Content for TS 38.401 Word version: 18.3.0

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3.1 Definitions 3.2 Abbreviations
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1 Scope p. 8

The present document describes the overall architecture of the NG-RAN, including interfaces NG, Xn and F1 interfaces and their interaction with the radio interface.

2 References p. 8

The following documents contain provisions which, through reference in this text, constitute provisions of the present document.

References are either specific (identified by date of publication, edition number, version number, etc.) or non-specific.
For a specific reference, subsequent revisions do not apply.
For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same Release as the present document.

[1]

TR 21.905: "Vocabulary for 3GPP Specifications".

[2]

TS 38.300: "NR; Overall description; Stage-2".

[3]

TS 23.501: "System Architecture for the 5G System".

[4]

TS 38.473: "NG-RAN; F1 application protocol (F1AP)".

[5]

TS 38.414: "NG-RAN; NG data transport".

[6]

TS 38.424: "NG-RAN; Xn data transport".

[7]

TS 38.474: "NG-RAN; F1 data transport".

[8]

ITU-T Recommendation G.823 (2000-03): "The control of jitter and wander within digital networks which are based on the 2048 kbit/s hierarchy".

[9]

ITU-T Recommendation G.824 (2000-03): "The control of jitter and wander within digital networks which are based on the 1544 kbit/s hierarchy".

[10]

ITU-T Recommendation G.825 (2001-08): "The control of jitter and wander within digital networks which are based on the synchronous digital hierarchy (SDH)".

[11]

ITU-T Recommendation G.8261/Y.1361 (2008-04): "Timing and Synchronization aspects in Packet networks".

[12]

TS 37.340: "NR; Multi-connectivity; Overall description; Stage-2".

[13]

TS 33.501: "Security Architecture and Procedures for 5G System".

[14]

TS 38.410: "NG-RAN; NG general aspect and principles".

[15]

TS 38.420: "NG-RAN; Xn general aspects and principles"

[16]

TS 38.470: "NG-RAN; F1 general aspects and principles".

[17]

TS 38.460: "NG-RAN; E1 general aspects and principles".

[18]

TS 37.480: "E1 general aspects and principles".

[19]

TS 36.300: "Evolved Universal Terrestrial Radio Access (E-UTRA), Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Overall description; Stage 2".

[20]

TS 32.422: "Trace control and configuration management".

[21]

TS 37.470: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN) and NG-RAN; W1 general aspects and principles; Stage-2".

[22]

TS 38.340: "NR; Backhaul Adaptation Protocol (BAP) specification".

[23]

TS 38.331: "NR; Radio Resource Control (RRC) protocol specification".

[24]

TS 38.425: "NG-RAN; NR user plane Protocol".

[25]

TS 38.305: "NG Radio Access Network (NG-RAN); Stage 2 functional specification of User Equipment (UE) positioning in NG-RAN".

[26]

TS 38.472: "NG-RAN; F1 signalling transport".

[27]

TS 23.247: "Architectural enhancements for 5G multicast-broadcast services; Stage 2".

[28]

TS 36.401: "Evolved Universal Terrestrial Radio Access Network (E-UTRAN); Architecture Description".

[29]

RFC 4555: (2006-06) "RFC IKEv2 Mobility and Multihoming Protocol (MOBIKE)".

[30]

TS 38.321: "NR; Medium Access Control (MAC) protocol specification".

[31]

TS 37.320: "Radio measurement collection for Minimization of Drive Tests (MDT); Overall description; Stage 2".

[32]

TS 23.502: "Procedures for the 5G System (5GS); Stage 2".

[33]

TS 28.532: "Management and orchestration; Generic management services".

[34]

TS 28.105: "Management and orchestration; Artificial Intelligence/ Machine Learning (AI/ML) management".

[35]

TS 37.460: "Iuant interface: General aspects and principles".

3 Definitions and abbreviations p. 9

3.1 Definitions p. 9

For the purpose of the present document, the terms and definitions given in TR 21.905 and the following apply.

A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905.

Associated QoS Flow:

as defined in TS 23.247.

AI/ML Model Inference:

follows the definition of "AI/ML inference" as specified in clause 3.1 of TS 28.105.

AI/ML Model Training:

follows the definition of "ML model training" as specified in clause 3.1 of TS 28.105.

Associated QoS flow information:

Information encompassing: QoS flow QoS parameters for associated QoS flows and mapping information between mapped (unicast) QoS flows and associated QoS flows. The respective information is included in a way that non-supporting RAN nodes would not establish respective RAN resources irrespective the multicast session state.

Boundary IAB-node:

an IAB-node with one RRC interface terminating at a different IAB-donor-CU than the F1 interface. This definition applies to partial migration, inter-donor redundancy and inter-donor RLF recovery.

Conditional Handover:

as defined in TS 38.300.

