3 Definitions, symbols and abbreviations

36.4233GPPEvolved Universal Terrestrial Radio Access Network (E-UTRAN)Release 17TSX2 Application Protocol (X2AP)

3.1 Definitions

For the purposes of the present document, the terms and definitions given in TR 21.905 [1] 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 [1].

ACL functionality: A functionality controlling the access to network nodes. In case of Access Control Lists (ACL) functionality is applied in a network node the network node may only accept connections from other peer network nodes once the source addresses of the sending network node is already known in the target node.

Elementary Procedure: X2AP protocol consists of Elementary Procedures (EPs). An X2AP Elementary Procedure is a unit of interaction between two eNBs. An EP consists of an initiating message and possibly a response message. Two kinds of EPs are used:

– Class 1: Elementary Procedures with response (success or failure),

– Class 2: Elementary Procedures without response.

E-RAB: Defined in TS 36.401 [2].

CSG Cell: as defined in TS 36.300 [15].

Dual Connectivity: as defined in TS 36.300 [15].

E-UTRA-NR Dual Connectivity: as defined in TS 37.340 [32].

E-UTRAN node: either an eNB or an en-gNB.

Hybrid cell: as defined in TS 36.300 [15].

Master eNB: as defined in TS 36.300 [15].

Secondary Cell Group: as defined in TS 36.300 [15].

Secondary eNB: as defined in TS 36.300 [15].

en-gNB: as defined in TS 37.340 [32].

Conditional Handover: As defined in TS 36.300 [15].

DAPS HO: As defined in TS 36.300 [15].

Conditional PSCell Change: As defined in TS 37.340 [32].

Immediate Handover: Used in the context of Conditional Handover, to refer to a handover that is executed immediately after the UE receives the Handover Command.

IAB-node: as defined in TS 38.300 [47].

3.2 Symbols

For the purposes of the present document, the following symbols apply:

<symbol> <Explanation>

3.3 Abbreviations

For the purposes of the present document, the abbreviations given in TR 21.905 [1] and the following apply. An abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in TR 21.905 [1].

ABS Almost Blank Subframe

ARPI Additional RRM Policy Index

ACL Access Control List

BBF Broadband Forum

BL Bandwidth reduced Low complexity

CCO Cell Change Order

CE Coverage Enhancement

CHO Conditional Handover

CoMP Coordinated Multi Point

CPA Conditional PSCell Addition

CPAC Conditional PSCell Addition or Change.

CPC Conditional PSCell Change

DAPS Dual Active Protocol Stacks

DC Dual Connectivity

DL Downlink

EARFCN E-UTRA Absolute Radio Frequency Channel Number

E-CID Enhanced Cell-ID (positioning method)

eNB E-UTRAN NodeB

EN-DC E-UTRA-NR Dual Connectivity

EP Elementary Procedure

EPC Evolved Packet Core

E-RAB E-UTRAN Radio Access Bearer

E-UTRAN Evolved UTRAN

GNSS Global Navigation Satellite System

GUMMEI Globally Unique MME Identifier

HFN Hyper Frame Number

IAB Integrated Access and Backhaul

IE Information Element

L-GW Local GateWay

LWA LTE-WLAN Aggregation

MCG Master Cell Group

MDT Minimization of Drive Tests

MeNB Master eNB

MME Mobility Management Entity

MTSI Multimedia Telephony Service for IMS

NAICS Network-Assisted Interference Cancellation and Suppression

NR New Radio

PDCP Packet Data Convergence Protocol

PLMN Public Land Mobile Network

ProSe Proximity Service

QMC QoE Measurement Collection

QoE Quality of Experience

SCG Secondary Cell Group

S-GW Serving Gateway

SeNB Secondary eNB

SgNB Secondary gNB

SIPTO Selected IP Traffic Offload

SIPTO@LN Selected IP Traffic Offload at the Local Network

SN Sequence Number

SSID Service Set Identifier

TAC Tracking Area Code

UE User Equipment

UL Uplink

V2X Vehicle-to-Everything

WLAN Wireless Local Area Network

WT WLAN Termination