Awareness Messages by Vulnerable Road Users and Vehicles: Field Tests via LTE-V2X

Awareness messages have been recently introduced to extend the information horizon of connected vehicles and Vulnerable Road Users (VRUs) beyond their line-of-sight range. As of today, only a handful of studies has experimentally analyzed the awareness messages generated by cars, and no existing work has concentrated on VRU awareness messages. The intent of this work is to fill the gap of missing experimental activities by analyzing the results of an extensive measurement campaign, aimed at investigating the awareness messages generated by cars and VRUs in a real-world context. Field tests have been performed employing an LTE-V2X prototype with connected VRUs in the urban scenario, while cars have been considered in urban, suburban, and highway environments. In all cases, the paper details the conditions that trigger the generation of awareness messages, presents the Probability Mass Function (PMF) of the time interval between consecutive messages, and relates it to the triggering conditions. As the findings indicate that many awareness messages from VRUs were generated under non-relevant circumstances, the paper also proposes an adjustment to the standard and evaluates its effectiveness in the field, showing a notable improvement with respect to the original setting. Finally, this study evaluates the Packet Delivery Ratio (PDR) experienced by vehicle-to-vehicle communications in the above scenarios and, for the first time, determines the PDR attained by bicycle-to-vehicle communications in the urban setting.