] or IEEE Std 1588 [126] for Ethernet or IP type PDU Sessions, the DS-TT, NW-TT and Time Sensitive Communication and Time Synchronization Function (TSCTSF) are required in order to support the features in IEEE Std 802.1AS [104] or IEEE Std 1588 [126] as described in clause 5.27. The NEF exposes 5GS capability to support Time Synchronization service as described in clause 5.27.1.8. TSCTSF controls the DS-TT(s) and NW-TT for the (g)PTP based time synchronization service. In addition, TSCTSF supports TSC assistance container related functionalities.
Figure 4.4.8.3-1: Architecture to enable Time Sensitive Communication and Time Synchronization services
NOTE 1: If the AF is considered to be trusted by the operator, the AF could interact directly with TSCTSF, the connection between AF and TSCTSF is not depicted in the architecture diagram for brevity.
UPF/NW-TT distributes the (g)PTP messages as described in clause 5.27.1.
When the UPF supports one or more NW-TT(s), there is one-to-one association between an NW-TT and the network instance or between an NW-TT and network instance together with DNN/S-NSSAI in the UPF. When there are multiple network instances within a UPF, each network instance is considered logically separate. The network instance for the N6 interface (clause 5.6.12) may be indicated by the SMF to the UPF for a given PDU Session during PDU Session establishment procedure. UPF allocates resources based on the Network Instance and S-NSSAI and it is supported according to TS 29.244 [65]. DNN/S-NSSAI may be indicated by the SMF together with the network instance to the UPF for a given PDU Session during PDU Session establishment procedure.
NOTE 2: The same NW-TT is used for all PDU Sessions in the UPF for the given DNN/S-NSSAI; the NW-TT is unique per DNN/S-NSSAI. This ensures that the UPF selects an N4 session associated with the correct TSCTSF when the NW-TT initiates an UMIC or PMIC. At any given time, the NW-TT is associated with a single TSCTSF. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 4.4.8.4 Architecture to support IETF Deterministic Networking | The 5G System is integrated with the Deterministic Network as defined in IETF RFC 8655 [150] as a logical DetNet transit router, see Figure 4.4.8.4-1. The TSCTSF performs mapping in the control plane between the 5GS internal functions and the DetNet controller. 5G System specific procedures in 5GC and RAN remain hidden from the DetNet controller.
Figure 4.4.8.4-1: 5GS Architecture to support IETF Deterministic Networking
On the device side, the UE is connected with a DetNet system, which may be a DetNet End System or a DetNet Node.
The architecture does not require the DS-TT functionality to be supported in the device nor require the user plane NW-TT functionality to be supported in the UPF, however, it can co-exist with such functions. For the reporting of information of the network side ports, NW-TT control plane function is used. The architecture can be combined with architecture in clause 4.4.8.3 to support time synchronization and TSC.
DetNet may be used in combination with time synchronization mechanisms as defined in clause 5.27, but it does not require usage of these mechanisms.
5GS acts as a DetNet router in the DetNet domain. Use cases where the 5GS acts as a sub-network (see clause 4.1.2 of IETF RFC 8655 [150]) are also possible but do not require any additional 3GPP standardization. A special case where the 5GS can act as a sub-network is when the 5GS acts as a TSN network, which is supported by the 3GPP specifications based on the architecture in clause 4.4.8.2.
NOTE: For DetNet interworking, it is assumed that there is a business agreement to support the use of the DetNet controller so that it can be regarded trusted for the operator. Depending on the needs of a given deployment, functions such as the authentication, authorization and potential throttling of signalling from the DetNet controller can be achieved by including such functionalities in the TSCTSF.
The routing of the downlink packets is achieved using the existing 3GPP functions. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5 High level features | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.1 General | Clause 5 specifies the high level functionality and features of the 5G System for both 3GPP and Non-3GPP access and for the interoperability with the EPC defined in TS 23.401 [26]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.2 Network Access Control | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.2.1 General | Network access is the means for the user to connect to 5G CN. Network access control comprises the following functionality:
- Network selection,
- Identification and authentication,
- Authorisation,
- Access control and barring,
- Policy control,
- Lawful Interception. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.2.2 Network selection | In order to determine to which PLMN to attempt registration, the UE performs network selection. The network selection procedure comprises two main parts, PLMN selection and access network selection. The requirements for the PLMN selection are specified in TS 22.011 [25] and the procedures are in TS 23.122 [17]. The access network selection part for the 3GPP access networks is specified in TS 36.300 [30] for E-UTRAN and in TS 38.300 [27] for the NR.
The network selection for the Disaster Roaming is described in TS 23.122 [17] and TS 24.501 [47].
5.2.2a Void |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.2.3 Identification and authentication | The network may authenticate the UE during any procedure establishing a NAS signalling connection with the UE. The security architecture is specified in TS 33.501 [29]. The network may optionally perform an PEI check with 5G-EIR. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.2.4 Authorisation | The authorisation for connectivity of the subscriber to the 5GC and the authorization for the services that the user is allowed to access based on subscription (e.g. Operator Determined Barring, Roaming restrictions, Access Type and RAT Type currently in use) is evaluated once the user is successfully identified and authenticated. This authorization is executed during UE Registration procedure. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.2.5 Access control and barring | When the UE needs to transmit an initial NAS message, the UE shall request to establish or resume an RRC Connection first and the NAS shall provide the RRC establishment or resume related information to the lower layer. The RAN handles the RRC Connection with priority during and after the RRC Connection Establishment procedure or RRC Connection Resume procedure, when UE indicates priority in Establishment or Resume related information
Under high network load conditions, the network may protect itself against overload by using the Unified Access Control functionality for 3GPP access specified in TS 22.261 [2], TS 24.501 [47] and TS 38.300 [27] to limit access attempts from UEs. Depending on network configuration, the network may determine whether certain access attempt should be allowed or blocked based on categorized criteria, as specified in TS 22.261 [2] and TS 24.501 [47]. The NG-RAN may broadcast barring control information associated with Access Categories and Access Identities as specified in TS 38.300 [27].
The NG-RAN node may initiate such Unified Access Control when:
- AMFs request to restrict the load for UEs that access the network by sending OVERLOAD START message containing conditions defined in clause 5.19.5.2, or
- requested by OAM, or
- triggered by NG-RAN itself.
If the NG-RAN node takes a decision to initiate UAC because of the reception of the N2 interface OVERLOAD START messages, the NG-RAN should only initiate such procedure if all the AMFs relevant to the request contained in the OVERLOAD START message and connected to this NG-RAN node request to restrict the load for UEs that access the network.
If the UE supports both N1 and S1 modes NAS and, as defined in TS 23.401 [26], the UE is configured for Extended Access Barring (EAB) but is not configured with a permission for overriding Extended Access Barring (EAB), when the UE wants to access the 5GS it shall perform Unified Access Control checks for Access Category 1 on receiving an indication from the upper layers as defined in TS 24.501 [47], TS 38.331 [28], TS 36.331 [51].
If the UE supports both N1 and S1 modes NAS and, as defined in TS 23.401 [26], the UE is configured with a permission for overriding Extended Access Barring (EAB), when the UE wants to access the 5GS it shall ignore Unified Access Control checks for Access Category 1 on receiving an indication from the upper layers, as defined in TS 24.501 [47].
NOTE: UE signalling of Low Access Priority indication over N1 in 5GS is not supported in this release of the specification.
Operator may provide one or more PLMN-specific Operator-defined access category definitions to the UE using NAS signalling and the UE handles the Operator-defined access category definitions stored for the Registered PLMN, as specified in TS 24.501 [47].
The access control for the Disaster Roaming is described in TS 23.122 [17] and TS 24.501 [47]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.2.6 Policy control | Network access control including service authorization may be influenced by Policy control, as specified in clause 5.14. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.2.7 Lawful Interception | For definition and functionality of Lawful Interception, please see TS 33.126 [35]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3 Registration and Connection Management | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.1 General | The Registration Management is used to register or deregister a UE/user with the network and establish the user context in the network. The Connection Management is used to establish and release the signalling connection between the UE and the AMF. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.2 Registration Management | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.2.1 General | A UE/user needs to register with the network to receive services that requires registration. Once registered and if applicable the UE updates its registration with the network (see TS 23.502 [3]):
- periodically, in order to remain reachable (Periodic Registration Update); or
- upon mobility (Mobility Registration Update); or
- to update its capabilities or re-negotiate protocol parameters (Mobility Registration Update).
The Initial Registration procedure involves execution of Network Access Control functions as defined in clause 5.2 (i.e. user authentication and access authorization based on subscription profiles in UDM). As result of the Registration procedure, the identifier of the serving AMF serving the UE in the access through which the UE has registered will be registered in UDM.
The registration management procedures are applicable over both 3GPP access and Non-3GPP access. The 3GPP and Non-3GPP RM states are independent of each other, see clause 5.3.2.4. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.2.2 5GS Registration Management states | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.2.2.1 General | Two RM states are used in the UE and the AMF that reflect the registration status of the UE in the selected PLMN:
- RM-DEREGISTERED.
- RM-REGISTERED. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.2.2.2 RM-DEREGISTERED state | In the RM‑DEREGISTERED state, the UE is not registered with the network. The UE context in AMF holds no valid location or routing information for the UE so the UE is not reachable by the AMF. However, some parts of UE context may still be stored in the UE and the AMF e.g. to avoid running an authentication procedure during every Registration procedure.
In the RM-DEREGISTERED state, the UE shall:
- attempt to register with the selected PLMN using the Initial Registration procedure if it needs to receive service that requires registration (see clause 4.2.2.2 of TS 23.502 [3]).
- remain in RM-DEREGISTERED state if receiving a Registration Reject upon Initial Registration (see clause 4.2.2.2 of TS 23.502 [3]).
- enter RM-REGISTERED state upon receiving a Registration Accept (see clause 4.2.2.2 of TS 23.502 [3]).
When the UE RM state in the AMF is RM-DEREGISTERED, the AMF shall:
- when applicable, accept the Initial Registration of a UE by sending a Registration Accept to this UE and enter RM-REGISTERED state for the UE (see clause 4.2.2.2 of TS 23.502 [3]); or
- when applicable, reject the Initial Registration of a UE by sending a Registration Reject to this UE (see clause 4.2.2.2 of TS 23.502 [3]). |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.2.2.3 RM-REGISTERED state | In the RM‑REGISTERED state, the UE is registered with the network. In the RM-REGISTERED state, the UE can receive services that require registration with the network.
In the RM-REGISTERED state, the UE shall:
- perform Mobility Registration Update procedure if the current TAI of the serving cell (see TS 37.340 [31]) is not in the list of TAIs that the UE has received from the network in order to maintain the registration and enable the AMF to page the UE;
NOTE: Additional considerations for Mobility Registration Update in case of NR satellite access are provided in clause 5.4.11.6.
- perform Periodic Registration Update procedure triggered by expiration of the periodic update timer to notify the network that the UE is still active.
- perform a Mobility Registration Update procedure to update its capability information or to re-negotiate protocol parameters with the network;
- perform Deregistration procedure (see clause 4.2.2.3.1 of TS 23.502 [3]) and enter RM-DEREGISTERED state, when the UE needs to be no longer registered with the PLMN. The UE may decide to deregister from the network at any time.
- enter RM-DEREGISTERED state when receiving a Registration Reject message or a Deregistration message. The actions of the UE depend upon the cause value' in the Registration Reject or Deregistration message. See clause 4.2.2 of TS 23.502 [3].
When the UE RM state in the AMF is RM-REGISTERED, the AMF shall:
- perform Deregistration procedure (see clauses 4.2.2.3.2, 4.2.2.3.3 of TS 23.502 [3]) and enter RM-DEREGISTERED state for the UE, when the UE needs to be no longer registered with the PLMN. The network may decide to deregister the UE at any time;
- perform Implicit Deregistration at any time after the Implicit Deregistration timer expires. The AMF shall enter RM-DEREGISTERED state for the UE after Implicit Deregistration;
- when applicable, accept or reject Registration Requests or Service Requests from the UE. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.2.2.4 5GS Registration Management State models | Figure 5.3.2.2.4-1: RM state model in UE
Figure 5.3.2.2.4-2: RM state model in AMF |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.2.3 Registration Area management | Registration Area management comprises the functions to allocate and reallocate a Registration area to a UE. Registration area is managed per access type i.e. 3GPP access or Non-3GPP access.
When a UE registers with the network over the 3GPP access, the AMF allocates a set of tracking areas in TAI List to the UE. When the AMF allocates registration area, i.e. the set of tracking areas in TAI List, to the UE it may take into account various information (e.g. Mobility Pattern and Allowed/Non-Allowed Area (refer to clause 5.3.4.1)). An AMF which has the whole PLMN as serving area may alternatively allocate the whole PLMN ("all PLMN") as registration area to a UE in MICO mode (refer to clause 5.4.1.3). When AMF allocates registration area for UE registered for Disaster Roaming service as specified in clause 5.40.4, AMF shall only consider TAIs covering the area with the Disaster Condition.
The 5G System shall support allocating a Registration Area using a single TAI List which includes tracking areas of any NG-RAN nodes in the Registration Area for a UE.
In the case of SNPN, the TAI list allocated by AMF does not support Tracking Areas belonging to different SNPNs.
TAI used for non-3GPP access shall be dedicated to non-3GPP access. TAI(s) dedicated to Non-3GPP access may be defined in a PLMN and apply within this PLMN. Each N3IWF, TNGF, TWIF and W-AGF is locally configured with one TAI value. Each N3IWF, TNGF, TWIF and W-AGF may be configured with a different TAI value or with the same TAI value as other N3IWFs, TNGFs, TWIFs and/or W-AGFs. The TAI is provided to the AMF during N2 interface setup and as part of the User Location Information in UE associated messages as described in TS 38.413 [34].
When a UE registers with the network over a Non-3GPP access, the AMF allocates to the UE a registration area that only includes the TAI received from the serving N3IWF, TNGF, TWIF or W-AGF.
NOTE 1: For example, two W-AGFs can each correspond to a different TAI (one TAI per W-AGF) and thus support different sets of S-NSSAI(s).
When generating the TAI list, the AMF shall include only TAIs that are applicable on the access type (i.e. 3GPP access or Non-3GPP access) where the TAI list is sent.
NOTE 2: To prevent extra signalling load resulting from Mobility Registration Update occurring at every RAT change, it is preferable to avoid generating a RAT-specific TAI list for a UE supporting more than one RAT.
NOTE 3: For a UE registered on N3GPP access the TAI(s) provided to the UE as part of the Registration Area is expected to enable the support of the slices that are intended to be provided for this UE over this specific Non-3GPP access. In addition, the Registration Area provided to the UE for non-3GPP access will never change until the UE deregisters from non-3GPP access (either explicit deregistration or implicit deregistration due to Deregistration timer expiring due to UE entering CM_IDLE state).
For all 3GPP Access RATs in NG-RAN and for Non-3GPP Access, the 5G System supports the TAI format as specified in TS 23.003 [19] consisting of MCC, MNC and a 3-byte TAC only.
The additional aspects for registration management when a UE is registered over one access type while the UE is already registered over the other access type is further described in clause 5.3.2.4.
To ensure a UE initiates a Mobility Registration procedure when performing inter-RAT mobility to or from NB-IoT, a Tracking Area shall not contain both NB-IoT and other RATs cells (e.g. WB-E-UTRA, NR) and the AMF shall not allocate a TAI list that contains both NB-IoT and other RATs Tracking Areas.
For 3GPP access the AMF determines the RAT type the UE is camping on based on the Global RAN Node IDs associated with the N2 interface and additionally the Tracking Area indicated by NG-RAN. When the UE is accessing NR using unlicensed bands, as defined in clause 5.4.8, an indication is provided in N2 interface as defined in TS 38.413 [34].
The AMF may also determine more precise RAT Type information based on further information received from NG-RAN:
- The AMF may determine the RAT Type to be LTE-M as defined in clause 5.31.20; or
- The AMF may determine the RAT Type to be NR using unlicensed bands, as defined in clause 5.4.8.
- The AMF may determine the RAT Type to be one of the RAT types for satellite access, as defined in clause 5.4.10.
- The AMF may determine the RAT Type to be NR RedCap as defined in clause 5.41.
For Non-3GPP accesses the AMF determines the RAT type the UE is camping based on the 5G-AN node associated with N2 interface as follows:
- The RAT type is Untrusted Non-3GPP if the 5G-AN node has a Global N3IWF Node ID;
- The RAT type is Trusted Non-3GPP if the 5G-AN node has a Global TNGF Node ID or a Global TWIF Node ID; and
- The RAT type is Wireline -BBF if the 5G-AN node has a Global W-AGF Node ID corresponding to a W-AGF supporting the Wireline BBF Access Network. The RAT type is Wireline-Cable if the 5G-AN node has a Global W-AGF Node ID corresponding to a W-AGF supporting the Wireline Cable Access Network. If not possible to distinguish between the two, the RAT type is Wireline.
NOTE 4: How to differentiate between W-AGF supporting either Wireline BBF Access Network or the Wireline (e.g. different Global W-AGF Node ID IE or the Global W-AGF Node ID including a field to distinguish between them) is left to Stage 3 definition.
NOTE 5: If an operator supports only one kind of Wireline Access Network (either Wireline BBF Access Network or a Wireline Cable Access Network) the AMF may be configured to use RAT type Wireline or the specific one.
For Non-3GPP access the AMF may also use the User Location Information provided at N2 connection setup to determine a more precise RAT Type, e.g. identifying IEEE 802.11 access, Wireline-Cable access, Wireline-BBF access.
When the 5G-AN node has either a Global N3IWF Node ID, or a Global TNGF Node ID, or a Global TWIF Node ID, or a Global W-AGF Node ID, the Access Type is Non-3GPP Access. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.2.4 Support of a UE registered over both 3GPP and Non-3GPP access | This clause applies to Non-3GPP access network corresponding to the Untrusted Non-3GPP access network, to the Trusted Non-3GPP and to the W-5GAN. In the case of W-5GAN the UE mentioned in this clause corresponds to the 5G-RG.
For a given serving PLMN there is one RM context for a UE for each access, e.g. when the UE is consecutively or simultaneously served by a 3GPP access and by a non-3GPP access (i.e. via an N3IWF, TNGF and W-AGF) of the same PLMN. UDM manages separate/independent UE Registration procedures for each access.
When served by the same PLMN for 3GPP and non-3GPP accesses, an UE is served by the same AMF except in the temporary situation described in clause 5.17 i.e. after a mobility from EPS while the UE has PDU Sessions associated with non-3GPP access.
The 5G NSWO authentication as defined in Annex S of TS 33.501 [29] does not impact the RM state.
An AMF associates multiple access-specific RM contexts for an UE with:
- a 5G-GUTI that is common to both 3GPP and Non-3GPP accesses. This 5G-GUTI is globally unique.
- a Registration state per access type (3GPP / Non-3GPP)
- a Registration Area per access type: one Registration Area for 3GPP access and another Registration Area for non 3GPP access. Registration Areas for the 3GPP access and the Non-3GPP access are independent.
- timers for 3GPP access:
- a Periodic Registration timer; and
- a Mobile Reachable timer and an Implicit Deregistration timer.
- timers for non-3GPP access:
- a UE Non-3GPP Deregistration timer; and
- a Network Non-3GPP Implicit Deregistration timer.
The AMF shall not provide a Periodic Registration Timer for the UE over a Non-3GPP access. Consequently, the UE need not perform Periodic Registration Update procedure over Non-3GPP access. Instead, during the Initial Registration procedure and Re-registration, the UE is provided by the network with a UE Non-3GPP Deregistration timer that starts when the UE enters non-3GPP CM-IDLE state.
When the 3GPP access and the non-3GPP access for the same UE are served by the same PLMN, the AMF assigns the same 5G-GUTI for use over both accesses. Such a 5G-GUTI may be assigned or re-assigned over any of the 3GPP and Non-3GPP accesses. The 5G-GUTI is assigned upon a successful registration of the UE and is valid over both 3GPP and Non-3GPP access to the same PLMN for the UE. Upon performing an initial access over the Non-3GPP access or over the 3GPP access while the UE is already registered with the 5G System over another access of the same PLMN, the UE provides the native 5G-GUTI for the other access. This enables the AN to select an AMF that maintains the UE context created at the previous Registration procedure via the GUAMI derived from the 5G-GUTI and enables the AMF to correlate the UE request to the existing UE context via the 5G-GUTI.
