Content for  TS 23.501  Word version:  19.2.1

Mobile gNB with Wireless Access Backhauling (MWAB) provides an NR access link to UEs in proximity and connects to the 5GC serving the UE through an IP connectivity provided by a Backhaul PDU session(s), as illustrated in Figure 5.49.1.1-1. The MWAB consists of a gNB component (MWAB-gNB) and a UE component (MWAB-UE). The MWAB-gNB is based on the gNB functionality specified in TS 38.300 and TS 38.401. The MWAB may be mounted on a moving vehicle and may serve UEs inside or outside the vehicle. The MWAB-UE establishes the IP connectivity for the backhaul links for the MWAB-gNB, via NR Uu, using the existing registration procedure and PDU session establishment procedure. The backhaul links are between the MWAB-gNB and entities of the network (e.g. AMF, UPF, other gNBs and OAM server) that a MWAB-gNB cell serves. The IP connectivity provided by the MWAB-UE may be either via the same PLMN/SNPN that the MWAB-gNB serves or a different PLMN/SNPN, depending on the MWAB-UE PLMN selection mechanism as specified in TS 23.122. Different possible deployment scenarios are presented in Annex S. MWAB operation supports both PLMN and SNPN cases. When the MWAB-gNB is serving a PLMN, the UEs served by MWAB may be non-roaming or roaming in the MWAB Broadcasted PLMN. In case the MWAB-gNB is serving a SNPN, the subscribed SNPN of the UEs may be different from the MWAB Announced SNPN. The UEs served by the MWAB are not aware of the network serving the MWAB-UE.

MWAB-UE has a single NR Uu hop to the BH NG-RAN, using either TN or NTN access technology. The NR Uu access link between the MWAB-gNB and the served UE(s) does not use NTN access technology. 5G MOCN can be supported by the MWAB-gNB. The details of the MWAB configuration/provisioning process are described in clause 5.49.2. In order to operate as MWAB, the MWAB-gNB component and MWAB-UE component are authorized and controlled separately. The detailed procedures for the authorization of MWAB are described in clause 5.49.3. When UE(s) are served by MWAB, the MWAB-gNB provides additional User Location Information to the 5GC as described in clause 5.49.4. Service continuity for the UE(s) served by the MWAB-gNB is supported when the MWAB moves. The UE(s) move or do not move together with the MWAB. The detailed procedures for the support of mobility are described in clause 5.49.5. The MWAB shall be able to serve UE(s) without any MWAB-specific enhancements. For some operations, the MWAB may be configured to provide access only to certain UEs. Existing access control mechanisms, e.g. CAG control, can be used to manage the UE(s)'s access to the MWAB-gNB. The details of the access control for the UEs served by MWAB are described in clause 5.49.6. The LCS framework as defined in TS 23.273 is used for providing the location service to the UE(s) served by MWAB. Details on supporting the LCS over MWAB are described in clause 5.49.7. Regulatory services (e.g. emergency services, priority services) can be supported by the MWAB and the details are provided in clause 5.49.8. Details on MWAB-gNB's Xn connection are specified in TS 38.401.

The use of multiple BH PDU Sessions for MWAB-gNB N2, N3, Xn interfaces and OAM access is based on configuration from OAM of the MWAB Broadcasted PLMN/SNPN. The MWAB-gNB requests BH PDU Session(s) from the MWAB-UE by providing corresponding traffic descriptors specified in TS 23.503 and TS 24.526, via the implementation based internal communication between the MWAB-gNB and the MWAB-UE. The MWAB-UE establishes, modifies BH PDU Sessions based on the received traffic descriptors from MWAB-gNB, configured URSP rules, and local configuration.

