NR sidelink lets nearby devices exchange data directly, without sending it through a base station. It was created for advanced vehicle communication, and later releases opened it to power-limited devices, coverage extension and commercial uses.

Two interfaces matter throughout. UEs talk to each other over the PC5 interface, which is the direct UE-to-UE sidelink interface. A UE talks to the gNB over Uu. This article follows how TS 38.331 (RRC) and TS 38.300 (stage-2 description) changed from Release 16 to Release 19. Sidelink positioning and core-network aspects are out of scope.

UEUE
Release 16 Direct sidelink between UEs
Remote UERelay UEgNB
Release 17 UE-to-Network relay
Remote UERelay UERemote UE
Release 18 UE-to-UE relay
direct pathPC5 or N3CRemote UERelay UEgNB
Release 18 Multi-path: direct and indirect path at once
Remote UEFirst relayIntermediateLast relaygNBFirst and Intermediate relays: up to two in total
Release 19 Multi-hop UE-to-Network relay: up to two Intermediate relays, the one next to the Remote UE is the First relay

PC5 (UE to UE) Uu (UE to gNB)

The diagram is a map of the article: it shows how the topology grows from direct PC5 links to relays, multi-path and relay chains.

Release 16: a first NR sidelink

LTE-based V2X from Releases 14 and 15 was judged sufficient only for basic road safety. Advanced use cases were identified in four groups: platooning, extended sensors, advanced driving and remote driving. These called for a new NR sidelink.

Release 16 therefore defined UEs that communicate directly over PC5 using unicast, groupcast and broadcast, while the network can still control them over Uu.

  • Two resource allocation modes. In mode 1 the network schedules sidelink resources, including configured grants. In mode 2 the UE selects resources itself from configured or pre-configured pools.
  • Physical layer procedures. UEs can exchange data and control on dedicated sidelink channels, use feedback for unicast and groupcast, report channel state and apply sidelink power control.
  • PC5-RRC signalling. This is the Radio Resource Control (RRC) signalling carried between peer UEs over PC5. Peer UEs can configure sidelink radio bearers, exchange capabilities and handle sidelink radio link failure between themselves.
  • Synchronization. UEs can synchronize even without GNSS and without a base station, by selecting a synchronization reference and sending sidelink synchronization signals.
  • Congestion control. A UE can measure how busy the sidelink channel is and report it, so that transmission parameters can depend on how busy the channel is.

On the network side, the gNB can configure sidelink for idle and inactive UEs through system information and for connected UEs through dedicated signalling.

Release 17: power saving and coverage

The Release 16 design assumed always-on vehicle UEs with ample battery.

Power-constrained UEs, such as vulnerable road users and public safety or commercial devices, needed ways to save energy.

Busy channels also limited reliability and latency.

Separately, coverage was a problem. A study found that two relaying approaches were feasible, one forwarding below PDCP and one forwarding IP traffic, and recommended NR sidelink relay for coverage extension. The earlier LTE-based UE-to-network relay could not serve NR.

  • Power-saving resource allocation. Mode 2 UEs can use partial sensing, which means sensing only part of the resources, or random resource selection, with the allowed scheme configured per resource pool. This lets a UE sense less and spend less energy.
  • Inter-UE coordination. One UE can send resource information to a peer, which takes it into account for its own transmission. This improves reliability and latency when the channel is busy.
  • Sidelink DRX. Sidelink UEs can use on and off durations to save power. It applies to unicast, groupcast and broadcast, and in connected state it can be aligned with Uu DRX.
  • Layer-2 (L2) UE-to-Network relay. A Remote UE is a UE that reaches the network through another UE, and that other UE is the Relay UE. A Remote UE reaches the gNB through a Relay UE and keeps its own connection to the gNB. The Relay UE forwards traffic below PDCP, and the Sidelink Relay Adaptation Protocol (SRAP) sublayer lets it map the Remote UE's traffic onto relay channels. SRAP is the adaptation layer used for bearer mapping and Remote UE identification.
  • Relay discovery, selection and path switch. A Remote UE can discover relays and choose either a cell or a relay using configured thresholds. The network can use new measurement events to move a UE between a direct path and an indirect path.

A Remote UE can also obtain system information and paging through its relay, and set up, resume or re-establish its connection via the relay.

Release 18: more relay types and more spectrum

Release 17 relaying covered only UE-to-network relay. In Layer-2 relay, service continuity was limited to switching between direct and indirect paths within one gNB.

Release 18 therefore added UE-to-UE relay, wider service continuity and multi-path relay, aiming at coverage extension, reliability and throughput.

Separately, NR sidelink had been built for V2X, while commercial use cases need higher data rates and new carrier frequencies.

  • Layer-2 UE-to-UE relay. Two Remote UEs can communicate through a relay UE, with end-to-end sidelink bearers configured over per-hop PC5 links. This extends sidelink coverage without relying on uplink and downlink. Discovery and selection work for both relay architectures.
  • Multi-path. A connected UE can use one direct Uu path plus one indirect path to the same gNB. The indirect path runs either over a PC5 relay or over a non-3GPP connection. The UE can add or change the indirect path and report its failure, and split bearers can use both paths. For a split bearer, the primary path is the one used for uplink data by default, and it can be placed on the indirect path.
  • Enhanced service continuity. A Layer-2 Remote UE can switch between gNBs and between relays, including indirect-to-indirect path switching. A new measurement event compares the serving relay against candidate relays.
  • Sidelink carrier aggregation. A UE can use several sidelink carriers in mode 2, where the UE selects resources itself, with carrier selection, adding and releasing of carriers, and a total transmit power limit. This raises the sidelink data rate.
  • Unlicensed spectrum. Sidelink can run in shared spectrum for both mode 1 and mode 2. Listen before talk means a device senses the channel and transmits only if it is free. The ITS band is limited to safety applications, so shared spectrum makes sidelink usable by commercial devices.

LTE and NR sidelink can also coexist dynamically on the same carrier through overlapping resource pools, so devices of both technologies do not harm each other.

Sidelink operation in FR2 was only studied in this release.

Release 19: relay chains

A single sidelink hop has limited range, so single-hop relays from Releases 17 and 18 have limited applicability. Release 19 specifies multi-hop Layer-2 UE-to-Network relay.

Two terms are needed. A parent is the next hop of a UE in the direction of the network. A child is the next hop of a relay in the direction of the Remote UE, and it can be the Remote UE or another relay.