If the UE is performing registration over one access and intends to perform registration over the other access in the same PLMN (e.g. the 3GPP access and the selected N3IWF, TNGF or W-AGF are located in the same PLMN), the UE shall not initiate the registration over the other access until the Registration procedure over first access is completed.
NOTE: To which access the UE performs registration first is up to UE implementation.
When the UE is successfully registered to an access (3GPP access or Non-3GPP access respectively) and the UE registers via the other access:
- if the second access is located in the same PLMN (e.g. the UE is registered via a 3GPP access and selects a N3IWF, TNGF or W-AGF located in the same PLMN), the UE shall use for the registration to the PLMN associated with the new access the 5G-GUTI that the UE has been provided with at the previous registration or UE configuration update procedure for the first access in the same PLMN. Upon successful completion of the registration to the second access, if the network included a 5G-GUTI in the Registration Accept, the UE shall use the 5G-GUTI received in the Registration Accept for both registrations. If no 5G-GUTI is included in the Registration Accept, then the UE uses the 5G-GUTI assigned for the existing registration also for the new registration.
- if the second access is located in a PLMN different from the registered PLMN of the first access (i.e. not the registered PLMN), (e.g. the UE is registered to a 3GPP access and selects a N3IWF, TNGF or W-AGF located in a PLMN different from the PLMN of the 3GPP access, or the UE is registered over Non-3GPP and registers to a 3GPP access in a PLMN different from the PLMN of the N3IWF, TNGF or W-AGF), the UE shall use for the registration to the PLMN associated with the new access a 5G-GUTI only if it has got one previously received from a PLMN that is not the same as the PLMN the UE is already registered with. If the UE does not include a 5G-GUTI, the SUCI shall be used for the new registration. Upon successful completion of the registration to the second access, the UE has the two 5G-GUTIs (one per PLMN).
A UE supporting registration over both 3GPP and Non-3GPP access to two PLMNs shall be able to handle two separate registrations, including two 5G-GUTIs, one per PLMN and two associated equivalent PLMN lists.
When a UE 5G-GUTI assigned during a Registration procedure over 3GPP (e.g. the UE registers first over a 3GPP access) is location-dependent, the same UE 5G-GUTI can be re-used over the Non-3GPP access when the selected N3IWF, TNGF or W-AGF function is in the same PLMN as the 3GPP access. When an UE 5G-GUTI is assigned during a Registration procedure performed over a Non 3GPP access (e.g. the UE registers first over a non-3GPP access), the UE 5G-GUTI may not be location-dependent, so that the UE 5G-GUTI may not be valid for NAS procedures over the 3GPP access and, in this case, a new AMF is allocated during the Registration procedure over the 3GPP access.
When the UE is registered first via 3GPP access, if the UE registers to the same PLMN via Non-3GPP access, the UE shall send the GUAMI or 5G-GUTI obtained via 3GPP access to the N3IWF, TNGF or W-AGF, which uses the received GUAMI or 5G-GUTI to select the same AMF as the 3GPP access. Whether GUAMI or 5G-GUTI is sent from the UE in a particular non-3GPP access is specified in TS 24.501 [47] and TS 24.502 [48].
The Deregistration Request message indicates whether it applies to the 3GPP access the Non-3GPP access, or both.
If the UE is registered on both 3GPP and Non-3GPP accesses and it is in CM-IDLE over Non-3GPP access, then the UE or AMF may initiate a Deregistration procedure over the 3GPP access to deregister the UE only on the Non-3GPP access, in which case all the PDU Sessions which are associated with the Non-3GPP access shall be released.
If the UE is registered on both 3GPP and non-3GPP accesses and it is in CM-IDLE over 3GPP access and in CM-CONNECTED over non-3GPP access, then the UE may initiate a Deregistration procedure over the non-3GPP access to deregister the UE only on the 3GPP access, in which case all the PDU Sessions which are associated with the 3GPP access shall be released.
Registration Management over Non-3GPP access is further defined in clause 5.5.1. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.3 Connection Management | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.3.1 General | Connection management comprises the functions of establishing and releasing a NAS signalling connection between a UE and the AMF over N1. This NAS signalling connection is used to enable NAS signalling exchange between the UE and the core network. It comprises both the AN signalling connection between the UE and the AN (RRC Connection over 3GPP access or UE-N3IWF connection over untrusted N3GPP access or UE-TNGF connection over trusted N3GPP access) and the N2 connection for this UE between the AN and the AMF. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.3.2 5GS Connection Management states | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.3.2.1 General | Two CM states are used to reflect the NAS signalling Connection of the UE with the AMF:
- CM-IDLE
- CM-CONNECTED
The CM state for 3GPP access and Non-3GPP access are independent of each other, i.e. one can be in CM-IDLE state at the same time when the other is in CM-CONNECTED state. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.3.2.2 CM-IDLE state | A UE in CM-IDLE state has no NAS signalling connection established with the AMF over N1. The UE performs cell selection/cell reselection according to TS 38.304 [50] and PLMN selection according to TS 23.122 [17].
There are no AN signalling connection, N2 connection and N3 connections for the UE in the CM-IDLE state.
If the UE is both in CM-IDLE state and in RM-REGISTERED state, the UE shall, unless otherwise specified in clause 5.3.4.1:
- Respond to paging by performing a Service Request procedure (see clause 4.2.3.2 of TS 23.502 [3]), unless the UE is in MICO mode (see clause 5.4.1.3);
- perform a Service Request procedure when the UE has uplink signalling or user data to be sent (see clause 4.2.3.2 of TS 23.502 [3]). Specific conditions apply for LADN, see clause 5.6.5.
When the UE state in the AMF is RM-REGISTERED, UE information required for initiating communication with the UE shall be stored. The AMF shall be able to retrieve stored information required for initiating communication with the UE using the 5G-GUTI.
NOTE: In 5GS there is no need for paging using the SUPI/SUCI of the UE.
The UE provides 5G-S-TMSI as part of AN parameters during AN signalling connection establishment as specified in TS 38.331 [28] and TS 36.331 [51]. The UE shall enter CM-CONNECTED state whenever an AN signalling connection is established between the UE and the AN (entering RRC_CONNECTED state over 3GPP access, or at the establishment of the UE-N3IWF connectivity over untrusted non-3GPP access or the UE-TNGF connectivity over trusted non-3GPP access). The transmission of an Initial NAS message (Registration Request, Service Request or Deregistration Request) initiates the transition from CM-IDLE to CM-CONNECTED state.
When the UE states in the AMF are CM-IDLE and RM-REGISTERED, the AMF shall:
- perform a network triggered Service Request procedure when it has signalling or mobile-terminated data to be sent to this UE, by sending a Paging Request to this UE (see clause 4.2.3.3 of TS 23.502 [3]), if a UE is not prevented from responding e.g. due to MICO mode or Mobility Restrictions.
The AMF shall enter CM-CONNECTED state for the UE whenever an N2 connection is established for this UE between the AN and the AMF. The reception of initial N2 message (e.g. N2 INITIAL UE MESSAGE) initiates the transition of AMF from CM-IDLE to CM-CONNECTED state.
The UE and the AMF may optimize the power efficiency and signalling efficiency of the UE when in CM-IDLE state e.g. by activating MICO mode (see clause 5.4.1.3). |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.3.2.3 CM-CONNECTED state | A UE in CM-CONNECTED state has a NAS signalling connection with the AMF over N1. A NAS signalling connection uses an RRC Connection between the UE and the NG-RAN and an NGAP UE association between the AN and the AMF for 3GPP access. A UE can be in CM-CONNECTED state with an NGAP UE association that is not bound to any TNLA between the AN and the AMF. See clause 5.21.1.2 for details on the state of NGAP UE association for an UE in CM-CONNECTED state. Upon completion of a NAS signalling procedure, the AMF may decide to release the NAS signalling connection with the UE.
In the CM-CONNECTED state, the UE shall:
- enter CM-IDLE state whenever the AN signalling connection is released (entering RRC_IDLE state over 3GPP access or when the release of the UE-N3IWF connectivity over untrusted non-3GPP access or the UE-TNGF connectivity over trusted non-3GPP access is detected by the UE), see TS 38.331 [28] for 3GPP access.
When the UE CM state in the AMF is CM-CONNECTED, the AMF shall:
- enter CM-IDLE state for the UE whenever the logical NGAP signalling connection and the N3 user plane connection for this UE are released upon completion of the AN Release procedure as specified in TS 23.502 [3].
The AMF may keep a UE CM state in the AMF in CM-CONNECTED state until the UE de-registers from the core network.
A UE in CM-CONNECTED state can be in RRC_INACTIVE state, see TS 38.300 [27]. When the UE is in RRC_INACTIVE state the following applies:
- UE reachability is managed by the RAN, with assistance information from core network;
- UE paging is managed by the RAN.
- UE monitors for paging with UE's CN (5G S-TMSI) and RAN identifier. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.3.2.4 5GS Connection Management State models | Figure 5.3.3.2.4-1: CM state transition in UE
Figure 5.3.3.2.4-2: CM state transition in AMF
When a UE enters CM-IDLE state, the UP connection of the PDU Sessions that were active on this access are deactivated.
NOTE: The activation of UP connection of PDU Sessions is documented in clause 5.6.8. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.3.2.5 CM-CONNECTED with RRC_INACTIVE state | RRC_INACTIVE state applies to NG-RAN. UE support for RRC_INACTIVE state is defined in TS 38.306 [69] for NR and TS 36.306 [70] for E-UTRA connected to 5GC. RRC_INACTIVE is not supported by NB-IoT connected to 5GC.
The AMF shall provide assistance information to the NG-RAN, to assist the NG-RAN's decision whether the UE can be sent to RRC_INACTIVE state except due to some exceptional cases such as:
- PLMN (or AMF set) does not support RRC_INACTIVE;
- The UE needs to be kept in CM-CONNECTED State (e.g. for tracking).
The "RRC Inactive Assistance Information" includes:
- UE specific DRX values;
- UE specific extended idle mode DRX values (cycle length and Paging Time Window length);
- The Registration Area provided to the UE;
- Periodic Registration Update timer;
- If the AMF has enabled MICO mode for the UE, an indication that the UE is in MICO mode;
- Information from the UE identifier, as defined in TS 38.304 [50] for NR and TS 36.304 [52] for E-UTRA connected to 5GC, that allows the RAN to calculate the UE's RAN paging occasions;
- An indication that Paging Cause Indication for Voice Service is supported;
- AMF PEIPS Assistance Information (see clause 5.4.12.2) for paging a UE in CM-CONNECTED with RRC_INACTIVE state over NR as defined in TS 38.300 [27];
- AMF LP-WUSPS Assistance Information (see clause 5.4.12A) for paging a UE in CM-CONNECTED with RRC_INACTIVE state over NR as defined in TS 38.300 [27];
- CN based MT communication handling support indication for RRC_INACATIVE state (see clause 5.31.7.2.1).
The RRC Inactive Assistance Information mentioned above is provided by the AMF during N2 activation with the (new) serving NG-RAN node (i.e. during Registration, Service Request, Handover) to assist the NG RAN's decision whether the UE can be sent to RRC_INACTIVE state. If the AMF allocates a new Registration Area to the UE, the AMF should update the NG-RAN with the new Registration Area by sending the RRC Inactive Assistance Information accordingly. The Paging Cause Indication for Voice Service is used to assist NG RAN to perform RAN based paging.
RRC_INACTIVE state is part of RRC state machine and it is up to the RAN to determine the conditions to enter RRC_INACTIVE state. If any of the parameters included in the RRC Inactive Assistance Information changes as the result of NAS procedure, the AMF shall update the RRC Inactive Assistance Information to the NG-RAN node.
When the UE is in CM-CONNECTED state, if the AMF has provided RRC Inactive assistance information, the RAN node may decide to move a UE to CM-CONNECTED with RRC_INACTIVE state.
The state and "endpoints" (in the case of Dual Connectivity configuration) of the N2 and N3 reference points are not changed by the UE entering CM-CONNECTED with RRC_INACTIVE state. A UE in RRC_INACTIVE state is aware of the RAN Notification area and periodic RAN Notification Area Update timer.
The 5GC network is not aware of the UE transitions between CM-CONNECTED with RRC_CONNECTED and CM-CONNECTED with RRC_INACTIVE state, unless the 5GC network is notified via N2 notification procedure in clause 4.8.3 of TS 23.502 [3].
At transition into CM-CONNECTED with RRC_INACTIVE state, the NG-RAN configures the UE with a periodic RAN Notification Area Update timer taking into account the value of the Periodic Registration Update timer value indicated in the RRC Inactive Assistance Information and uses a guard timer with a value longer than the RAN Notification Area Update timer value provided to the UE.
If the periodic RAN Notification Area Update guard timer expires in NG-RAN, the NG-RAN shall initiate AN Release procedure as specified in clause 4.2.6 of TS 23.502 [3].
When the UE is in CM-CONNECTED with RRC_INACTIVE state, the UE performs PLMN selection procedures as defined in TS 23.122 [17] and TS 24.501 [47].
When the UE is CM-CONNECTED with RRC_INACTIVE state, the UE may resume the RRC Connection due to:
- Uplink data pending;
- Mobile initiated NAS signalling procedure;
- As a response to RAN paging;
- Notifying the network that it has left the RAN Notification Area;
- Upon periodic RAN Notification Area Update timer expiration.
If the UE resumes the connection in a different NG-RAN node within the same PLMN or equivalent PLMN or within the same SNPN or equivalent SNPN, the UE AS context is retrieved from the old NG-RAN node and a procedure is triggered towards the CN (see clause 4.8.2 of TS 23.502 [3]).
NOTE 1: With Dual Connectivity configuration if the UE resumes the RRC connection in the Master RAN node, the Secondary RAN node configuration is defined in TS 38.300 [27].
If the RAN paging procedure applying DRX or eDRX value no longer than 10.24s, as defined in TS 38.300 [27], is not successful in establishing contact with the UE the procedure shall be handled by the network as follows:
- If NG-RAN has at least one pending NAS PDU for transmission, the RAN node shall initiate the AN Release procedure (see clause 4.2.6 of TS 23.502 [3]) to move the UE CM state in the AMF to CM-IDLE state and indicate to the AMF the NAS non-delivery.
- If NG RAN has only pending user plane data for transmission, the NG-RAN node may keep the N2 connection active or initiate the AN Release procedure (see clause 4.2.6 of TS 23.502 [3]) based on local configuration in NG-RAN.
NOTE 2: The user plane data which triggers the RAN paging can be lost, e.g. in the case of RAN paging failure.
If the RAN paging procedure applying eDRX value longer than 10.24s, as defined in TS 38.300 [27], has not requested the CN based mobile terminated (MT) communication handling as described in clause 5.31.7.2.1 and is not successful in establishing contact with the UE after paging the UE, the procedure shall be handled by network as follows:
- If NG-RAN has at least one pending NAS PDU for transmission, the RAN node shall initiate the AN Release procedure (see clause 4.2.6 of TS 23.502 [3]) to move the UE CM state in the AMF to CM-IDLE state and indicate to the AMF the NAS non-delivery.
- If NG-RAN has only pending user plane data for transmission, the NG-RAN node may keep the N2 connection active and based on implementation send indication to the CN requesting the CN based mobile terminated (MT) communication handling as described in clause 5.31.7.2.1, or initiate the AN Release procedure (see clause 4.2.6 of TS 23.502 [3]) based on local configuration in NG-RAN.
NOTE 3: The user plane data which triggers the RAN paging can be lost, e.g. in the case of RAN paging failure.
If a UE in CM-CONNECTED with RRC_INACTIVE state performs cell selection to GERAN/UTRAN/E-UTRAN, it shall follow idle mode procedures of the selected RAT as specified in clause 5.17.
In addition, a UE in CM-CONNECTED state with RRC_INACTIVE state shall enter CM-IDLE state and initiates the NAS signalling recovery (see TS 24.501 [47]) in the following cases:
- If RRC resume procedure fails,
If the UE receives Core Network paging,
- If the periodic RAN Notification Area Update timer expires and the UE cannot successfully resume the RRC Connection,
- In any other failure scenario that cannot be resolved in RRC_INACTIVE state and requires the UE to move to CM-IDLE state.
When a UE is in CM-CONNECTED with RRC_INACTIVE state and a trigger to change the UE's NG-RAN or E‑UTRAN UE Radio Capability information happens, the UE shall move to CM-IDLE state and initiate the procedure for updating UE Radio Capability defined in clause 5.4.4.1. (For specific requirements for a UE operating in dual-registration mode see clause 5.17.2.1)
When UE is in CM-CONNECTED with RRC_INACTIVE state, if RAN has received Location Reporting Control message from AMF with the Reporting Type indicating single stand-alone report or continuously reporting whenever the UE changes the cell, the RAN shall perform location reporting as specified in clause 4.10 of TS 23.502 [3].
When the UE is CM-CONNECTED with RRC_INACTIVE state. If the AMF receives Nudm_UECM_DeregistrationNotification from UDM, the AMF shall initiate AN Release procedure as specified in clause 4.2.6 of TS 23.502 [3].
When UE is in CM-CONNECTED with RRC_INACTIVE state, if RAN has received Location Reporting Control message from AMF with the Reporting Type of the Area Of Interest based reporting, the RAN shall send a Location Report message to AMF including UE presence in the Area Of Interest (i.e. IN, OUT, or UNKNOWN) and the UE's last known location with time stamp.
When the UE is in CM-CONNECTED with RRC_INACTIVE state, if the old NG-RAN node that sends the UE into RRC_INACTIVE state receives the downlink N2 signalling, it initiates the RAN paging as defined in TS 38.300 [27]. If the UE resumes the RRC Connection towards a different NG-RAN node, the old NG-RAN node includes the "UE Context Transfer" indication into a response container to the NF (e.g. AMF or SMF) that generates such N2 downlink signalling. Then the NF shall reattempt the same procedure when the path switch from the old NG-RAN node to the new NG-RAN node is complete. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.3.3 NAS signalling connection management | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.3.3.1 General | NAS signalling connection management includes the functions of establishing and releasing a NAS signalling connection. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.3.3.2 NAS signalling connection establishment | NAS signalling connection establishment function is provided by the UE and the AMF to establish a NAS signalling connection for a UE in CM-IDLE state. The AMF shall provide the list of recommended cells/ TAs / NG-RAN node identifiers for paging, if the NG-RAN had provided that information in an earlier AN Release Procedure in the AN (see clause 4.2.6 of TS 23.502 [3]).
When the UE in CM-IDLE state needs to transmit an NAS message, the UE shall initiate a Service Request, a Registration or a Deregistration procedure to establish a NAS signalling connection to the AMF as specified in clauses 4.2.2 and 4.2.3 of TS 23.502 [3]. If the NAS signalling connection is to be established via an NG-RAN node, but the AMF detects that this UE has already established a NAS signalling connection via old NG-RAN node, the AMF shall release the old established NAS signalling connection by triggering AN Release Procedure.
Based on UE preferences, UE subscription, Mobility Pattern and network configuration, the AMF may keep the NAS signalling connection until the UE de-registers from the network. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.3.3.3 NAS signalling connection Release | The procedure of releasing a NAS signalling connection is initiated by the AN node (either 5G (R)AN node or N3IWF) or the AMF. The NG-RAN node may include the list of recommended cells/ TAs / NG-RAN node identifiers for paging, during the AN Release Procedure in the AN (see clause 4.2.6 of TS 23.502 [3]). The AMF stores this information, if provided by the NG-RAN.
The UE considers the NAS signalling connection is released if it detects the AN signalling connection is released. The AMF considers the NAS signalling connection is released if it detects the N2 context is released. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.3.4 Support of a UE connected over both 3GPP and Non-3GPP access | The AMF manages two CM states for an UE: a CM state for 3GPP access and a CM state for Non-3GPP access. An N2 interface can serve the UE for either 3GPP access or for Non 3GPP access. UE connected over both 3GPP and Non-3GPP has got two N2 interfaces, one for each access. A UE may be in any combination of the CM states between 3GPP and Non-3GPP access, e.g. a UE may be CM-IDLE for one access and CM-CONNECTED for the other access, CM-IDLE for both accesses or CM-CONNECTED for both accesses.
When the UE CM state in the AMF is CM-IDLE for 3GPP access and CM-CONNECTED for Non-3GPP access, the AMF shall perform a network triggered Service Request procedure, when it has downlink data to be sent to this UE for 3GPP access, by sending either the Paging Request via 3GPP access or the NAS notification via Non-3GPP access to this UE (see clause 4.2.3.3 of TS 23.502 [3]).
