## 5 Implementation and Deployment
### Test Procedure  
To promote the C-V2X field testing standardization process, we combined many vehicle test originations, Tier 1 companies, and OEMs to discuss the test data interface's specifications, including the test process, data exchange process, and data interface norm. In March 2021, the standard project was approved by the China Communication Standard Association (CCSA), while a series of tests were conducted to improve the validation of the proposed method. Figure 7 shows the test process of the TS.  
This test system supports two types of test objects, vehicles and roadside systems, and covers indoor and field testing environments.  
By incorporating a GNSS signal simulator, the system can perform testing functions in an indoor environment. Specifically, the simulator provides the necessary satellite positioning signal conditions (including module communication and timing services) for all V2X terminals and transmits satellite navigation data to the DUT.  
The following diagram provides a detailed overview of the main processes in the test system. These processes can be divided into four stages: preparation, test management, application scenario injection, and test data collection.  
* Preparation Stage This stage mainly involves setting up the test type, scenario, and scale. Firstly, the test type must be specified, i.e., whether indoor or field tests are being conducted. Subsequently, the corresponding test scenario and scale are selected, and testbed nodes are allocated accordingly. The test scenario here refers to the actual physical environment; the allocated nodes are the device nodes connected to that physical environment.  
The GNSS signal simulator will provide satellite signals for field tests and timing services and simulated positioning functions for indoor tests.
* Test Management Stage This stage focuses on node management, task configuration, and task management.  
Once the test is officially initiated, the testbed will receive real-time status data from testbed nodes (including TBOBU and TBRSU) and the DUT to manage these nodes.  
Management includes device control (such as device on/off, start/stop of data reporting, congestion control activation/deactivation, device restart, and command execution), task configuration (such as setting test task types, configuring data content), and task management (including task start, pause, resume, and end).  
Notably, task configuration and task management functions are only practical for testbed nodes.
* Application Scenario Injection StageThe testbed generates and transparently transmits realistic scenario data simulated by the node array.  
This stage involves communication scenarios and application scenarios. Data injection for static communication scenarios originates from task configuration information, specifically including parameters such as node message transmission power and broadcast message frequency. Data injection for application scenarios is dynamically generated by the testbed and transparently transmitted to the testbed nodes in real-time.  
After receiving the scenario messages simulated by the test system, the testbed nodes will send out V2X-simulated data, completing the entire scenario injection process.
* Test Data Collection Stage  
Test data are continuously collected during the test run for subsequent analysis and evaluation.  
During the test, the testbed nodes send out V2X-simulated data and transmit their business data back to the C-V2X testbed.  
Simultaneously, the DUT will send its data and receive V2X-simulated data to trigger corresponding scenarios. Subsequently, the DUT will transmit its business data and application result data back to the C-V2X testbed.  
The test system can efficiently and accurately complete various testing tasks through these four closely interconnected stages.  
Figure 7: Testing system’s test process.