  • Relay chain. Up to three relay UEs can serve one Remote UE: a First relay next to the Remote UE, optionally an Intermediate relay, and a Last relay holding the Uu connection to the network. Each relay keeps one PC5 connection to its parent and one to each child.
  • Discovery and selection. Relays announce multi-hop service when system information enables it. Last and intermediate relays check threshold conditions before sending discovery messages. A Remote UE can tell single-hop from multi-hop relays by hop type and can prefer relays by their RRC state.
  • Hop-by-hop forwarding. A relay can be configured with SRAP entries for each indirectly connected child. It maps ingress traffic to egress RLC channels on the next PC5 hop in uplink and downlink, and the Last relay terminates the Uu relay channels.
  • Control plane. An intermediate relay can trigger RRC connection establishment or resumption when a message arrives from a child relay, and can pass system information and paging requests upstream. If a relay reselects, loses its parent link or suffers a Uu failure, it informs its children with a notification message. The Remote UE's connection timers are scaled by hop count.
  • Path switching. Within one gNB, a Remote UE can switch between multi-hop indirect, single-hop indirect and direct paths. For a multi-hop target path, all relays on it must be connected, and the gNB reconfigures every relay on that path.

UEs signal multi-hop capabilities, and relay behaviour can come from dedicated configuration, system information or preconfiguration.

How the role of NR sidelink changed

In Release 16 a UE could reach only other UEs within direct PC5 range, with the network able to control it. By Release 19 a UE can reach the gNB or another UE through up to three relays, or over direct and indirect paths at once.

What remains open

Sidelink operation in FR2 was only studied in Release 18, so no specification support exists yet. Path switching with multi-hop paths is limited to one gNB. Signalling for relay and Remote UE authorization is waiting on the core-network conclusions, in both Release 18 and Release 19.

Reference

Work items, clauses and information elements are generated from the specification data. The work-item objectives handled outside these specifications are quoted from the work item descriptions, which assign them to another working group or to a study.

Work items and where their changes appear

ReleaseWork itemChanges found inNote
Release 165G_V2X_NRSL
5G V2X with NR sidelink · WID RP-200129		TS 38.300, TS 38.331
Release 17NR_SL_enh
NR sidelink enhancement · WID RP-202846		TS 38.300, TS 38.331
Release 17NR_SL_relay
NR sidelink relay · WID RP-212819		TS 38.300, TS 38.331
Release 17NR_LTE_V2X_PC5_combos
NR/LTE V2X PC5 band combinations · WID RP-213297		NoneRadio requirements (RAN4); no RRC or stage-2 content is expected
Release 18NR_SL_enh2
NR sidelink evolution · WID RP-232789		TS 38.300, TS 38.331
Release 18NR_SL_relay_enh
NR sidelink relay enhancements · WID RP-232972		TS 38.300, TS 38.331
Release 18NR_LTE_V2X_PC5_combos_R18
NR/LTE V2X band combinations, Release 18 · WID RP-230390		NoneRadio requirements (RAN4); no RRC or stage-2 content is expected
Release 19NR_SL_relay_multihop
NR sidelink multi-hop relay · WID RP-250188		TS 38.300, TS 38.331
Release 19NR_SL_intraB_CA_ITS
NR sidelink intra-band carrier aggregation in the ITS band · WID RP-250997		NoneRadio requirements (RAN4); no RRC or stage-2 content is expected

Work-item objectives handled outside these specifications

ReleaseWork itemObjectiveWhere it belongs
Release 165G_V2X_NRSLNetwork solutions to support NR sidelink: V2X service authorization [RAN3]RAN3 (network interfaces)
Release 165G_V2X_NRSLF1 signalling for support of NR V2X [RAN3]RAN3 (network interfaces)
Release 165G_V2X_NRSLResource coordination between NG-RAN nodes for V2X sidelink communication [RAN3]RAN3 (network interfaces)
Release 165G_V2X_NRSLUE Tx and Rx RF requirement [RAN4]RAN4 (RF and RRM requirements)
Release 165G_V2X_NRSLRRM core requirement [RAN4]RAN4 (RF and RRM requirements)
Release 17NR_SL_enhSupport of new sidelink frequency bands for single-carrier operations [RAN4]RAN4 (RF and RRM requirements)
Release 17NR_SL_enhUE Tx and Rx RF requirement for the new features introduced in this WI [RAN4]RAN4 (RF and RRM requirements)
Release 17NR_SL_enhUE RRM core requirement for the new features introduced in this WI [RAN4]RAN4 (RF and RRM requirements)
Release 17NR_SL_relaySpecify mechanisms for Relay and Remote UE authorization for L3 and L2 relaying [RAN3]RAN3 (network interfaces)
Release 17NR_SL_relayDefine additional RRM performance requirements for Relay discovery and (re)selection [RAN4]RAN4 (RF and RRM requirements)
Release 18NR_SL_enh2Study enhanced sidelink operation on FR2 licensed spectrum (sidelink beam management) [RAN1, RAN2]study only
Release 18NR_SL_relay_enhSpecify RRM core requirements for relay discovery and (re)selection in UE-to-UE relay [RAN4]RAN4 (RF and RRM requirements)
Release 18NR_SL_relay_enhSignalling support for Relay and remote UE authorization if SA2 concludes it is needed [RAN3]RAN3 (network interfaces)
Release 18NR_SL_relay_enhDefine RRM performance requirements for relay discovery and (re)selection in UE-to-UE relay [RAN4]RAN4 (RF and RRM requirements)
Release 19NR_SL_relay_multihopSignalling support for relay UEs and remote UE authorization if SA2 concludes it is needed [RAN3]RAN3 (network interfaces)

