One area that needs further study is enhancements to the 5GS in order to enable support for SNPN along with subscriptions or credentials owned by an entity separate from the SNPN. Studying 5GS enhancements specifically oriented towards support of SNPN with credentials owned by an entity separate from the SNPN is necessary to enable some of the main use cases for Non-Public Networks, such as wireless connectivity for industry, large residential buildings, campuses, malls, and merged SNPNs, which all contain several specialized and stringent requirements. Many of the relevant use cases may in turn potentially have an impact on the architecture. This key issue aims at addressing the following points for SNPN along with subscription owned by an entity separate from the SNPN:

• How to identify the separate entity providing the subscription;
• Network selection enhancements, including UEs with multiple subscriptions;
  • E.g. how does the UE discover and select an SNPN which provides authentication in an external entity;
• Architecture enhancements needed to support multiple separate entities, e.g.:
  • What are the interfaces exposed and/or used by SNPN and the separate entity;
  • What is the architecture and solution for a UE accessing a separate entity via SNPN access network;
• How to exchange authentication signalling between the SNPN and the separate entity, including:
  • Authentication by the PLMN, based on PLMN identities and credentials, for access to the SNPN;
  • Authentication via SNPN to separate entity based on non-3GPP identities (e.g. non-IMSI) and credentials;
• Mobility scenarios, including service continuity, for:
  • UE moving from SNPN#1 with separate entity#1 to SNPN#2 with separate entity#1 available; and
  • UE moving between SNPN#1 (where separate entity=PLMN) and PLMN.

The TS 22.263 captures the service requirements for "Video, Imaging and Audio for Professional Applications (VIAPA)". This key issue aims at addressing the following aspects:

1. Study whether there are support for service continuity (assuming PSA may reside in either PLMN or in the NPN) between PLMN and NPN (SNPN or PNI-NPN) with overlapping radio coverage areas;
2. Study means to enable a UE to receive data services from one network (e.g. NPN), and paging as well as data services from another network (e.g. PLMN) simultaneously.

3GPP Rel-16 includes IMS voice and emergency services support for Public network integrated Non-Public Networks, while for SNPNs the following was captured in TS 23.501: This key issue aims at addressing the following points for SNPN:

1. Study the architectural impacts for support of IMS voice and emergency services offered by SNPN;
2. Study whether basic IMS functionality for SNPN via 3GPP access requires any specification changes to enable non-IMSI based IMPI usage over 3GPP access;
3. Study whether and how SNPN selection is impacted when taking into account IMS voice support.

The Key Issue is aiming to study the architecture and solutions to support UE onboarding and provisioning for the NPN. This key issue includes some common aspects such as:

• Means for a UE, that is verifiably secure and uniquely identifiable to 5GS, for onboarding and remote provisioning;
• Support of exposure via APIs to support UE onboarding and remote provisioning, if required.

But also specific aspects for component 1 (UE onboarding i.e. to enable 3GPP connectivity):

• How does the UE discover and select the onboarding SNPN before UE NPN credentials and other information to enable UE to get 3GPP connectivity are provisioned.
• How and whether the onboarding SNPN authenticates the UE, and establishes a secure 3GPP connectivity, before the UE's NPN credentials and other information to enable SNPN access are provisioned.
• How to establish a secure connectivity between the UE and the network entity for provisioning the NPN credentials and other information to enable SNPN access, i.e. how to enable ciphering and integrity protection of the connection and the authentication of UE at the Provisioning Server.
• How does the 5G system provides and updates in the network the subscription of an authorized UE in order to allow the UE to request connectivity to a desired SNPN.
• Architecture including which NFs are involved, and which scenario(s) the solution is addressing, including:
  • Which network entity performs UE's subscription provisioning and where is the network entity located.
  • If the network entity performing UE subscription provisioning is external to the SNPN, what is the service-based interface exposed by the SNPN towards that network entity for UE onboarding and provisioning.

And for component 2 (remote provisioning of credentials to allow access to NPN services):

• SNPN case: provisioning of NPN credentials (i.e. for primary authentication) and other information to enable SNPN access.
• PNI-NPN case: provisioning of NPN credentials for access to specific slice(s) and/or PDU Sessions offering NPN services, i.e. for Network Slice Specific Authentication and Authorization and/or secondary authentication for PDU Sessions
• Means to remotely provision the required new or updated information to the UE for enabling the UE to access the NPN using 5GS, including e.g.:
  • Triggers and procedures used to initiate the provisioning procedure.
  • How the network entity provisions the NPN credentials to the UE.

The associated solutions need to consider the following UE characteristics:

• Before the UE onboarding process there should be information in the UE for it to be "uniquely identifiable and verifiably secure".
• A TE might not have an interface that can be used to provision the MT.

This key issue is to enable a UE access multiple SNPNs and the ability to support optimized access control and service continuity between SNPNs. This is to enable support for equivalent SNPN (similar to equivalent PLMN) and/or equivalent home SNPN (similar to equivalent HPLMN). Impact to 5G System due to the following scenarios are in the scope:

• Individual SNPNs with their own PLMN ID and NID identification but they are all equivalent. This implies that the UE with subscription for one of the SNPN has access to its equivalent SNPN(s). This also implies that the UE treat individual SNPNs with equal priority for network selection.

It has the following objectives for study:

• Enabling an authorized UE to be able to efficiently access and move between equivalent SNPNs; and
• Enabling an authorized UE to be able to efficiently select equivalent SNPNs during network selection.

One area that needs further study is enhancements to the 5GS in order to enable support for direct connection of non-3GPP access networks to the SNPN's 5GC. There are already non-3GPP access technologies which are in use in enterprises and campuses and it is foreseen that such non-3GPP access technologies will continue to evolve. The integration of these existing assets in the SNPN would add flexibility to the SNPN operators. This key issue aims at addressing the following points for SNPN:

• How to provide direct access to SNPN services via non-3GPP access networks:
  • Support of trusted non-3GPP access network (TNAN);
  • Support of untrusted non-3GPP access network; and
  • Whether and how Wireline 5G Access Network can be used to connect to SNPN.