Mode 0: A New 3GPP V2X Resource Allocation Category for Roadside Computing Unit-Assisted Safety Communication

2026-05-25

AI Summary

This study addresses the limitations of existing 3GPP V2X resource allocation in high-density scenarios, where scheduling saturation and insufficient blind-spot awareness hinder reliable low-latency safety communications. To overcome these challenges, the authors propose a new V2X Mode 0 category centered on Roadside Computing Units (RCUs), introducing for the first time an infrastructure-aided cooperative scheduling mechanism within the 3GPP framework. They further develop a tiered collaboration architecture that spans from fully passive to fully active user equipment, enabling effective perception of occluded objects and large-scale risk areas along with coordinated resource allocation. Multi-agent simulations based on MAPPO, calibrated against C-V2X deployment practices in China, Europe, and the U.S., validate the efficacy of the proposed Mode 0a–0c evolution path. Notably, Mode 0c achieves packet delivery rates of 0.999 and 0.998 for two critical services, elevating the worst-case TTI delivery rate from near zero to 0.601—the only configuration meeting stringent structural low-latency safety requirements.

Abstract

The 3GPP V2X resource allocation framework defines two entity classes -- the base station and the vehicle UE -- and four modes across LTE and NR generations. We demonstrate that this binary taxonomy is structurally incomplete. Base station-led scheduling saturates at high-density traffic nodes, producing latency-tail failures that persist even when mean packet delivery ratios approach the service-class target. UE autonomy is categorically incapable of pre-emergence warning for occluded traffic participants and insufficient for large-scope cascading environmental hazards. We propose Mode 0, a new 3GPP V2X category whose defining entity is the Roadside Computing Unit (RCU) -- an infrastructure ensemble integrating elevated sensing (Seeing), sidelink communication (Speaking), and local computational evaluation (Thinking), owned by traffic management authorities. Mode 0 defines a subfamily spectrum from Mode 0a (all-passive UEs, the guaranteed minimum) through Mode 0c (all-active UEs, the optimal target). Convergent deployment evidence from Chinese national standards (DB11/T 2329.1-2024, T/ITS 0224.1-2025), China Unicom RS-MEC infrastructure, and European and US C-V2X programs confirms that both institutional sides are converging on the roadside traffic node without a coordination standard. A fifteen-run Multi-Agent Proximal Policy Optimization (MAPPO) simulation validates the architectural family: Mode 0a in shared-pool baseline sits at the analytical symmetric-Nash coordination floor; Mode 0c with demand separation achieves strict Pareto improvement for both traffic classes (M0 PDR 0.999, M1 PDR 0.998 at $ρ_{\rm pool} \leq 1$) and lifts the worst-TTI delivery ratio from near-zero to 0.601 -- the only configuration satisfying the latency safety requirement structurally. We call for a 3GPP study item on Mode 0 within the NR-V2X sidelink enhancement work programme.

Problem

• V2X
• resource allocation
• roadside unit
• latency
• safety communication

Innovation

• Mode 0
• Roadside Computing Unit (RCU)
• NR-V2X
• Resource Allocation
• MAPPO