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Content for  TS 38.300  Word version:  17.2.0

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16.4  Public Warning Systemp. 142

NR connected to 5GC provides support for public warning systems (PWS) through means of system information broadcast capability. NR is responsible for scheduling and broadcasting of the warning messages as well as for paging the UE to provide indication that the warning message is being broadcast:
  • Earthquake and Tsunami Warning System: ETWS is a public warning system developed to meet the regulatory requirements for warning notifications related to earthquake and/or tsunami events (see TS 22.168). ETWS warning notifications can either be a primary notification (short notification) or secondary notification (providing detailed information).
  • Commercial Mobile Alert System: CMAS is a public warning system developed for the delivery of multiple, concurrent warning notifications (see TS 22.268).
Different SIBs are defined for ETWS primary notification, ETWS secondary notification and CMAS notification. Paging is used to inform UEs about ETWS indication and CMAS indication (see clause 9.2.5). UE monitors ETWS/CMAS indication in its own paging occasion for RRC_IDLE and for RRC_INACTIVE while no SDT procedure (see clause 18.0) is ongoing. UE monitors ETWS/CMAS indication in any paging occasion for RRC Connected and during the SDT procedure in RRC_INACTIVE. Paging indicating ETWS/CMAS notification triggers acquisition of system information (without delaying until the next modification period).
KPAS and EU-Alert are public warning systems developed for the delivery of multiple, concurrent warning notifications (see TS 22.268). KPAS and EU-Alert uses the same AS mechanisms as CMAS. Therefore, the NR procedures defined for CMAS equally apply for KPAS and EU-Alert.
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16.5  Emergency Servicesp. 143

16.5.1  Overviewp. 143

NG-RAN provides support for Emergency Services either directly or through fallback mechanisms towards E-UTRA. The support of Emergency Services is broadcast in system information (see TS 38.331).

16.5.2  IMS Emergency callp. 143

An IMS Emergency call support indication is provided to inform the UE that emergency bearer services are supported. In normal service state the UE is informed if the PLMN supports emergency services through an Emergency Service Support indicator in the Attach and TAU procedures (see TS 23.501). In limited service state and for emergency services other than eCall over IMS, a UE is informed about if a cell supports emergency services over NG-RAN from a broadcast indication (ims-EmergencySupport). The broadcast indicator is set to "support" if any AMF in a non-shared environment or at least one of the PLMN's in a shared environment supports IMS emergency bearer services.
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16.5.3  eCall over IMSp. 143

NG-RAN broadcast an indication to indicate support of eCall over IMS (eCallOverIMS-Support). UEs that are in limited service state need to consider both eCallOverIMS-Support and ims-EmergencySupport to determine if eCall over IMS is possible. UEs that are not in limited service state need to only consider eCallOverIMS-Support to determine if eCall over IMS is possible. The broadcast indicator is set to "support" if the PLMN in a non-shared environment, or all PLMNs in a shared environment, supports eCall over IMS.
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16.5.4  Fallbackp. 143

RAT fallback towards E-UTRA connected to 5GC is performed when NR does not support Emergency Services and System fallback towards E-UTRA connected to EPS is performed when 5GC does not support Emergency Services. Depending on factors such as CN interface availability, network configuration and radio conditions, the fallback procedure results in either CONNECTED state mobility (handover procedure) or IDLE state mobility (redirection) - see TS 23.501 and TS 38.331.
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16.6  Stand-Alone NPN |R16|p. 143

