## 3 Principles of the Electromagnetic Radiation Testing Method  
Through in-depth analysis of existing standards, we can explore the interrelationship between S-parameters and throughput. This analysis can not only help identify the potential connection between the two, but also provide critical evidence for assessing communication quality in connected vehicles. S-parameters, or scattering parameters, are key parameters describing the signal reflection and transmission characteristics between RF and microwave components, while throughput refers to the amount of data successfully transmitted per unit of time by the system. By studying the relationship between S-parameters and throughput in depth, we can effectively evaluate the communication quality of connected vehicles and provide scientific evidence for improving their application effectiveness. Figure 9: The three-dimensional electromagnetic simulation model. This process can lay a theoretical foundation for advancing intelligent transportation and connected vehicle technologies, as well as guide the establishment of industry standards. Principle Analysis Based on the Electromagnetic Radiation Testing Method  
In the design and operation process of wireless communication systems for connected vehicles, the MCL is a key parameter closely related to the definitions and calculations of S-parameters. Hence, when designing wireless communication systems for connected vehicles, the influence of S-parameters on the MCL must be comprehensively considered. By reasonably optimizing S-parameters, coupling losses can be effectively controlled, thus enhancing the coverage and service quality of the system. Moreover, understanding and applying these parameters is vital for improving the efficiency of wireless communication systems in connected vehicles, providing important reference for future development. The MCL refers to the total channel loss mobile UE experiences between its antenna port and the base station. In calculating the MCL, the antenna's directional gain is not considered, allowing the MCL to provide a simplified metric for assessing the quality of communication links. Generally, a higher MCL value indicates a stronger signal link, enhancing the system's anti-interference capability and robustness. The calculation formula for the MCL is as follows: uplink MCL = uplink maximum transmit power--base station receive sensitivity (NF + SINR + thermal noise); downlink MCL = downlink maximum transmit power--terminal receive sensitivity (NF + SINR + thermal noise). Since we only studied the communication sent by the base station and satellites to connected vehicles, we only utilized the calculation formula for the downlink MCL [8]. Assuming the external environment of the receiving terminal remains unchanged, the terminal's receive sensitivity can be considered a fixed value. This implies that if the receiver sensitivity does not change, then there exists a proportional relationship between the downlink power and the downlink MCL. This relationship suggests that increasing the downlink power can effectively improve the signal quality, thereby enhancing communication reliability. Once the downlink power and MCL exhibit a proportional relationship, we can leverage the correlation between the downlink power and throughput to indirectly deduce the mathematical relationship between the MCL and throughput. This correlation implies that as the downlink power increases, the throughput may also improve, suggesting that variations in the MCL could significantly impact throughput. Specifically, if we continually increase the downlink power while keeping the other conditions constant, an increase in the MCL could lead to improved signal quality, thus influencing the final throughput. Therefore, the MCL not only serves as a characterization index of link quality, but also has a direct impact on the transmission capacity of connected vehicle communication systems.