Characterizing the Impact of C-V2X PC5 Radio on Cooperative Driving Automation in Hardware-in-the-Loop Experiments

The SAE J3216 standard defines Cooperative Driving Automation (CDA), which has gained increasing attention in recent years as an umbrella framework encompassing a wide range of automated vehicle applications enabled by Vehicle-to-Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) technologies. However, limited research has investigated how Cellular Vehicle-to-Everything (C-V2X) technology affects CDA applications, especially the agreement seeking operations. This work presents a hardware-in-the-loop (HIL) experimental study designed to evaluate the Argonne CDA controller under varying C-V2X radio transmission frequencies and message configurations. A three-vehicle car-following scenario was implemented in the Argonne-developed Roadrunner Simulator, incorporating CDA agreement-seeking operations, vehicle powertrain models, and V2V communication modules. The CDA messages were then exchanged through two actual C-V2X radios with realistic communication impairment caused by the hardware characteristics, such as packet delay and packet loss. Metrics of packet delay and loss were analyzed with respect to transmission frequency and CDA algorithm performance. To further investigate the role of packet loss in the agreement-seeking process, a four-state Markov chain model was applied to characterize mechanisms that reduce cooperation duration. Results show that sending CDA messages synchronously imposes half-duplex constraint and therefore increases the percentage of packet loss and reduces the vehicle cooperation time. Meanwhile, increasing frequency to transmit CDA messages benefits the vehicle cooperation although the percentage of packet loss also increases. This study provides insights into the characterization of C-V2X radio behavior and its impact on CDA, with a particular focus on cooperation duration rather than controller performance.