Clauses and information elements by release

Release 16

SpecificationWork itemNew clausesChanged clausesNew IEs and messagesExtended IEs
TS 38.3315G_V2X_NRSL
63
  • 5.2.2.4.13 Actions upon reception of SIB12
  • 5.2.2.4.15 Actions upon reception of SIB14
  • 5.3.3.1a Conditions for establishing RRC Connection for NR sidelink communication/V2X sidelink communication
  • 5.3.5.14 Sidelink dedicated configuration
  • 5.3.13.1a Conditions for resuming RRC Connection for NR sidelink communication/V2X sidelink communication
  • 5.5.4.11 Event C1 (The NR sidelink channel busy ratio is above a threshold)
  • 5.5.4.12 Event C2 (The NR sidelink channel busy ratio is below a threshold)
  • 5.8.1 General
  • 5.8.2 Conditions for NR sidelink communication operation
  • 5.8.3.1 General
  • 5.8.3.2 Initiation
  • 5.8.3.3 Actions related to transmission of SidelinkUEInformationNR message
  • 5.8.5.1 General
  • 5.8.5.2 Initiation
  • 5.8.5.3 Transmission of SLSS
  • 5.8.5a.1 General
  • 5.8.5a.2 Initiation
  • 5.8.6.1 General
  • 5.8.6.2 Selection and reselection of synchronisation reference
  • 5.8.6.3 Sidelink communication transmission reference cell selection
  • 5.8.7 Sidelink communication reception
  • 5.8.8 Sidelink communication transmission
  • 5.8.9.1.1 General
  • 5.8.9.1.2 Actions related to transmission of RRCReconfigurationSidelink message
  • 5.8.9.1.3 Reception of an RRCReconfigurationSidelink by the UE
  • 5.8.9.1.8 Reception of an RRCReconfigurationFailureSidelink by the UE
  • 5.8.9.1.9 Reception of an RRCReconfigurationCompleteSidelink by the UE
  • 5.8.9.1.10 Sidelink reset configuration
  • 5.8.9.1a.1.1 Sidelink DRB release conditions
  • 5.8.9.1a.1.2 Sidelink DRB release operations
  • 5.8.9.1a.2.1 Sidelink DRB addition/modification conditions
  • 5.8.9.1a.2.2 Sidelink DRB addition/modification operations
  • 5.8.9.1a.3 Sidelink SRB release
  • 5.8.9.1a.4 Sidelink SRB addition
  • 5.8.9.2.1 General
  • 5.8.9.2.2 Initiation
  • 5.8.9.2.3 Actions related to transmission of the UECapabilityEnquirySidelink by the UE
  • 5.8.9.2.4 Actions related to reception of the UECapabilityEnquirySidelink by the UE
  • 5.8.9.3 Sidelink radio link failure related actions
  • 5.8.9.4.1 General
  • 5.8.9.4.2 Actions related to reception of MasterInformationBlockSidelink message
  • 5.8.9.4.3 Transmission of MasterInformationBlockSidelink message
  • 5.8.9.5 Actions related to PC5-RRC connection release requested by upper layers
  • 5.8.10.1 Introduction
  • 5.8.10.2.1 General
  • 5.8.10.2.2 Sidelink measurement identity removal
  • 5.8.10.2.3 Sidelink measurement identity addition/modification
  • 5.8.10.2.4 Sidelink measurement object removal
  • 5.8.10.2.5 Sidelink measurement object addition/modification
  • 5.8.10.2.6 Sidelink reporting configuration removal
  • 5.8.10.2.7 Sidelink reporting configuration addition/modification
  • 5.8.10.2.8 Sidelink quantity configuration
  • 5.8.10.3.1 General
  • 5.8.10.3.2 Derivation of NR sidelink measurement results
  • 5.8.10.4.1 General
  • 5.8.10.4.2 Event S1 (Serving becomes better than threshold)
  • 5.8.10.4.3 Event S2 (Serving becomes worse than threshold)
  • 5.8.10.5.1 General
  • 5.8.11 Zone identity calculation
  • 5.8.12 DFN derivation from GNSS
  • 9.1.1.4 SCCH configuration
  • 9.1.1.5 STCH configuration
  • 9.3 Sidelink pre-configured parameters
23
  • 3.1 Definitions
  • 3.2 Abbreviations
  • 5.2.2.1 General UE requirements
  • 5.2.2.3.2 Acquisition of an SI message
  • 5.3.1.1 RRC connection control
  • 5.3.3.2 Initiation
  • 5.3.5.3 Reception of an RRCReconfiguration by the UE
  • 5.3.5.8.2 Inability to comply with RRCReconfiguration
  • 5.3.5.11 Full configuration
  • 5.3.8.3 Reception of the RRCRelease by the UE
  • 5.3.13.2 Initiation
  • 5.5.1 Introduction
  • 5.5.2.5 Measurement object addition/modification
  • 5.5.3.1 General
  • 5.5.3.2 Layer 3 filtering
  • 5.5.4.1 General
  • 5.5.5.1 General
  • 5.7.4.3 Actions related to transmission of UEAssistanceInformation message
  • 6.1.2 Need codes and conditions for optional fields
  • 7.1.1 Timers (Informative)
  • 10.4 Mandatory field missing
  • 10.2 ASN.1 violation or encoding error
  • 10.3 Field set to a not comprehended value
63
  • SidelinkUEInformationNR
  • ULInformationTransferIRAT
  • SIB12
  • SIB13
  • SIB14
  • MeasObjectNR-SL
  • MeasResultsSL
  • ReportConfigNR-SL
  • BandCombinationListSidelinkEUTRA-NR
  • SidelinkParameters
  • SL-BWP-Config
  • SL-BWP-ConfigCommon
  • SL-BWP-PoolConfig
  • SL-BWP-PoolConfigCommon
  • SL-CBR-PriorityTxConfigList
  • SL-CBR-CommonTxConfigList
  • SL-ConfigDedicatedNR
  • SL-ConfiguredGrantConfig
  • SL-DestinationIdentity
  • SL-FreqConfig
  • SL-FreqConfigCommon
  • SL-LogicalChannelConfig
  • SL-MeasConfigCommon
  • SL-MeasConfigInfo
  • SL-MeasIdList
  • SL-MeasObjectList
  • SL-PDCP-Config
  • SL-PSBCH-Config
  • SL-PSSCH-TxConfigList
  • SL-QoS-FlowIdentity
  • SL-QoS-Profile
  • SL-QuantityConfig
  • SL-RadioBearerConfig
  • SL-ReportConfigList
  • SL-ResourcePool
  • SL-RLC-BearerConfig
  • SL-RLC-BearerConfigIndex
  • SL-RLC-Config
  • SL-ScheduledConfig
  • SL-SDAP-Config
  • SL-SyncConfig
  • SL-Thres-RSRP-List
  • SL-TxPower
  • SL-TypeTxSync
  • SL-UE-SelectedConfig
  • SL-ZoneConfig
  • SLRB-Uu-ConfigIndex
  • PC5-RRC-Definitions
  • SBCCH-SL-BCH-Message
  • SCCH-Message
  • MasterInformationBlockSidelink
  • MeasurementReportSidelink
  • RRCReconfigurationSidelink
  • RRCReconfigurationCompleteSidelink
  • RRCReconfigurationFailureSidelink
  • UECapabilityEnquirySidelink
  • UECapabilityInformationSidelink
  • End of PC5-RRC-Definitions
  • VarMeasConfigSL
  • VarMeasReportListSL
  • NR-Sidelink-Preconf
  • SL-PreconfigurationNR
  • End of NR-Sidelink-Preconf
14
  • UL-DCCH-Message
  • RRCReconfiguration
  • SystemInformation
  • BWP-DownlinkDedicated
  • BWP-UplinkDedicated
  • MeasObjectToAddModList
  • MeasResults
  • ReportConfigToAddModList
  • BandCombinationList
  • RF-Parameters
  • UE-NR-Capability
  • Multiplicity and type constraint definitions
  • VarMeasReportList
  • HandoverPreparationInformation
TS 38.3005G_V2X_NRSL
21
  • 5.7.1 General
  • 5.7.2 Sidelink resource allocation modes
  • 5.7.3 Physical sidelink channels and signals
  • 5.7.4.1 HARQ feedback
  • 5.7.4.2 Power Control
  • 5.7.4.3 CSI report
  • 5.7.5 Physical layer measurement definition
  • 8.4 NR sidelink communication and V2X sidelink communication related identities
  • 16.9.1 General
  • 16.9.2.1 Overview
  • 16.9.2.2 MAC
  • 16.9.2.3 RLC
  • 16.9.2.4 PDCP
  • 16.9.2.5 SDAP
  • 16.9.2.6 RRC
  • 16.9.3.1 General
  • 16.9.3.2 Scheduled Resource Allocation
  • 16.9.3.3 UE Autonomous Resource Selection
  • 16.9.4.1 General
  • 16.9.4.2 Control of connected UEs
  • 16.9.4.3 Control of idle/inactive UEs
4
  • 5.5 Transport Channels
  • 7.1 Services and Functions
  • 7.9 UE Assistance Information
  • 3.1 Abbreviations
NoneNone

