7 NG-RAN functions description

38.4013GPPArchitecture descriptionNG-RANRelease 17TS

7.0 General

For the list of functions refer to TS 38.300 [2].

7.1 NG-RAN sharing

NG-RAN supports radio access network sharing as specified in TS 23.501 [3] and TS 38.300 [2] and TS 36.300 [19].

7.2 Remote Interference Management

The Remote Interference Management function in non-split gNB case is specified in TS 38.300 [2].

In case of split gNB architecture, in the victim set, a gNB-DU detects the remote interference. If remote interference is detected, the gNB-DU can send out the RIM-RS. In the aggressor set, if a gNB-DU detects the RIM-RS sent by the victim gNB(s), it sends to the gNB-CU the RIM-RS detection status and the victim Set ID. The gNB-CU acts as a coordinator on behalf of its affiliated gNB-DUs, where the gNB-CU merges the outgoing RIM information received from its gNB-DUs in the aggressor set and forwards the merged information to all the gNBs in the victim set.

Similarly, in the victim set, the gNB-CU distributes the incoming RIM information to all the gNB-DUs in the set, as indicated in the RIM information received from the aggressor set.

In addition, to facilitate consolidation of RIM information, the gNB-DU provides the associated aggressor set ID and the victim set ID of each serving cell to the gNB-CU.

7.3 Cross-Link Interference Management

The Cross-Link Interference Management function in non-split gNB case is specified in TS 38.300 [2].

In case of split gNB architecture, the gNB-CU forwards the TDD DL/UL patterns received from neighboring nodes to each concerned gNB-DU. The gNB-DU reports the TDD DL/UL patterns of its serving cells to the gNB-CU if Cross-Link Interference is detected.

7.4 Support for Non-Public Networks

NG-RAN supports NPN as specified in TS 23.501 [3] and TS 38.300 [2].

7.5 RACH Optimisation Function

The RACH Optimization Function in non-split gNB case is specified in TS 38.300 [2].

In case of split gNB architecture, RACH configuration conflict detection and resolution function is located at the gNB-DU. To perform RACH optimisation at gNB-DU, gNB-CU sends the RACH report reported by the UE to gNB-DU via F1AP signalling. The gNB-DU signals the PRACH configuration per-cell to gNB-CU. The gNB-CU may forward a limited set of neighbour cell’s PRACH configurations received from neighbour gNBs and other gNB-DUs to the gNB-DU to resolve the configuration conflict.

7.6 Positioning

The NG-RAN supports the positioning functionality as specified in TS 38.305 [25].

7.7 Support for NR MBS

The Support of NR MBS in non-split gNB case is specified in TS 38.300 [2].

7.7.1 Support of dynamic PTP and PTM switching

NG-RAN supports dynamic switch between PTP and PTM for MBS as specified in TS 38.300 [2].

In case of split gNB architecture, for a split MRB bearer with common PDCP, upon receiving the MBS data from the gNB-CU via a shared F1-U tunnel, the gNB-DU makes decision of using PTP (RLC leg) or PTM (RLC leg).

7.8 PCI Optimisation Function

The PCI Optimization Function in non-split gNB case is specified in TS 38.300 [2].

In split gNB architecture, the OAM configures a PCI for each NR cell to the gNB-DU.

For centralized PCI assignment in split gNB architecture, the gNB-CU detects PCI conflict of NR cells and reports the NR cells suffering PCI conflict to OAM directly. The OAM is in charge of reassigning a new PCI for the NR cell subject to PCI conflict.

For distributed PCI assignment in split gNB architecture, the OAM assigns a list of PCIs for each NR cell and sends the configured PCI list to the gNB-CU. If the gNB-CU detects PCI conflict, the gNB-CU may select a new PCI value from the preconfigured PCI list for the NR cell and send it to the gNB-DU by either F1 Setup procedure or gNB-CU configuration update procedure.

7.9 Support for CCO

7.9.1 General

The NR Capacity and Coverage Optimization (CCO) Function in non-split gNB case is specified in TS 38.300 [2]. The objective of this function is to detect and mitigate coverage and cell edge interference issues.

7.9.2 OAM requirements

Each gNB-DU may be configured with alternative coverage configurations by OAM. The alternative coverage configurations contain relevant radio parameters and may also include a range for how each parameter is allowed to be adjusted.

7.9.3 Dynamic coverage configuration changes

In case of split gNB architecture, CCO detection function is located at the gNB-CU. The gNB-CU signals to the gNB-DU the CCO issue and the affected cells and beams. The gNB-DU resolves the CCO issue concerning own served cell by local action within the OAM configured limits. The gNB-DU may also take into account information received for other cells when adopting the CCO configuration. The gNB-DU informs the gNB-CU of the new coverage states adopted.

7.10 Support of RAN visible QoE measurement

The RAN visible QoE measurement function is specified in TS 38.300 [2].

In split gNB architecture, upon the reception of the RAN visible QoE measurement report from the UE, the gNB-CU may forward it to the gNB-DU.