3.2 Definitions

For the purposes of the present document, the terms and definitions given in TR 21.905 [1], in TS 36.300 [2] 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] and TS 36.300 [2].

2Rx XR UE: two antenna port XR UE as specified in TS 38.101-1 [18].

A2X communication: A communication to support A2X services leveraging PC5 reference points. A2X services are realized by various types of A2X applications, i.e. BRID or DAA.

Access occasion: a time-frequency resource for A-IoT device(s) to transmit A-IoT MSG1 (i.e., the Random ID message) during an A-IoT CBRA procedure.

Activated AI/ML functionality: AI/ML functionality that is already enabled for performing inference.

Aerial UE communication: functionality enabling Aerial UE function, as defined in 16.18.

AI/ML functionality: inference configuration or a set of inference related parameters.

AI/ML Model: a data driven algorithm that applies AI/ML techniques to generate a set of outputs based on a set of inputs.

A-IoT CN node: The core network node which the gNB connects to 5GC for A-IoT operation. More specifically, it is the AIOTF in case the gNB directly connects with the AIOTF, and it includes both the AMF and AIOTF in case the gNB connects with the AIOTF via AMF.

A-IoT device: a device that supports A-IoT radio interface towards A-IoT reader, as defined in 16.23.

A-IoT MSG1: first D2R message transmission in the A-IoT CBRA procedure, as defined in 16.23.

A-IoT MSG2: R2D message in response to A-IoT MSG1 in the A-IoT CBRA procedure, as defined in 16.23.

A-IoT reader: reader providing A-IoT protocol terminations towards the A-IoT device, as defined in 16.23.

Air to Ground network: An NG-RAN consisting of ground-based gNBs, which provide cell towers that send signals up to an aircraft's antenna(s) of onboard ATG terminal, with typical vertical altitude of around 10,000m and take-off/landing altitudes down to 3000m.

Applicable AI/ML functionality: AI/ML functionality for which the UE is ready to perform inference.

AS ID: the AS layer identifier to address the specific A-IoT device for R2D reception and D2R scheduling.

BH RLC channel: an RLC channel between two nodes, which is used to transport backhaul packets.

Boundary IAB-node: as defined in TS 38.401 [4].

Broadcast MRB: A radio bearer configured for MBS broadcast delivery.

CAG Cell: a PLMN cell broadcasting at least one Closed Access Group identity.

CAG Member Cell: for a UE, a CAG cell broadcasting the identity of the selected PLMN, registered PLMN or equivalent PLMN, and for that PLMN, a CAG identifier belonging to the Allowed CAG list of the UE for that PLMN.

CAG-only cell: a CAG cell that is only available for normal service for CAG UEs.

Cell-Defining SSB: an SSB with an RMSI associated.

Child node: IAB-DU's and IAB-donor-DU's next hop neighbour node; the child node is also an IAB-node.

Child UE: a U2N Relay UE’s next hop in downstream direction for serving a U2N Remote UE in U2N Relay communication. Child UE can be the U2N Remote UE or a U2N Relay UE.

Conditional Handover (CHO): a handover procedure that is executed only when execution condition(s) are met.

Conditional L1/L2 Triggered Mobility (CLTM): an LTM cell switch procedure that is executed only when execution condition(s) are met.

CORESET#0: the control resource set for at least SIB1 scheduling, can be configured either via MIB or via dedicated RRC signalling.

DAPS Handover: a handover procedure that maintains the source gNB connection after reception of RRC message for handover and until releasing the source cell after successful random access to the target gNB.

Data Burst: A set of multiple PDUs generated and sent by the application in a short period of time, as defined in TS 23.501 [3].

Direct Path: a type of UE-to-Network transmission path, where data is transmitted between a UE and the network without sidelink relaying.

Downstream: direction toward child node or UE in IAB-topology or U2N Remote UE in U2N Relay communication.

Early Data Forwarding: data forwarding that is initiated before the UE executes the handover.

Earth-centered, earth-fixed: a global geodetic reference system for the Earth intended for practical applications of mapping, charting, geopositioning and navigation, as specified in NIMA TR 8350.2 [51].

eRedCap UE: a UE with enhanced reduced capabilities as specified in clause 4.2.22.1 in TS 38.306 [11].

