Research On Technologies Of VANET Data Transmission In Highway Scenarios

Vehicular Ad Hoc Network(VANET),as a key research focus for road safety in intelligent transportation systems,aims to provide communication services for vehicles.The information provided by VANET will greatly reduce the occurrence of traffic accidents and increase the efficiency of theroad.With the in-depth research of outo-driving,various applications of VANET have higher and higher requirements for the service quality of data transmission.It is urgent to design efficient and reliable routing algorithms to meet the growing demand,provide more reliable network connections for vehicles,and higher network throughput rate.Currently,VANET’s routing algorithm is one of the most challenging research hotspots in this field.The high-speed movement of vehicles in the highway scene,frequent changes in network topology,and wireless channel fading and interference make VANET data transmission face severe challenges.On the basis of tracking the latest research at home and abroad,this dissertation conducts indepth research from two aspects of broadcast routing algorithm and cluster routing algorithm for different application requirements of high-speed scenes.First,aiming at the application of information to the highway from the external environment,a relay broadcast algorithm based on the dynamic backbone network is proposed to optimize the network throughput.Then,in response to the application requirements of information generated inside the highway,a vehicle motion model in high-speed scenes was established,and machine learning algorithm was used to predict the vehicle motion mode,and a stable clustering algorithm was designed.Finally,based on the consistency of vehicle motion and link status,an inter-cluster routing algorithm is designed to ensure the reliable transmission of data,and the cluster routing algorithm is improved.The specific research work and innovations of this dissertation include the following three aspects:Firstly,this dissertation proposes a relay-based broadcast strategy.The algorithm selects vehicles as relay nodes based on the nominal location of geographic information.Relay nodes form a dynamic backbone network in the network to improve the packet broadcast capacity of vehicles in highway scenarios.On the premise of isomorphic nominal positions and directional antennas,this dissertation continues to analyze the broadcast capacity under ideal and non-ideal traffic conditions,and designs a mathematical model to configure the parameters of the vehicular backbone network system,and gives the joint configuration of best nominal location selection,time division multiplexing coefficient,and vehicle coding scheme which aims to maximize system throughput.The data simulation results confirm the correctness of the model and the superiority of the algorithm.It also shows that the design has good robustness to the statistical fluctuation of the vehicle density rate.The proposed system design can achieve excellent performance without rate adaptation and other system configurations.Secondly,this dissertation proposes a stable clustering algorithm based on machine learning to predict vehicle movement patterns.A discrete vehicle motion model is established by analyzing the relationship between vehicle motion and road topology and vehicle driving decision-making.And a prediction method of vehicle motion mode based on naive Bayes classification algorithm is designed.In order to better simulate the operating conditions of vehicles in realistic highway scenes,the training example set of the algorithm is generated from real vehicle data recorded by the performance measurement system of the California State Highway Traffic Administration.The prediction result is provided as support for the subsequent clustering algorithm.Subsequently,this dissertation designs a complete stable clustering algorithm,including neighbor node perception,cluster head election,joining the cluster structure,cluster head declaration and cluster maintenance.After theoretical analysis,the election criteria for cluster heads are determined by the relative speed of the vehicle and the movement pattern of the vehicle.Finally,this section analyzes the influence of vehicle operating mode on the stability of the clustering algorithm through simulation,and compares and discusses the performance of the clustering algorithm proposed in this dissertation and the existing algorithm under different vehicle mobility.Furthermore,this dissertation uses the real road topology and traffic flow data of California highways as the simulation basis to compare with the existing algorithms.The simulation results prove the superiority of the algorithm in the real highway environment.Finally,this dissertation proposes an inter-cluster routing algorithm based on vehicle mobility and link status.This dissertation first derives the expressions of theoretical indicators such as the transmission success rate,packet loss rate,and end-to-end delay of the cluster-head multi-hop transmission in cluster routing,and then simulates and verifies the theoretical derivation under the Nakagami-m fading channel.Then,under the guidance of theoretical analysis,the High Reliable Clustering Routing Algorithm(HRCR)was designed to cope with the challenges of fast moving VANET nodes and poor link stability caused by frequent network topology changes.The HRCR algorithm takes node movement trend consistency and link status as indicators for the selection of relay routing nodes to obtain links with high reliability and good communication quality.The algorithm modifies the format of HELLO data packet,local link set and neighbor information database to obtain the relevant data for calculating the routing node selection index,but it also causes the increase of routing overhead.In order to reduce the routing cost of nodes and avoid redundant transmission of control information when the network topology is stable,the HRCR algorithm monitors the link changes of the local link set and adjusts the sending interval of HELLO packets to make it more suitable for the network topology change.Furthermore,by comparing the performance of the HRCR algorithm with fixed sending interval,the HRCR algorithm with improved sending interval and the classic routing algorithm,as well as the existing cluster routing algorithm in terms of average end-to-end communication delay,packet reception rate and routing overhead,it proves that the HRCR algorithm proposed in this dissertation has higher reliability in high-speed scenarios.