Research On V2V Information Transmission And Variable Speed Limit Control For Vehicle Network Security Environment

The information explosion has promoted the development of smart cities,and people's satisfaction with travel requirements has become higher and higher.The demand for intelligent transportation has grown rapidly.Under the continuous development of information technology,the next-generation transportation system is that vehicles can broadcast their own information at any time in any place,and they can also receive various traffic information from surrounding vehicles.All the vehicles are networked to form a huge interactive network—the Internet of Vehicles.The main function of the vehicle networking system is to ensure the safety and efficiency of traffic,reduce traffic accidents caused by weather and other reasons,and also maximize the efficiency of transportation.It can also reduce energy consumption and reduce environmental pollution caused by traffic.Another technical difficulty in the realization of car networking is the vehicle-to-vehicle information transmission problem,including the propagation characteristics of wireless signals in the traffic flow and the rapid changes in the network topology caused by the rapid movement of vehicles.These will cause great impact on the information transmission at the bottom of the car network.Therefore,this dissertation conducts an in-depth study on vehicle safety and traffic efficiency in the Vehicular Network and vehicle-to-vehicle communication problems.The main research results are summarized as follows:(1)Study the influence of adverse weather and traffic congestion on traffic,analytical technical methods for taking into account safety and speed limit values and congestion effects under adverse weather conditions.The study begins with the mechanism of the weather affecting the drivers and the vehicles.We study the influence of different weather conditions on traffic,and combine theoretical calculations with actual data to obtain safe speed and safe traffic flow thresholds under different weather conditions.Simulations were then used to quantify and analyze the impact of traffic congestion on traffic efficiency.Finally,using data fitting and analytic hierarchy process,the research on road safety pre-judgment based on traffic flow data is carried out,and the impact of vehicle congestion on traffic safety is analyzed.(2)Study the signal transmission characteristics of vehicle-to-vehicle(V2V)at different traffic flow densities.The large-scale and small-scale channel analysis models under three traffic flow conditions in a typical environment are proposed and measured data of 5.9G V2 V are compared with each other.The research includes 5.9G Hz vehicle-borne wireless channel measurement system development and measurement scheme design.First,the electromagnetic wave propagation characteristics of V2 V signals in dense urban areas and three different traffic flow densities in highways are studied.Then the differences between the small-scale fading distribution and the K-factor are compared between these scenarios.In terms of the time delay domain,the average delay and the rms delay spread are also compared,and the mean square is compared in the frequency domain.Root Doppler spread,followed by a comparison of shadow fading and the difference between the level pass rate and the average fade time.In terms of large scale,multiple models are used to match them,and the model selection algorithms are used to find the matching degree of different path loss models.The results show that the study of wireless channel characteristics under three kinds of traffic flow can help to reveal the features of V2 V signals under different traffic conditions.(3)Study the physical link connectivity of vehicle-mounted networks based on measured V2 V signal data at different traffic flow densities and adverse weather conditions.A vehicle link connectivity model and analysis method based on(Line of Sight,LOS)and(Obstructed Line of Sight,OLOS)transmission states are proposed.The research contents include simulating different traffic flow scenarios,using the big and small scale data model of the measured signal of the corresponding scene,and obtaining the link continuous connectivity probability based on different traffic flow density and path loss threshold.And then we consider the impact of vehicle occlusion on the signal.The relationship between single vehicle link connectivity and vehicle distance at different traffic density and different weather conditions are studied.Simulation results show that the model we use can more accurately and truly reflect the status of vehicle communication links in the actual environment.(4)Study the multi-objective optimization variable speed limit control model based on efficiency considerations and the improvement method.Under the communication conditions of the Internet of Vehicles,a multi-objective genetic algorithm based on variable speed limit is used to optimize the downstream traffic flow when congestion occurs.The research results show that the congested highway can take into consideration various factors such as safety,traffic capacity,energy consumption and environmental impact.And the method can improve the overall traffic flow in terms of travel time,total fuel consumption and total pollution.At the same time,this dissertation adopts the set algorithm to generate the individual who meets the constraint in the optimization algorithm.This method makes the individual can always meet the constraints to be satisfied in the crossover mutation.The simulation results show that the proposed algorithm can obtain better optimization results and greatly improve the performance of the highway,and the method converges faster than the penalty function method.