School of Specs 38.300v19.3.0

3GPP 38.300 v19.3.0 — the document's own text

4.10.2.3 NR Femto GW

Taught in 4. What NR actually is, in the shape its own document gives it (TSG RAN — the group that specifies the radio, overview).

The NR Femto GW hosts the following functions:

  • Relaying UE-associated NGAP messages between the AMF and the NR Femto node serving the UE, applying the following additional functions:
    • Terminating the UE Context Release Request procedure if an explicit GW Context Release Indication is included. In this case, the NR Femto GW releases the UE context if it determines that the UE identified by the received UE NGAP IDs is no longer served by another NR Femto node attached to it.
    • At UE context establishment (Initial Context Setup or NG Handover) the NR Femto GW sends to the NR Femto node the serving AMF’s GUAMI as well as the AMF UE NGAP ID assigned by the AMF and the AMF UE NGAP ID assigned by the NR Femto GW for the UE.
    • At Path Switch, the NR Femto GW sends to the NR Femto node the AMF UE NGAP ID assigned by the AMF and the AMF UE NGAP ID assigned by the NR Femto GW for the UE.
    • At Initial UE Message and NG Handover procedures, the NR Femto GW verifies, as defined in TS 33.545 [70], that the reported CAG ID list is valid for the indicated cell of the NR Femto node.
  • Terminating non-UE associated NGAP procedures towards the NR Femto node and towards the AMF, applying the following additional functions:
    • At NG Setup, the NR Femto GW verifies, as defined in TS 33.545 [70], that the identity used by the NR Femto node is valid.
    • In case of NG PWS Restart Indication and PWS Failure Indication, the NR Femto GW verifies, as defined in TS 33.545 [70], that the indicated cell identity is valid and replaces the Global gNB ID of the NR Femto node with the NR Femto GW ID before sending the respective message to the AMF.
    • At Overload Start/Stop, the NR Femto GW should provide the NR Femto node with the identities of the affected AMF node(s). The NR Femto node uses the received information to identify the traffic and the AMF to which the overload indication applies. The NR Femto node shall apply the defined rejections until reception of an OVERLOAD STOP message applicable to this traffic, or until the NR Femto node receives a further OVERLOAD START message applicable to the same traffic, in which case it shall replace the ongoing overload action with the newly requested one.
  • Supporting TAC(s) and PLMN ID(s) used by the NR Femto node.
  • Relaying the PATH SWITCH REQUEST message towards the AMF indicated by the GUAMI of the serving AMF received from the NR Femto node.
  • Selecting AMF at UE attachment based on the GUAMI, GUAMI type or Requested NSSAI provided by the NR Femto node in the INITIAL UE MESSAGE message.

A TAI used in a NR Femto GW shall not be reused in another NR Femto GW.