Intelligent Transport Systems

Description

Intelligent Transport Systems (ITS) in 3GPP refers to the standardization of cellular network capabilities to support vehicular communication, commonly known as V2X (Vehicle-to-Everything). It is a service layer framework that leverages both evolved LTE and 5G NR radio access technologies. The architecture supports two fundamental communication modes: direct communication over the PC5 interface (sidelink) and network-based communication over the Uu interface. The PC5 interface enables low-latency, direct device-to-device communication critical for safety applications like collision avoidance, even outside network coverage. The Uu interface utilizes the traditional cellular link between the UE (vehicle) and the base station (gNB or eNB) for longer-range, network-managed services like traffic flow optimization and infotainment.

The ITS framework defines a full stack, including application layer support, security, and QoS management. At the application layer, it supports standardized message sets like the ETSI ITS Cooperative Awareness Messages (CAM) and Decentralized Environmental Notification Messages (DENM). These messages carry information such as vehicle position, speed, direction, and event warnings. The 3GPP system provides the transport for these messages with stringent reliability and latency requirements. For network-based communication (V2N), the UE connects to a V2X Application Server (AS) via the core network. For direct communication (V2V, V2I, V2P), the UE can use either LTE-V2X (based on LTE sidelink) or NR-V2X (based on 5G NR sidelink) over the PC5 interface, with resource allocation managed by the network (mode 3/4 for LTE, mode 1/2 for NR) or selected autonomously by the vehicle.

Key network components include the V2X Control Function, which resides in the core network and is responsible for authorizing UEs for V2X services and provisioning them with necessary parameters like geographical mapping of resources for PC5. The Policy Control Function (PCF) plays a crucial role in enforcing V2X-specific policies. A critical aspect is the ITS Application Identifier, a globally unique number that identifies a specific ITS application object (e.g., a particular safety service). This identifier is used within the network to apply the correct policies, routing, and QoS treatment to the data flows associated with that application. The evolution from LTE-based V2X in Release 14 to enhanced V2X (eV2X) in Release 15 and NR-V2X in Release 16+ has continuously expanded the capabilities, supporting advanced use cases like sensor sharing, platooning, and automated driving with ultra-high reliability and low latency.

Purpose & Motivation

ITS was standardized by 3GPP to address the growing global need for safer, more efficient, and automated road transportation. Traditional vehicular safety systems (like radar) were limited to line-of-sight and the sensor suite of a single vehicle. The motivation was to create a standardized, cellular-based communication system that could extend a vehicle's awareness far beyond its sensors, enabling cooperative perception. This addresses limitations such as blind spot detection, intersection collision warnings, and emergency brake light warnings communicated from vehicles ahead.

The creation of 3GPP ITS was also driven by the desire to leverage the ubiquitous deployment and continuous evolution of cellular networks. While dedicated short-range communication (DSRC) standards existed, 3GPP provided a path for integration with wide-area cellular services, offering longer range via network (V2N), enhanced security through the cellular ecosystem, and a clear evolution path towards 5G. Starting in Release 14 with basic LTE-based V2X safety services, the scope expanded to support increasingly demanding use cases for automated driving, which require extreme reliability, very low latency, and high data rates—capabilities provided by the NR-V2X sidelink introduced in later releases. This work solves the problem of fragmented vehicular communication standards by providing a unified, globally scalable platform that supports both immediate safety applications and the long-term vision of connected and automated mobility.