Feeder link: wireless transport link between the NTN Gateway and the NTN payload.

First U2N Relay UE: an Intermediate U2N Relay UE having both PC5 connection to a parent UE and PC5 connection to a U2N Remote UE for serving the U2N Remote UE in case of multi-hop L2 U2N Relay communication. In this release, a first U2N Relay UE first establishes a connection to the network before beginning to relay traffic for connected U2N Remote UEs.

Geosynchronous Orbit: earth-centered orbit at approximately 35786 kilometres above Earth's surface and synchronised with Earth's rotation. A geostationary orbit is a non-inclined geosynchronous orbit, i.e. in the Earth's equator plane.

Group ID for Network Selection: an identifier used during SNPN selection to enhance the likelihood of selecting a preferred SNPN that supports a Default Credentials Server or a Credentials Holder, as specified in TS 23.501 [3].

gNB: node providing NR user plane and control plane protocol terminations towards the UE, and connected via the NG interface to the 5GC.

gNB-reader: an A-IoT reader that is deployed within the gNB, as defined in 16.23.

High Altitude Platform Station: airborne vehicle embarking the NTN payload placed at an altitude between 8 and 50 km.

IAB-donor: gNB that provides network access to UEs via a network of backhaul and access links.

IAB-donor-CU: as defined in TS 38.401 [4].

IAB-donor-DU: as defined in TS 38.401 [4].

IAB-DU: gNB-DU functionality supported by the IAB-node to terminate the NR access interface to UEs and next-hop IAB-nodes, and to terminate the F1 protocol to the gNB-CU functionality, as defined in TS 38.401 [4], on the IAB-donor.

IAB-MT: IAB-node function that terminates the Uu interface to the parent node using the procedures and behaviours specified for UEs unless stated otherwise. IAB-MT function used in 38-series of 3GPP Specifications corresponds to IAB-UE function defined in TS 23.501 [3].

IAB-node: RAN node that supports NR access links to UEs and NR backhaul links to parent nodes and child nodes. The IAB-node does not support backhauling via LTE.

IAB topology: the unison of all IAB-nodes and IAB-donor-DUs whose F1 and/or RRC connections are terminated at the same IAB-donor-CU.

Indirect Path: a type of UE-to-Network transmission path, where data is forwarded via a U2N Relay UE between a U2N Remote UE and the network.

Inter-donor partial migration: migration of an IAB-MT to a parent node underneath a different IAB-donor-CU while the collocated IAB-DU and its descendant IAB-node(s), if any, are terminated at the initial IAB-donor-CU. The procedure renders the said IAB-node as a boundary IAB-node.

Intermediate U2N Relay UE: a U2N Relay UE having both PC5 connection to a parent UE and PC5 connection to a child UE or a U2N Remote UE for serving the U2N Remote UE in case of multi-hop L2 U2N Relay communication. In this release, an intermediate U2N Relay UE first establishes a connection to the network as a U2N Remote UE before beginning to relay traffic for connected U2N Remote UEs.

Inter-satellite link: wireless transport link between two regenerative NTN payloads.

Intra-system Handover: handover that does not involve a CN change (EPC or 5GC).

Inter-system Handover: handover that involves a CN change (EPC or 5GC).

Last U2N Relay UE: a U2N Relay UE having both Uu connection to the network and PC5 connection to a child UE for serving a U2N Remote UE in case of L2 U2N Relay communication. The child UE is the U2N Remote UE in case of single-hop L2 U2N Relay communication.

Late Data Forwarding: data forwarding that is initiated after the source NG-RAN node knows that the UE has successfully accessed a target NG-RAN node.

L1/L2 Triggered Mobility: a cell switch procedure that the network triggers via MAC CE based on L1 or L3 measurement report.

Mapped Cell ID: in NTN, it corresponds to a fixed geographical area.

MBS Radio Bearer: A radio bearer configured for MBS delivery.

Mobile-IAB cell: a cell of a mobile IAB-DU.

Mobile IAB-DU: gNB-DU functionality supported by the mobile IAB-node to terminate the NR access interface to UEs, and to terminate the F1 protocol to the gNB-CU functionality on the IAB-donor, as defined in TS 38.401 [4].