Connection Management over Non-3GPP access is further defined in clause 5.5.2. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.4 UE Mobility | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.4.1 Mobility Restrictions | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.4.1.1 General | Mobility Restrictions restrict mobility handling or service access of a UE. The Mobility Restriction functionality is provided by the UE (only for mobility restriction categories provided to the UE), the radio access network and the core network.
Unless otherwise stated, Mobility Restrictions only apply to 3GPP access and wireline access, they do not apply to other non-3GPP accesses.
The UE and the network shall override Mobility restriction as specified in clause 5.16.4.3 when accessing the network for Emergency Services. For MPS and MCX, based on operator policy or regional/national regulations, service area restrictions do not apply, as specified in TS 24.501 [47].
For UE requesting Disaster Roaming service, the UE is only allowed to receive services in the area with Disaster Condition as specified in clause 5.40.4. The other areas within the PLMN shall be considered as forbidden area for the UE registered for Disaster Roaming service.
Service Area restrictions and handling of Forbidden Areas for CM-IDLE state and, for CM-CONNECTED state when in RRC_INACTIVE state are executed by the UE based on information received from the core network. Mobility Restrictions for CM-CONNECTED state when in RRC_CONNECTED state are executed by the radio access network and the core network.
In CM-CONNECTED state, the core network provides Mobility Restrictions to the radio access network within Mobility Restriction List.
Mobility Restrictions consists of RAT restriction, Forbidden Area, Service Area Restrictions, Core Network type restriction and Closed Access Group information as follows:
- RAT restriction:
Defines the 3GPP and non-3GPP Radio Access Technology(ies), a UE is not allowed to access in a PLMN. In a restricted RAT a UE based on subscription is not permitted access to the network for this PLMN. For 3GPP access and CM-CONNECTED state, when radio access network determines target RAT and target PLMN during Handover or redirection procedure, it should take per PLMN RAT restriction into consideration. The RAT restriction is enforced in the network and not provided to the UE.
- Forbidden Area:
In a Forbidden Area, the UE, based on subscription, is not permitted to initiate any communication with the network for this PLMN. The UE behaviour in terms of cell selection, RAT selection and PLMN selection depends on the network response that informs the UE of Forbidden Area. A Forbidden Area applies either to 3GPP access or to non-3GPP access.
Further description on Forbidden Area when using wireline access is available in TS 23.316 [84].
Support for Forbidden Area with NR satellite access is described in clause 5.4.11.8.
Forbidden Areas should not be used for Untrusted or Trusted non-3GPP access.
NOTE 1: If a UE receives that the UE is accessing from a forbidden tracking area when registering over untrusted non-3GPP access or trusted non-3GPP access, the UE cannot determine the corresponding TAI and thus needs to consider that access to untrusted non-3GPP access and to trusted non-3GPP access in this PLMN is forbidden until the forbidden area list is removed as described in TS 24.501 [47].
NOTE 2: The UE reactions to specific network responses are described in TS 24.501 [47].
- Service Area Restriction:
Defines areas in which the UE may or may not initiate communication with the network as follows:
- Allowed Area:
In an Allowed Area, the UE is permitted to initiate communication with the network as allowed by the subscription.
- Non-Allowed Area:
In a Non-Allowed Area a UE is service area restricted based on subscription. The UE and the network are not allowed to initiate Service Request, or any connection requests for user plane data, control plane data, exception data reporting, or SM signalling (except for PS Data Off status change reporting) to obtain user services that are not related to mobility.
The UE shall not use the entering of a Non-Allowed Area as a criterion for Cell Reselection, a trigger for PLMN Selection or Domain selection for UE originating sessions or calls. The RRC procedures while the UE is in CM-CONNECTED with RRC_INACTIVE state are unchanged compared to when the UE is in an Allowed Area. The RM procedures are unchanged compared to when the UE is in an Allowed Area.
The UE in a Non-Allowed Area may initiate MA PDU Session establishment or activation over a non-3GPP access other than wireline access, but the User Plane resources on the 3GPP access for the MA-PDU shall not be established or activated. The handling of Non-Allowed Area when using wireline access is described in TS 23.316 [84].
The UE in a Non-Allowed Area:
- shall respond with a Service Request to core network paging indicating 3GPP access type or to a NAS Notification message received over non-3GPP access indicating 3GPP access type or when RAN paging failed, but the UE shall not request User Plane resource establishment, except for emergency services or when the UE is MPS-subscribed or MCX-subscribed.
- shall respond with Service Request to core network paging indicating non-3GPP access type or NAS Notification message received over 3GPP access indicating non-3GPP access type but the UE shall not request User Plane resource establishment, except when the UE is MPS-subscribed.
NOTE 3: When the services are restricted in 5GS due to Service Area Restriction, then it is assumed that the services will be also restricted in all RATs/Systems at the same location(s) using appropriate mechanisms available in the other RATs/Systems.
NOTE 4: Delivery of SOR transparent container, UE policy container, UE parameters update transparent container as defined in TS 24.501 [47], or removal of any stored Paging Restriction Information from network via Registration Request (see clause 5.38), is part of the mobility related service and is allowed in an area with service restriction.
NOTE 5: For a UE in CM-CONNECTED state then neither control plane data transmission nor, if user plane resources are already established, user plane data transmission are restricted by a non-allowed area.
- Core Network type restriction:
Defines whether UE is allowed to connect to 5GC only, EPC only, both 5GC and EPC for this PLMN. The Core Network type restriction when received applies in the PLMN either to both 3GPP and non-3GPP Access Types or to non-3GPP Access Type only.
NOTE 6: The Core Network type restriction can be used e.g. in network deployments where the E-UTRAN connects to both EPC and 5GC as described in clause 5.17. When the Core Network type restriction applies to non-3GPP Access Type, the UE is restricted from using any connectivity to an N3IWF.
- Closed Access Group information:
As defined in clause 5.30.3.
For a given UE, the core network determines the Mobility Restrictions based on UE subscription information, UE location and/or local policy (e.g. if the HPLMN has not deployed 5GC, HPLMN ID of the UE and the operator's policy are used in the VPLMN for determining the Core Network type restriction). The Mobility Restriction may change due to e.g. UE's subscription, location change and local policy. Optionally the Service Area Restrictions or the Non-Allowed Area may in addition be fine-tuned by the PCF e.g. based on UE location, PEI and network policies. Service Area Restrictions may be updated during a Registration procedure or UE Configuration Update procedure.
If the network sends Service Area Restrictions to the UE, the network sends only either an Allowed Area, or a Non-Allowed Area, but not both at the same time, to the UE. If the UE has received an Allowed Area from the network, any TA not part of the Allowed Area is considered by the UE as non-allowed. If the UE has received a Non-Allowed Area from the network, any TA not part of the Non-Allowed Area is considered by the UE as allowed. If the UE has not received any Service Area Restrictions, any TA in the PLMN is considered as allowed.
If the UE has overlapping areas between Forbidden Areas, Service Area Restrictions, or any combination of them, the UE shall proceed in the following precedence order:
- The evaluation of Forbidden Areas shall take precedence over the evaluation of Service Area Restrictions.
The UDM shall provide to the AMF the information defined in TS 23.008 [119] about the subscriber's NR or E-UTRA access restriction set by the operator determined e.g. by subscription scenario and roaming scenario:
- For NR:
- NR not allowed as primary RAT, however any of the NR categories listed below may still be allowed.
- NR not allowed as secondary RAT.
- NR in unlicensed bands not allowed as primary RAT.
- NR in unlicensed bands not allowed as secondary RAT.
- NR(LEO) satellite access not allowed as primary RAT.
- NR(MEO) satellite access not allowed as primary RAT.
- NR(GEO) satellite access not allowed as primary RAT.
- NR(OTHERSAT) satellite access not allowed as primary RAT.
- NR RedCap not allowed as primary RAT.
- NR eRedCap not allowed as primary RAT.
- For E-UTRA:
- E-UTRA not allowed as primary RAT.
- E-UTRA not allowed as secondary RAT.
- E-UTRA in unlicensed bands not allowed as secondary RAT.
- NB-IoT not allowed as primary RAT.
- LTE-M not allowed as primary RAT.
- WB-E-UTRAN (LEO) satellite access not allowed as primary access.
- WB-E-UTRAN (MEO) satellite access not allowed as primary access.
- WB-E-UTRAN (GEO) satellite access not allowed as primary access.
- WB-E-UTRAN (OTHERSAT) satellite access not allowed as primary access.
- LTE-M (LEO) satellite access not allowed as primary access.
- LTE-M (MEO) satellite access not allowed as primary access.
- LTE-M (GEO) satellite access not allowed as primary access.
- LTE-M (OTHERSAT) satellite access not allowed as primary access.
NOTE 7: The use of WB-E-UTRAN satellite accesses, NB-IoT satellite accesses or LTE-M satellite accesses to connect to 5GC is not supported in this Release of the specification. The access restriction data for LTE-M satellite accesses above is supported only to allow the AMF to provide it to MME in case of mobility from 5GS to EPS.
In order to enforce all primary RAT restrictions, the related RAT has to be deployed in different Tracking Area Codes and the subscriber shall not be allowed to access the network in TAs using the particular RAT.
With all secondary RAT restrictions, the subscriber shall not be allowed to use this RAT as secondary RAT. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.4.1.2 Management of Service Area Restrictions | This clause describes Service Area Restrictions for 3GPP access. For Service Area Restrictions when using wireline access, see TS 23.316 [84].
A Service Area Restriction may contain one or more (e.g. up to 16) entire Tracking Areas each or the Service Area Restriction may be set as unlimited (i.e. contain all Tracking Areas of the PLMN). The UE's subscription data in the UDM includes a Service Area Restriction which may contain either Allowed or Non-Allowed Areas–specified by using explicit Tracking Area identities and/or other geographical information (e.g. longitude/latitude, zip code, etc). The geographical information used to specify Allowed or Non-Allowed Area is only managed in the network and the network will map it to a list of TAs before sending Service Area Restriction information to the PCF, NG-RAN and UE.
When the AMF assigns a limited allowed area to the UE, the AMF shall provide the UE with Service Area Restrictions which consist of either Allowed Areas or Non-Allowed Areas. The Allowed Areas included in the Service Area Restrictions can be pre-configured and/or dynamically assigned by the AMF.
The Allowed Area may alternatively be configured as unlimited i.e. it may contain all Tracking Areas of the PLMN. The Registration Area of a UE in the Non-Allowed Area should consist of a set of TAs which belongs to a Non-Allowed Area of the UE. The Registration Area of a UE in the Allowed Area should consist of a set of TAs which belongs to an Allowed Area of the UE. The AMF provides the Service Area Restriction in the form of TA(s), which may be a subset of full list stored in UE's subscription data or provided by the PCF, to the UE during the Registration procedure.
NOTE: As the finest granularity for Service Area Restrictions are at TA level, subscriptions with limited geographical extent, like subscriptions for Fixed Wireless Access, will be allocated one or a few TAs and will consequently be allowed to access services in a larger area than in e.g. a FWA system.
The limited allowed area may also be limited by the AMF by a maximum allowed number of Tracking Areas, even though this limitation is not sent to the UE. If maximum allowed number of Tracking Areas is used in combination with Allowed Area, the maximum allowed number of Tracking Areas indicates (to the AMF) the maximum number of TAs allowed in limited allowed area inside the Allowed Area. If maximum allowed number of Tracking Areas is used in combination with Non-Allowed Area, the maximum allowed number of Tracking Areas indicates (to the AMF) the maximum number of TAs allowed in limited allowed area outside of the Non-Allowed Area.
The UDM stores the Service Area Restrictions of a UE as part of the UE's subscription data. The PCF in the serving network may (e.g. due to varying conditions such as UE's location, application in use, time and date) further adjust Service Area Restrictions of a UE, either by expanding an Allowed Area or by reducing a Non-Allowed Area or by increasing the maximum allowed number of Tracking Areas. If NWDAF is deployed, the PCF may use analytics (i.e. statistics or predictions) on UE mobility from NWDAF (see TS 23.288 [86]) to adjust Service Area Restrictions. The UDM and the PCF may update the Service Area Restrictions of a UE at any time. For the UE in CM-CONNECTED state the AMF updates the UE and RAN immediately. For UE in CM-IDLE state the AMF may page the UE immediately or store the updated service area restriction and update the UE upon next signalling interaction with the UE, as defined in TS 24.501 [47].
During registration, if the Service Area Restrictions of the UE is not present in the AMF, the AMF fetches from the UDM the Service Area Restrictions of the UE that may be further adjusted by the PCF. The serving AMF shall enforce the Service Area Restrictions of a UE. A limited allowed area given by a maximum allowed number of Tracking Areas, may be dynamically assigned by the AMF adding any not yet visited (by the UE) Tracking Areas to the limited allowed area until the maximum allowed number of Tracking Areas is reached (i.e. the AMF adds new TAs to the limited allowed area until the number of TAs is equal to the maximum allowed number of Tracking Areas). The AMF deletes the list of TAs that have been used up under the maximum allowed number of Tracking Areas quota at every Initial Registration.
For a UE in CM-CONNECTED state the AMF shall indicate the Service Area Restrictions of this UE to the RAN, using a Mobility Restriction List.
The UE shall store the received Service Area Restrictions and, if there is previously stored Service Area Restrictions, replace them with the newly received information. If the Service Area Restrictions include a limited allowed area, the Service Area Restrictions are applicable for the Tracking areas indicated in Service Area Restrictions. If the Service Area Restrictions included an unlimited allowed area, the received Service Area Restrictions are either applicable for the registered PLMN and its equivalent PLMN(s) that are available in the Registration Area, or the registered SNPN that is available in the Registration Area. The RAN uses the Service Area Restrictions for target cell selection in Xn and N2 based handover.
Upon change of serving AMF due to mobility, the old AMF may provide the new AMF with the Service Area Restrictions of the UE that may be further adjusted by the PCF.
The network may perform paging for a UE to update Service Area Restrictions with Generic UE Configuration Update procedure (see clause 4.2.4 of TS 23.502 [3]).
In the case of roaming, the Service Area Restrictions are transferred from the UDM via the serving AMF to the serving PCF in the visited network. The serving PCF in the visited network may further adjust the Service Area Restrictions.
Support for Service Area Restrictions with NR satellite access is described in clause 5.4.11.8. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.4.2 Mobility Pattern | The Mobility Pattern is a concept that may be used by the AMF to characterise and optimise the UE mobility. The AMF determines and updates Mobility Pattern of the UE based on subscription of the UE, statistics of the UE mobility, network local policy and the UE assisted information, or any combination of them. The statistics of the UE mobility can be historical or expected UE moving trajectory. If NWDAF is deployed, the statistics of the UE mobility can also be analytics (i.e. statistics or predictions) provided by the NWDAF (see TS 23.288 [86]).
The Mobility Pattern can be used by the AMF to optimize mobility support provided to the UE, for example, Registration area allocation. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.4.3 Radio Resource Management functions | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.4.3.1 General | To support radio resource management in NG-RAN the AMF provides the parameter 'Index to RAT/Frequency Selection Priority' (RFSP Index) to NG-RAN across N2. The RFSP Index is mapped by the RAN to locally defined configuration in order to apply specific RRM strategies, taking into account any available information in RAN. The RFSP Index is UE specific and applies to all the Radio Bearers. Examples of how this parameter may be used by the RAN:
- to derive UE specific cell reselection priorities to control idle mode camping.
- to decide on redirecting active mode UEs to different frequency layers or RATs (e.g. see clause 5.3.4.3.2).
The HPLMN may set the RFSP Index taking into account the Subscribed S-NSSAIs. The AMF receives the subscribed RFSP Index from the UDM (e.g. during the Registration procedure). For non-roaming subscribers, the AMF chooses the RFSP Index in use according to one of the following procedures, depending on operator's configuration:
- the RFSP Index in use is identical to the subscribed RFSP Index, or
- the AMF chooses the RFSP Index in use based on the subscribed RFSP Index, the locally configured operator's policies, the Allowed NSSAI and any Partially Allowed NSSAI, S-NSSAI(s) rejected partially in the RA, Rejected S-NSSAI(s) for the RA, Pending NSSAI and the UE related context information available at the AMF, including UE's usage setting, if received during Registration procedures (see clause TS 23.502 [3]).
NOTE 1: One example of how the AMF can use the "UE's usage setting," is to select an RFSP value that enforces idle mode camping on E-UTRA for a UE acting in a "Voice centric" way, in the case voice over NR is not supported in the specific Registration Area and it contains NR cells.
The AMF may report to the PCF the subscribed RFSP Index received from the UDM for further evaluation as described in clause 6.1.2.1 of TS 23.503 [45]. When receiving the authorized RFSP Index from the PCF, the AMF shall apply the authorized RFSP Index instead of the subscribed RFSP Index for choosing the RFSP index in use (as described above).
For roaming subscribers, the AMF may choose the RFSP Index in use based on the visited network policy, but can take input from the HPLMN into account (e.g. an RFSP Index value pre-configured per HPLMN, or a single RFSP Index value to be used for all roamers independent of the HPLMN). If the AMF receives authorized RFSP Index value from the V-PCF, the AMF chooses the RFSP index in use based on the authorized RFSP Index value.
NOTE 2: The PCF can provide validity time together with the authorized RFSP Index indicating a change in priority from 5G access to E-UTRAN access as specified in clause 5.17.2.2.
The RFSP Index in use is also forwarded from source to target NG-RAN node when Xn or N2 is used for intra-NG-RAN handover.
The AMF stores the subscribed RFSP Index value received and the RFSP Index value in use. During the Registration procedure, the AMF may update the RFSP Index value in use (e.g. the AMF may need to update the RFSP Index value in use if the UE related context information in the AMF has changed). When the RFSP Index value in use is changed, the AMF immediately provides the updated RFSP Index value in use to NG-RAN node by modifying an existing UE context or by establishing a new UE context in RAN or by being configured to include the updated RFSP Index value in use in the NGAP DOWNLINK NAS TRANSPORT message if the user plane establishment is not needed. During inter-AMF mobility procedures, the source AMF forwards both RFSP Index values to the target AMF. The target AMF may replace the received RFSP Index value in use with a new RFSP Index value in use that is based on the operator's policies and the UE related context information available at the target AMF.
In order to enable UE idle mode mobility control and priority-based reselection mechanism considering availability of Network Slices at the network and the Network Slices allowed for a UE, an RFSP is derived as described in clause 5.3.4.3, considering also the Allowed NSSAI and any Partially Allowed NSSAI for the UE.
A UE supporting NSAG (see clause 5.15.14) may be configured, for some of the S-NSSAIs in the configured NSSAI, with NSAGs it can use as described in TS 38.300 [27], TS 38.304 [50], TS 38.331 [28], TS 38.321 [143], TS 24.501 [47] and as described in clause 5.3.4.3.4. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.4.3.2 Preferred band(s) per data radio bearer(s) | The NG-RAN may prefer to use specific radio resources per data radio bearer(s), e.g. depending on the Network Slices associated to the data radio bearer used by the UE. The UE idle mode mobility control and priority-based reselection mechanism operates as described in clause 5.3.4.3.1 and when UP resources are activated e.g. for a specific S-NSSAI the NG-RAN can use local policies to decide on what specific radio resources to use for the associated data radio bearer(s). A UE may be served by a set of data radio bearers which may be served by cells in different bands, selected based on RRM policies. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.4.3.3 Redirection to dedicated frequency band(s) for an S-NSSAI | If a Network Slice, S-NSSAI, is configured to be available only in TAs covering specific dedicated frequency band(s), then there may be a need to redirect the UE to the dedicated frequency band(s) when such S-NSSAI is requested. If the Requested NSSAI contains S-NSSAI(s) that are not available in the UE's current TA, see clause 5.15.8, the AMF itself or by interacting with the NSSF as described in clause 5.15.5.2.1 may determine a Target NSSAI to be used by the NG-RAN, in addition to the information the AMF receives, such as the Allowed NSSAI and the RFSP for the Allowed NSSAI, to attempt to redirect the UE to a cell and TA in another frequency band and TA that supports the S-NSSAIs in the Target NSSAI. The Target NSSAI includes at least one S-NSSAI from the Requested NSSAI not available in the current TA, but available in another TA in different frequency band possibly overlapping with the current TA and optionally additional S-NSSAIs from the Requested NSSAI that are configured to be available within the same TAs as the S-NSSAIs not available in the current TA. If the serving PLMN supports the subscription-based restrictions to simultaneous registration of network slices (see clause 5.15.12) and if the UE has NSSRG as part of the subscription information received from the HPLMN, the Target NSSAI includes only S-NSSAIs sharing at least one NSSRG.