Release 17

SpecificationWork itemNew clausesChanged clausesNew IEs and messagesExtended IEs
TS 38.331NR_SL_relay
32
  • 5.3.5.5.12 Uu Relay RLC channel release
  • 5.3.5.5.13 Uu Relay RLC channel addition/modification
  • 5.3.5.15.1 General
  • 5.3.5.15.2 L2 U2N Remote UE Release
  • 5.3.5.15.3 L2 U2N Remote UE Addition/Modification
  • 5.3.5.16 L2 U2N Remote UE configuration
  • 5.3.7.3a Actions following relay selection while T311 is running
  • 5.5.3.4 Derivation of L2 U2N Relay UE measurement results
  • 5.5.4.17 Event X1 (Serving L2 U2N Relay UE becomes worse than threshold1 and NR Cell becomes better than threshold2)
  • 5.5.4.18 Event X2 (Serving L2 U2N Relay UE becomes worse than threshold)
  • 5.5.4.19 Event Y1 (PCell becomes worse than threshold1 and candidate L2 U2N Relay UE becomes better than threshold2)
  • 5.5.4.20 Event Y2 (Candidate L2 U2N Relay UE becomes better than threshold)
  • 5.8.9.7.1 PC5 Relay RLC channel release
  • 5.8.9.7.2 PC5 Relay RLC channel addition/modification
  • 5.8.9.8.1 General
  • 5.8.9.8.2 Actions related to transmission of RemoteUEInformationSidelink message
  • 5.8.9.8.3 Reception of RemoteUEInformationSidelink message by the L2 U2N Relay UE
  • 5.8.9.9.1 General
  • 5.8.9.9.2 Actions related to transmission of UuMessageTransferSidelink message
  • 5.8.9.9.3 Reception of the UuMessageTransferSidelink
  • 5.8.9.10.1 General
  • 5.8.9.10.2 Initiation
  • 5.8.9.10.3 Actions related to transmission of NotificationMessageSidelink message
  • 5.8.9.10.4 Actions related to reception of NotificationMessageSidelink message
  • 5.8.14.1 General
  • 5.8.14.2 NR sidelink U2N Relay UE threshold conditions
  • 5.8.15.1 General
  • 5.8.15.2 NR Sidelink U2N Remote UE threshold conditions
  • 5.8.15.3 Selection and reselection of NR sidelink U2N Relay UE
  • 9.2.4 Default PC5 Relay RLC Channel
  • 9.2.5 Default SRAP configurations
  • 9.4 Radio Information Related to Discovery Message
58
  • 3.1 Definitions
  • 4.2.1 UE states and state transitions including inter RAT
  • 4.2.2 Signalling radio bearers
  • 4.4 Functions
  • 5.2.2.2.1 SIB validity
  • 5.2.2.2.2 SI change indication and PWS notification
  • 5.2.2.3.5 Acquisition of SIB(s) or posSIB(s) in RRC_CONNECTED
  • 5.2.2.4.2 Actions upon reception of the SIB1
  • 5.3.2.1 General
  • 5.3.2.3 Reception of the Paging message by the UE or PagingRecord by the L2 U2N Remote UE
  • 5.3.3.1a Conditions for establishing RRC Connection for NR sidelink communication/discovery/V2X sidelink communication
  • 5.3.3.3 Actions related to transmission of RRCSetupRequest message
  • 5.3.3.4 Reception of the RRCSetup by the UE
  • 5.3.3.6 Cell re-selection or cell selection or relay (re)selection while T390, T300 or T302 is running (UE in RRC_IDLE)
  • 5.3.3.7 T300 expiry
  • 5.3.3.8 Abortion of RRC connection establishment
  • 5.3.5.1 General
  • 5.3.5.2 Initiation
  • 5.3.5.3 Reception of an RRCReconfiguration by the UE
  • 5.3.5.5.1 General
  • 5.3.5.5.2 Reconfiguration with sync
  • 5.3.5.5.7 SpCell Configuration
  • 5.3.5.8.3 T304 expiry (Reconfiguration with sync Failure) or T420 expiry (Path switch failure)
  • 5.3.5.11 Full configuration
  • 5.3.7.2 Initiation
  • 5.3.7.3 Actions following cell selection while T311 is running
  • 5.3.7.4 Actions related to transmission of RRCReestablishmentRequest message
  • 5.3.7.5 Reception of the RRCReestablishment by the UE
  • 5.3.7.7 T301 expiry or selected cell/L2 U2N Relay UE no longer suitable
  • 5.3.8.1 General
  • 5.3.8.3 Reception of the RRCRelease by the UE
  • 5.3.10.3 Detection of radio link failure
  • 5.3.11 UE actions upon going to RRC_IDLE
  • 5.3.13.1a Conditions for resuming RRC Connection for NR sidelink communication/discovery/V2X sidelink communication
  • 5.3.13.2 Initiation
  • 5.3.13.3 Actions related to transmission of RRCResumeRequest or RRCResumeRequest1 message
  • 5.3.13.4 Reception of the RRCResume by the UE
  • 5.3.13.5 Handling of failure to resume RRC Connection
  • 5.3.13.6 Cell re-selection or cell selection or L2 U2N relay (re)selection while T390, T319 or T302 is running or SDT procedure is ongoing (UE in RRC_INACTIVE) or SRS transmission in RRC_INACTIVE is configured
  • 5.3.14.1 General
  • 5.3.15.2 Reception of the RRCReject by the UE
  • 5.5.1 Introduction
  • 5.5.3.1 General
  • 5.5.3.2 Layer 3 filtering
  • 5.5.4.1 General
  • 5.5.5.1 General
  • 5.5.5.3 Sorting of cell measurement results
