Home and small-business 5G base stations have existed in 3GPP specifications only in fragments. A new Release 19 work item, approved at TSG SA Meeting #105, turns two completed studies into actual normative text covering deployment architecture, access control and access to local services.
The device in question is a Premises Radio Access Station (PRAS) — a 5G New Radio (NR) femto access point installed on customer premises, connected back to the operator's 5G Core (5GC). Until now, NR Femto appeared in 3GPP only in limited form, notably in TS 38.104 on radio transmission and reception. What was missing was the system side: how such a node attaches to the core, who is allowed to use it, and how a user on the premises reaches a printer or a local server rather than transiting the operator network. That gap is what the work item closes.
Two studies feed it. On the radio network side, TR 38.799 records that direct connection of an NR Femto node to the 5GC over the NG interface is already possible, and that direct Xn-interface connection between NR Femto nodes and gNBs is likewise already possible. It also recommends the architecture option with an optional NR Femto Gateway for the normative phase, to preserve existing infrastructure for operators who have deployed LTE Home eNodeBs. On access control it states that NR Femto reuses the existing Closed Access Group (CAG) functionality with no Stage 3 impact, and that access to local services reuses Local Area Data Network (LADN) and edge computing functionality from TS 23.501 and TS 23.548. On the system architecture side, TR 23.700-45 decides that the CAG owner or an authorised administrator provides CAG information via the Network Exposure Function (NEF), by enhancing the existing Parameter Provisioning service of TS 23.502 towards the Unified Data Management/Unified Data Repository (UDM/UDR) and the Access and Mobility Management Function (AMF).
The two studies do not cover everything the work item names. Integrating Access to Local Services into the 5G NR Femto framework appears in the work item's own list of innovations, and the ownership concept and mechanism for 5G NR Femto and CAG is flagged in TR 23.700-45 as still to be defined together with SA WG3 — so parts of the normative programme run ahead of a settled study conclusion. Mobility between a CAG cell and a Closed Subscriber Group (CSG) cell, studied as a separate key issue, was explicitly closed off: no normative work will be done in this release, a decision the parallel security study 33.745 repeats.
The concrete deployments are ordinary ones. A femto in a residential home, an enterprise building or a small business, sitting outside direct operator control and reaching the core over a public or third-party network. Devices on the premises get operator service, Internet access, and access to local services such as printers or servers — the local User Plane Function (UPF) can be standalone or co-located with the femto node for edge computing. And a household or site administrator, rather than an operator provisioning team, manages which subscribers may use the CAG cell, for non-roaming scenarios only.
The work item was approved at TSG SA Meeting #105 as SP-241327, with Malla Reddy Sama of NTT DOCOMO as rapporteur and 24 supporting companies. The list mixes operators (NTT DOCOMO, Verizon, T-Mobile USA, AT&T, BT, SK Telecom, Charter Communications, Rakuten Mobile, Reliance Jio, Telefonica, KPN, DISH Network, FirstNet, Comcast), vendors (Nokia, Samsung, Casa Systems, Cisco, NEC, ZTE, Oppo, LG Electronics) and software suppliers (Oracle, MATRIXX Software). The presence of several cable and fixed-line operators alongside mobile incumbents points to where the commercial pressure for premises-based 5G actually sits.
The documents are candid about what is unresolved. TR 38.799 lists scalability of local UPF discovery, for instance when mobile edge computing solutions are used, plus switching the N4 interface on and off and N4 aggregation. The security study TR 33.745 defers several items to the normative phase: whether multi-factor authentication can be an optional alternative for NR Femto hosting party authentication, and the impact on network functions and on backhaul link protection of supporting EAP-AKA'. Roaming is out of scope in this release for CAG provisioning entirely.
Between the specification and a shipping product sits the trust boundary. The security study assumes the backhaul to the Security Gateway (SeGW) is protected by IPsec with pre-configured, certificate-based keys, and that the CAG owner or administrator is authenticated and authorised by the 5GC before touching users' allowed CAG lists — while the ownership concept underpinning that authorisation is still to be defined with SA WG3. A device shipped to a customer's premises has to arrive with a credential and an owner binding already in place, and that provisioning chain is not something a Stage 2 architecture specification settles.