The Target NSSAI may be excluding some of the S-NSSAIs in the Allowed NSSAI and include some of the rejected S-NSSAIs due to lack of support in the TA where the UE is located based on network policies that are in line with customer and operator agreements.
The Target NSSAI shall only include S-NSSAIs that can be provided in an Allowed NSSAI, or in an Allowed NSSAI and Partially Allowed NSSAI, for the UE. The Target NSSAI includes at least one Rejected S-NSSAI and may include e.g.:
- all or a subset of the Rejected S-NSSAIs for RA, all or a subset of the S-NSSAIs rejected partially in the RA, all or a subset of Partially Allowed NSSAI when none of the S-NSSAIs in the Requested S-NSSAI were available in the TA where the UE is;
- all the S-NSSAIs of the Allowed NSSAI, all the S-NSSAIs of the Partially Allowed NSSAI and all or a subset of the Rejected S-NSSAIs for the RA and all or subset of S-NSSAIs rejected partially in the RA;
- a subset of the S-NSSAIs in the Allowed NSSAI, a subset of the S-NSSAIs in the Partially Allowed NSSAI and all or a subset of the Rejected S-NSSAIs for the RA and all or subset of S-NSSAIs rejected partially in the RA, if the operator policy is to prefer this Target S-NSSAI to the Allowed NSSAI.
The AMF should retrieve an RFSP Index suitable for the Target NSSAI and includes the RFSP Index in the information sent to the NG-RAN. The AMF retrieves the RFSP Index from the PCF or, in case PCF is not deployed the AMF determines the RFSP Index according to local configuration. The RFSP index associated to the Target NSSAI is considered if the NG-RAN succeeds to redirect the UE to a new TA where the Target NSSAI, or some S-NSSAIs of the Target NSSAI are supported, otherwise the RFSP index of the Allowed NSSAI is considered.
If the Requested NSSAI contains S-NSSAI(s) which map to S-NSSAI(s) of the HPLMN subject to Network Slice-Specific Authentication and Authorization that are not available in the UE's current TA, the AMF shall proceed with the Network Slice-Specific Authentication and Authorization procedure as described in clause 4.2.9 of TS 23.502 [3]. If the AMF determines a new Allowed NSSAI and/or Partially Allowed NSSAI at the end of Network Slice-Specific Authentication and Authorization steps and some S-NSSAI is not available in the UE's current TA, a Target NSSAI and corresponding RFSP index may be determined and provided to NG-RAN during UE Configuration Update procedure as described in clause 4.2.4.2 of TS 23.502 [3].
The NG-RAN shall attempt to find cells of TAs that can support all the S-NSSAIs in the Target S-NSSAIs and if no such cell of a TA is available the RAN can attempt to select cells of TAs that best match the Target S-NSSAI. The NG-RAN shall attempt to ensure continuity of the PDU Sessions with activated User Plane associated with the S-NSSAIs in the Allowed NSSAI and/or Partially Allowed NSSAI which are in the Target NSSAI. Also, the NG-RAN should attempt to ensure continuity of service for the S-NSSAIs of the Allowed NSSAI and/or Partially Allowed NSSAI also available in the Target NSSAI, before prioritizing cells that are not supporting one or more of the S-NSSAI of the Allowed NSSAI and/or Partially Allowed NSSAI also available in the Target NSSAI.
The NG-RAN attempts to determine target cell(s) supporting the Target NSSAI considering the UE Radio Capabilities (i.e. the AMF (if available in the UE context) shall provide the NG-RAN with the current UE Radio Capability Information or the RACS UE Radio Capability ID when a Target NSSAI is provided, if the NG-RAN had not yet received any of them, or, if the AMF cannot provide any of these, the UE Radio Capability Information may be retrieved by the NG-RAN from the UE).
Once the target cells are determined, the NG-RAN initiates RRC redirection procedure towards the target cells, or the NG-RAN initiates handover for the UE with active PDU Sessions associated with the S-NSSAIs which are in the Target NSSAI, if possible.
After a successful redirection or handover of the UE to a new TA inside the current RA, the UE may request a PDU Session and activate UP resources for a PDU Session for S-NSSAIs of Partially Allowed NSSAI that are supported in the new TA and the UE may request to register S-NSSAIs rejected partially in the RA that are not rejected in the new TA, as described in clause 5.15.17.
After a successful redirection or handover of the UE to a new TA outside the current RA, the UE shall perform a Mobility Registration Update procedure and the S-NSSAIs that the new TA supports can be allowed if the UE requests them. In order to ensure that the UE is redirected to a TA outside the current RA when there are S-NSSAIs Rejected for the RA, thus triggering a Mobility Registration Update procedure enabling the UE to request the S-NSSAI(s) that were rejected for the RA, the AMF shall set the RA so that the RA does not include TAs supporting the S-NSSAIs rejected for the RA included in the Target NSSAI when the AMF provides a Target NSSAI to the RAN. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.4.3.4 Network Slice based cell reselection and Random Access | When one or more S-NSSAI(s) are associated with NSAG(s), the UE may perform Network Slice based cell reselection and Random Access as described in TS 38.300 [27], TS 38.304 [50], TS 38.331 [28], TS 38.321 [143] and TS 24.501 [47].
When providing NSAG Information to the UE, the AMF shall also provide the NSAG priority information for the NSAGs provided in the NSAG Information. The AMF determines the NSAG priority information based on configured local policy of the serving PLMN or SNPN.
NOTE 1: How the AMF assigns the NSAG priority information per UE is not specified but AMF can take into account information like e.g. UE MM capabilities, Subscribed S-NSSAIs and HPLMN.
NOTE 2: The AMF can assign same priority value for NSAGs provided in the NSAG Information.
If the UE has received NSAG Information from the AMF, the UE shall use the NSAG Information provided by the AMF for cell reselection and Random Access as described below. If the UE has not received any NSAG Information from the AMF, the UE shall not use Network Slice based cell reselection and Random Access at all.
The UE NAS provides to the UE AS the NSAG Information as received from the AMF and the S-NSSAIs in the Allowed NSSAI and any Partially Allowed NSSAI as input to cell reselection, except when the UE intends to register with a new (including any S-NSSAIs rejected partially in the RA) set of S-NSSAIs with a Requested NSSAI different from the current Allowed NSSAI and any Partially Allowed NSSAI, in which case the UE NAS provides to the UE AS layer the NSAG Information as received from the AMF and the S-NSSAIs in the Requested NSSAI and this may trigger a cell reselection, before sending the Registration Request including the new Requested NSSAI.
For Network Slice based Random Access, different Random Access resources may be assigned to different NSAG(s). The UE determines Random Access configuration among NSAGs that are published in SIB for Random Access and that are associated to the S-NSSAIs triggering the access. If the signalling transaction triggering the access attempt is related to more than one network slice and the S-NSSAIs of these network slices are associated with more than one NSAG for Random Access, the NSAG with the highest priority is selected.
NOTE 3: How the UE NAS provides the NSAGs priorities to UE AS is based internal UE interface and not specified.
When a S-NSSAI is replaced by an Alternative S-NSSAI for a UE supporting the Network Slice Replacement feature (see clause 5.15.19) then the AMF provides updated NSAG information also including the Alternative S-NSSAI to the UE when the Alternative S-NSSAI was not part of the UE Configured NSSAI and is Added to the UE configured NSSAI. The NSAG priority may take into account the Alternative S-NSSAI is a replacement of the replaced NSSAI if the Alternative S-NSSAI is not part of the UE subscription. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.4.4 UE mobility event notification | 5G System supports the functionality of tracking and reporting UE mobility events.
The AMF provides the UE mobility related event reporting to NF that has been authorized to subscribe to the UE mobility event reporting service. Any NF service consumer such as SMF, NEF, LMF, TSCTSF or NWDAF that wants to be reported on the UE location is able to subscribe to the UE mobility event notification service to the AMF with the following parameters:
- Event reporting type that specifies what to be reported on UE mobility (e.g. UE location, UE mobility on Area of Interest).
- Event filters indicating the:
- Area Of Interest that specifies a location area within 3GPP system. The Area Of Interest is represented by a list of Tracking Areas, list of cells or list of (R)AN node identifiers. In the case of LADN, the event consumer (e.g. SMF) provides the "LADN DNN" or "LADN DNN and S-NSSAI" to refer the LADN service area as the Area Of Interest. In the case of PRA, the event consumer (e.g. SMF or PCF) may provide an identifier for Area Of Interest to refer predefined area as the Area Of Interest. In the case of Partial Network Slice Support and Support for Network Slices with Network Slice Area of Service not matching deployed Tracking Areas as described in clauses 5.15.17 and 5.15.18, the event consumer (e.g. SMF) provides the S-NSSAI to refer the slice restriction area (area restriction applies for the S-NSSAI) as the Area Of Interest.
- The Area Of Interest may include a "RAN timing synchronization status change event" indicator, indicating that the presence in Area of Interest can be determined based on the most recent N2 connection.
- The Area Of Interest may include an "Adjust AoI based on RA" indicator, indicating that the Area of Interest may be adjusted depending on UE's RA.
- The Area Of Interest may include the "Notify the consumer considering UE identity" indicator, containing a list of UE identities or Internal Group ID and informing the AMF to notify the NF consumer about Area of Interest events only if an event is for the UE belonging to the provided list UEs. The indicator may be included when the request is targeted to Any UE.
- The Area Of Interest may include the "Notify the consumer considering DNN/S-NSSAI" indicator, containing one or more DNN(s)/S-NSSAI(s) and informing the AMF to notify the NF consumer about Area of Interest events only if an event is for the UE having a PDU sessions established for the specified DNN(s)/S-NSSAI(s).
- S-NSSAI and optionally the NSI ID(s).
- Event Reporting Information: event reporting mode, number of reports, maximum duration of reporting, event reporting condition (e.g. when the target UE moved into a specified Area Of Interest, immediate reporting flag, reporting threshold reached).
- Notification Endpoint of NF service consumer to be notified.
- The target of event reporting that indicates a (list of) specific UE(s), a group of UE(s) or any UE (i.e. all UEs served by the AMF). Further details on the information provided by the NF service consumer are provided in clause 4.15 of TS 23.502 [3].
If an NF service consumer subscribes to the UE mobility event notification service provided by AMF for reporting of UE presence in Area Of Interest, the AMF tracks UE's location considering UE's CM state and using NG-RAN procedures (if RRC_INACTIVE state applies to NG-RAN) in order to determine the UE presence in the Area Of Interest, as described in clause 4.15.4.2 of TS 23.502 [3]. Upon detecting the change of the UE presence in the Area Of Interest, the AMF notifies the UE presence in the Area Of Interest and the new UE location to the subscribed NF service consumer.
If the Area Of Interest in the subscription to the UE mobility event notification includes "RAN timing synchronization status change event" indicator as described in Table 5.2.2.3.1-1 of TS 23.502 [3] and the registration request from the UE includes a UE 5GMM Core Network Capability with an indication for "support for network reconnection due to RAN timing synchronization status change " as described in clause 5.4.4a, the AMF reports the UE presence in Area of Interest based on the most recent N2 connection as described in Annex D of TS 23.502 [3].
If the Area Of Interest in the subscription to the UE mobility event notification includes "Adjust AoI based on RA" indicator as described in Table 5.2.2.3.1-1 in TS 23.502 [3], the AMF reports the UE presence in Area of Interest based on the most recent N2 connection as described in Annex D in TS 23.502 [3].
When the AMF is changed, the subscription of mobility event for a UE or group of UEs is transferred from the old AMF. Subscriptions targeted to Any UE shall not be moved to another AMF due to UE mobility. The new AMF may decide not to notify the SMF with the current status related to the subscription of mobility event if the new AMF determines that, based on MM Context of the UE, the event is reported by the old AMF.
In the network deployment where a UE may leave or enter the Area Of Interest without any notification to the 5GC in CM-CONNECTED state (i.e. in the case that RRC_INACTIVE state applies to the NG-RAN), the AMF may initiate the NG-RAN location reporting as described in clause 5.4.7 or N2 Notification as described in clause 4.8.3 of TS 23.502 [3] to track the UE presence in the Area Of Interest.
The AMF may provide UE mobility event reporting to PCF, using Policy Control Request Triggers defined in TS 23.503 [45]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.3.5 Triggers for network analytics | Triggers for the AMF to request for or subscribe to the analytics information from the NWDAF are internal logic in the AMF and may include for example:
- UE access and mobility related event subscription by other NFs (e.g. SMF, NEF);
- locally detected events;
- analytics information received.
The trigger conditions may depend on operator and implementation policy in the AMF. When a trigger condition happens, the AMF may decide if any analytics information is needed and if so, request for or subscription to the analytics information from the NWDAF.
The AMF may, upon detection of certain local events, e.g. frequent mobility re-registration of one or more UEs, subscribe to mobility related abnormal behaviour analytics of the UE(s) as described in TS 23.288 [86] in order to trace UE mobility trend and take appropriate actions. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4 3GPP access specific aspects | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.1 UE reachability in CM-IDLE | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.1.1 General | Reachability management is responsible for detecting whether the UE is reachable and providing UE location (i.e. access node) for the network to reach the UE. This is done by paging UE and UE location tracking. The UE location tracking includes both UE registration area tracking (i.e. UE registration area update) and UE reachability tracking ((i.e. UE periodic registration area update)). Such functionalities can be either located at 5GC (in the case of CM-IDLE state) or NG-RAN (in the case of CM-CONNECTED state).
The UE and the AMF negotiate UE reachability characteristics for CM-IDLE state during Registration procedures.
Three UE reachability categories are negotiated between UE and AMF for CM-IDLE state:
1. UE reachability allowing Mobile Terminated data while the UE is CM-IDLE state.
- The UE location is known by the network on a Tracking Area List granularity
- Paging procedures apply to this category.
- Mobile originating and mobile terminated data apply in this category for both CM-CONNECTED and CM-IDLE state.
2. Mobile Initiated Connection Only (MICO) mode:
- Mobile originated data applies in this category for both CM-CONNECTED and CM-IDLE state.
- Mobile terminated data is only supported when the UE is in CM-CONNECTED state.
3. UE unreachability due to Unavailability Period:
- Mobile originated data and Mobile terminated data are not transmitted in this category (handling of data by extending buffering may apply).
- Paging procedure is not applicable to this category.
Whenever a UE in RM-REGISTERED state enters CM-IDLE state, it starts a periodic registration timer according to the periodic registration timer value received from the AMF during a Registration procedure.
The AMF allocates a periodic registration timer value to the UE based on local policies, subscription information and information provided by the UE. After the expiry of the periodic registration timer, the UE shall perform a periodic registration. If the UE moves out of network coverage when its periodic registration timer expires, the UE shall perform a Registration procedure when it next returns to the coverage.
The AMF runs a Mobile Reachable timer for the UE. The timer is started with a value longer than the UE's periodic registration timer whenever the CM state for the UE in RM-REGISTERED state changes to CM-IDLE. If the AMF receives an elapsed time from RAN when RAN initiate UE context release indicating UE unreachable, the AMF should deduce a Mobile Reachable timer value based on the elapsed time received from RAN and the normal Mobile Reachable timer value. The AMF stops the Mobile Reachable timer, if the UE CM state in the AMF moves to CM-CONNECTED state. If the Mobile Reachable timer expires, the AMF determines that the UE is not reachable.
However, the AMF does not know for how long the UE remains not reachable, thus the AMF shall not immediately de-register the UE. Instead, after the expiry of the Mobile Reachable timer, the AMF should clear the PPF and shall start an Implicit De-registration timer, with a relatively large value. The AMF shall stop the Implicit De-registration timer and set the PPF if the AMF moves the UE CM state in the AMF to CM-CONNECTED state.
NOTE: If the UE CM state in the AMF is CM-IDLE, then AMF considers the UE always unreachable if the UE is in MICO mode (refer to clause 5.4.1.3).
If the UE indicates an Unavailability Period Duration, then AMF shall consider the UE as unreachable during the unreachability period as described in clause 5.4.1.4.
If the UE is unreachable (i.e. the PPF is not set), the AMF does not page the UE and shall reject any request for delivering DL signalling or data to this UE.
If the Implicit De-registration timer expires before the UE contacts the network, the AMF implicitly de-register the UE.
As part of deregistration for a particular access (3GPP or non-3GPP), the AMF shall request the UE's related SMF to release the PDU Sessions established on that access. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.1.2 UE reachability allowing mobile terminated data while the UE is CM-IDLE | The AMF considers a UE in RM-REGISTERED state to be reachable by CN paging if the UE CM state in the AMF is CM-IDLE state unless the UE applies MICO mode or the UE has indicated Unavailability Period Duration. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.1.3 Mobile Initiated Connection Only (MICO) mode | A UE may indicate preference for MICO mode during Initial Registration or Mobility Registration Update procedure. The AMF, based on local configuration, Expected UE Behaviour and/or Network Configuration parameters if available from the UDM, UE indicated preferences, UE subscription information and network policies, or any combination of them, determines whether MICO mode is allowed for the UE and indicates it to the UE during Registration procedure. If NWDAF is deployed, the AMF may also use analytics on UE mobility and/or UE communication generated by NWDAF (see TS 23.288 [86]) to decide MICO mode parameters. If the UE does not indicate preference for MICO mode during Registration procedure, the AMF shall not activate MICO mode for this UE.
The UE and the AMF re- negotiate the MICO mode at every subsequent Registration procedure. When the UE is in CM-CONNECTED, the AMF may deactivate MICO mode by triggering Mobility Registration Update procedure through UE Configuration Update procedure as described in clause 4.2.4 of TS 23.502 [3].
The AMF assigns a registration area to the UE during the Registration procedure. When the AMF indicates MICO mode to a UE, the registration area is not constrained by paging area size. If the AMF serving area is the whole PLMN, based on local policy and subscription information, may decide to provide an "all PLMN" registration area to the UE. In that case, re-registration to the same PLMN due to mobility does not apply.
If Mobility Restrictions are applied to a UE in MICO mode, the AMF needs to allocate an Allowed Area/Non-Allowed Area to the UE as specified in clause 5.3.4.1.
When the AMF indicates MICO mode to a UE, the AMF considers the UE always unreachable while the UE CM state in the AMF is CM-IDLE. The AMF rejects any request for downlink data delivery for UE in MICO mode and whose UE CM state in the AMF is CM-IDLE with an appropriate cause. For MT-SMS over NAS, the AMF notifies the SMSF that UE is not reachable, then the procedure of the unsuccessful Mobile terminating SMS delivery described in clause 4.13.3.9 of TS 23.502 [3] is performed. The AMF also defers location services, etc. The UE in MICO mode is only reachable for mobile terminated data or signalling when the UE is in CM-CONNECTED.
A UE in MICO mode need not listen to paging while in CM-IDLE. A UE in MICO mode may stop any access stratum procedures in CM-IDLE, until the UE initiates transition from CM-IDLE to CM-CONNECTED due to one of the following triggers:
- A change in the UE (e.g. change in configuration) requires an update of its registration with the network.
- Periodic registration timer expires.
- MO data pending.
- MO signalling pending (e.g. SM procedure initiated).
If a registration area that is not the "all PLMN" registration area is allocated to a UE in MICO mode, then the UE determines if it is within the registration area or not when it has MO data or MO signalling and the UE performs Mobility Registration Update before the UE initiates the MO data or MO signalling if it is not within the registration area.
A UE initiating emergency service shall not indicate MICO preference during Registration procedure. When the MICO mode is already activated in the UE, the UE and AMF shall locally disable MICO mode after PDU Session Establishment procedure for Emergency Services is completed successfully. The UE and the AMF shall not enable MICO mode until the AMF accepts the use of MICO mode in the next registration procedure. To enable an emergency call back, the UE should wait for a UE implementation-specific duration of time before requesting the use of MICO mode after the release of the emergency PDU session.
In order to enable power saving for MT reachability e.g. for Cellular IoT, enhancements to MICO mode are specified in clause 5.31.7:
- MICO mode with Extended Connected Time.
- MICO mode with Active Time.