  • 5.8.3.3 Actions related to transmission of SidelinkUEInformationNR message
  • 5.8.6.2 Selection and reselection of synchronisation reference
  • 5.8.9.1.1 General
  • 5.8.9.1.3 Reception of an RRCReconfigurationSidelink by the UE
  • 5.8.9.1a.3 Sidelink SRB release
  • 5.8.9.1a.4 Sidelink SRB addition
  • 5.8.9.3 Sidelink radio link failure related actions
  • 5.8.9.4.1 General
  • 5.8.9.5 Actions related to PC5-RRC connection release requested by upper layers
  • 7.1.1 Timers (Informative)
  • 5.8.3.2 Initiation
17
  • UE-TimersAndConstantsRemoteUE
  • Uu-RelayRLC-ChannelConfig
  • Uu-RelayRLC-ChannelID
  • SL-L2RelayUE-Config
  • SL-L2RemoteUE-Config
  • SL-PagingIdentityRemoteUE
  • SL-RelayUE-Config
  • SL-RemoteUE-Config
  • SL-RLC-ChannelConfig
  • SL-RLC-ChannelID
  • SL-ServingCellInfo
  • SL-SourceIdentity
  • SL-SRAP-Config
  • NotificationMessageSidelink
  • RemoteUEInformationSidelink
  • UuMessageTransferSidelink
  • SL-AccessInfo-L2U2N
22
  • RRCReestablishment
  • RRCReconfiguration
  • RRCRelease
  • SidelinkUEInformationNR
  • SIB12
  • CellGroupConfig
  • MeasObjectToAddModList
  • MeasResults
  • ReportConfigInterRAT
  • ReportConfigNR
  • BandCombinationList
  • RF-Parameters
  • SidelinkParameters
  • Multiplicity and type constraint definitions
  • SCCH-Message
  • MeasurementReportSidelink
  • RRCReconfigurationSidelink
  • RRCReconfigurationCompleteSidelink
  • UEAssistanceInformationSidelink
  • UECapabilityInformationSidelink
  • VarMeasReportList
  • SL-PreconfigurationNR
TS 38.331NR_SL_enh
6
  • 5.8.9.6.1 General
  • 5.8.9.6.2 Initiation
  • 5.8.9.6.3 Actions related to reception of UEAssistanceInformationSidelink message
  • 5.8.13.1 General
  • 5.8.13.2 NR sidelink discovery monitoring
  • 5.8.13.3 NR sidelink discovery transmission
17
  • 5.6.1.4 Setting band combinations, feature set combinations and feature sets supported by the UE
  • 5.8.3.3 Actions related to transmission of SidelinkUEInformationNR message
  • 3.1 Definitions
  • 5.2.2.4.13 Actions upon reception of SIB12
  • 5.3.5.14 Sidelink dedicated configuration
  • 5.5.3.1 General
  • 5.8.1 General
  • 5.8.3.1 General
  • 5.8.8 Sidelink communication transmission
  • 5.8.9.1.1 General
  • 5.8.9.1.2 Actions related to transmission of RRCReconfigurationSidelink message
  • 5.8.9.1.3 Reception of an RRCReconfigurationSidelink by the UE
  • 5.8.9.1.9 Reception of an RRCReconfigurationCompleteSidelink by the UE
  • 5.8.2 Conditions for NR sidelink communication/discovery operation
  • 5.8.3.2 Initiation
  • 5.8.9.5 Actions related to PC5-RRC connection release requested by upper layers
  • 5.3.13.2 Initiation
11
  • DRX-ConfigSL
  • BandCombinationListSL-Discovery
  • SL-BWP-DiscPoolConfig
  • SL-BWP-DiscPoolConfigCommon
  • SL-DRX-Config
  • SL-DRX-ConfigGC-BC
  • SL-DRX-ConfigUC
  • SL-DRX-ConfigUC-SemiStatic
  • SL-InterUE-CoordinationConfig
  • SL-PBPS-CPS-Config
  • UEAssistanceInformationSidelink
13
  • RRCResume
  • SidelinkUEInformationNR
  • SIB12
  • MeasObjectNR
  • BandCombinationListSidelinkEUTRA-NR
  • SidelinkParameters
  • UE-CapabilityRequestFilterNR
  • SL-BWP-Config
  • SL-BWP-ConfigCommon
  • SL-ConfigDedicatedNR
  • SL-PSBCH-Config
  • SL-ResourcePool
  • SL-ServingCellInfo
TS 38.331Other NR sidelink changesNone
3
  • 5.8.3.3 Actions related to transmission of SidelinkUEInformationNR message
  • 5.8.5.1 General
  • 5.8.6.1 General
NoneNone
TS 38.300NR_SL_relay
15
  • 16.12.1 General
  • 16.12.2.1 L2 UE-to-Network Relay
  • 16.12.3 Relay Discovery
  • 16.12.4 Relay Selection/Reselection
  • 16.12.5.1 RRC Connection Management
  • 16.12.5.2 Radio Link Failure
  • 16.12.5.3 RRC Connection Re-establishment
  • 16.12.5.4 RRC Connection Resume
  • 16.12.5.5 System Information
  • 16.12.5.6 Paging
  • 16.12.5.7 Access Control
  • 16.12.5.8 Mobility Registration Update and RAN Area Update
  • 16.12.6.0 General
  • 16.12.6.1 Switching from indirect to direct path
  • 16.12.6.2 Switching from direct to indirect path
1
  • 3.2 Definitions
NoneNone
TS 38.300NR_SL_enh
7
  • 16.9.5 Sidelink Discovery
  • 16.9.6.1 General
  • 16.9.6.2 Unicast
  • 16.9.6.3 Groupcast/Broadcast
  • 16.9.6.4 Alignment between Uu DRX and SL DRX
  • 16.9.7 Power Savings Resource Allocation
  • 16.9.8 Inter-UE Coordination (IUC)
5
  • 5.5 Transport Channels
  • 11 UE Power Saving
  • 15.5.4 UE History Information from the UE
  • 16.9.2.2 MAC
  • 16.9.4.3 Control of idle/inactive UEs
NoneNone