Mobile IAB-DU migration: procedure for a mobile IAB-node as defined in TS 38.401 [4].

Mobile IAB-MT: mobile IAB-node function that terminates the Uu interface to the parent node using the procedures and behaviours specified for UEs unless stated otherwise.

Mobile IAB-MT migration: procedure for a mobile IAB-MT as defined in TS 38.401 [4].

Mobile IAB-node: RAN node that supports NR access links to UEs and an NR backhaul link to a parent node, and that can conduct physical mobility across the RAN area. The mobile IAB-node function used in 38-series of 3GPP Specifications corresponds to the MBSR function defined in TS 23.501 [3].

MP Relay UE: a UE that provides functionality to support connectivity to the network for MP Remote UE(s).

MP Remote UE: a UE that communicates with the network via a direct Uu link and a MP Relay UE.

MSG1: preamble transmission of the random access procedure for 4-step random access (RA) type.

MSG3: first scheduled transmission of the random access procedure.

MSGA: preamble and payload transmissions of the random access procedure for 2-step RA type.

MSGB: response to MSGA in the 2-step random access procedure. MSGB may consist of response(s) for contention resolution, fallback indication(s), and backoff indication.

Multicast/Broadcast Service: A point-to-multipoint service as defined in TS 23.247 [45].

Multicast MRB: A radio bearer configured for MBS multicast delivery.

Multi-hop backhauling: using a chain of NR backhaul links between an IAB-node and an IAB-donor.

NCR-Fwd: Network-Controlled Repeater node function, which performs amplifying-and-forwarding of UL/DL RF signals between gNB and UE. The behaviour of the NCR-Fwd is controlled according to the side control information received by the NCR-MT from a gNB.

NCR-Fwd access link: link used for transmissions between the NCR-Fwd and UEs.

NCR-Fwd backhaul link: link used for backhauling between the NCR-Fwd and gNB.

NCR-MT: NCR-node entity which communicates with a gNB via a control link to receive side control information. The control link is based on NR Uu interface.

NCR-node: RAN node comprising NCR-MT and NCR-Fwd.

Network-side (AI/ML) model: an AI/ML model whose inference is performed at the network.

ng-eNB: node providing E-UTRA user plane and control plane protocol terminations towards the UE, and connected via the NG interface to the 5GC.

NG-C: control plane interface between NG-RAN and 5GC.

NG-U: user plane interface between NG-RAN and 5GC.

NG-RAN node: either a gNB or an ng-eNB.

Non-CAG Cell: a PLMN cell which does not broadcast any Closed Access Group identity.

Non-Cell Defining SSB: an SSB without an RMSI associated.

Non-Geosynchronous orbit: earth-centered orbit with an orbital period that does not match Earth's rotation on its axis. This includes Low and Medium Earth Orbit (LEO and MEO). LEO operates at altitudes between 300 km and 1500 km and MEO at altitudes between 7000 km and 25000 km, approximately.

Non-terrestrial network: an NG-RAN consisting of gNBs, which provide non-terrestrial NR access to UEs by means of an NTN payload embarked on an airborne or space-borne NTN vehicle and an NTN Gateway.

NR backhaul link: NR link used for backhauling between an IAB-node and an IAB-donor, and between IAB-nodes in case of a multi-hop backhauling.

NR sidelink communication: AS functionality enabling at least V2X communication as defined in TS 23.287 [40] and/or A2X communication as defined in TS 23.256 [60] and/or the ProSe communication (including ProSe non-Relay and UE-to-Network Relay communication) as defined in TS 23.304 [48], between two or more nearby UEs, using NR technology but not traversing any network node.

NR sidelink discovery: AS functionality enabling ProSe non-Relay Discovery and ProSe UE-to-Network Relay discovery for Proximity based Services as defined in TS 23.304 [48] between two or more nearby UEs, using NR technology but not traversing any network node.

NTN Gateway: an earth station located at the surface of the earth, providing connectivity to the NTN payload using the feeder link. An NTN Gateway is a TNL node.

NTN payload: a network node, embarked on board a satellite or high altitude platform station, providing connectivity functions, between the service link and the feeder link. The NTN payload may be a TNL node (transparent payload) or a gNB (regenerative payload).