- MICO mode and Periodic Registration Timer Control. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.1.4 Support of Unavailability Period | During Registration procedure, the UE supporting the Unavailability Period feature provides "Unavailability Period Support" indication as part of 5GMM Core Network Capability in Registration Request message for initial registration and for every mobility registration. The AMF indicates whether the corresponding feature is supported in the AMF by providing the "Unavailability Period Support" indication in Registration Accept message.
If the UE and network support Unavailability Period and an event is triggered in the UE that would make the UE unavailable or lose coverage (see clause 5.4.13.1) for a certain period of time, the UE uses Support of Unavailability Period to inform the AMF of the expected unavailability and whether it is due to NR satellite access discontinuous coverage. Use of Support of Unavailability Period for loss of coverage due to NR satellite access discontinuous coverage shall only be used if both UE and the AMF signalled "Unavailability Period Support", see clause 5.4.13.1.
If the use of Support of Unavailability Period procedure is not due to NR satellite access discontinuous coverage, the UE may store its MM and SM context in the USIM or Non-Volatile memory in the ME to be able to reuse it after its unavailability period. If the UE can store its contexts the UE may trigger Mobility Registration Update procedure otherwise the UE shall trigger UE-initiated Deregistration procedure.
NOTE 1: How and where the UE stores its contexts depends upon the UE implementation and the Unavailability Type. The UE can store some or all of its contexts in the ME or USIM using existing ME or USIM functionality.
Before the start of an event that makes the UE unavailable, the UE triggers either Mobility Registration Update or UE initiated Deregistration procedure:
a) If the UE initiates Mobility Registration Update procedure:
0) The UE includes an Unavailability Type to describe the cause of unavailability (e.g. the unavailability caused by NR satellite access discontinuous coverage), the Start of the Unavailability Period if known and the Unavailability Period Duration (if known).
1) If the UE did not include a Start of Unavailability Period, the AMF considers implicitly the Start of Unavailability Period to be the time at which it has received the Registration Request message from the UE. If the UE included a Start of Unavailability Period, the Start of Unavailability Period indicates the time at which the UE determines it expects to be unavailable, i.e. time until which the UE determines it is available.
2) The AMF may determine, if not provided by the UE, or update the Unavailability Period Duration and/or the Start of Unavailability Period.
If unavailability is caused by NR satellite access discontinuous coverage and the AMF knows an Unavailability Period Duration and/or the Start of Unavailability Period (e.g. based on the Unavailability Type and other information available to the AMF as described in clause 5.4.13.3) and the UE did not include an Unavailability Period Duration and/or the Start of Unavailability Period or the UE included an Unavailability Period Duration and/or the Start of Unavailability Period different to the Unavailability Period Duration and/or the Start of Unavailability Period known to the AMF, the AMF should include the Unavailability Period Duration and/or the Start of Unavailability Period known to the AMF in the Registration Accept and use those values in subsequent steps of this procedure. How the UE treats the AMF provided Unavailability Period Duration and/or the Start of Unavailability Period is up to UE implementation e.g. to help to determine when to return to coverage after a discontinuous coverage period, whether to listen to paging in eDRX, not to initiate any NAS signalling (including Service Request for MO data) within the discontinuous coverage period in case of any UL signalling/data request or the UE may deactivate its Access Stratum functions for NR satellite access in order to optimise power consumption until coverage returns, etc.
If unavailability is not caused due to NR satellite access discontinuous coverage then AMF uses the Unavailability Period Duration and/or the Start of Unavailability Period as indicated by the UE in the subsequent steps of this procedure.
3) The AMF indicates to the UE in the Registration Accept whether the UE is not required to perform a Registration procedure when the unavailability period has ended.
4) The AMF may take the Unavailability Period Duration (if available) and Start of Unavailability Period into account when determining Periodic Registration Update timer value. The AMF may provide a Periodic Registration Update so the timer does not expire during the Unavailability Period to avoid interfering with the UE dealing with the event that causes the unavailability;
5) The AMF stores the information that the UE is unavailable at the Start of Unavailability Period in UE context and considers the UE is unreachable (i.e. clear the PPF in AMF) from then until the UE enters CM-CONNECTED state;
6) While the UE is unreachable, all high latency communication solutions (see clause 5.31.8) apply if supported in the network, e.g. extended data buffering, downlink data buffering status report, etc; and
7) If there is "Loss of Connectivity" event subscription for the UE by AF, the AMF at the start of Unavailability Period considers the remaining time in the Unavailability Period (if available) when constructing the "Loss of Connectivity" event report towards the NEF and the remaining time in the Unavailability Period is reported to the respective subscribed AF.
b) If the UE initiates UE-initiated Deregistration procedure:
0) The UE includes Unavailability Period Duration (if known).
1) If there is "Loss of Connectivity" event subscription for the UE by AF, the AMF considers the remaining time in the Unavailability Period when constructing the "Loss of Connectivity" event report towards the NEF and the Unavailability Period is reported to the respective subscribed AF;
Furthermore, if the UE initiates Initial Registration procedure and indicates supporting the Unavailability Period feature by providing "Unavailability Period Support" indication as part of 5GMM Core Network Capability, if the AMF is able to determine the Unavailability Period Duration and/or the Start of Unavailability Period of a UE during the UE's initial Registration procedure, the AMF should provide the Unavailability Period Duration and/or the Start of Unavailability Period to the UE in the Registration Accept message and follow the procedure described in bullet a), steps 2 to 7 above.
NOTE 2: The Unavailability Period Duration and/or the Start of Unavailability Period when received in Registration Accept during the initial registration is for NR satellite access discontinuous coverage.
Unless the AMF indicated that the UE is not required to perform a Registration procedure when the unavailability period has ended, then once the event which makes the UE unavailable is completed in the UE, the UE triggers a Registration procedure. If the event which makes the UE unavailable is delayed to a future time or cancelled in the UE or unavailability period deviates from negotiated value, the UE triggers Registration procedure. The UE may also trigger a Registration procedure before the Unavailability Period has started for other reasons. Depending on the UE state, the Registration procedure can be Initial Registration procedure or Mobility Registration Update procedure.
While the UE is in 5GS and if the UE determines that an upcoming loss of coverage no longer applies or determines a new Start of Unavailability Period or Unavailability Period Duration related to the upcoming loss of coverage, the UE sends a new Mobility Registration Update Request to the AMF to update the Start of Unavailability Period and/or Unavailability Period Duration.
The UE and the AMF re-negotiate unavailability at every Registration procedure, if it is required. If Start of Unavailability Period and/or Unavailability Period Duration is not included in a Registration procedure any pending unavailability configuration stored in the UE context at AMF is discarded.
If the UE moves to EPS, the UE performs Attach or Tracking Area update procedure depending on the interworking mechanisms defined in clause 5.17.2.
For discontinuous coverage in E-UTRAN satellite access in EPS, the "Unavailability Period" is also supported (see clause 4.13.8.2 of TS 23.401 [26]).
NOTE 3: In this release of specification there is no transfer of "unavailability period" between AMF and MME and vice versa. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.2 UE reachability in CM-CONNECTED | For a UE in CM-CONNECTED state:
- the AMF knows the UE location on a serving (R)AN node granularity.
- the NG-RAN notifies the AMF when UE becomes unreachable from RAN point of view.
UE RAN reachability management is used by RAN for UEs in RRC_INACTIVE state, see TS 38.300 [27]. The location of a UE in RRC_INACTIVE state is known by the RAN on a RAN Notification area granularity. A UE in RRC_INACTIVE state is paged in cells of the RAN Notification area that is assigned to the UEs. The RAN Notification area can be a subset of cells configured in UE's Registration Area or all cells configured in the UE's Registration Area. UE in RRC_INACTIVE state performs RAN Notification Area Update when entering a cell that is not part of the RAN Notification area that is assigned to the UE.
At transition into RRC_INACTIVE state RAN configures the UE with a periodic RAN Notification Area Update timer value and the timer is restarted in the UE with this initial timer value. After the expiry of the periodic RAN Notification Area Update timer in the UE, the UE in RRC_INACTIVE state performs periodic RAN Notification Area Update, as specified in TS 38.300 [27].
To aid the UE reachability management in the AMF, RAN uses a guard timer with a value longer than the RAN Notification Area Update timer value provided to the UE. Upon the expiry of the periodic RAN Notification Area Update guard timer in RAN, the RAN shall initiate the AN Release procedure as specified in TS 23.502 [3]. The RAN may provide the elapsed time since RAN's last contact with the UE to AMF. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.3 Paging strategy handling | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.3.1 General | Based on operator configuration, the 5GS supports the AMF and NG-RAN to apply different paging strategies for different types of traffic.
In the case of UE in CM-IDLE state, the AMF performs paging and determines the paging strategy based on e.g. local configuration, what NF triggered the paging and information available in the request that triggered the paging. If NWDAF is deployed, the AMF may also use analytics (i.e. statistics or predictions) on the UE's mobility as provided by NWDAF (see TS 23.288 [86]).
In the case of UE in CM-CONNECTED with RRC_INACTIVE state, the NG-RAN performs paging and determines the paging strategy based on e.g. local configuration and information received from AMF as described in clause 5.4.6.3 and SMF as described in clause 5.4.3.2.
In the case of Network Triggered Service Request from SMF, the SMF determines the 5QI and ARP based on the downlink packet (if the SMF performs buffering) or the Downlink Data Report received from UPF (if the UPF performs buffering). The SMF includes the 5QI and ARP corresponding to the QoS Flow of the received downlink PDU in the request sent to the AMF. If the UE is in CM IDLE, the AMF uses e.g. the 5QI and ARP to derive different paging strategies as described in clause 4.2.3.3 of TS 23.502 [3].
NOTE: The 5QI is used by AMF to determine suitable paging strategies. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.3.2 Paging Policy Differentiation | Paging policy differentiation is an optional feature that allows the AMF, based on operator configuration, to apply different paging strategies for different traffic or service types provided within the same PDU Session. In this Release of the specification this feature applies only to PDU Session of IP type.
When the 5GS supports the Paging Policy Differentiation (PPD) feature, the DSCP value (TOS in IPv4 / TC in IPv6) is set by the application to indicate to the 5GS which Paging Policy should be applied for a certain IP packet. For example, as defined in TS 23.228 [15], the P-CSCF may support Paging Policy Differentiation by marking packet(s) to be sent towards the UE that relate to a specific IMS services (e.g. conversational voice as defined in IMS multimedia telephony service).
NOTE 1: This PPD feature may be used to determine the Paging Cause Indication for Voice Service, as described in clause 5.38.3.
It shall be possible for the operator to configure the SMF in such a way that the Paging Policy Differentiation feature only applies to certain HPLMNs, DNNs and 5QIs. In the case of HR roaming, this configuration is done in the SMF in the VPLMN.
NOTE 2: Support of Paging Policy Differentiation in the case of HR roaming requires inter operator agreements including on the DSCP value associated with this feature.
In the case of Network Triggered Service Request and UPF buffering downlink packets, the UPF shall include the DSCP in TOS (IPv4) / TC (IPv6) value from the IP header of the downlink packet and an indication of the corresponding QoS Flow in the Downlink Data Report sent to the SMF. When PPD applies, the SMF determines the Paging Policy Indicator (PPI) based on the DSCP received from the UPF.
In the case of Network Triggered Service Request and SMF buffering downlink packets, when PPD applies, the SMF determines the PPI based on the DSCP in TOS (IPv4) / TC (IPv6) value from the IP header of the received downlink packet and identifies the corresponding QoS Flow from the QFI of the received downlink packet.
The SMF includes the PPI, the ARP and the 5QI of the corresponding QoS Flow in the N11 message sent to the AMF. If the UE is in CM IDLE, the AMF uses this information to derive a paging strategy and sends paging messages to NG-RAN over N2.
NOTE 3: Network configuration needs to ensure that the information used as a trigger for Paging Policy Indication is not changed within the 5GS.
NOTE 4: Network configuration needs to ensure that the specific DSCP in TOS (IPv4) / TC (IPv6) value, used as a trigger for Paging Policy Indication, is managed correctly in order to avoid the accidental use of certain paging policies.
For a UE in RRC_INACTIVE state the NG-RAN may enforce specific paging policies in the case of NG-RAN paging, based on 5QI, ARP and PPI associated with an incoming DL PDU. To enable this, the SMF instructs the UPF to detect the DSCP in the TOS (IPv4) / TC (IPv6) value in the IP header of the DL PDU (by using a DL PDR with the DSCP for this traffic) and to transfer the corresponding PPI in the CN tunnel header (by using a QER with the PPI value). The NG-RAN can then utilize the PPI received in the CN tunnel header of an incoming DL PDU in order to apply the corresponding paging policy for the case the UE needs to be paged when in RRC_INACTIVE state. In the case of Home-Routed roaming, the V-SMF is responsible of controlling UPF setting of the PPI. In the case of PDU Session with I-SMF, the I-SMF is responsible of controlling UPF setting of the PPI. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.3.3 Paging Priority | Paging Priority is a feature that allows the AMF to include an indication in the Paging Message sent to NG-RAN that the UE be paged with priority. The decision by the AMF whether to include Paging Priority in the Paging Message is based on the ARP value in the message received from the SMF for an IP packet waiting to be delivered in the UPF. If the ARP value is associated with select priority services (e.g. MPS, MCS), the AMF includes Paging Priority in the Paging Message. When the NG-RAN receives a Paging Message with Paging Priority, it handles the page with priority.
The AMF while waiting for the UE to respond to a page sent without priority receives another message from the SMF with an ARP associated with select priority services (e.g. MPS, MCS), the AMF sends another Paging message to the (R)AN including the Paging Priority. For subsequent messages, the AMF may determine whether to send the Paging message with higher Paging Priority based on local policy.
For a UE in RRC_INACTIVE state, the NG-RAN determines Paging Priority based on the ARP associated with the QoS Flow as provisioned by the operator policy and the service priority. Service priority is specified as RAN Paging Priority in TS 38.413 [34]. Service priority (values 1 to 256) provides the AN with the importance of the downlink data and signalling. The AMF derives this service priority based on available information as described in clause 5.4.6.3. The method to derive the service priority is implementation dependent and can be controlled by an operator. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.4 UE Radio Capability handling | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.4.1 UE radio capability information storage in the AMF | This clause applies when no radio capability signalling optimisation is used between a UE and the network.
The UE Radio Capability information is defined in TS 38.300 [27] and contains information on RATs that the UE supports (e.g. power class, frequency bands, etc). Consequently, this information can be sufficiently large that it is undesirable to send it across the radio interface at every transition of UE CM state in the AMF from CM‑IDLE to CM‑CONNECTED. To avoid this radio overhead, the AMF shall store the UE Radio Capability information during CM‑IDLE state for the UE and RM-REGISTERED state for the UE and the AMF shall if it is available, send its most up to date UE Radio Capability information to the RAN in the N2 REQUEST message, i.e. INITIAL CONTEXT SETUP REQUEST or UE RADIO CAPABILITY CHECK REQUEST.
NOTE 1: Due to issues with the handling of dynamic UMTS security parameters, the UTRA UE Radio Capability information is excluded from the information that is uploaded and stored in the AMF (see TS 38.300 [27]).
The AMF deletes the UE radio capability when the UE RM state in the AMF transitions to RM-DEREGISTERED. When the AMF receives Registration Request with the Registration type set to Initial Registration or when it receives the first Registration Request after E-UTRA/EPC Attach with Registration type set to Mobility Registration Update, the AMF deletes the UE radio capability.
The UE Radio Capability is maintained in the core network, even during AMF reselection.
NOTE 2: The UE Radio Capability is not transferred to EPC during the inter-system mobility.
If the UE's NG-RAN or E‑UTRAN UE Radio Capability information changes while in CM-IDLE state, the UE shall perform the Registration procedure with the Registration type set to Mobility Registration Update and it also includes "UE Radio Capability Update". (For specific requirements for a UE operating in dual-registration mode see clause 5.17.2.1). When the AMF receives Mobility Registration Update Request with "UE Radio Capability Update" requested by the UE, it shall delete any UE Radio Capability information that it has stored for the UE. If the UE's NG-RAN UE Radio Capability information changes when the UE is in CM-IDLE with Suspend, NAS shall trigger AS to establish a new RRC connection and not resume the existing one in order to perform the Registration procedure with the Registration type set to Mobility Registration Update including "UE Radio Capability Update". As a result of this, the access stratum in the UE will discard the AS information and establish a new RRC connection as defined in TS 36.331 [51].
If the trigger to change the UE's NG-RAN or E‑UTRAN UE Radio Capability information happens when the UE is in CM-CONNECTED state, the UE shall first enter CM-IDLE state and then perform the Registration procedure with the Registration type set to Mobility Registration Update and it also includes "UE Radio Capability Update".
The RAN stores the UE Radio Capability information, received in the N2 message or obtained from the UE, for the duration of the UE staying in RRC_CONNECTED or RRC_INACTIVE state. Before any 5G SRVCC handover attempt from NG-RAN to UTRAN, the RAN retrieves the UE's UTRA UE Radio Capabilities from the UE. (For specific requirements for a UE operating in dual-registration mode see clause 5.17.2.1).
If the AMF sends N2 REQUEST (i.e. INITIAL CONTEXT SETUP REQUEST or UE RADIO CAPABILITY CHECK REQUEST) message to NG-RAN without UE Radio Capability information in that message and there is no UE Radio Capability information available in RAN, this triggers the RAN to request the UE Radio Capability from the UE and to upload it to the AMF in the N2 UE RADIO CAPABILITY INFO INDICATION message.
If a UE supports both NB-IoT and other RATs the UE handles the UE Radio capability information as follows:
- When the UE is camping on NB-IoT the UE provides only NB-IoT UE radio capabilities to the network.
- When the UE is not camping on NB-IoT, the UE provides UE radio capabilities for the RAT but not NB-IoT UE radio capabilities to the network.
In order to handle the distinct UE radio capabilities, the AMF stores a separate NB-IoT specific UE Radio Capability information when the UE provides the UE Radio Capability information while camping on NB-IoT.
When the UE is camping on NB-IoT, the AMF sends, if available, the NB-IoT RAT specific UE Radio Capability information to the E-UTRAN.
When the UE is not camping on NB-IoT, the AMF sends, if available, UE radio capabilities for the RAT but not NB-IoT radio capabilities.
5.4.4.1a UE radio capability signalling optimisation (RACS)
With the increase of the size of UE radio capabilities driven e.g. by additional frequency bands and combinations thereof for E-UTRA and NR, an efficient approach to signal UE Radio Capability Information over the radio interface and other network interfaces is defined with RACS.
In this Release of the specification, RACS does not apply to NB-IOT.
RACS works by assigning an identifier to represent a set of UE radio capabilities. This identifier is called UE Radio Capability ID. A UE Radio Capability ID can be either UE manufacturer-assigned or PLMN-assigned, as specified in clause 5.9.10. The UE Radio Capability ID is an alternative to the signalling of the UE Radio Capability information over the radio interface, within NG-RAN, from NG-RAN to E-UTRAN, from AMF to NG-RAN and between CN nodes supporting RACS.
PLMN-assigned UE Radio Capability ID is assigned to the UE using the UE Configuration Update Command, or Registration Accept as defined in TS 23.502 [3]. The UCMF shall be configured with a Version ID for PLMN-assigned UE Radio Capability IDs, defined in clause 5.9.10.
The UCMF (UE radio Capability Management Function) stores all UE Radio Capability ID mappings in a PLMN and is responsible for assigning every PLMN-assigned UE Radio Capability ID in this PLMN, see clause 6.2.21. The UCMF stores the UE Radio Capability IDs alongside the UE Radio Capability information and the UE Radio Capability for Paging they map to. Each UE Radio Capability ID stored in the UCMF can be associated to one or both UE radio capabilities formats specified in TS 36.331 [51] and TS 38.331 [28]. The two UE radio capabilities formats shall be identifiable by the AMF and UCMF and the AMF shall store the TS 38.331 [28] format only.
An NG-RAN which supports RACS can be configured to operate with one of two modes of operation when providing the UE radio capabilities to the AMF when the NG-RAN executes a UE Radio Capability Enquiry procedure (see TS 38.331 [28]) to retrieve UE radio capabilities from the UE:
- Mode of operation A): The NG-RAN provides to the AMF both formats (i.e. the TS 38.331 [28] format and TS 36.331 [51] format). The NG-RAN derives one of the UE Radio Capability formats using local transcoding of the other format it receives from the UE and extracts the E-UTRAN UE Radio Capability for Paging and NR UE Radio Capability for Paging from the UE Radio capabilities.
