Studies On Vehicle Communication And Safety Technology Based On VANETs

In recent years,with the rapid development of economy,science and technology,people's living standard has been gradually improved,which is not only reflected in the food,clothing and shelter,but also in terms of travel.Recently,more and more people choose to drive by themselves.As a result,the number of vehicle has increased year by year.However,the dramatic increase in the number of vehicles has also caused a series of adverse effects on society and people's lives.The increase in traffic accidents and traffic congestion caused a large number of casualties and property damages.Therefore,this paper will mainly focus on vehicle information exchange and driving safety.The main work of this paper is as follows:(1)Studying and analyzing the cooperative communication methods,network coding and the mechanism of vehicle collision warning.Firstly,we introduce the cooperative communication system model as well as the working process of the cooperative communication in detail.And the cooperative communication model protocol is briefly described.According to the different processing methods of the relay nodes for the signals,the two methods of amplify-and-forward(AF)and decode-and-forward(DF)are introduced respectively.Secondly,the article describes the network coding technology particularly,and provides the coding and decoding process of linear network coding and random network coding.In addition,the definition and calculation of outage probability in the cooperative mode is given,and the connectivity probability is briefly explained.Finally,the vehicle collision warning mechanism is briefly described.(2)In order to reduce the computational overhead,the exact expression and approximate expression of outage probability are compared and analyzed.Firstly,the Nakagami-m channel environment is set up and Dynamic Network Coding(DNC)is selected to calculate the exact and approximate outage probability.Secondly,Rayleigh channel environment is set up,and the Nonbinary Network Coding(NBNC)and Generalized Dynamic Network Coding(GDNC)are simulated and compared.Thus the reasonableness and correctness of approximate probability can be verified.(3)Focusing on the analysis and research of the vehicles' connectivity and safety.In order to ensure the transmission of information safely and the safety of driving,we take the safety distance into consideration when study the connectivity of vehicles.In addition,this paper also analyzes and discusses the connectivity probability obtained under different driving environment parameter settings,such as different vehicle density,different vehicle information radiation radius,and different safety distances.Finally,this paper also make a more detailed and specific discussion on the connectivity probability considering the safety distance,and obtains the influence of the minimum safety distance on the connection probability of the vehicle.(4)Finally,this paper takes the safety distance into consideration in the collision warning mechanism of the vehicle,under certain circumstances of the vehicle's movement characteristics and driving scenarios(crossroads,the front car needs an emergency brake at a red light or other situation,a single lane driving environment).It is assumed that the vehicle can know its location through GPS and GIS and the location of other vehicles can be known through periodic beacon information.The vehicles tested in this article have common braking characteristics.The discussion of the safety distance that the rear vehicle needs to reserve for ensuring safe driving is separately considered under different environment that the initial speed of the front vehicle is less than the initial speed of the rear vehicle or on the contrary.