16.6.1  Generalp. 143

An SNPN is a network deployed for non-public use which does not rely on network functions provided by a PLMN (see clause 4.8). An SNPN is identified by a PLMN ID and NID (see clause 8.2) broadcast in SIB1.
An SNPN-capable UE supports the SNPN access mode. When the UE is set to operate in SNPN access mode, the UE only selects and registers with SNPNs. When the UE is not set to operate in SNPN access mode, the UE performs normal PLMN selection procedures.
Emergency services and ETWS /CMAS can be supported by SNPNs. An IMS Emergency call support indication is provided per SNPN to inform the UE which SNPN(s) support emergency bearer. In normal service state the indication is provided in the same way as in case of PLMNs (see clause 16.5.2). In limited service state and for emergency services other than eCall over IMS, a UE is informed whether an SNPN of the cell supports emergency services over NG-RAN from a per SNPN broadcast indication (imsEmergencySupportForSNPN). The broadcast indicator for an SNPN may be set to "support" if any AMF of the SNPN supports IMS emergency bearer services.
NR-NR Dual Connectivity within a single SNPN is supported.
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16.6.2  Mobilityp. 144

16.6.2.1  Generalp. 144

The same principles as described in clause 9.2 apply to SNPN except for what is described below.
UEs operating in SNPN access mode only (re)select cells within the selected/registered SNPN and a cell can only be considered as suitable if the PLMN and NID broadcast by the cell matches the selected/registered SNPN.
In addition, manual selection of SNPN(s) is supported, for which HRNN(s) can be optionally provided.
The roaming and access restrictions applicable to SNPN are described in clause 9.4.
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16.6.2.2  Inactive Modep. 144

The mobility of a UE in inactive mode builds on existing functionality described in clause 9.2.2 and is limited to the SNPN identified within the mobility restrictions received in the UE context.

16.6.2.3  Connected Modep. 144

The NG-RAN node is aware of the SNPN ID(s) supported by neighbour cells.
At the time of handover, cells that do not support the serving SNPN ID are not considered as candidate target cells by the source NG-RAN node.
The target NG-RAN node performs access control. In case it cannot accept the handover for the serving SNPN the target NG-RAN node fails the handover including an appropriate cause value.

16.6.3  Self-Configuration for SNPNp. 144

Self-configuration is described in clause 15. In addition, on NG, the NG-RAN node signals the SNPN ID(s) supported per tracking area and the AMF signals the SNPN ID(s) supported per node; on Xn, NG-RAN nodes exchange SNPN ID(s) supported per cell.

16.6.4  Access Controlp. 144

During the establishment of the UE-associated logical NG-connection towards the 5GC, the AMF checks whether the UE is allowed to access the cell for the signalled SNPN ID as specified in TS 23.501.
If the check is successful, the AMF sets up the UE-associated logical NG-connection and provides the NG-RAN node with the mobility restrictions applicable for the SNPN.
If the check is not successful, the AMF shall reject setting up the UE-associated NG connection and inform the NG-RAN node with an appropriate cause value as specified in TS 23.501.
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16.6.5  Access with subscription/credentials owned by a Credentials Holder |R17|p. 144

An SNPN may allow access to UEs being authorized using credentials or subscription owned by a separate Credentials Holder (CH). The support of this feature is uniform across the SNPN as specified in TS 23.501.
The following information is broadcast to support SNPN access with subscription of a Credentials Holder:
  • an indication per SNPN in SIB1 that access using credentials from a Credentials Holder is supported;
  • optionally a list of supported GINs in SIB18 (each GIN may be assigned to one or more SNPNs);
  • an optional indication per SNPN in SIB1 that the SNPN allows registration attempts from UEs that are not explicitly configured to select the SNPN.
The above listed items are forwarded to the UE NAS layer that uses them for SNPN selection.
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16.6.6  Support of UE onboarding and remote provisioning |R17|p. 144

An SNPN may offer support for restricted 3GPP connectivity for remote provisioning of credentials. The feature is enabled/disabled per cell.
The following information is broadcast to support UE onboarding and remote provisioning:
  • an indication per onboarding SNPN in SIB1 that UE onboarding is enabled;
  • optionally a list of supported GINs in SIB18 (each GIN may be assigned to one or more onboarding SNPNs).
The above listed items are forwarded to the UE NAS layer that uses them for onboarding SNPN selection. When a UE intends to perform onboarding, it sends the onboarding request indication to the gNB during RRC connection establishment.
The NG-RAN nodes receive information about onboarding support capabilities of the AMF(s). This information is used by the NG-RAN node to select a suitable AMF when receiving the onboarding request indication from the UE.
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16.7  Public Network Integrated NPN |R16|p. 145