- Mode of operation B): The NG-RAN provides to the AMF the TS 38.331 [28] format only.
In a PLMN supporting RACS only in 5GS, Mode of Operation B shall be configured.
If the PLMN supports RACS in both EPS and 5GS:
- If RAN nodes in the EPS and 5GS are configured in Mode of operation B, then the UCMF shall be capable to transcode between TS 36.331 [51] and TS 38.331 [28] formats and the UCMF shall be able to generate the RAT-specific UE Radio Capability for Paging information from the UE Radio Capability.
- If the NG-RAN is configured to operate according to Mode A, then also the E-UTRAN shall be configured to operate according to mode A and the UMCF is not required to transcode between TS 36.331 [51] and TS 38.331 [28] formats and the AMF shall provide the UE Radio Capability for Paging information.
When the NG-RAN updates the AMF with new UE radio capabilities information, the AMF provides the information obtained from the NG-RAN to the UCMF even if the AMF already has a UE Radio Capability ID for that UE. The UCMF then returns a value of UE Radio Capability ID. If the value is different from the one stored in the AMF, the AMF updates the UE Radio Capability ID it stores and provides this new value to the NG-RAN (if applicable) and to the UE.
In order to be able to interpret the UE Radio Capability ID a Network Function or node may store a local copy of the mapping between the UE Radio Capability ID and its corresponding UE Radio Capability information i.e. a dictionary entry. When no mapping is available between a UE Radio Capability ID and the corresponding UE Radio Capability information in a Network Function or node, this Network Function or node shall be able to retrieve this mapping and store it.
- An AMF which supports RACS shall store such UE Radio Capability ID mapping at least for all the UEs that it serves that have a UE Radio Capability ID assigned.
- The NG-RAN performs local caching of the UE Radio Capability information for the UE Radio Capability IDs for the UEs it is serving and potentially for other UE Radio Capability IDs according to suitable local policies.
- When the NG-RAN needs to retrieve the mapping of a UE Radio Capability ID to the corresponding UE Radio Capability information, it queries the AMF using N2 signalling defined in TS 38.413 [34].
- When the AMF needs to obtain a PLMN-assigned UE Radio Capability ID for a UE from the UCMF, it provides the UE Radio Capability information it has for the current radio configuration of the UE and the IMEI/TAC for the UE and the UCMF returns a UE Radio Capability ID. The AMF shall provide to the UCMF the UE Radio Capability information (and at least in Mode A, the UE Radio Capability for Paging) obtained from the NG-RAN in one or both the TS 36.331 [51] and TS 38.331 [28] formats depending on how the RAN is configured. The UCMF stores the association of this IMEI/TAC with this UE Radio Capability ID and the UE Radio Capability information and the UE Radio Capability for Paging in all the formats it receives. The UE Radio Capability information formats the AMF provides shall be identifiable at the UCMF.
- When the AMF needs to obtain the UE Radio Capability information and the UE Radio Capability for Paging associated to a UE Radio Capability ID it provides the UE Radio Capability ID to the UCMF with an indication that it is requesting the TS 38.331 [28] format and the UCMF returns a mapping of the UE Radio Capability ID to the corresponding UE Radio Capability information in TS 38.331 [28] format to the AMF.
- UEs, AMFs and RAN nodes which support RACS learn the current value of the Version ID when a new PLMN-assigned UE Radio Capability ID is received from the UCMF and the Version ID it contains is different from the ones in their PLMN Assigned UE Radio Capability ID cache. For a PLMN, PLMN-assigned UE Radio Capability IDs related to old values (i.e. not current value) of the Version ID can be removed from cache but, if so, prior to removing any cached PLMN-assigned UE radio Capability IDs with the current value of the Version ID. The AMF, RAN and UE may continue to use the stored PLMN assigned UE Radio Capability IDs with old values of the Version ID, until these are purged from cache. If an out of date PLMN assigned UE Radio Capability ID is removed form an AMF cache, the AMF shall proceed to assign a new PLMN assigned UE Radio Capability ID to all the UEs for which the UE context includes the removed PLMN-assigned UE Radio Capability ID using a UE Configuration Update procedure, or when these UEs perform a Registration. If the AMF attempts to resolve a PLMN assigned UE Radio capability ID with an old Version ID, the UCMF shall return an error code indicating that the Version ID in the UE radio capability ID is no longer current and proceed to assign a new UE Radio Capability ID to the UE.
If at any time the AMF has neither a valid UE Radio Capability ID nor any stored UE radio capabilities for the UE, the AMF may trigger the RAN to provide the UE Radio Capability information and subsequently request the UCMF to allocate a UE Radio Capability ID.
- The RAN, in order to support MOCN network sharing scenarios, shall be capable to cache PLMN assigned UE Radio Capability IDs per PLMN ID.
A network may utilise the PLMN-assigned UE Radio Capability ID, without involving the UE, e.g. for use with legacy UEs.
Mutual detection of the support of the RACS feature happens between directly connected NG-RAN nodes and between NG-RAN and AMF using protocol means as defined in TS 38.413 [34] and TS 38.423 [99]. To allow for a mix of RACS-supporting and non-RACS-supporting RAN nodes over the Xn interfaces, the UE Radio Capability ID should be included in the Path Switch signalling during Xn based handover and Handover Request during N2 based handover between AMF and NG-RAN. In addition, RACS-supporting RAN nodes can be discovered across inter-CN node boundaries by using the mechanism defined in TS 38.413 [34] that allows the source NG-RAN node to retrieve information on the level of support for a certain feature at the target NG-RAN side by means of information provided within the Source to Target and Target to Source transparent handover containers during handover procedure. The support of RACS by peer AMFs or MMEs is based on configuration in a PLMN or across PLMNs.
A UE that supports WB-E-UTRA and/or NR indicates its support for RACS to AMF using UE MM Core Network Capability as defined in clause 5.4.4a.
A UE that supports RACS and stores an applicable UE Radio Capability ID for the current UE Radio Configuration in the PLMN, shall signal the UE Radio Capability ID in the Initial and Mobility Registration procedure as defined in TS 23.502 [3] and based on triggers defined in TS 24.501 [47]. If both PLMN-assigned for the current PLMN and UE manufacturer-assigned UE Radio Capability IDs are stored in the UE and applicable in the PLMN, the UE shall signal the PLMN-assigned UE Radio Capability ID in the Registration Request message.
When a PLMN decides to switch to request a particular type of UE to use UE manufacturer-assigned UE Radio Capability ID(s):
- The UCMF sends a Nucmf_UECapabilityManagement_Notify message to the AMF including either a list of UE Radio Capability IDs (if the UE was previously using any PLMN-assigned IDs) or the IMEI/TAC values corresponding to UE types that are requested to use UE manufacturer-assigned UE Radio Capability ID. These values are stored in a "UE Manufacturer Assigned operation requested list" in the AMF.
- The AMF uses the Registration Accept message or the UE Configuration Update command message to request the UE to delete all the PLMN-assigned UE Radio Capability ID(s) for this PLMN if the UE is, respectively, registering or is registered with PLMN-assigned ID or IMEI/TAC values matching one value in the "UE Manufacturer Assigned operation requested list".
NOTE 1: It is expected that in a given PLMN the UCMF and AMFs will be configured to either use a UE manufacturer-assigned operation requested list based on a list of PLMN-assigned UE Radio Capability IDs or a list of IMEI/TACs, but not both.
NOTE 2: The strategy for triggering of the deletion of PLMN-assigned UE Radio Capability ID(s) in the UE by the AMF is implementation-specific (e.g. can be used only towards UEs in CM-CONNECTED state).
- a UE that receives indication to delete all the PLMN-assigned UE Radio Capability IDs in the Registration Accept message, or UE Configuration Update command message, shall delete any PLMN-assigned UE Radio Capability IDs for this PLMN. The UE proceeds to register with a UE manufacturer-assigned UE Radio Capability ID that is applicable to the current UE Radio configuration.
- When the "UE Manufacturer Assigned operation requested list" contains PLMN-assigned UE Radio Capability IDs, the UCMF shall avoid re-assigning PLMN-assigned UE Radio Capability IDs that were added to the "UE Manufacturer Assigned operation requested list" in the AMFs to any UE.
- The AMF stores a PLMN-assigned ID in the "UE Manufacturer Assigned operation requested list" for a time duration that is implementation specific, but IMEI/TACs are stored until the UCMF require to remove certain TACs from the list (i.e. the list of IMEI/TACs which are requested to use UE manufacturer-assigned IDs in the AMF and UCMF is synchronised at all times).
- The UCMF can request at any time the AMF to remove PLMN-assigned ID(s) or IMEI/TAC(s) values from the UE manufacturer-assigned operation requested list.
NOTE 3: The AMF can decide to remove a UE Radio Capability ID from the "UE Manufacturer Assigned operation requested list" list e.g. because no UE with that UE Radio Capability ID has connected to the network for long time. If later a UE with such UE Radio Capability ID connects to the network, the AMF contacts the UCMF to resolve the UE Radio Capability ID and at this point the UCMF can trigger again the deletion of the UE Radio Capability ID by including this in the "UE Manufacturer Assigned operation requested list" of the AMF.
The serving AMF stores the UE Radio Capability ID related to selected PLMN for a UE in the UE context and provides this UE Radio Capability ID to NG-RAN as part of the UE context information using N2 signalling. During inter PLMN mobility which includes mobility between participating and hosting operator AMFs (see clause 5.18.1), the new AMF shall delete the UE Radio Capability ID received from the old AMF, unless the operator policy indicates that all UE Radio Capability IDs used in the old PLMN is also valid in the new PLMN.
NOTE 4: If AMF decides to allocate TAIs of multiple PLMN IDs as part of Registration Area to the UE then AMF provides the UE Radio Capability ID of the new selected PLMN to the NG-RAN during UE mobility, whether the UE Radio Capability ID is taken from stored UE context previously assigned by the same new selected PLMN or generated freshly each time a new PLMN is selected is up to AMF implementation.
The UE stores the PLMN-assigned UE Radio Capability ID in non-volatile memory when in RM-DEREGISTERED state and can use it again when it registers in the same PLMN.
NOTE 5: It is assumed that UE does not need to store the access stratum information (i.e. UE-E-UTRA-Capability and UE-NR-Capability specified in TS 36.331 [51] and TS 38.331 [28], respectively) that was indicated by the UE to the network when the PLMN-assigned UE Radio Capability ID was assigned by the network. However, it is assumed that the UE does store the related UE configuration (e.g. whether or not GERAN or UTRAN or MBMS is enabled/disabled).
At any given time at most one UE Radio Capability ID is used from the UE context in CN and RAN which is related to the selected PLMN.
The number of PLMN-assigned UE Radio Capability IDs that the UE stores in non-volatile memory is left up to UE implementation. However, to minimise the load (e.g. from radio signalling) on the Uu interface and to provide smoother inter-PLMN mobility (e.g. at land borders) the UE shall be able to store at least the latest 16 PLMN-assigned UE Radio Capability IDs (along with the PLMN that assigned them). This number is independent of the UE manufacturer-assigned UE Radio Capability ID(s) the UE may store.
It shall be possible for a UE to change, e.g. upon change in its usage settings, the set of UE radio capabilities in time and signal the associated UE Radio Capability ID, if available. The UE stores the mapping between the UE Radio Capability ID and the corresponding UE Radio Capability Information for every UE Radio Capability ID it stores.
If the UE's Radio Capability Information changes and regardless of whether the UE has an associated UE Radio Capability ID for the updated UE Radio Capability information, the UE shall perform the Registration procedure by sending a Registration Request message to the AMF with the Registration type set to Mobility Registration Update which includes "UE Radio Capability Update" and:
- If the UE has an associated UE Radio Capability ID for the updated UE Radio Capability information, the UE shall include it in the Registration Request message so that the AMF, upon receiving it, shall update the UE's context with this UE Radio Capability ID.
- If the UE does not have an associated UE Radio Capability ID for the updated UE Radio Capability information, the UE shall not include any UE Radio Capability ID in the Registration Request message so that the AMF, upon receiving this Registration Request without any UE Radio Capability ID, retrieves the UE radio capabilities from the UE as defined in clause 5.4.4.1.
The NG-RAN may apply RRC filtering of UE radio capabilities when it retrieves the UE Radio Capability Information from the UE as defined in TS 38.331 [28].
NOTE 6: In a RACS supporting PLMN, the filter of UE radio capabilities configured in NG-RAN is preferably as wide in scope as possible (e.g. PLMN-wide). In this case, it corresponds e.g. to the super-set of bands, band-combinations and RATs the PLMN deploys and not only to the specific NG-RAN node or region.
NOTE 7: If the filter, included in the UE Radio Capability information, of UE radio capabilities configured in two NG-RAN nodes is different, during handover between these two nodes, it is possible that the target NG-RAN node might need to enquire the UE for its UE Radio Capability Information again and trigger re-allocation of a PLMN-assigned UE Radio Capability ID leading to extra signalling. Additionally, a narrow filter might reduce the list of candidate target nodes.
If a UE supports both NB-IoT and other RATs that do support RACS (e.g. WB-E-UTRA and/or NR) then (since there is no support for RACS in NB-IoT) the UE handles the RACS procedures as follows:
- NB-IoT specific UE Radio Capability Information is handled in UE, NG-RAN and AMF according to clause 5.4.4.1 and in EPS according to TS 23.401 [26].
- when the UE is not camping on NB-IoT, the RAN provides UE radio capabilities for other RATs but not NB-IoT UE radio capabilities, according to TS 38.300 [27] and TS 36.300 [30]. As a result the UE Radio Capability ID that is assigned by the network corresponds only to the UE radio capabilities of the non-NB-IoT RATs. The UE uses the UE Radio Capability IDs assigned only in Mobility Registration Update procedures performed over non-NB-IoT RATs.
Support for RACS in EPS is defined in TS 23.401 [26]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.4.2 Void | 5.4.4.2a UE Radio Capability Match Request
If the AMF requires more information on the UE radio capabilities support to be able to set the IMS voice over PS Session Supported Indication (see clause 5.16.3), then the AMF may send a UE Radio Capability Match Request message to the NG-RAN. This procedure is typically used during the Registration Procedure or when AMF has not received the Voice Support Match Indicator (as part of the 5GMM Context).
NOTE: During the Registration Procedure, if the AMF does not already have the UEs radio capabilities and if the RAT where the UE is requires the establishment of AN security context prior to retrieval of radio capabilities, the AMF needs to initiate "Initial Context Setup" procedure as defined in TS 38.413 [34] to provide the 5G-AN with security context, before sending a UE Radio Capability Match Request message. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.4.3 Paging assistance information | The paging assistance information contains UE radio related information that assists the RAN for efficient paging. The Paging assistance information contains:
a) UE radio capability for paging information:
- The UE Radio Capability for Paging Information contains information derived by the NG-RAN node (e.g. band support information) from the UE Radio Capability information. The AMF stores this information without needing to understand its contents.
As the AMF only infrequently (e.g. at Initial Registration) prompts the NG-RAN to retrieve and upload the UE radio capabilities i.e. UE Radio Capability information to the AMF and the AMF may be connected to more than one NG-RAN RAT, it is the responsibility of the NG-RAN to ensure that UE Radio Capability for Paging Information (which is derived by the NG-RAN node) contains information on all NG-RAN RATs that the UE supports in that PLMN. To assist the NG-RAN in this task, as specified in TS 38.413 [34], the AMF provides its stored UE Radio Capability for Paging Information in every NG-AP INITIAL CONTEXT SETUP REQUEST message sent to the NG-RAN.
- The UE Radio Capability for Paging Information is maintained in the core network, even during AMF reselection and is stored in the UCMF alongside the UE Radio Capability information associated to a UE Radio Capability ID.
b) Information On Recommended Cells And RAN nodes For Paging:
- Information sent by the NG-RAN and used by the AMF when paging the UE to help determining the NG RAN nodes to be paged as well as to provide the information on recommended cells to each of these RAN nodes, in order to optimize the probability of successful paging while minimizing the signalling load on the radio path.
- The RAN provides this information during N2 release.
5.4.4a UE MM Core Network Capability handling
The UE MM Core Network Capability is split into the S1 UE network capability (mostly for E-UTRAN access related core network parameters) and the UE 5GMM Core Network Capability (mostly to include other UE capabilities related to 5GCN or interworking with EPS) as defined in TS 24.501 [47] and contains non radio-related capabilities, e.g. the NAS security algorithms, etc. The S1 UE network capability is transferred between all CN nodes at AMF to AMF, AMF to MME, MME to MME and MME to AMF changes. The UE 5GMM Core Network Capability is transferred only at AMF to AMF changes.
In order to ensure that the UE MM Core Network Capability information stored in the AMF is up to date (e.g. to handle the situation when the USIM is moved into a different device while out of coverage and the old device did not send the Detach message; and the cases of inter-RAT Registration Area Update), the UE shall send the UE MM Core Network Capability information to the AMF during the Initial Registration and Mobility Registration Update procedure within the NAS message.
The AMF shall store always the latest UE MM Core Network Capability received from the UE. Any UE MM Core Network Capability that an AMF receives from an old AMF/MME is replaced when the UE provides the UE MM Core Network Capability with Registration signalling.
If the UE's UE MM Core Network Capability information changes (in either CM-CONNECTED or in CM-IDLE state), the UE shall perform a Mobility Registration Update procedure when it next returns to NG-RAN coverage. See clause 4.2.2 of TS 23.502 [3].
The UE shall indicate in the UE 5GMM Core Network Capability if the UE supports:
- Attach in EPC with Request type "Handover" in PDN CONNECTIVITY Request message (clause 5.3.2.1 of TS 23.401 [26]).
- EPC NAS.
- SMS over NAS.
- LCS.
- 5G SRVCC from NG-RAN to UTRAN, as specified in TS 23.216 [88].
- Radio Capabilities Signalling optimisation (RACS).
- Network Slice-Specific Authentication and Authorization.
- Network Slice Replacement as described in clause 5.15.19.
- Parameters in Supported Network Behaviour for 5G CIoT as described in clause 5.31.2.
- Receiving WUS Assistance Information (E-UTRA) see clause 5.4.9.
- Paging Subgrouping Support Indication (NR) see clause 5.4.12.
- LP-WUS Paging Subgrouping Support Indication, see clause 5.4.12a.
- CAG, see clause 5.30.3.3.
- CAG with validity information (if UE supports CAG), see clause 5.30.3.3.
- Subscription-based restrictions to simultaneous registration of network slices (see clause 5.15.12).
- Support of NSAG (see clause 5.15.14).
- Partial Network Slice support in a RA (see clause 5.15.17).
- Minimization of Service Interruption (MINT), as described in clause 5.40.
- Equivalent SNPNs (see clause 5.30.2.11).
- Unavailability Period Support, as described in clause 5.4.1.4.
- Support for network reconnection due to RAN timing synchronization status change, see clauses 5.27.1.12 and 5.3.4.4.
- UE Configuration of network-controlled Slice Usage Policy (see clause 5.15.15.2).
- Temporarily available network slices (see clause 5.15.16).
- Support of S-NSSAI location availability information, as described in clause 5.15.18.2.
- Support of network verified UE location over NR NTN (see clause 5.4.11.4).
If a UE operating two or more USIMs, supports and intends to use one or more Multi-USIM features (see clause 5.38) in a PLMN for a USIM, it shall indicate in the UE 5GMM Core Network Capability for this USIM in this PLMN that it supports these one or more Multi-USIM features with the following indications:
- Connection Release Supported.
- Paging Cause Indication for Voice Service Supported.
- Reject Paging Request Supported.
- Paging Restriction Supported.
Otherwise, the UE with the capabilities of Multi-USIM features but does not intend to use them shall not indicate support of these one or more Multi-USIM features.
A UE not operating two or more USIMs shall indicate the Multi-USIM features are not supported.
NOTE: It is not necessary for a UE operating two or more USIMs to use Multi-USIM features with all USIMs.
5.4.4b UE 5GSM Core Network Capability handling
The UE 5GSM Core Network Capability is included in PDU Session Establishment/Modification Request.
