Implementation and experimental evaluation of Cooperative Awareness Basic Service for V2X Communications

Abstract

A key aspect of Vehicle-to-Everything (V2X) communication is the concept of cooperative awareness, wherein the periodic exchange of status information allows vehicles to become aware of their surroundings for increased traffic safety and efficiency. This project aimed to implement the Cooperative Awareness (CA) basic service through the development of a low-cost, open-source On-board Unit (OBU)/Roadside Unit (RSU) that periodically broadcasts Cooperative Awareness Messages (CAM) using the 5.9 GHz band. Its proper operation and interoperability were verified by testing it with a commercial V2X device. This project also aimed to evaluate the effectiveness of the CA basic service through the development of an IEEE 802.11p-based V2X system simulator. The simulations were executed with varying vehicle traffic load (by changing the vehicle speed and the number of lanes) and CAM transmit frequency. The performance was then assessed by analyzing the Packet Reception Ratio (PRR), position error and Neighborhood Awareness Ratio (NAR) metrics. The presence of more vehicles in the slow speed and high lane count scenarios caused higher packet losses due to increased interference and collision probability, leading to low PRR and NAR values. Despite losing more CAMs, the slow speed scenarios had lower position errors since the displacement of vehicles was small. When the CAM transmit frequency was increased, the PRR decreased due to packet collisions. However, the position error was kept low as it benefited from the more frequent CAM transmissions and local database updates. Increasing the transmit frequency also increased the NAR, at least until a certain frequency threshold, beyond which the NAR started to worsen due to the dominant effect of interference in high message traffic situations