Research On VANETs Data Distribution Method Based On Priority

Vehicular Ad-hoc Networks(VANETs)carry two main types of application services,one is security applications and the other is user applications.Among them,the safety application relates to vehicles and personnel safety,and the data transmission performance requirements are strict;the user application provides users with value-added services such as entertainment,and needs to meet the individual needs of the user.Due to the uneven density of VANETs vehicles and high-speed changes of nodes,the network topology changes drastically and the communication link is unstable,resulting in a decline in data transmission performance.Especially in the highway environment,the roadside unit RSU(Road Side Unit)signal coverage is limited,the vehicle node moves fast,so when the vehicle passes the RSU coverage,it is only a short time from the establishment of the network to the disconnection.In a relatively short period of time,how to schedule data to ensure the data transmission performance of the VANETs system is a difficult point for VANETs data distribution.Aiming at this problem,this paper proposes a priority-based VANETs data distribution method to improve the data transmission efficiency of RSU.This method mainly conducts optimization research from two aspects of data distribution and admission control.To tackle these issues,this paper proposes a novel algorithm which firstly prioritize data based on their applications.After that,the algorithm schedules the most rewarding data item based on utility values that are calculated with multiple parameters,including the data requirements of vehicles,vehicles density,speeds and locations.Finally,the algorithm applies the instantly decodable network coding technique on the scheduled data,and broadcasts coded packets for all vehicles in coverage.Extensive simulation results approve that the proposed algorithm achieve shorter access delay,lower deadline miss ratio and higher download success ratio,comparing with classical algorithms and other network coding based method.Further,comparing with non-priority methods,the proposed algorithm guarantees the service quality for high priority data applications,without sacrificing the service quality forlow priority data applications,thus advances the whole system performance for data dissemination in VANETs.For admission control,this paper proposes an admission control algorithm based on priority-based association network coding.The algorithm differentiates service types in the V2 R communication mode and satisfies the principle of prioritizing high-priority data requests.In the implementation process of admission control,high-priority data requests can be directly accepted.Low priority data requests can only be accessed if certain conditions are met.In order to determine whether the low priority data request satisfies the admission condition,combined with the proposed network coding based data distribution scheduling algorithm,the precoding of the request request is performed to find the maximum weighted group of the instant decodable network coding,and the vertices in the maximum weighted group The weights and the pending requests are vectorized,and the vector similarity is used as the admission control decision basis,and the request vector to be judged is subjected to admission control.The simulation results show that the proposed admission control algorithm effectively controls the load of low priority data on the system,ensures the success rate of high priority data downloading,and improves the utilization of system resources.