The UE shall indicate in the UE 5GSM Core Network Capability whether the UE supports:
- "Ethernet" PDU Session Type supported in EPC as PDN Type "Ethernet";
- Reflective QoS;
- Multi-homed IPv6 PDU Session (only if the Requested PDU Type was set to "IPv6" or "IPv4v6");
- ATSSS capability (as referred to clause 5.32.2);
- Transfer of Port Management Information containers;
- Support for secondary DN authentication and authorization over EPC (as referred to clause 5.17.2.5);
- (S)RTP Multiplexed Media Identification Information in IP Packet Filters.
The 5GSM Core Network Capability is transferred, if needed, from V-SMF to H-SMF during PDU Session Establishment/Modification procedure.
After the first inter-system change from EPS to 5GS for a PDU session established in EPS, the 5GSM Core Network Capability is also included in the PDU Session Modification if the Reflective QoS and/or Multi-homed IPv6 PDU Session is present. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.5 DRX (Discontinuous Reception) framework | The 5G System supports DRX architecture which allows Idle mode DRX cycle is negotiated between UE and the AMF. The Idle mode DRX cycle applies in CM-IDLE state and in CM-CONNECTED with RRC_INACTIVE state.
If the UE wants to use UE specific DRX parameters, the UE shall include its preferred values consistently in every Initial Registration and Mobility Registration procedure separately for NR/WB-EUTRA and NB-IoT. During Initial Registration and Mobility Registration procedures performed on NB-IoT cells, the normal 5GS procedures apply. For NB-IoT, the cell broadcasts an indication of support of UE specific DRX for NB-IoT in that cell and the UE can request UE specific DRX for NB-IoT in the Registration procedure irrespective of whether the cell broadcasts that support indication.
The AMF shall determine Accepted DRX parameters based on the received UE specific DRX parameters and the AMF should accept the UE requested values, but subject to operator policy the AMF may change the UE requested values.
The AMF shall respond to the UE with the Accepted DRX parameters separately for NR/WB-EUTRA and NB-IoT.
For details of DRX parameters, see TS 38.331 [28] and TS 36.331 [51].
The UE shall apply the DRX cycle broadcast in the cell by the RAN unless it has received Accepted DRX parameters for the RAT from the AMF and for NB-IoT the cell supports UE specific DRX for NB-IoT, in which case the UE shall apply either the DRX cycle broadcast in the cell or the Accepted DRX parameters for the RAT, as defined in TS 38.304 [50] and TS 36.304 [52].
The Periodic Registration procedure does not change the UE's DRX settings.
In CM-CONNECTED with RRC_INACTIVE state, the UE applies either the DRX cycle negotiated with AMF, or the DRX cycle broadcast by RAN or the UE specific DRX cycle configured by RAN, as defined in TS 38.300 [27] and TS 38.304 [50]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.6 Core Network assistance information for RAN optimization | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.6.1 General | Core Network assistance information for RAN aids the RAN to optimize the UE state transition steering and the RAN paging strategy formulation in RRC_INACTIVE state. The Core Network assistance information includes the information set, Core Network assisted RAN parameters tuning, which assist RAN optimize the UE RRC state transition and CM state transition decision. It also includes the information set, Core Network assisted RAN paging information, which assist RAN to formulate an optimized paging strategy when RAN paging is triggered. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.6.2 Core Network assisted RAN parameters tuning | Core Network assisted RAN parameters tuning aids the RAN to minimize the UE state transitions and achieve optimum network behaviour. How the RAN uses the CN assistance information is not defined in this specification.
Core Network assisted RAN parameters tuning may be derived by the AMF per UE in the AMF based on collection of UE behaviour statistics, Expected UE Behaviour and/or other available information about the UE (such as subscribed DNN, SUPI ranges, or other information). If the AMF maintains Expected UE Behaviour parameters, Network Configuration parameters (as described in clause 4.15.6.3 or 4.15.6.3a, TS 23.502 [3]) or SMF derived CN assisted RAN parameters tuning, the AMF may use this information for selecting the CN assisted RAN parameter values. If the AMF is able to derive the Mobility Pattern of the UE (as described in clause 5.3.4.2), the AMF may take the Mobility Pattern information into account when selecting the CN assisted RAN parameter values.
The SMF uses the SMF-Associated parameters (e.g. Expected UE Behaviour parameters or Network Configuration parameters of the UE) to derive the SMF derived CN assisted RAN parameters tuning. The SMF sends the SMF derived CN assisted RAN parameters tuning to the AMF during the PDU Session establishment procedure and if the SMF-Associated parameters change the PDU Session modification procedure is applied. The AMF stores the SMF derived CN assisted RAN parameters tuning in the PDU Session level context. The AMF uses the SMF derived CN assisted RAN parameters tuning to determine a PDU Session level "Expected UE activity behaviour" parameters set, which may be associated with a PDU Session ID, as described below in this clause.
The Expected UE Behaviour parameters or the Network Configuration parameters can be provisioned by external party via the NEF to the AMF or SMF, as described in clause 5.20.
The CN assisted RAN parameters tuning provides the RAN with a way to understand the UE behaviour for these aspects:
- "Expected UE activity behaviour", i.e. the expected pattern of the UE's changes between CM-CONNECTED and CM-IDLE states or the duration of CM-CONNECTED state. This may be derived e.g. from the statistical information, or Expected UE Behaviour or from subscription information. The AMF derives one or more sets of the "Expected UE activity behaviour" parameters for the UE as follows:
- AMF may derive and provide to the RAN a UE level of "Expected UE activity behaviour" parameters set considering the Expected UE Behaviour parameters or Network Configuration parameters received from the UDM (see clauses 4.15.6.3 or 4.15.6.3a of TS 23.502 [3]) and the SMF derived CN assisted RAN parameters tuning associated with a PDU Session using Control Plane CIoT 5GS Optimisation. This set of "Expected UE activity behaviour" parameters is valid for the UE; and
- AMF may provide to the RAN a PDU Session level "Expected UE activity behaviour" parameters set, e.g. considering the SMF derived CN assisted RAN parameters tuning, per established PDU Session. The PDU Session level "Expected UE activity behaviour" set of parameters is associated with and valid for a PDU Session ID. The RAN may consider the PDU Session level "Expected UE activity behaviour" parameters when the User Plane resources for the PDU Session are activated;
- "Expected HO behaviour", i.e. the expected interval between inter-RAN handovers. This may be derived by the AMF e.g. from the Mobility Pattern information;
- "Expected UE mobility", i.e. whether the UE is expected to be stationary or mobile. This may be derived e.g. from the statistical information or Expected UE Behaviour parameters or from subscription information;
- "Expected UE moving trajectory" which may be derived e.g. from the statistical information or Expected UE Behaviour parameters or from subscription information; or
- "UE Differentiation Information" including the Expected UE Behaviour parameters excluding the Expected UE moving trajectory (see clause 4.15.6.3 of TS 23.502 [3]) to support Uu operation optimisation for NB-IoT UE differentiation if the RAT type is NB-IoT.
The AMF decides when to send this information to the RAN as "Expected UE activity behaviour" carried in N2 request over the N2 interface (see TS 38.413 [34]).
NOTE: The calculation of the CN assistance information, i.e. the algorithms used and related criteria and the decision when it is considered suitable and stable to send to the RAN are vendor specific. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.6.3 Core Network assisted RAN paging information | Core Network assisted RAN paging information aids the RAN to formulate a RAN paging policy and strategy in RRC_INACTIVE state, besides the PPI and QoS information associated to the QoS Flows as indicated in clause 5.4.3.
CN assisted RAN paging information may be derived by the AMF per UE and/or per PDU Session based on collection of UE behaviour statistics, Expected UE Behaviour and/or other available information about the UE (such as subscribed DNN, SUPI ranges, Multimedia priority services) and/or information received from other network functions when downlink signalling is triggered.
The Core Network may provide the CN assisted RAN paging information to RAN in different occasions, e.g. during downlink N1 and N2 message delivery, etc. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.7 NG-RAN location reporting | NG-RAN supports the NG-RAN location reporting for the services that require accurate cell identification (e.g. emergency services, lawful intercept, charging) or for the UE mobility event notification service subscribed to the AMF by other NFs. The NG-RAN location reporting may be used by the AMF when the target UE is in CM-CONNECTED state. The NG-RAN location reporting may be used by the AMF to determine the geographically located TAI in the case of NR satellite access.
The AMF may request the NG-RAN location reporting with event reporting type (e.g. UE location or UE presence in Area of Interest), reporting mode and its related parameters (e.g. number of reporting).
If the AMF requests UE location, the NG-RAN reports the current UE location (or last known UE location with time stamp if the UE is in RRC_INACTIVE state) based on the requested reporting parameter (e.g. one-time reporting or continuous reporting).
If the AMF requests UE location, in the case of NR satellite access, the NG-RAN provides all broadcast TAIs to the AMF as part of the ULI. The NG-RAN also reports the TAI where the UE is geographically located if this TAI can be determined.
If the AMF requests UE presence in the Area Of Interest, the NG-RAN reports the UE location and the indication (i.e. IN, OUT or UNKNOWN) when the NG-RAN determines the change of UE presence in Area Of Interest.
After N2 based Handover, if the NG-RAN location reporting information is required, the AMF shall re-request the NG-RAN location reporting to the target NG-RAN node. For Xn based Handover, the source NG-RAN shall transfer the requested NG-RAN location reporting information to target NG-RAN node.
The AMF requests the location information of the UE either through independent N2 procedure (i.e. NG-RAN location reporting as specified in clause 4.10 of TS 23.502 [3]), or by including the request in some specific N2 messages as specified in TS 38.413 [34]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.8 Support for identification and restriction of using unlicensed spectrum | Support for NG-RAN using unlicensed spectrum is defined in TS 38.300 [27] and TS 36.300 [30].
For NG-RAN, in the case of NR in stand-alone mode, all cells are in unlicensed spectrum and the NR is used as primary RAT. NR or E-UTRA cells in unlicensed spectrum, can be used as secondary cells as specified in the Dual Connectivity architecture defined in clause 5.11 or in addition can be configured to support the Carrier Aggregation Architecture (CA) defined in TS 38.300 [27] and TS 36.300 [30].
For either case the serving PLMN can enforce Access Restriction for Unlicensed Spectrum (either signalled from the UDM, or, locally generated by VPLMN policy in the AMF) with the following:
- To restrict the use of NR in unlicensed spectrum as primary RAT, the AMF rejects the UE Registration procedure with appropriate cause code defined in TS 24.501 [47] if the UE performs initial access from NR using unlicensed spectrum. If the UE is accessing through some other allowed RAT, the AMF signals this access restriction to NG-RAN as part of Mobility Restriction List.
- To restrict the use of use of unlicensed spectrum with NR or E-UTRA as secondary RAT using Dual Connectivity or Carrier Aggregation Architecture (CA) defined in TS 38.300 [27] and TS 36.300 [30], the AMF signals this access restriction to NG-RAN as part of Mobility Restriction List.
An NG-RAN node supporting aggregation with unlicensed spectrum using either NR or E-UTRA checks whether the UE is allowed to use unlicensed spectrum based on received Mobility Restriction List. If the UE is not allowed to use Unlicensed Spectrum, the NG-RAN node shall restrict the using of unlicensed spectrum, either NR or E-UTRA as secondary RATs when using either Dual Connectivity or Carrier Aggregation (CA) as defined in TS 38.300 [27] and TS 36.300 [30].
At inter-RAT handover from E-UTRAN/EPS, the Access Restriction for Unlicensed Spectrum is either already in the AMF's UE context, or is obtained from the UDM during the subsequent Registration Area Update procedure (i.e. not from the source MME or source RAN). In both inter-RAT handover cases, any Access Restriction for use of Unlicensed Spectrum is then signalled to NG-RAN or enforced in AMF.
NOTE: This signalling of the Access Restriction during the Registration Area Update after the inter-RAT handover procedure means that there is a small risk that unlicensed spectrum resources are transiently allocated.
When the UE is accessing 5GS using unlicensed spectrum as primary RAT:
- The NG-RAN node shall provide an indication to the AMF in N2 interface that NR access is using unlicensed spectrum as defined in TS 38.413 [34].
- In order to restrict access to NR in unlicensed spectrum, cells supporting NR in unlicensed spectrum have to be deployed in Tracking Area(s) different to cells supporting licensed spectrum.
- When the AMF receives an indication from NG-RAN over N2 whether NR in unlicensed spectrum is being used as defined in TS 38.413 [34], the AMF provides to the SMF an indication that the RAT type is NR with usage of unlicensed spectrum during PDU Session Establishment or as part of the UP activation and Handover procedures.
- The PCF can also receive the indication whether the UE is using NR in unlicensed spectrum, when applicable, from the AMF using the PCRT on Access Type change specified in clause 6.1.2.5 of TS 23.503 [45] during AM Policy Association Establishment or AM Policy Association Modification procedure and from the SMF using the PCRT on Access Type change specified in clause 6.1.3.5 of TS 23.503 [45] during SM Policy Association Establishment or SM Policy Association Modification procedure.
- The NFs generating CDRs shall include the indication that the UE is using NR in unlicensed spectrum in their CDRs.
When the UE is accessing NR or E-UTRA using unlicensed spectrum as secondary RAT, procedures for Usage Data Reporting for Secondary RAT as defined in clause 5.12.2 can apply. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.9 Wake Up Signal Assistance | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.9.1 General | The RAN and UE may use a Wake Up Signal (WUS) to reduce the UE's idle mode power consumption. The RAN sends the WUS shortly before the UE's paging occasion. The WUS feature enables UEs to determine that in the paging occasions immediately following their WUS occasion they will not be paged if their WUS is not transmitted, or that they might be paged if their WUS is transmitted (see TS 36.304 [52]).
To avoid waking up UEs due to an AMF paging other UEs across multiple cells (e.g. due to frequent UE mobility and/or for low paging latency services such as VoLTE), the use of WUS by the ng-eNB and the UE is restricted to the last used cell, i.e. the cell in which the UE's RRC connection was last released. To support this:
a) ng-eNBs should provide the Recommended Cells for Paging IE in the Information on Recommended Cells and RAN Nodes for Paging IE (see TS 38.413 [34]) to the AMF in the NGAP UE Context Release Complete, UE Context Suspend Request and UE Context Resume Request messages;
b) if received during the last NGAP UE Context Release Complete or UE Context Suspend Request message, the AMF provides (without modification) the Recommended Cells for Paging as Assistance Data for Recommended Cells IE in the Assistance Data for Paging IE within the NGAP Paging message to the RAN (see also TS 38.413 [34]); and
c) the AMF shall delete (or mark as invalid) the Information On Recommended Cells And RAND nodes For Paging when a new NGAP association is established for the UE.
In the NGAP Paging message, the last used cell ID is sent in the Assistance Data for Recommended Cells IE in the Assistance Data for Paging IE (see TS 38.413 [34]). When receiving an NGAP Paging message for a WUS-capable UE that also includes the Assistance Data for Recommended Cells IE then a WUS-capable ng-eNB shall only broadcast the WUS on the cell that matches the last used cell ID. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.9.2 Group Wake Up Signal | To support the Wake Up Signal (WUS), the WUS Assistance Information is used by the ng-eNB to help determine the WUS group used when paging the UE (see TS 36.300 [30]).
The content of the WUS Assistance Information consists of the paging probability information. The paging probability information provides a metric on the probability of a UE receiving a paging message based on, e.g. statistical information.
The UE may in the Registration Request message provide its capability to support receiving WUS Assistance Information. If WUS Assistance Information is supported by the UE, then the UE in the Registration Request message may provide the additional UE paging probability information. The AMF may use the UE provided paging probability, local configuration and/or previous statistical information for the UE, when determining the WUS Assistance Information. If the UE supports WUS Assistance Information, the AMF may assign WUS Assistance Information to the UE, even when the UE has not provided the additional UE paging probability information.
If the AMF has determined WUS Assistance Information for the UE, the AMF provides it to the UE in every Registration Accept message. The AMF stores the WUS Assistance Information parameter in the MM context and provides it to the ng-eNB when paging the UE.
UE and AMF shall not signal WUS Assistance Information in Registration Request, Registration Accept messages when the UE has an active emergency PDU session. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.10 Support for identification and restriction of using NR satellite access | Support for NR satellite access is specified in TS 38.300 [27].
Editor's note: TS 38.300 [27] not yet updated by RAN groups.
The AMF determines the RAT Type for NR satellite access, i.e. NR(LEO), NR(MEO), NR(GEO) and NR(OTHERSAT). When the UE is accessing NR using satellite access, an indication is provided in N2 interface indicating the type of NR satellite access, as defined in TS 38.413 [34]. The PCF can receive the RAT Type for NR satellite access, when applicable, from the AMF using the PCRT on Access Type change specified in clause 6.1.2.5 of TS 23.503 [45] during AM Policy Association Establishment or AM Policy Association Modification procedure and from the SMF using the PCRT on Access Type change specified in clause 6.1.3.5 of TS 23.503 [45] during SM Policy Association Establishment or SM Policy Association Modification procedure.
Editor's note: Further details on what type of satellite platforms OTHERSAT includes is FFS and to be aligned with RAN WG3.
The serving PLMN can enforce mobility restrictions for NR satellite access as specified in clause 5.3.4.1.
In order to enable efficient enforcement of Mobility Restrictions, cells of each NR satellite RAT Type (NR(LEO), NR(MEO), NR(GEO) or NR(OTHERSAT)) need to be deployed in TAs different from TAs for other NR satellite RAT Types as well as different from TAs supporting terrestrial access RAT Types.
The AMF may initiate deregistration of the UE when an N2 UE Context Release Request is received with cause value indicating that the UE is not in PLMN serving area, as specified in TS 38.413 [34]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.11 Support for integrating NR satellite access into 5GS | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.11.1 General | This clause describes the specific aspects for NR satellite access, including transparent satellite payloads and regenerative satellite payloads, as defined in TS 38.300 [27]. The description for satellite access in this specification is applicable to both transparent satellite payload and regenerative satellite payload, unless otherwise stated. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.11.2 Support of RAT types defined in 5GC for satellite access | In case of NR satellite access, the RAT Types values "NR(LEO)", "NR(MEO)", "NR(GEO)" and "NR(OTHERSAT)" are used in 5GC to distinguish the different NR satellite access types (see clause 5.4.10).
When a UE is accessing to the network via satellite access, the AMF determines the RAT type as specified in clause 5.4.10.
NOTE: The transparent satellite payload and regenerative satellite payload share the same set of RAT type values specified in this clause. If there is a need for differentiating between the payload types, the determination of what kind of payload is based on operator configuration. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.11.3 Void | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.11.4 Verification of UE location | In order to ensure that the regulatory requirements are met, the network may be configured to enforce that the selected PLMN is allowed to operate in the current UE location by verifying the UE location during Mobility Management and Session Management procedures. The UE that supports network verified UE location over NTN NR shall indicate this capability in UE 5GMM Core Network Capability and LPP as defined in TS 37.355 [191].
In this case, when the AMF receives a NGAP message containing User Location Information for a UE using NR satellite access, the AMF takes into account the capability of the UE in UE 5GMM Core Network Capability for the support by the UE of network verified UE location over NR NTN and may decide to verify the UE location. If the AMF determines based on the Selected PLMN ID and ULI (including Cell ID) received from the gNB that it is not allowed to operate at the present UE location the AMF should reject any NAS request with a suitable cause value. If the UE is already registered to the network when the AMF determines that it is not allowed to operate at the present UE location, the AMF may initiate deregistration of the UE. The AMF should not reject the request or deregister the UE unless it has sufficiently accurate UE location information to determine that the UE is located in a geographical area where the PLMN is not allowed to operate.
NOTE 1: The area where the UE is allowed to operate can be determined based on the regulatory area where the PLMN is allowed to operate based on its licensing conditions.
If the AMF, based on the ULI, is not able to determine the UE's location with sufficient accuracy to make a final decision or if the received ULI is not sufficiently reliable, the AMF takes into account the UE 5GMM Core Network Capability related to the UE support of network verified UE location over NR NTN and may proceed with the Mobility Management or Session Management procedure and may initiate UE location procedure after the Mobility Management or Session Management procedure is complete, as specified in clause 6.10.1 of TS 23.273 [87], to determine the UE location.
NOTE 2: In order to ensure that the regulatory requirements are met, based on operator configuration, the AMF can prevent the UE from accessing certain services (e.g. services related with NAS messages initiated by UE or network except services related with UE location procedures or NAS procedures required for location verification) while location determination is ongoing. This can be done by, for example, the AMF providing a back-off time to the UE, such as described in clause 5.19.7.2 NAS level congestion control.