Release 18

SpecificationWork itemNew clausesChanged clausesNew IEs and messagesExtended IEs
TS 38.331NR_SL_relay_enh
32
  • 5.3.5.16.1 L2 U2U Relay UE Release
  • 5.3.5.16.2 L2 U2U Relay UE Addition/Modification
  • 5.3.5.17.1 Introduction
  • 5.3.5.17.2.1 General
  • 5.3.5.17.2.2 SL indirect path specific configuration
  • 5.3.5.17.2.3 T421 expiry (Indirect path addition/change failure)
  • 5.3.5.17.3.1 General
  • 5.3.5.17.3.2 N3C remote UE configuration
  • 5.3.5.17.3.2a N3C Indirect path addition/change failure
  • 5.3.5.17.3.3 N3C relay UE configuration
  • 5.3.5.17.3.4.1 Bearer mapping release
  • 5.3.5.17.3.4.2 Bearer mapping addition and modification
  • 5.5.4.20b Event Z1 (Serving L2 U2N Relay UE becomes worse than threshold1 and Candidate L2 U2N Relay UE becomes better than threshold2)
  • 5.7.3c.1 General
  • 5.7.3c.2 Initiation
  • 5.7.3c.3 Failure type determination
  • 5.7.3c.4 Actions related to transmission of IndirectPathFailureInformation message
  • 5.8.9.3a End-to-end PC5 connection failure related actions performed by L2 U2U Remote UE
  • 5.8.9.3b End-to-end PC5 connection failure/release related actions performed by L2 U2U Relay UE
  • 5.8.9.5a Actions related to end-to-end PC5-RRC connection release performed by L2 U2U Remote UE
  • 5.8.9.7.0 Deriviation of PC5 Relay RLC channel configuration
  • 5.8.9.11.1 General
  • 5.8.9.11.2 Actions related to transmission of the UEInformationRequestSidelink by the UE
  • 5.8.9.11.3 Actions related to reception of the UEInformationRequestSidelink by the UE
  • 5.8.9.11.4 Actions related to reception of the UEInformationResponseSidelink by the UE
  • 5.8.16.1 General
  • 5.8.16.2 NR sidelink U2U Relay UE threshold conditions
  • 5.8.16.3 Neighbor UE(s) in proximity conditions
  • 5.8.17.1 General
  • 5.8.17.2 NR Sidelink U2U Remote UE threshold conditions
  • 5.8.17.3 Conditions for selection and reselection of NR sidelink U2U Relay UE
  • 5.8.17.4 Actions related to selection and reselection of NR sidelink U2U Relay UE
61
  • 5.3.3.1a Conditions for establishing RRC Connection for NR sidelink communication/discovery/V2X sidelink communication/MP operation
  • 3.1 Definitions
  • 4.2.1 UE states and state transitions including inter RAT
  • 4.4 Functions
  • 5.2.2.2.1 SIB validity
  • 5.2.2.4.13 Actions upon reception of SIB12
  • 5.3.3.3 Actions related to transmission of RRCSetupRequest message
  • 5.3.5.2 Initiation
  • 5.3.5.5.2 Reconfiguration with sync
  • 5.3.5.15.1 General
  • 5.3.5.15.2 L2 U2N or U2U Remote UE Release
  • 5.3.5.15.3 L2 U2N or U2U Remote UE Addition/Modification
  • 5.3.5.16 L2 U2N or U2U Remote UE configuration
  • 5.3.7.2 Initiation
  • 5.3.8.3 Reception of the RRCRelease by the UE
  • 5.3.10.3 Detection of radio link failure
  • 5.3.11 UE actions upon going to RRC_IDLE
  • 5.3.13.1a Conditions for resuming RRC Connection for NR sidelink communication/positioning/discovery/V2X sidelink communication
  • 5.3.13.2 Initiation
  • 5.5.3.2 Layer 3 filtering
  • 5.5.4.1 General
  • 5.5.5.1 General
  • 5.7.3b.2 Initiation
  • 5.7.3b.4 Actions related to transmission of MCGFailureInformation message
  • 5.8.3.1 General
  • 5.8.3.2 Initiation
  • 5.8.3.3 Actions related to transmission of SidelinkUEInformationNR message
  • 5.8.8 Sidelink communication transmission
  • 5.8.9.1.1 General
  • 5.8.9.1.2 Actions related to transmission of RRCReconfigurationSidelink message
  • 5.8.9.1.3 Reception of an RRCReconfigurationSidelink by the UE
  • 5.8.9.1.10 Sidelink reset configuration
  • 5.8.9.1a.1.1 Sidelink DRB release conditions
  • 5.8.9.1a.1.2 Sidelink DRB release operations
  • 5.8.9.1a.2.1 Sidelink DRB addition/modification conditions
  • 5.8.9.1a.2.2 Sidelink DRB addition/modification operations
  • 5.8.9.1a.3 Sidelink SRB release
  • 5.8.9.2.3 Actions related to transmission of the UECapabilityEnquirySidelink by the UE
  • 5.8.9.2.4 Actions related to reception of the UECapabilityEnquirySidelink by the UE
  • 5.8.9.3 Sidelink radio link failure related actions
  • 5.8.9.5 Actions related to PC5-RRC connection release requested by upper layers
  • 5.8.9.7.1 PC5 Relay RLC channel release
  • 5.8.9.7.2 PC5 Relay RLC channel addition/modification
  • 5.8.9.8.1 General
  • 5.8.9.8.2 Actions related to transmission of RemoteUEInformationSidelink message
  • 5.8.9.8.3 Reception of RemoteUEInformationSidelink message by the L2 U2N/U2U Relay UE
  • 5.8.9.9.2 Actions related to transmission of UuMessageTransferSidelink message
  • 5.8.9.10.1 General
  • 5.8.9.10.2 Initiation