The MWAB-UE considers the traffic from the MWAB-gNB as application layer traffic and applies the related QoS handling as specified in clause 5.7 for BH PDU Session(s). The MWAB-UE may establish and modify the BH PDU Sessions based on necessary information provided by MWAB-gNB (e.g. according to the QoS requirements identified by the MWAB-gNB based on the QoS information of the PDU Session(s) in the UE contexts of the MWAB-gNB and/or based on OAM configuration) via implementation-based internal communication between MWAB-gNB and MWAB-UE. Based on configuration and traffic mapping specified in TS 38.414 and clause 5.7.1.5, the MWAB-gNB (in the Uplink direction) and the UPFs (in the Downlink direction) in the MWAB Broadcasted PLMN/SNPN set proper marking information (DSCP) for the N3 GTP-U traffic for the UE(s) served by the MWAB-gNB. The MWAB gNB additionally marks the DSCP value based on configuration for N2, N3, Xn and OAM traffic it sources, i.e. not related to PDU Sessions(s) of the UE. The MWAB-gNB provides the information to the MWAB-UE for the mapping of DSCP values used for N3 traffic in the MWAB Broadcasted PLMN/SNPN to QoS flows to be used in the BH PLMN/SNPN (including the required Packet Filter Set for filtering of packets) and the corresponding QoS requirements (e.g. QoS Flow level parameters including e.g. 5QI). The MWAB-UE then initiates PDU session establishment or modification procedure to establish or update the BH PDU session(s) for N3 traffic delivery based on the received information. Based on the information provided by the MWAB-gNB and received during the PDU session establishment/modification, the MWAB-UE processes the UL N3 traffic as described in clause 5.7.1.7. The BH UPF processes the DL N3 traffic as described in clause 5.7.1.6. The MWAB-UE may indicate to the MWAB-gNB the current BH PDU Session's QoS Flow level QoS parameters, e.g. for admission control of the QoS-Flows of the UEs served by the MWAB.

A MWAB-gNB can be configured to associate S-NSSAI(s) in the MWAB-Broadcasted PLMN/SNPN to the traffic descriptor for selection of the BH PDU Sessions parameters e.g. use dedicated S-NSSAI in BH PLMN. If no such association exists for a specific S-NSSAIs of the MWAB Broadcasted PLMN/SNPN, the MWAB-gNB associates this S-NSSAI to default traffic descriptors for the selection of BH PDU Session(s) for the related N2 and/or N3 backhauling. The MWAB-gNB requests the BH PDU sessions as specified in clause 5.49.1.2. When the MWAB-gNB obtains the S-NSSAI of a UE PDU Sessions from the UE PDU session context during PDU session establishment, it checks whether a configured association exists for the S-NSSAI of the PDU session of the UE and, if so, it uses the related BH PDU session for the UE's PDU Session. If a new BH PDU Session needs to be established for supporting a UE's traffic for a S-NSSAI in the MWAB-Broadcasted PLMN/SNPN, after the completion of the PDU session establishment procedure, the MWAB-UE may trigger a PDU session resource modification procedure to shift the N3 traffic for the UE to the new BH PDU sessions.

The MWAB-UE manages the BH PDU Session(s) for the MWAB operation based on the configuration by the HPLMN or Subscribed SNPN of the MWAB-UE. The configuration of the MWAB-UE can be UE Local Configuration, or URSP rules as defined in TS 23.503, for the determination of the proper PDU session parameters, e.g. the DNN, S-NSSAI, the SSC Mode, etc. The URSP rules can be preconfigured or provisioned to the MWAB-UE by its HPLMN using UE Policy delivery as described in clause 4.2.4.3 of TS 23.502.

The MWAB-gNB's configuration is managed by the OAM of the MWAB Broadcasted PLMN/SNPN and the address (or FQDN) of the OAM server per MWAB Broadcasted PLMN/SNPN may be configured at the MWAB-gNB. The OAM server of the MWAB Broadcasted PLMN/SNPN provides (re-)configuration parameters considering location of MWAB as specified in TS 38.401, e.g. for the purpose including the access stratum operation of the MWAB-gNB, the N2, N3 and Xn interface management, activating/deactivating the MWAB-gNB operation and to assist the MWAB-gNB providing information used by MWAB-UE for the BH PDU Session(s) management via URSP processing. The MWAB-gNB shall be configured with the supported S-NSSAI(s) in the MWAB Broadcasted PLMN/SNPN.

There are two aspects related to the authorization of an MWAB. One aspect is the authorization of the MWAB-UE to establish a BH PDU Session. The other aspect is related to the authorization of the MWAB-gNB to operate as a gNB logically belonging to a MWAB Broadcasted PLMN/SNPN which the MWAB-gNB announces in the SIB.

