1. Introduction

As one of the methods to achieve high-level autonomous driving, V2X (Vehicle-to-Everything) encompasses various communication application scenarios such as vehicle-to-vehicle (V2V), vehicle-to-infrastructure (V2I), vehicle-to-pedestrian (V2P), and vehicle-to-network (V2N). Through modern communication and network technologies, V2X enables the exchange and sharing of information between vehicles and their surroundings (real-time traffic, road information, pedestrian information, etc.), thereby improving driving safety, reducing traffic congestion, and enhancing traffic efficiency.

Currently, the validation of C-V2X functionalities mainly relies on two methods: bench simulation and real vehicle testing. Bench simulation testing is based on simulating real road environments, including road scenes, vehicles, pedestrians, road events, signs, traffic lights, and other information to realize V2X application scenarios. For example, it simulates BSM, RSM, RSI, SPAT, and MAP messages sent by vehicles and roadside units. However, in actual simulation testing systems, it can only approximate road condition information to a high degree and cannot fully replicate real road scenes and vehicle states. Real vehicle testing, on the other hand, is conducted in real road environments using test vehicles, mock pedestrians, and roadside equipment to generate real V2X messages. While this offers an advantage of real-world environments, it poses safety concerns and low vehicle coordination efficiency.

2. Introduction to the C-V2X Digital Twin Testing Method

The vehicle-in-the-loop (ViL) based C-V2X digital twin testing method adopts a "virtual and real combination." The "real" part refers to the use of a real vehicle, where the vehicle state, kinematics, and behavior decisions are all genuine. The "virtual" part refers to all other traffic participants (background vehicles, pedestrians, roadside units), which are simulated. The framework is illustrated in the figure below:

Figure 1: Vehicle-in-the-Loop (ViL) Based C-V2X Digital Twin Testing Method Framework

This method combines bench simulation and real vehicle testing, offering the following advantages:

· High safety

· Improved testing efficiency and reduced R&D costs

· Not restricted by testing locations: can be performed on urban roads or closed roads

3. Vehicle-Mounted Test Bench

In the vehicle-in-the-loop (ViL) based C-V2X digital twin testing method, the simulation of V2X signals (BSM, RSM, SPAT, RSI, MAP) from background vehicles, pedestrians, and roadside units is mainly achieved through a test bench mounted in the test vehicle. The vehicle-mounted test bench consists of the test vehicle, high-precision positioning system, bus communication interface card, V2X simulator, CANoe, and more. Its functions include:

· The ability to construct V2X test scenarios and define the operation trajectory of simulated background vehicles

· Support for the simulation of different national ITS protocol stacks, meeting the testing requirements of the European EU ITS-G5 standard, the U.S. WAVE standard, and the Chinese GB/T 31024-3 / CSAE-53/CSAE-157 standards

· Display of V2X data for the test vehicle and all simulated traffic participants, with centralized parsing, display, and test management execution

· Support for connection to a cloud control management platform, enabling remote monitoring and test execution

· Execution of automated tests, with support for automatic generation of test reports

Figure 3: Vehicle-Mounted Test Bench Framework

4. Test Scenarios

The test scenarios cover 16 typical application scenarios, excluding near-field payment, in the T/CSAE 53 standard. The details are shown in the table below:

5. Test Process

The test vehicle receives messages from the V2X simulator simulating roadside units (RSM, SPAT, RSI, MAP) and background vehicle BSM messages. Various simulated V2X messages, as shown in Figure 5, are combined with the onboard unit (OBU) algorithm logic in the test vehicle to complete V2X function warnings in each test scenario. The bus communication interface card collects the V2X function warning signals from the vehicle bus and sends them to CANoe for functional test verification.

Figure 4: V2X Messages Received by CANoe

Conclusion

Polelink, based on the C-V2X digital twin testing solution, offers services for V2X test site construction, vehicle-mounted simulation testing system integration, and V2X real vehicle function testing. This solution supports the simulation of application scenarios and communication environment testing in real road conditions. Several systems have already been deployed in China, significantly accelerating the V2X R&D verification process for customers.

As a member of the IMT-2020 (5G) Promotion Group's Cellular Vehicle-to-Everything (C-V2X) Working Group, Polelink is actively engaged in research and testing technology for LTE-V2X and 5G-V2X and is committed to advancing the V2X industry in China. We provide comprehensive V2X testing systems and services to customers.