5.50.2 5GS architecture to support NR Femto

In 5GS, an NR Femto node connects to 5GC directly or via NR Femto Gateway (NR Femto GW) as specified in TS 38.300 [27] (see Annex V).

The NR Femto GW serves as a concentrator for the N2 interface, as described in TS 38.300 [27]. The NR Femto GW appears to the AMF as a gNB. The NR Femto GW appears to the NR Femto node(s) as an AMF. The N2 and N3 interface between the NR Femto node(s) and the 5GC is the same, regardless whether the NR Femto node(s) is(are) connected to the 5GC via an NR Femto GW or not.

NOTE: The AMF knows whether an NR Femto node is connected via NR Femto GW based on implementation.

When NG-RAN triggers N2 based handover to a target NG-RAN, if the target NG-RAN is an NR Femto node connected via NR Femto GW, the AMF shall include the Target RAN Node ID in the Handover Request message based on Target ID provided by source NG-RAN as described in TS 38.300 [34]. The NR Femto GW shall, if supported, use it for routing the Handover Request message to the target NG-RAN as described in TS 38.413 [10].

In a deployment with a locally deployed UPF close to the location of NR Femto node(s), the edge computing functionality specified in clause 5.13 can be applied.