The AMF shall be prepared to deregister the UE if the information received from LMF indicates that the UE is registered to a PLMN that is not allowed to operate in the UE location. In the case of a NAS procedure, the AMF should either reject any NAS request targeted towards a PLMN that is not allowed to operate in the known UE location and indicate a suitable cause value, or accept the NAS procedure and initiate deregistration procedure once the UE location is known. In the deregistration message to the UE, the AMF shall include a suitable cause value. For UE processing of the cause value indicating that the PLMN is not allowed to operate in the current UE location, see TS 23.122 [17] and TS 24.501 [47].
In the case of a handover procedure, if the (target) AMF determines that it is not allowed to operate at the current UE location, the AMF either rejects the handover, or accepts the handover and later deregisters the UE. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.11.5 Network selection for NR satellite access | Network selection principles specified in clause 5.2.2 apply also for NR satellite access.
For NR satellite access, a UE with location capability should use its awareness of its location to select a PLMN that is allowed to operate in the UE location as specified in TS 23.122 [17].
In order to ensure that the regulatory requirements are met, the network may be configured to enforce this UE choice by verifying the UE location, as described in clause 5.4.11.4. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.11.6 Support of Mobility Registration Update | A moving radio cell for NR satellite access may indicate support for one or more TACs for each PLMN. A UE that is registered with a PLMN may access a radio cell and does not need to perform a Mobility Registration Update procedure as long as at least one supported TAC for the RPLMN or equivalent to the RPLMN is part of the UE Registration Area. A UE shall perform a Mobility Registration Update procedure when accessing a radio cell where none of the supported TACs for the RPLMN or equivalent to the RPLMN are part of the UE Registration Area.
When indicating a last visited TAI in a Registration Update, a UE may indicate any TAI supported in a radio cell for the RPLMN or equivalent to the RPLMN for the last UE access prior to the Registration Update that is part of the UE Registration Area. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.11.7 Tracking Area handling for NR satellite access | In the case of NR satellite access with moving cells, in order to ensure that each TA is Earth-stationary even if the radio cells are moving across the Earth's surface, the NG-RAN may change the TAC values that are broadcast in a cell's system information as the cell moves, as described in TS 38.300 [27] and TS 38.331 [28].
NG-RAN may broadcast in a cell a single TAC per PLMN and change that TAC value as the cell moves. Alternatively, the NG-RAN may broadcast in a cell more than one TAC for a PLMN and add or remove TAC values as the cell moves. The NG-RAN provides either the single broadcast TAI or all broadcast TAIs corresponding to the Selected PLMN as described in TS 38.413 [34] to the AMF as part of the ULI, whenever the ULI is included in the NGAP message as described in TS 38.413 [34]. The NG-RAN indicates, if known, also the TAI where the UE is geographically located. When supplying location information to another NF (e.g. SMF, PCF), the AMF shall include the TAI where the UE is located (if known) and the broadcast TAI(s), excluding all forbidden TAI(s).
NOTE: The AMF may take the TAI where the UE is geographically located into account to generate a suitable Registration Area for the UE. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.11.8 Support for mobility Forbidden Area and Service Area Restrictions for NR satellite access | Forbidden Area functionality is supported as described in clause 5.3.4.1.1 with the modifications described below:
- The AMF and the UE receive the broadcast TAI (if a single TAI is broadcast) or all broadcast TAIs (if multiple TAIs are broadcast) from the NG-RAN as described clause 5.4.11.7. The AMF considers the UE to be in a Forbidden Area if the only received TAI is forbidden or if all received TAIs are forbidden based on subscription data. The UE considers it is in a Forbidden Area if the only received TAI is forbidden, or if all received TAIs are forbidden and is not within a Forbidden Area in the case that at least one broadcast TAI is not forbidden.
- If AMF receives multiple TAIs from the NG-RAN and determines that some, but not all of them are forbidden by subscription or by operator policy, the AMF shall send the forbidden TAI(s) to the UE as described in clauses 4.2.2.2 and 4.2.3 in TS 23.502 [3]. The UE stores the TAI(s) in the appropriate Forbidden Area list and removes the TAI(s) from Registration Area if present.
Service Area Restrictions functionality is supported as described in clause 5.3.4.1.2 with the modifications described below:
- The AMF receives the broadcast TAI (if a single TAI is broadcast) or all broadcast TAIs (if multiple TAIs are broadcast) from the NG-RAN as described clause 5.4.11.7. The AMF provides the UE with Service Area Restrictions which consist of either Allowed Areas or Non-Allowed Areas, as described in clause 5.3.4.1.2. The UE and AMF consider the UE to be in a Non-Allowed Area if none of the broadcast TAIs is Allowed. The UE and AMF consider the UE to be in an Allowed Area if at least one broadcast TAI is allowed. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.11.9 N2 interface and connection management for regenerative satellite payload | The NG Removal procedure defined in TS 38.413 [34] can be used to remove the interface between a gNB and an AMF in a controlled manner, e.g. when the gNB is leaving the service area of an AMF when using regenerative satellite payload.
The serving AMF for a UE can remain the same during feeder link switchover.
NOTE 1: If a gNB IP address changes due to feeder link switchover, then the procedures described in e.g. clause 5.21.1 can be used.
NOTE 2: RAN transitioning between different NTN GWs, TAIs and potentially between AMFs can be supported by using existing procedures, e.g. the gNB releasing UEs to CM-IDLE before changing NTN gateway, or by using existing load re-balancing, triggering handover when it realizes it is going to leave a tracking area due to its own movement, etc. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.12 Paging Early Indication with Paging Subgrouping Assistance | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.12.1 General | The RAN and UE may use a Paging Early Indication with Paging Subgrouping (PEIPS) to reduce the UE's power consumption in RRC_IDLE and RRC_INACTIVE over NR (see TS 38.304 [50]).
The paging subgrouping can be based on either the UE's temporary ID or a Paging Subgroup ID allocated by the AMF. Paging subgrouping based on the UE's temporary ID is implemented within the NG-RAN. For paging subgrouping based on UE's temporary ID, the UE's support is included in the UE Radio Capability for Paging, either derived by the NG-RAN from UE provided UE radio capability (see clause 5.4.4) or based on UE Radio Capability ID if UE radio capability signalling optimisation is used (see clause 5.4.4.1a).
The AMF, when determining its paging strategy (see clause 5.4.3), should take into consideration whether a gNB is using Paging subgrouping based on the UE's temporary ID.
NOTE: Paging messages sent to that gNB can increase UE power consumption for other UEs that support Paging Subgrouping based on the UE's temporary ID.
If paging subgroups are being allocated by the AMF, then all AMFs connected to one gNB (including the AMFs in different PLMNs using 5G MOCN network sharing) shall use a consistent policy in allocating UEs to the paging subgroups. The AMF may configure up to 8 different Paging Subgroup IDs.
NOTE: Because the UE uses the AMF allocated paging subgroup across all cells in its TAI-list and, different, overlapping TAI lists can be allocated to different UEs, then to avoid UE power consumption increasing, it is likely to be necessary that all AMFs with an overlapping coverage area use a consistent policy in allocating UEs to the paging subgroups.
The NG-RAN node and the UE determine per cell which paging subgrouping method to use as defined in TS 38.304 [50] and TS 38.331 [28]. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.12.2 Core Network Assistance for PEIPS | To support the Paging Early Indication with Paging Subgrouping (PEIPS), Paging Subgrouping Support Indication and the PEIPS Assistance Information is used by the AMF and NG-RAN to help determine whether PEIPS applies to the UE and which paging subgroup used when paging the UE (see TS 38.300 [27]).
In the Registration Request message, the Paging Subgrouping Support Indication indicates whether the UE supports PEIPS with AMF PEIPS Assistance Information. If the UE includes Paging Subgrouping Support Indication, the UE may also include the paging probability information to assist the AMF. If the AMF supports PEIPS assistance and if the UE provided Paging Subgrouping Support Indication, the AMF stores the indication in the UE context in AMF. The AMF may use local configuration, the UE's paging probability information if provided, information provided by the RAN (e.g. any of the Information On Recommended Cells And RAN nodes For Paging) and/or previous statistical information for the UE to determine the AMF PEIPS Assistance Information. The AMF PEIPS Assistance Information includes the Paging Subgroup ID.
NOTE 1: To minimise MT voice call setup latency, the AMF could allocate Paging Subgroup IDs taking into account whether or not the UE is likely to receive IMS voice over PS session calls.
NOTE 2: To avoid MT traffic for more mobile UEs causing more stationary UEs to be woken up, the AMF could allocate Paging Subgroup IDs taking into account the UE's mobility pattern.
If the AMF has determined AMF PEIPS Assistance Information for the UE, the AMF stores it in the UE context in AMF and provides it to the UE in every Registration Accept message.
If the AMF has determined AMF PEIPS Assistance Information, the AMF shall provide it to NG RAN when paging the UE. In addition, in order to support PEIPS for UEs in RRC_INACTIVE mode, the AMF shall provide the AMF PEIPS Assistance Information to NG-RAN as part of the RRC Inactive Assistance Information.
The NG-RAN chooses on a per-cell basis whether to use PEIPS and which paging subgrouping mechanism to use. When using AMF allocated subgroups, both the UE and NG-RAN use the AMF PEIPS Assistance Information to determine the paging subgroup to apply as defined in TS 38.300 [27].
The AMF may use the UE Configuration Update procedure (as described in clause 4.2.4 of TS 23.502 [3]) and N2 UE Context Modification procedure (as described in clause 8.3.4 of TS 38.413 [34]) to update the AMF PEIPS Assistance Information in the UE and NG-RAN.
5.4.12a LP-WUS with Paging Subgrouping Assistance
5.4.12a.1 General
The RAN and UE may use Low Power Wake UP Signal with Paging Subgrouping (LP-WUSPS) to reduce the power consumption of the UE in RRC_IDLE and RRC_INACTIVE over NR (see TS 38.304 [50]).
Editor's note: The terminology of "LP-WUS" and "LP-WUSPS" will be further aligned with the terminology used in specifications at RAN Side.
The LP-WUSPS can be based on a LP-WUS Subgroup ID allocated by the AMF, or is determined by the RAN on its own as defined in TS 38.304 [50] and TS 38.331 [28].
The AMF, when determining its paging strategy (see clause 5.4.3), should take into consideration whether a gNB is using LP-WUSPS determined by the RAN on its own.
If paging subgroups for LP-WUS are being allocated by the AMF, then all AMFs connected to one gNB (including the AMFs in different PLMNs using 5G MOCN network sharing) shall use a consistent policy in allocating UEs to the paging subgroups. The AMF may configure up to 32 different LP-WUS Subgroup IDs.
NOTE: Because the UE uses the AMF allocated LP-WUSPS across all cells in its TAI-list, and, different, overlapping TAI lists can be allocated to different UEs, then to avoid UE power consumption increasing, it is likely to be necessary that all AMFs with an overlapping coverage area use a consistent policy in allocating UEs to the LP-WUSPS.
The NG-RAN node and the UE determine per cell which LP-WUSPS method to use as defined in TS 38.304 [50] and TS 38.331 [28].
5.4.12a.2 Core Network Assistance for LP-WUSPS
To support the LP-WUSPS, the LP-WUS Paging Subgrouping Support Indication and the LP-WUSPS Assistance Information are used by the AMF and NG-RAN to help determine whether LP-WUSPS applies to the UE and which paging subgroup is used when paging the UE (see TS 38.300 [27]).
In the Registration Request message, the UE includes the LP-WUS Paging Subgrouping Support Indication if the UE supports AMF LP-WUSPS Assistance Information for LP-WUS Paging Subgrouping. If the UE includes the LP-WUS Paging Subgrouping Support Indication, the UE may also include the paging probability information to assist the AMF. An AMF supporting LP-WUSPS stores the UE provided LP-WUS Paging Subgrouping Support Indication and the AMF determined AMF LP-WUSPS Assistance Information in the UE context. The AMF may use local configuration, the UE's paging probability information if provided, information provided by the RAN (e.g. any of the Information On Recommended Cells And RAN nodes For Paging), and/or previous statistical information for the UE to determine AMF LP-WUSPS Assistance Information. The AMF LP-WUSPS Assistance Information includes the Paging Subgroup ID.
NOTE 1: To minimise MT voice call setup latency, the AMF could allocate Paging Subgroup IDs for LP-WUS taking into account whether or not the UE is likely to receive IMS voice over PS session calls.
NOTE 2: To avoid MT traffic for more mobile UEs causing more stationary UEs to be woken up, the AMF could allocate Paging Subgroup IDs for LP-WUS taking into account the UE's mobility pattern.
If the AMF has determined AMF LP-WUSPS Assistance Information for the UE, the AMF stores it in the UE context in AMF and provides it to the UE in every Registration Accept message.
If the AMF has determined AMF LP-WUSPS Assistance Information, the AMF shall provide it to NG RAN when paging the UE. In addition, in order to support LP-WUSPS for UEs in RRC_INACTIVE mode, the AMF shall provide the AMF LP-WUSPS Assistance Information to NG-RAN as part of the RRC Inactive Assistance Information.
When the NG-RAN is using AMF allocated subgroups for LP-WUSPS, both the UE and NG-RAN use the AMF LP-WUSPS Assistance Information to determine the paging subgroup to apply as defined in TS 38.300 [27].
The AMF may use the UE Configuration Update procedure (as described in clause 4.2.4 of TS 23.502 [3]) and N2 UE Context Modification procedure (as described in clause 8.3.4 of TS 38.413 [34]) to update the AMF LP-WUSPS Assistance Information in the UE and NG-RAN. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.13 Support of discontinuous network coverage for satellite access | |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.13.0 General | The present clause 5.4.13 provides optional enhancements to support discontinuous coverage:
- Mobility management and power saving optimization, see clause 5.4.13.1; and
- Coverage availability information provisioning to the UE, see clause 5.4.13.2; and
- Coverage availability information provisioning to the AMF, see clause 5.4.13.3; and
- Paging, see clause 5.4.13.4; and
- Overload control, see clause 5.4.13.5.
NOTE: In this Release, there is no specified support for discontinuous coverage over NR in RAN specifications. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.13.1 Mobility Management and Power Saving Optimization | For NR satellite access that provides discontinuous network coverage the Mobility Management and Power Saving Optimization functionality may be used.
If both the UE and the network support "Unavailability Period Support" and if the UE determines it will lose coverage and will become unavailable and the UE decides to remain in no service during that time, then:
- the UE triggers the Mobility Registration Update procedure to inform the network of its unavailability, as described in clause 5.4.1.4.
- The UE may be able to determine, including considering current and expected future locations of the UE, a Start of Unavailability Period and/or Unavailability Period Duration for when it expects to be out of coverage and include them in the Mobility Registration Update procedure, as described in clause 5.4.1.4.
- The UE should trigger the Mobility Registration Update procedure early enough such that the procedure, under normal conditions, is able to complete before the start of the unreachability period.
NOTE 1: A UE based on implementation can combine successive periods of no satellite coverage into a single continuous period that is notified to the network if the UE does not require network access during this period.
NOTE 2: UE informing the network of coverage gaps would increase signalling and UE power consumption if coverage gaps are more frequent than UE's communication period.
In case the UE requests power saving features the AMF uses the procedures defined in other clauses to provide the UE with timers (e.g. Periodic Registration Update timer), extended DRX in CM-IDLE configuration (see clause 5.31.7.2) and MICO mode configuration (see clause 5.4.1.3) and to provide the NG-RAN with Extended Connected Time (see clause 5.31.7.3) and may also consider the Unavailability Period Duration and Start of Unavailability Period (if available). This is to keep UE in power saving mode and avoid the network attempting to page the UE if it is out of satellite network coverage.
The AMF should adjust the mobile reachable timer or Implicit Deregistration timer or both such that the AMF does not implicitly deregister the UE while the UE is unavailable, see clause 5.4.1. Features described for High latency communication in clause 5.31.8 may be used to handle mobile terminated (MT) communication with UEs being unreachable due to NR satellite access discontinuous coverage and the Unavailability Period Duration (if available) and Start of Unavailability Period (if available) may be used when determining the Estimated Maximum Wait Time.
Tracking Area or RAT specific configuration in the AMF may be used to set timer values based on typical coverage periods of a satellite system.
NOTE 3: For example, if a satellite system only provides coverage to a UE for 20 minutes when a satellite passes and the maximum time before a satellite passes any point on the earth is 10 hours, the AMF could configure the periodic registration timer and Mobile Reachable timer to be just greater than 20 minutes and the Implicit Deregistration timer to be greater than 10 hours to avoid unintended implicit detach due to coverage gap. Such configuration does not require AMF to be aware of detailed coverage times for each UE or for different locations.
The UE may send Mobility Registration Update procedure to inform the network of its UE unavailability period (see clause 5.4.1.4) even if Mobility Management back-off timer is running. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.13.2 Coverage availability information provisioning to the UE | A UE may use satellite coverage availability information for satellite access to support discontinuous coverage operations. Satellite coverage availability information can be provided to a UE by an external server via a PDU Session or SMS. The protocol and format of satellite coverage availability information via PDU session or SMS is not defined in this release of the specification, but some examples on possible information that constitutes the satellite coverage availability information is defined in Annex Q.
NOTE: The satellite coverage availability information provisioned to the UE describes when and where satellite coverage with both service link and feeder link connectivity is expected or not expected to be available in an area. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.13.3 Coverage availability information provisioning to the AMF | The AMF may use satellite coverage availability information to support satellite access by UEs with discontinuous coverage operation. Satellite coverage availability information may be provisioned to the AMF by O&M.
NOTE: The satellite coverage availability information provisioned to the AMF describes when and where satellite coverage with both service link and feeder link connectivity is expected or not expected to be available in an area.
The satellite coverage availability information is not UE specific and can be applied by the AMF for any UE in the affected area. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.13.4 Paging | In the case of NR satellite access that provides discontinuous network coverage, AMF may utilize sub-area paging as described in clause 4.2.3.3 of TS 23.502 [3] (e.g. first page in the last known cell-id or TA and retransmission in all registered TAs). The AMF may utilize the location information as received at or before the AN release due to the discontinuous coverage for paging optimisation.
The AMF may e.g. receive UE location from NG-RAN during the Registration procedure e.g. triggered for Mobility Management and Power Saving Optimization for discontinuous network coverage as described in clause 5.4.13.1, or the AMF may request NG-RAN location reporting when the UE is in CM-CONNECTED state as described in clause 5.4.7. |
fbecc7f0dcf9784c6066646052ab0c0e | 23.501 | 5.4.13.5 Overload control | The AMF and UE may only use the procedure defined in this clause if both the UE and AMF indicate support for "Unavailability Period Support", see clause 5.4.13.1. A UE indicating support for "Unavailability Period Support" shall support the procedures defined in this clause when leaving coverage and re-gaining coverage for an NR satellite access.
In order to avoid a large number of UEs causing excessive signalling load on the network when leaving coverage or re-gaining coverage after being out of coverage, the AMF may determine a Maximum Time Offset controlling when UEs are allowed to initiate NAS signalling with the network, as described in this clause.
In this case, the AMF determines this Maximum Time Offset based on network configuration, high priority access and priority service as specified in TS 23.122 [17] and TS 24.501 [47]. The AMF sends this Maximum Time Offset to individual UEs during the Registration procedure or UE Configuration Update procedure.
If the UE receives a Maximum Time Offset from the network in a Registration Accept or UE Configuration Update Command message, the UE shall replace any previously received Maximum Time Offset on the same RAT type and PLMN with this one.
When the UE knows a later time at which coverage will be lost and when the UE does not send Mobility Registration Update to the AMF in advance (see clause 5.4.13.1), the UE determines a random value up to the minimum of the latest Maximum Time Offset for this PLMN and RAT type and the time until coverage will be lost. The UE shall send the Mobility Registration Update at the time when coverage will be lost less the random value to the AMF indicating the loss of coverage.
Upon returning to coverage after being out of coverage due to discontinuous coverage, the UE sets the discontinuous coverage wait timer value to a random value up to and including the latest Maximum Time Offset for this PLMN and RAT type and starts this timer. The UE shall not initiate any NAS signalling on that RAT Type and PLMN while the discontinuous coverage wait timer is running.
The UE shall stop the discontinuous coverage wait timer and initiate NAS signalling if the UE receives paging message, has pending emergency services or when UE enters a TAI outside the registration area. |
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