The 3GPP platform was first expanded to the automotive industry by the introduction of support for V2V and V2X services in Release 14. This support forms Phase 1 of 3GPP's ongoing project relating to V2X, and was intended to support a set of requirements sufficient for basic road safety services. Vehicles containing UEs with these features can use the uplink, downlink and sidelink to exchange information on their own status, such as position, speed, and heading with other nearby vehicles, infrastructure nodes, and pedestrians. Phase 2 of the V2X project was standardised in Release 15, and adds a number of new features to the sidelink intended to enhance efficiency and exploit developments in UE and network designs. These enhancements include sidelink carrier aggregation, higher-order modulation, and reduced latency. Phase 3 of V2X, in Release 16, adds support to NR (and also 5GC, not addressed in this TR) for advanced V2X use cases, and includes introduction of the NR sidelink. The use-cases are broadly grouped to enable vehicular platooning, exchange of extended sensor information, advanced driving, and remote driving. Phase 3 also allows either RAT's sidelink to be operated under control of the other RAT's Uu interface, as well as permitting connection to EPC or 5GC, to enable usage in the main MR-DC deployment scenarios. In the following clauses, LTE-V2X is described first, then NR-V2X, and finally certain aspects which have a degree of commonality to both RATs. Although this TR deals with RAN aspects, note that the core network architectures also have many adaptations to support V2X in both EPC and 5GC. These are referred to only as needed for other explanations in this TR, and details can be found in the relevant specifications.

The present document provides an overall description of the features introduced by 3GPP to LTE and NR in support of V2X services, starting from Rel-14. The purpose of this TR is to give an overview across the RAN specifications of how the features have been designed, and how they operate together. This document addresses LTE V2X and NR V2X via both sidelink, i.e. the PC5 interfaces, and via the cellular uplink/downlink, i.e. the Uu interfaces. It covers V2V, V2I/N, and V2P, as well as the eNB/gNB, UE, and RSU nodes. The intention is to provide descriptions at approximately the Stage 2 level of detail, and thus references are provided to RAN specifications for the reader to obtain precise details. The document is a 'living' document, i.e. it is permanently updated and presented to TSG-RAN meetings.