Vehicle-to-Everything Policy

Description

Vehicle-to-Everything Policy (V2XP) refers to the set of rules and parameters that govern the behavior and resource allocation for V2X communication within a 3GPP network. It is a specialized subset of the broader Policy and Charging Control (PCC) framework, tailored specifically for the unique requirements of V2X services, which often involve low latency, high reliability, and dynamic geographic constraints. The V2XP framework is implemented and enforced by the Policy Control Function (PCF) in the 5G core network. The PCF generates V2XP rules based on input from the V2X Application Server (V2X AS), network operator configurations, and subscriber information from the Unified Data Management (UDM).

These policies are then delivered to the relevant network functions and the User Equipment (UE). For network-based communication (Uu), V2XP rules are provided to the Session Management Function (SMF) and Access and Mobility Management Function (AMF) to influence QoS flows, packet forwarding, and session management. For direct communication over the PC5 sidelink, V2XP rules are provided to the UE to govern its behavior on the sidelink interface. Key parameters within a V2XP rule include the ProSe Per-Packet Priority (PPPP), ProSe Per-Packet Reliability (PPPR), allowed V2X service areas, maximum transmission power, and resource allocation modes (scheduled vs. autonomous). The PCF may also provide V2X-specific Policy and Charging Control (PCC) rules that include parameters for charging and QoS enforcement.

The operation of V2XP involves dynamic policy decisions. For instance, when a UE initiates a V2X service, the V2X AS may request a specific policy from the PCF based on the service type (e.g., basic safety vs. advanced teleoperation). The PCF evaluates this request against the user's subscription and network conditions to formulate the appropriate V2XP. This policy is then activated and enforced for the duration of the V2X session. V2XP is crucial for managing radio congestion, especially in dense vehicular scenarios, by prioritizing safety messages and efficiently allocating sidelink resources. It provides a standardized mechanism for the network to control and optimize V2X communication, ensuring that the diverse and stringent requirements of different V2X applications are met consistently across the network.

Purpose & Motivation

V2XP was created to address the need for granular, dynamic, and service-aware control over V2X communications within the 3GPP policy framework. Early V2X implementations, including the initial Release 14 specifications, had policy mechanisms but the formalized V2XP framework, emphasized from Release 16 onwards, was driven by the introduction of more advanced and diverse eV2X services. These new services (e.g., platooning, remote driving) have vastly different requirements in terms of latency, reliability, data rate, and communication range compared to basic safety messages. A one-size-fits-all policy approach was insufficient.

The V2XP framework solves the problem of how to efficiently map diverse V2X application requirements onto network and radio resources. It allows the network operator and service provider to define policies that dictate, for example, that a collision-avoidance message must have higher priority and lower latency than an infotainment-related V2X update. This is critical for managing limited radio spectrum, preventing congestion, and ensuring that safety-of-life messages are never delayed due to network resource contention. V2XP also enables service differentiation and monetization, as operators can offer tiered V2X service levels with corresponding policy guarantees. By integrating V2X policy into the core PCC architecture, 3GPP ensured that V2X communication could be managed with the same robustness, security, and scalability as traditional cellular services.