Tagless Tolling Using DSRC for Intelligent Transport System: An Interference Study

Modern electronic tolling systems consists of on board units (OBUs) or tags that are carried in a vehicles and has a unique code that is used to identify a customer account. The wireless communications between the on-board unit or tag and road side unit is the most critical function. The DSRC communication technology intended for vehicle safety applications in Intelligent Transport Systems which can be used for applications such as tolling and is expected to be integrated into all new vehicles manufactured in the future. A design for tagless tolling system using DSRC to communicate with an OBU instead of tags is presented in this report. Analysis of the wireless signal propagation at 5.9GHz for a model of a 4 lane tolling point is completed using a simulation in MATLAB. The Signal-to-Interference ratio is used to characterise the quality of the wireless channel under shadowing. Results of the simulation show that co-channel interference from communications in adjacent lanes is a significant problem especially in multi lane free flow tolling points. Outage probability calculations show a small communications zone close to the gantry that can be used to complete the tolling transactions.