Conditional PSCell Addition:

as defined in TS 37.340.

Conditional PSCell Change:

as defined in TS 37.340.

DAPS Handover:

as defined in TS 38.300.

eNB-CP:

as defined in TS 36.401.

eNB-UP:

as defined in TS 36.401.

en-gNB:

as defined in TS 37.340.

Early Data Forwarding:

as defined in TS 38.300.

F1-terminating IAB-donor:

Refers to the IAB-donor that terminates F1 for the boundary IAB-node or a mobile IAB-node.

gNB:

as defined in TS 38.300.

gNB Central Unit (gNB-CU):

a logical node hosting RRC, SDAP and PDCP protocols of the gNB or RRC and PDCP protocols of the en-gNB that controls the operation of one or more gNB-DUs. The gNB-CU terminates the F1 interface connected with the gNB-DU.

gNB Distributed Unit (gNB-DU):

a logical node hosting RLC, MAC and PHY layers of the gNB or en-gNB, and its operation is partly controlled by gNB-CU. One gNB-DU supports one or multiple cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the F1 interface connected with the gNB-CU. For DC operation, the MgNB-DU designates the gNB-DU of an en-gNB or a gNB acting as master node, and the SgNB-DU designates the gNB-DU of an en-gNB or a gNB acting as secondary node.

gNB-CU-Control Plane (gNB-CU-CP):

a logical node hosting the RRC and the control plane part of the PDCP protocol of the gNB-CU for an en-gNB or a gNB. The gNB-CU-CP terminates the E1 interface connected with the gNB-CU-UP and the F1-C interface connected with the gNB-DU. For DC operation, the MgNB-CU-CP designates the gNB-CU-CP of the gNB-CU for an en-gNB or a gNB acting as master node, and the SgNB-CU-CP designates the gNB-CU-CP of the gNB-CU for an en-gNB or a gNB acting as secondary node.

gNB-CU-User Plane (gNB-CU-UP):

a logical node hosting the user plane part of the PDCP protocol of the gNB-CU for an en-gNB, and the user plane part of the PDCP protocol and the SDAP protocol of the gNB-CU for a gNB. The gNB-CU-UP terminates the E1 interface connected with the gNB-CU-CP and the F1-U interface connected with the gNB-DU. For DC operation, the MgNB-CU-UP designates the gNB-CU-UP of the gNB-CU for an en-gNB or a gNB acting as master node, and the the SgNB-CU-UP designates the gNB-CU-UP of the gNB-CU for an en-gNB or a gNB acting as secondary node.

IAB-node:

as defined in TS 38.300.

IAB-donor:

as defined in TS 38.300.

IAB-donor-CU:

the gNB-CU of an IAB-donor, terminating the F1 interface towards IAB-nodes and IAB-donor-DU.

IAB-donor-DU:

the gNB-DU of an IAB-donor, hosting the IAB BAP sublayer (as defined in TS 38.340), providing wireless backhaul to IAB-nodes.

IAB-DU:

as defined in TS 38.300.

IAB-MT:

as defined in TS 38.300.

IAB Topology:

as defined in TS 38.300.

Mapped QoS flows:

Unicast QoS flows requested to be established, i.e. included in the legacy QoS flow lists in a way, that non-support RAN nodes would attempt to establish unicast QoS flows and supporting RAN nodes can identify them as mapped QoS flows based on the associated QoS information.

Master node:

as defined in TS 37.340.

Master gNB:

see TS 37.340.

MBS session resource:

This term is used for specification of NG, Xn, F1 and E1 interfaces. It denotes NG-RAN interface and radio resources provided to support an MBS Session.

MP Relay UE:

as defined in TS 38.300.

MP Remote UE:

as defined in TS 38.300.

Multi-path:

as defined in TS 38.300.

NCR-MT:

as defined in TS 38.300.

ng-eNB:

as defined in TS 38.300.

ng-eNB Central Unit (ng-eNB-CU):

as defined in TS 37.470.

ng-eNB Distributed Unit (ng-eNB-DU):

as defined in TS 37.470.

ng-eNB-CU-Control Plane (ng-eNB-CU-CP):

a logical node hosting the RRC and the control plane part of the PDCP protocol of the ng-eNB-CU for an ng-eNB. The ng-eNB-CU-CP terminates the E1 interface connected with the ng-eNB-CU-UP and the W1-C interface connected with the ng-eNB-DU.

ng-eNB-CU-User Plane (ng-eNB-CU-UP):

a logical node hosting the user plane part of the PDCP protocol and the SDAP protocol of the ng-eNB-CU for an ng-eNB. The ng-eNB-CU-UP terminates the E1 interface connected with the ng-eNB-CU-CP and the W1-U interface connected with the ng-eNB-DU.

NG-RAN node:

as defined in TS 38.300.

