Research On Data Transmission Mechanism In Vehicular Ad Hoc Network

Vehicular Ad Hoc Network(VANET)technology is one of the important technologies of modern intelligent transportation.In VANET,the network characteristics such as high mobility of vehicles and rapid topological structure changes lead to vehicles being vulnerable to interference during data transmission.High throughput and low latency data transmission mechanism has always been the focus of VANET research.In this thesis,with high throughput and low latency of data transmission as the optimization objectives,the application of data priority in data transmission scheduling and Medium Access Control(MAC)protocols are studied respectively,and the main research contents are as follows:(1)A multi-channel data transmission cooperative scheduling algorithm is proposed.In the scheduling cycle,firstly,the initial scheduling operations are generated based on the data transmission requests of the vehicles in the network,and then constructs the scheduling conflict graph based on the conflict relationship between the initial scheduling operations.Secondly,the channel allocation scheme satisfying the minimum Signal-toInterference-Ratio(SINR)is used to allocate channels and improve the scheduling conflict graph.Finally,the greedy algorithm based on ISing model according to data priority is used to select nodes from the scheduling conflict graph for data transmission.The simulation results show that compared with the traditional algorithm,the weighted network service capacity of the algorithm is increased by about 31%,and the service delay is reduced by about 20%.This not only ensures the priority transmission of emergency data to the target vehicle,but also improves the network weighted service capacity.(2)An adaptive multi-channel Time Division Multiple Access(TDMA)MAC protocol is proposed.The protocol first divides the road into different subnets according to the communication radius of Road Side Unit(RSU),and classifies the vehicle transmission conflicts in the network into inter-subnet conflicts and intra-subnet conflicts.Secondly,the inter-subnet vehicle transmission conflicts are resolved by assigning orthogonal channels to adjacent subnets.Finally,the RSU constructs an interference graph based on the conflict relationship of vehicle communication within its subnetwork,and then solves the intra-subnetwork vehicle transmission conflict by solving the maximum independent set in the interference graph to assign channels and time slots for vehicles.The simulation results show that the proposed protocol reduces the merge conflict rate and packet loss rate by about 38% and 25% respectively,compared with the mainstream protocols,which has the advantages of low merge conflict rate and strong robustness.The multi-channel data transmission cooperative scheduling algorithm and adaptive multi-channel TDMA MAC protocol proposed in this thesis can solve the vehicle data transmission instability problem in VANET more effectively,which lays the foundation for the subsequent implementation of advanced assisted driving and fully automated unmanned driving technology on the road.