16.7.1  Generalp. 145

A PNI-NPN is a network deployed for non-public use which relies on network functions provided by a PLMN (see clause 4.8). In PNI-NPN, a Closed Access Groups (CAG) identifies a group of subscribers who are permitted to access one or more CAG cells associated to the CAG. A CAG is identified by a CAG identifier broadcast in SIB1.
A CAG-capable UE can be configured with the following per PLMN (see clause 5.30.3.3 of TS 23.501):
  • an Allowed CAG list containing the CAG identifiers which the UE is allowed to access; and
  • a CAG-only indication if the UE is only allowed to access 5GS via CAG cells.
Dual Connectivity is supported and may involve both PNI-NPN and PLMN cells, according to the mobility restrictions in the UE context as described in TS 37.340.
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16.7.2  Mobilityp. 145

16.7.2.1  Generalp. 145

The same principles as described in clause 9.2 apply to CAG cells except for what is described below.
Cell selection/reselection to CAG cells may be based on a UE autonomous search function, which determines itself when/where to search, but cannot contradict the dedicated cell reselection priority information if any is stored.
A range of PCI values reserved by the network for use by CAG cells may be broadcast.
A CAG Member Cell for a UE is a cell broadcasting the identity of the selected PLMN, registered PLMN or equivalent PLMN, and for that PLMN, a CAG identifier belonging to the Allowed CAG list of the UE for that PLMN. The UE checks the suitability of CAG cells based on the Allowed CAG list provided by upper layers and a CAG-only cell can only be suitable for its subscribers but can be acceptable for the rest.
When the UE is configured with a CAG-only indication, only CAG Member Cells can be suitable. A non-suitable cell can be acceptable though if the UE is configured with a CAG-only indication for one of the PLMN broadcast by the cell.
In addition, manual selection of CAG cell(s) is supported, for which an HRNN(s) can be optionally provided.
The roaming and access restrictions applicable to PNI-NPN are described in clause 9.4.
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16.7.2.2  Inactive Modep. 146

The mobility of a UE in inactive mode builds on existing functionality described in clause 9.2.2 according to the mobility restrictions received in the UE context.

16.7.2.3  Connected Modep. 146

The source NG-RAN node is aware of the list of CAG IDs supported by the candidate target cells which are CAG cells.
At the time of handover, the source NG-RAN node determines a target cell among the candidates which is compatible with the received PNI-NPN restrictions.
At incoming handover, the target NG-RAN node receives the PNI-NPN mobility restrictions and checks that the selected target cell is compatible with the received mobility restrictions.
Mobility between PNI-NPN and PLMN cells is supported according to the mobility restrictions in the UE context.
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16.7.3  Self-Configuration for PNI-NPNp. 146

Self-configuration is described in clause 15.
In addition, each NG-RAN node informs the connected neighbour NG-RAN nodes of the list of supported CAG ID(s) per CAG cell in the appropriate Xn interface management procedures.

16.7.4  Access Controlp. 146

During the establishment of the UE-associated logical NG-connection towards the 5GC, the AMF checks whether the UE is allowed to access the cell as specified in TS 23.501.
If the check is successful, the AMF sets up the UE-associated logical NG-connection and provides the NG-RAN node with the list of CAGs allowed for the UE and, whether the UE is allowed to access non-CAG cells. This information is used by the NG-RAN for access control of subsequent mobility.
If the check is not successful, the AMF shall reject setting up the UE-associated NG connection and inform the NG-RAN node with an appropriate cause value as specified in TS 23.501.
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16.7.5  Pagingp. 146

