ETC Propagation Loss Model Based On MLFF Mode

With the rapid development of the Intelligent Transportation System(ITS),the vehicle communication system as a part of it,is getting more and more attention.The vehicle communication system combines vehicles,roads,people and the environment through vehicle-to-vehicle communication and vehicle-to-road communication,which improves the safety of the road system and the traffic efficiency of the vehicle.The Electronic Toll Collection(ETC)system based on Radio Frequency Identification(RFID)and Dedicated Short Range Communication(DSRC)is a typical application of vehicle-to-road communication.At present,ETC communication system applications are mostly single-lane barrier mode,vehicles need to slow down,in order to meet the current situation of increasing traffic flow and solve the problem of toll vehicles congestion,multi-lane free flow(MLFF)application mode come into being,no barriers to access.As the medium of the ETC system communicates,the characteristic of wireless channel directly affects the system performance.Therefore,it is very important to use a reasonable method to accurately model the propagation channel of the ETC system.This paper first introduces the research status of vehicle communication system and vehicle communication wireless channel modeling.In the ETC communication system,the wireless signal is easily interfered by the front and side vehicles during the propagation process,and there are propagation mechanisms such as reflection,diffraction and scattering.Therefore,the new propagation loss model of the ETC system based on MLFF mode is proposed,which is a deterministic model based on ray tracing and consistent diffraction theory.In this paper,the channel model of ETC system is divided into propagation loss model based on front vehicle interference and propagation loss model based on sidecar interference for the interference of vehicle communication in ETC system.According to the geometry of the vehicle,the vehicle is divided into two types: small car and large truck.Based on the type of the front car,the side car and the tested vehicle,the two types of models are divided into four kinds of propagation loss models.The ray tracing technique is used to describe the propagation path of the signal.The theory and formula of the transfer function on each propagation path are deduced by the uniform diffraction theory,and the propagation loss of the wireless signal is obtained according to the signal propagation loss formula.Thereby a signal propagation loss model is obtained.Simulation and analysis were performed by Matlab to verify the effectiveness of the propagation loss model.For the front vehicle interference,the influence of the distance between the roadside unit(RSU)and the vehicle tag unit(OBU)and the distance between the OBU and the preceding vehicle on the propagation loss is analyzed.For the sidecar interference,the distance between the OBU and the RSU is analyzed.The effect of the horizontal distance of the bypass vehicle and the RSU on the propagation loss.Finally,the accuracy of the model is verified by experiments under the ETC system characteristic scenario.