The MWAB-UE is authorized based on its subscription information which includes dedicated S-NSSAI(s) and DNN for MWAB operation. Such dedicated S-NSSAI(s) and DNN(s) shall be part of the subscription information for the MWAB-UE as specified in clause 5.2.3.3.1 of TS 23.502. The authorization of the MWAB-UE to establish connectivity in a BH PLMN/SNPN is based on whether dedicated S-NSSAI(s) for MWAB operations are received as part of Allowed NSSAI in BH PLMN/SNPN following existing procedures as described in clause 5.15 and whether it can establish BH PDU session(s) in the BH PLMN/SNPN using the dedicated S-NSSAI(s) and DNN(s). The MWAB-UE authorization supports time-based or location-based control.

• For time-based control, existing time-based network slice subscription control can be reused (including the enhancements in clause 5.15.16).
• For location-based control, existing mechanism, e.g. service area restriction, LADN based control (see e.g. clauses 5.6.5 and 5.6.5a) can be reused.

The MWAB-UE may be connected to the BH PLMN/SNPN for other services, if allowed by the subscription data, even if the S-NSSAIs and DNNs for Backhaul PDU sessions are no longer authorized.

The authorization of the MWAB-gNB is managed by the OAM system of the MWAB-Broadcasted PLMN/SNPN as specified in TS 38.401. The MWAB-gNB establishes a secure and trusted connection to the OAM server using the IP connectivity provided by the MWAB-UE via the Backhaul PDU Session(s) as specified in clause 5.49.1. The OAM of the MWAB Broadcasted PLMN/SNPN determines when/where the MWAB-gNB can operate or when/where it needs to shut down. The OAM of the MWAB Broadcasted PLMN/SNPN may pre-configure the MWAB-gNB to turn on/shut down the operations of respective MWAB Broadcasted PLMN/SNPN part. When the MWAB-gNB is no longer authorized to operate by OAM of the MWAB Broadcasted PLMN/SNPN, the MWAB-gNB should handover the UE(s) of the MWAB Broadcasted PLMN/SNPN to other cells. When the MWAB-gNB stops operating under OAM control, the MWAB-gNB may trigger the MWAB-UE to release the BH PDU sessions.

The existing UE mobility procedures without MWAB UE specific enhancements can be reused to handle a UE mobility to and from a MWAB-gNB while the UE is in CM-IDLE or CM-CONNECTED modes, irrespective of whether the MWAB is static or the MWAB is moving, i.e.:

• For UEs in RRC_IDLE and RRC_INACTIVE state, procedure for cell (re) selection as specified in TS 38.304 and TS 23.122 for RRC_IDLE and RRC_INACTIVE is used irrespective of cells are belonging to a MWAB-gNB or a gNB.
• For UEs in RRC_CONNECTED state, the MWAB-gNB or gNB triggers the handover procedures to the neighbouring cells as specified in TS 38.300 and TS 23.502 irrespective of whether they are belonging to a MWAB-gNB or a gNB.

For a UE served by an MWAB-gNB cell, the MWAB-gNB may trigger the handover procedures for UEs in CM-CONNECTED mode as specified in TS 38.401.

The mobility of MWAB includes the MWAB-UE and the MWAB-gNB aspect.

• The mobility of the MWAB-UE reuses the exiting UE mobility procedures specified for normal UE.
• During Mobility, a MWAB-gNB can obtain or apply a new configuration as specified in TS 38.401 from the OAM server of MWAB Broadcasted PLMN and, if any new AMF was provided as part of the new configuration, the MWAB-gNB sets up the N2 connection with the new AMF and it releases the N2 connection with any old AMF removed from the MWAB-gNB configuration.
• The MWAB-UE may request new or modify existing BH PDU Sessions for the corresponding N2, N3 and Xn interfaces, upon request from the MWAB-gNB as it moves in the network and the MWAB-gNB updates the TNL association as specified in clause 5.21.1 and TS 38.401 to use the new TNL information associated with the new BH PDU Session(s) as needed.
• SSC mode 3 may be applied to the BH PDU Sessions to minimize traffic interruption when UPF re-allocation for these BH PDU Sessions is required during the MWAB mobility.
• When it is required to change AMF for the UEs served by the MWAB-gNB upon mobility of a MWAB into a new region, the TAC(s) and Cell ID(s) the MWAB-gNB announces also change.