Non-F1-terminating IAB-donor of boundary IAB-node:

Refers to the IAB-donor that has an RRC connection with the boundary node but does not terminate F1 with this boundary node.

PDU Session Resource:

This term is used for specification of NG, Xn, and E1 interfaces. It denotes NG-RAN interface and radio resources provided to support a PDU Session.

Public Network Integrated NPN:

as defined in TS 23.501.

RRC-terminating IAB-donor:

Refers to the IAB-donor that terminates the RRC connection of the mobile IAB-node. The RRC-terminating IAB-donor may also be an F1-terminating IAB-donor.

Secondary gNB:

see TS 37.340.

Stand-alone Non-Public Network:

as defined in TS 23.501.

Subsequent CPAC:

see TS 37.340.

U2N Relay UE:

as defined in TS 38.300.

U2N Remote UE:

as defined in TS 38.300.

3.2 Abbreviations p. 11

For the purposes of the present document, the terms and definitions given in TR 21.905 and the following apply.

A term defined in the present document takes precedence over the definition of the same term, if any, in TR 21.905.

5GC

5G Core Network

AMF

Access and Mobility Management Function

Application Protocol

Access Stratum

Artificial Intelligence

BAP

Backhaul Adaptation Protocol

Backhaul

BSR

Buffer Status Report

CAG

Closed Access Group

CHO

Conditional Handover

CLI

Cross-Link Interference

Connection Management

CMAS

Commercial Mobile Alert Service

CPA

Conditional PSCell Addition

CPC

Conditional PSCell Change

DAPS

Dual Active Protocol Stack

Distributed Unit

Element Manager

EN-DC

E-UTRA-NR Dual Connectivity

ETWS

Earthquake and Tsunami Warning System

F1-U

F1 User plane interface

F1-C

F1 Control plane interface

F1AP

F1 Application Protocol

FDD

Frequency Division Duplex

FTEID

Fully Qualified TEID

GTP-U

GPRS Tunnelling Protocol

IAB

Integrated Access and Backhaul

Internet Protocol

Layer-2

LBT

Listen Before Talk

LTM

L1/L2 Triggered Mobility

MBS

Multicast Broadcast Service

MCG

Master Cell Group

MDT

Minimization of Drive Tests

MOCN

Multi-Operator Core Network

Master Node

MgNB

Master gNB

mIAB

Mobile IAB

mIAB-DU

Mobile IAB Distributed Unit

mIAB-MT

Mobile IAB Mobile Termination

Multi-Path

MRB

MBS Radio Bearer

MRDC

Multi-Radio Dual Connectivity

Machine Learning

MT-SDT

Mobile Terminated Small Data Transmission

N3C

Non-3GPP Connection

NAS

Non-Access Stratum

NCI

NR Cell Identity

NDS

Network Domain Security

NID

Network identifier

NPN

Non-Public Network

NSA

Non Standalone

OAM

Operation, Administration and Maintenance

PNI-NPN

Public Network Integrated Non-Public Network

PTP

Point to Point

PTM

Point to Multipoint

PWS

Public Warning System

QoE

Quality of Experience

QoS

Quality of Service

RANAC

RAN Area Code

RET

Remote Electrical Tilting

RIM

Remote Interference Management

RIM-RS

Remote Interference Management Reference Signal

RLF

Radio Link Failure

RNL

Radio Network Layer

RRC

Radio Resource Control

Standalone

SAP

Service Access Point

SCG

Secondary Cell Group

SCTP

Stream Control Transmission Protocol

SDT

Small Data Transmission

SFN

System Frame Number

SgNB

Secondary gNB

Session Management

SMF

Session Management Function

Secondary Node

SNPN

Stand-alone Non-Public Network

SRAP

Sidelink Relay Adaptation Protocol

TAC

Tracking Area Code

TCE

Trace Collection Entity

TDD

Time Division Duplex

TDM

Time Division Multiplexing

TEID

Tunnel Endpoint Identifier

TMA

Tower Mounted Amplifier

TNL

Transport Network Layer

U2N

UE-to-Network

Uplink

4 General principles p. 13

The general principles guiding the definition of NG-RAN architecture as well as the NG-RAN interfaces are the following:

Logical separation of signalling and data transport networks.
NG-RAN and 5GC functions are fully separated from transport functions. Addressing scheme used in NG-RAN and 5GC shall not be tied to the addressing schemes of transport functions. The fact that some NG-RAN or 5GC functions reside in the same equipment as some transport functions does not make the transport functions part of the NG-RAN or the 5GC.
Mobility for an RRC connection is fully controlled by the NG-RAN.
The NG-RAN interfaces are defined along the following principles:
- The functional division across the interfaces have as few options as possible.
- Interfaces are based on a logical model of the entity controlled through this interface.
- One physical network element can implement multiple logical nodes.