16.6 Stand-Alone NPN
38.3003GPPNRNR and NG-RAN Overall descriptionRelease 17Stage 2TS
16.6.1 General
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.
16.6.2 Mobility
16.6.2.1 General
The same principles as described in 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.
16.6.2.2 Inactive Mode
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 Mode
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 SNPN
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 Control
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 [3].
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 [3].
16.6.5 Access with subscription/credentials owned by a Credentials Holder
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 [3].
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.
16.6.6 Support of UE onboarding and remote provisioning
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.