Control of UE access to MWAB is supported. If the MWAB-gNB is serving a PNI-NPN, the CAG mechanism described in clause 5.49.6.2 is used. If the MWAB-gNB is serving an SNPN, the SNPN control mechanism described in clause 5.49.6.3 is used. The MWAB-gNB and the 5GC can reuse other existing mechanisms e.g. forbidden Tracking Area, UAC, to manage the UE's access to an MWAB-gNB cell.

According to operator's policy, access control may be applied to UE access to MWAB-gNB cell supporting a PNI-NPN. If the MWAB-gNB is serving a PNI-NPN, the CAG mechanism defined in clause 5.30.3 can be used for managing UE's access to the MWAB-gNB cell, with the following additional considerations:

• The MWAB-gNB is configured either during the communication with the OAM of MWAB-gNB or (pre-)configuration mechanism, with one or more CAG identifiers which are unique within the scope of this PLMN.
• If the MWAB-gNB is (pre-)configured with the PLMN list supporting PNI-NPN, the corresponding CAG Identifiers per PLMN is also configured in the MWAB.
• The MWAB-gNB performs UE access control based on the CAG identifier associated with the MWAB-gNB cell, as defined in clause 5.30.3.4. The MWAB-gNB takes the role of the NG-RAN.
• Time validity information may be provided to the UE together with the CAG Identifier(s) of the MWAB-gNB(s) that the UE can access. If the evaluation of the time validity information of an entry in the Allowed CAG list changes, the updated Allowed CAG list will be provided to UE and MWAB-gNB by the AMF for enforcement, to make sure that UE not accessing the corresponding MWAB-gNB cell outside of the time duration.

Dedicated CAG ID(s) can be used for the control of UE access to a PNI-NPN via MWAB cells.

If the MWAB-gNB is serving an SNPN, as illustrated in Annex S, clause S.3, the existing SNPN control mechanism defined in clause 5.30.2.5 can be used to manage the UE's access to MWAB-gNB. Dedicated SNPN ID(s) or GIN(s) can be used if differentiation is desired in control of UE access to the SNPN via MWAB-gNB or other fixed gNBs.

The Energy Information Function (EIF) is defined to collect the UE related Energy Consumption information, calculate the Energy Consumption information at UE, PDU Session and/or QoS flow granularity and expose the Energy Consumption information to the authorized consumer NF(s) (AF/NEF or 5GC NF) subject to operator's policy. Node level energy consumption is reported PLMN-wide at a configurable period T.

The Energy Information Function (EIF) collects the UE related Energy Consumption information include Node-level energy consumption information, Node-level data volume from OAM and data volume of the required granularities (i.e. PDU Session and/or QoS flow) from UPF (via SMF). The serving SMFs are retrieved from the UDM of the UE based on the provided input parameters including the UE ID and (S-NSSAI, DNN). EIF provides UE ID, DNN/S-NSSAI, IP 5-tuple to retrieve the information from SMF. And the information collected from SMF by EIF, is shown in Table 5.51.2.2-1. The data volume reporting period from the SMFs is the period T with PLMN-wide configuration.

Table 5.51.2.2-2 provides the list of information received from OAM. EIF requests the OAM information with providing the serving gNB ID(s) and (I-)UPF ID(s), which provided by SMFs. The reporting period from the OAM is the period T which is the same as data volume reporting period from SMFs.

When the gNB and/or the (I-)UPF(s) which serving the UE are changed, the serving gNB ID and UPF ID will be updated to the EIF through SMF(s).

EIF calculates the Energy Consumption information of the required granularities (UE, PDU Session and/or QoS flow), based on input parameters from Table 5.51.2.2-1 and Table 5.51.2.2-2 and gets the results. Some example formulas to support the above calculation are described in Annex T.

AF/NEF or 5GC NF subscribes the EIF for Energy consumption information of required granularities (UE, PDU session and/or QoS flow).

• For UE level energy exposure, the consumer NF provides UE ID (SUPI/GPSI).
• For PDU session level exposure, the consumer NF provides UE ID (SUPI/GPSI), DNN/S-NSSAI.
• For QoS flow level exposure, the consumer NF provides UE ID (SUPI/GPSI), DNN/S-NSSAI and Flow description(s).
• The consumer NF may also subscribe the above information exposure with providing reporting period, reporting frequency.