  • 5.8.9.10.3 Actions related to transmission of NotificationMessageSidelink message
  • 5.8.9.10.4 Actions related to reception of NotificationMessageSidelink message
  • 5.8.13.3 NR sidelink discovery transmission
  • 7.1.1 Timers (Informative)
  • 5.3.5.5.12 Uu Relay RLC channel release
  • 5.3.5.5.13 Uu Relay RLC channel addition/modification
  • 5.5.4.18 Event X2 (Serving L2 U2N Relay UE becomes worse than threshold)
  • 5.5.5.3 Sorting of cell measurement results
  • 3.2 Abbreviations
  • 4.2.2 Signalling radio bearers
  • 5.5.4.17 Event X1 (Serving L2 U2N Relay UE becomes worse than threshold1 and NR Cell becomes better than threshold2)
  • 5.8.15.2 NR Sidelink U2N Remote UE threshold conditions
11
  • IndirectPathFailureInformation
  • N3C-IndirectPathConfigRelay
  • N3C-IndirectPathAddChange
  • N3C-RelayUE-Info
  • SL-IndirectPathAddChange
  • SL-RelayIndicationMP
  • SL-RelayUE-ConfigU2U
  • SL-RemoteUE-ConfigU2U
  • SL-SRAP-ConfigU2U
  • UEInformationRequestSidelink
  • UEInformationResponseSidelink
18
  • UL-DCCH-Message
  • RRCReconfiguration
  • SIB12
  • PDCP-Config
  • ReportConfigInterRAT
  • BandCombinationList
  • RF-Parameters
  • SidelinkParameters
  • OtherConfig
  • SL-ConfigDedicatedNR
  • SL-L2RelayUE-Config
  • SL-L2RemoteUE-Config
  • MeasurementReportSidelink
  • NotificationMessageSidelink
  • RemoteUEInformationSidelink
  • RRCReconfigurationSidelink
  • SL-PreconfigurationNR
  • SL-AccessInfo-L2U2N
TS 38.331NR_SL_enh2
10
  • 5.8.6.2a Sidelink synchronization reference priority group order
  • 5.8.6.2b Sidelink synchronization reference search
  • 5.8.9.1a.5.1 Additional Sidelink RLC Bearer release conditions
  • 5.8.9.1a.5.2 Additional Sidelink RLC Bearer release operation
  • 5.8.9.1a.6.1 Additional Sidelink RLC Bearer addition/modification conditions
  • 5.8.9.1a.6.2 Additional Sidelink RLC Bearer addition/modification operation
  • 5.8.9.1b.1.1 Sidelink Carrier Release Condition
  • 5.8.9.1b.1.2 Sidelink Carrier Release Operation
  • 5.8.9.1b.2.1 Sidelink Carrier Addition Condition
  • 5.8.9.1b.2.2 Sidelink Carrier Addition Operation
16
  • 5.3.5.14 Sidelink dedicated configuration
  • 5.7.4.3 Actions related to transmission of UEAssistanceInformation message
  • 5.8.3.1 General
  • 5.8.3.2 Initiation
  • 5.8.3.3 Actions related to transmission of SidelinkUEInformationNR message
  • 5.8.5.2 Initiation
  • 5.8.6.2 Selection and reselection of synchronisation reference
  • 5.8.9.1.3 Reception of an RRCReconfigurationSidelink by the UE
  • 5.8.9.1a.4 Sidelink SRB addition
  • 5.8.9.3 Sidelink radio link failure related actions
  • 5.8.9.7.2 PC5 Relay RLC channel addition/modification
  • 9.1.1.4 SCCH configuration
  • 9.1.1.5 STCH configuration
  • 5.6.1.4 Setting band combinations, feature set combinations and feature sets supported by the UE
  • 5.8.8 Sidelink communication transmission
  • 5.8.9.1.1 General
4
  • S haredSpectrumChAccessParamsSidelinkPerBand
  • SL-FreqSelectionConfig
  • SL-LBT-FailureRecoveryConfig
  • SL-RBSetConfig
23
  • SidelinkUEInformationNR
  • SIB12
  • MeasObjectNR-SL
  • MeasObjectToAddModList
  • SidelinkParameters
  • SL-BWP-Config
  • SL-BWP-ConfigCommon
  • SL-ConfigDedicatedNR
  • SL-ConfiguredGrantConfig
  • SL-FreqConfig
  • SL-FreqConfigCommon
  • SL-LogicalChannelConfig
  • SL-ResourcePool
  • SL-RLC-BearerConfig
  • SL-RLC-BearerConfigIndex
  • SCCH-Message
  • RemoteUEInformationSidelink
  • RRCReconfigurationSidelink
  • UECapabilityInformationSidelink
  • UEInformationRequestSidelink
  • UEInformationResponseSidelink
  • UuMessageTransferSidelink
  • SL-PreconfigurationNR
TS 38.331Other NR sidelink changesNoneNoneNoneNone
TS 38.300NR_SL_relay_enh
3
  • 16.12.2.2 L2 UE-to-UE Relay
  • 16.12.6.3 Switching from indirect to indirect path
  • 16.12.7 Control plane procedures for L2 U2U Relay
8
  • 3.2 Definitions
  • 16.12.1 General
  • 16.12.3 Relay Discovery
  • 16.12.4 Relay Selection/Reselection
  • 16.12.6.0 General
  • 16.12.6.1 Switching from indirect to direct path
  • 16.12.6.2 Switching from direct to indirect path
  • 3.1 Abbreviations
NoneNone
TS 38.300NR_SL_enh2
7
  • 16.9.3.4 LTE and NR Sidelink co-channel coexistence
  • 16.9.9.1 Overview
  • 16.9.9.2 Channel Access Priority Classes for Sidelink (SL-CAPC)
  • 16.9.9.3 Sidelink Specific Consistent LBT Failure
  • 16.9.9.4 COT Sharing
  • 16.9.9.5 Resource Allocation
  • 16.9.10 Sidelink CA
4
  • 3.2 Definitions
  • 5.7.4.1 HARQ feedback
  • 3.1 Abbreviations
  • 5.7.2 Sidelink resource allocation modes/schemes
NoneNone
TS 38.300Other NR sidelink changesNone
1
  • 16.9.2.4 PDCP
NoneNone