The NG-RAN node may receive a paging message including the list of CAGs allowed for the UE, and whether the UE is allowed to access non-CAG cells. The NG-RAN node may use this information to avoid paging in cells on which the UE is not allowed to camp.
For UEs in RRC_INACTIVE state, the NG-RAN node may page a neighbour NG-RAN node including the list of CAGs allowed for the UE, and whether the UE is allowed to access non-CAG cells. The neighbour NG-RAN node may use this information to avoid paging in cells on which the UE is not allowed to camp.
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16.8  Support for Time Sensitive Communications |R16|p. 147

Time Sensitive Communications (TSC), as defined in TS 23.501, is a communication service that supports deterministic communication and/or isochronous communication with high reliability and availability. Examples of such services are the ones in the area of Industrial Internet of Things, e.g. related to cyber-physical control applications as described in TS 22.104.
To support strict synchronization accuracy requirements of TSC applications, the gNB may signal 5G system time reference information to the UE using unicast or broadcast RRC signalling with a granularity of 10 ns. Uncertainty parameter may be included in reference time information to indicate its accuracy. The UE may indicate to the gNB a preference to be provisioned with reference time information using UE Assistance Information procedure. Propagation delay compensation (PDC) mechanisms may be applied based on RTT or TA, and can be performed at the UE or gNB side. When performed at UE side, the PDC mechanisms are controlled via RRC signalling by the gNB.
The RTT-based PDC mechanism is achieved by using Rx-Tx time difference measurements of a single pair of configured TRS/PRS and SRS. The following Figure describes the signalling procedures of UE-side RTT-based PDC:
Reproduction of 3GPP TS 38.300, Fig. 16.8-1: Signalling Procedure of UE-side RTT-based PDC
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Step 1.
The gNB provides measurement configurations to the UE;
Step 2a/b.
The gNB transmits TRS or PRS to the UE for measurements, and the UE transmits SRS to the gNB for measurement;
Step 3a/b.
Both the UE and the gNB perform Rx-Tx time difference measurements;
Step 4.
The gNB provides its Rx-Tx time difference measurement to the UE;
Step 5.
The UE performs PDC based on Rx-Tx time difference measurements from itself and the gNB.
The following Figure describes the signalling procedures of gNB-side RTT-based PDC:
Reproduction of 3GPP TS 38.300, Fig. 16.8-2: Signalling Procedure of gNB-side RTT-based PDC
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Step 1.
The gNB provides measurement configurations to the UE;
Step 2a/b.
The gNB transmits TRS or PRS to the UE for measurements, and the UE transmits SRS to the gNB for measurement;
Step 3a/b.
Both the UE and the gNB perform Rx-Tx time difference measurements;
Step 4.
The UE reports its Rx-Tx time difference measurement to the gNB;
Step 5.
The gNB performs PDC based on Rx-Tx time difference measurements from itself and the UE.
The gNB may also receive TSC Assistance Information (TSCAI), see TS 23.501, from the Core Network, e.g. during QoS flow establishment, or from another gNB during handover. TSCAI contains additional information about the traffic flow such as burst arrival time, burst periodicity, and survival time. TSCAI knowledge may be leveraged in the gNB's scheduler to more efficiently schedule periodic, deterministic traffic flows either via Configured Grants, Semi-Persistent Scheduling or with dynamic grants, and/or to improve the associated link reliability to meet the survival time requirement (see TS 22.104).
To support uplink periodic traffics of services with survival time requirement, configured grant resources can be used such that the mapping relation between the service and the configured grant is known to both gNB and UE, thus allowing the gNB to use configured grant retransmission scheduling (addressed by CS-RNTI) to trigger survival time state entry for the corresponding DRB. Upon survival time state entry, all RLC entities configured for the DRB are activated by the UE for duplication to prevent failure of subsequent messages and hence fulfilling the survival time requirement. If CA or DC duplication for the DRB is already activated, the DRB should enter survival time state when any retransmission grant for any of its active LCHs is received.
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