Numerology: corresponds to one subcarrier spacing in the frequency domain. By scaling a reference subcarrier spacing by an integer N, different numerologies can be defined.

Offline model training: an AI/ML training process where the model is trained based on collected dataset, and where the trained model is later used or delivered for inference.

Parent node: IAB-MT's or mobile IAB-MT's next hop neighbour node; the parent node can be an IAB-node or IAB-donor-DU

Parent UE: a U2N Remote UE or U2N Relay UE’s next hop U2N Relay UE in upstream direction for serving the U2N Remote UE in U2N Relay communication.

PC5 Relay RLC channel: an RLC channel between L2 U2N Remote UE and L2 U2N Relay UE, between L2 U2N Relay UEs (in case of multi-hop L2 U2N relay communication), or between L2 U2U Remote UE and L2 U2U Relay UE, which is used to transport packets over PC5 for L2 UE-to-Network/UE-to-UE Relay.

PDU Set: one or more PDUs carrying the payload of one unit of information generated at the application level (e.g. frame(s) or video slice(s) for XR Services), as defined in TS 23.501 [3].

PLMN Cell: a cell of the PLMN.

RACH-less LTM: an LTM cell switch procedure where UE skips the random access procedure.

RedCap UE: a UE with reduced capabilities as specified in clause 4.2.21.1 in TS 38.306 [11].

Relay discovery: AS functionality enabling 5G ProSe UE-to-Network Relay Discovery as defined in TS 23.304 [48], using NR technology but not traversing any network node.

Satellite: a space-borne vehicle orbiting the Earth embarking the NTN payload.

Service link: wireless link between the NTN payload and UE.

Sidelink Discovery RSRP: RSRP measurements on PC5 link related to NR sidelink discovery.

Sidelink RSRP: RSRP measurements on PC5 link related to NR sidelink communication.

SNPN Access Mode: mode of operation whereby a UE only accesses SNPNs.

SNPN-only cell: a cell that is only available for normal service for SNPN subscribers.

SNPN Identity: the identity of Stand-alone NPN defined by the pair (PLMN ID, NID).

Special Cell: For Dual Connectivity operation the term Special Cell refers to the PCell of the MCG or the PSCell of the SCG, otherwise, in case of NR Standalone, the term Special Cell refers to the PCell.

Supported (AI/ML) functionality: AI/ML functionality which can be indicated by using UE capability information.

Transmit/Receive Point: part of the gNB transmitting and receiving radio signals to/from UE according to physical layer properties and parameters inherent to that element.

U2N Relay UE: a UE that provides functionality to support connectivity to the network for U2N Remote UE(s). Up to three L2 U2N Relay UEs (i.e. one Last U2N Relay and up to two Intermediate U2N Relays including one First U2N Relay) can be configured for serving a L2 U2N Remote UE in multi-hop L2 U2N Relay communication in this release.

U2N Remote UE: a UE that communicates with the network via one or more U2N Relay UEs on an indirect path.

U2U Relay UE: a UE that provides functionality to support connectivity between two U2U Remote UEs.

U2U Remote UE: a UE that communicates with other UE(s) via a U2U Relay UE.

UE-side (AI/ML) model: an AI/ML model whose inference is performed at the UE.

UE-to-Network Relay communication: A mode of communication in which a UE communicates with the network through an indirect path involving only one U2N Relay UE for single-hop L2 U2N Relay communication or multiple L2 U2N Relay UEs for multi-hop L2 U2N Relay communication.

UE-to-Network Relay discovery: A mode of NR sidelink discovery in which a UE discovers other UEs for U2N Relay communication.

Upstream: direction toward parent node in IAB-topology or gNB in U2N Relay communication.

Uu Relay RLC channel: an RLC channel between L2 U2N Relay UE or MP Relay UE and gNB, which is used to transport packets over Uu for L2 UE-to-Network Relay or for indirect path in case of MP.

V2X sidelink communication: AS functionality enabling V2X communication as defined in TS 23.285 [41], between nearby UEs, using E-UTRA technology but not traversing any network node.

WAB-gNB: as defined in TS 38.401 [4].

WAB-MT: as defined in TS 38.401 [4].

WAB-node: as defined in TS 38.401 [4].

Xn: network interface between NG-RAN nodes.