Release 19

SpecificationWork itemNew clausesChanged clausesNew IEs and messagesExtended IEs
TS 38.331NR_SL_relay_multihop
3
  • 5.8.9.9.4 Reception of the UuMessageTransferSidelink by the L2 Intermediate U2N Relay UE
  • 5.8.19.1 General
  • 5.8.19.2 NR sidelink U2N Relay UE threshold conditions
46
  • 5.3.5.15.3 L2 U2N or U2U Remote UE Addition/Modification
  • 3.1 Definitions
  • 4.2.1 UE states and state transitions including inter RAT
  • 4.2.2 Signalling radio bearers
  • 4.4 Functions
  • 5.2.2.4.13 Actions upon reception of SIB12
  • 5.3.2.3 Reception of the Paging message by the UE or PagingRecord by the L2 U2N Remote UE
  • 5.3.3.1a Conditions for establishing RRC Connection for NR sidelink communication/discovery/V2X sidelink communication/MP operation
  • 5.3.3.2 Initiation
  • 5.3.3.6 Cell re-selection or cell selection or relay (re)selection while T390, T300 or T302 is running (UE in RRC_IDLE)
  • 5.3.5.1 General
  • 5.3.5.2 Initiation
  • 5.3.5.3 Reception of an RRCReconfiguration by the UE
  • 5.3.5.5.12 Uu Relay RLC channel release
  • 5.3.5.5.13 Uu Relay RLC channel addition/modification
  • 5.3.5.15.2 L2 U2N or U2U Remote UE Release
  • 5.3.13.1a Conditions for resuming RRC Connection for NR sidelink communication/positioning/discovery/V2X sidelink communication
  • 5.3.13.2 Initiation
  • 5.5.5.1 General
  • 5.8.2 Conditions for NR sidelink communication/discovery/positioning operation
  • 5.8.3.2 Initiation
  • 5.8.3.3 Actions related to transmission of SidelinkUEInformationNR message
  • 5.8.9.3 Sidelink radio link failure related actions
  • 5.8.9.7.2 PC5 Relay RLC channel addition/modification
  • 5.8.9.8.2 Actions related to transmission of RemoteUEInformationSidelink message
  • 5.8.9.8.3 Reception of RemoteUEInformationSidelink message by the L2 U2N/U2U Relay UE
  • 5.8.9.9.1 General
  • 5.8.9.10.2 Initiation
  • 5.8.9.10.3 Actions related to transmission of NotificationMessageSidelink message
  • 5.8.9.10.4 Actions related to reception of NotificationMessageSidelink message
  • 5.8.13.3 NR sidelink discovery transmission
  • 5.8.14.1 General
  • 5.8.14.2 NR sidelink U2N Relay UE threshold conditions
  • 5.8.15.2 NR Sidelink U2N Remote UE threshold conditions
  • 5.8.15.3 Selection and reselection of NR sidelink U2N Relay UE
  • 5.3.13.5 Handling of failure to resume RRC Connection
  • 5.3.13.6 Cell re-selection or cell selection or L2 U2N relay (re)selection while T390, T319 or T302 is running or SDT procedure is ongoing (UE in RRC_INACTIVE) or SRS transmission in RRC_INACTIVE is configured
  • 5.3.15.2 Reception of the RRCReject by the UE
  • 5.8.9.8.1 General
  • 5.2.2.4.2 Actions upon reception of the SIB1
  • 5.3.3.3 Actions related to transmission of RRCSetupRequest message
  • 5.3.3.4 Reception of the RRCSetup by the UE
  • 5.3.3.8 Abortion of RRC connection establishment
  • 5.3.7.2 Initiation
  • 5.3.10.3 Detection of radio link failure
  • 5.3.13.3 Actions related to transmission of RRCResumeRequest or RRCResumeRequest1 message
3
  • SL-RelayUE-ConfigMH
  • SL-SRAP-ConfigId
  • SL-RelayUE-RRC-State
12
  • RRCReconfiguration
  • SidelinkUEInformationNR
  • SIB12
  • SidelinkParameters
  • SL-ConfigDedicatedNR
  • SL-L2RelayUE-Config
  • SL-SRAP-Config
  • MeasurementReportSidelink
  • NotificationMessageSidelink
  • RemoteUEInformationSidelink
  • SL-PreconfigurationNR
  • SL-AccessInfo-L2U2N
TS 38.331Other NR sidelink changesNone
1
  • 5.8.9.10.1 General
NoneNone
TS 38.300NR_SL_relay_multihopNone
13
  • 16.12.1 General
  • 16.12.2.1 L2 UE-to-Network Relay
  • 16.12.3 Relay Discovery
  • 16.12.4 Relay Selection/Reselection
  • 16.12.5.1 RRC Connection Management
  • 16.12.5.5 System Information
  • 16.12.5.6 Paging
  • 16.12.6.0 General
  • 16.12.6.1 Switching from single/multi-hop indirect to direct path
  • 16.12.6.2 Switching from direct to indirect path
  • 16.12.6.3 Switching from multi/single-hop indirect to multi/single-hop indirect path
  • 3.2 Definitions
  • 16.12.5.2 Radio Link Failure
NoneNone

Abbreviations

DRXDiscontinuous ReceptionRAN23GPP radio protocols working group
F1Interface between the central and distributed units of a gNBRAN33GPP radio network interfaces working group
FR2Frequency Range 2 (millimetre wave)RAN43GPP radio performance and requirements working group
gNBNR base stationRFRadio Frequency
GNSSGlobal Navigation Satellite SystemRLCRadio Link Control
IPInternet ProtocolRRCRadio Resource Control
ITSIntelligent Transport SystemsRRMRadio Resource Management
L2Layer 2RxReceive
L3Layer 3SA23GPP architecture working group
LTELong Term EvolutionSRAPSidelink Relay Adaptation Protocol
NG-RANNext Generation Radio Access NetworkTSTechnical Specification
NRNew RadioTxTransmit
PC5Radio interface between two UEs (sidelink)UEUser Equipment
PC5-RRCRadio Resource Control signalling between two UEs over PC5UuRadio interface between a UE and the base station
PDCPPacket Data Convergence ProtocolV2XVehicle-to-Everything
RAN13GPP physical layer working groupWIWork Item