Research On Vertical Handoff Algorithm For Reducing Blocking In Ad Hoc Vehicle Heterogeneous Network

In recent years,the development of intelligent transportation system and various access networks has formed vehicle heterogeneous network overlapped by different types of networks.In the vehicle heterogeneous networks,when the number of vehicles in the road increases,the probability of network block will increase.Therefore,in the vehicle heterogeneous network,how to design a vertical handoff algorithm to reduce network block is the key research.In order to reduce the blocking probability of users,this thesis conducts research from two perspectives: reducing the number of terminals of base stations or access points and reducing the amount of communication transmission data,in order to improve the overall performance of ad hoc vehicle heterogeneous network.The main works of this thesis are as follows:1.In the vehicle heterogeneous network,aiming at the phenomenon that traffic density is large and a large number of vehicle terminals are clustered,while is easy to lead to network block,this thesis proposes combining ad hoc network to alleviate this problem.When the network is not blocked,the vehicle terminal uses the utility function algorithm for network selection to quickly complete the vertical handover;when the network is about to be blocked,first,the ad hoc vehicle heterogeneous network is designed,and ad hoc network is divided into several clusters by clustering algorithm;then,the transition between vehicle states is carried out;finally,the access algorithm is selected according to vehicle states.The simulation results show that the algorithm can reduce the probability of network block,improve the throughput of the system and the service quality of the vehicle terminal.2.In view of the above algorithm only reduces the number of terminals directly connected to the base station or access point,and the problem of the amount of data transmitted in the network is not reduced,a vertical handoff algorithm for reducing the amount of data is proposed.The main idea is: when the network is under light load,first,the initial candidate network set is established according to the network load,and the candidate network is filtered;then,the network access is selected according to the transmission requirements of the vehicle terminal service.When the network is under heavy load,first,the ad hoc network is divided into clusters according to the clustering algorithm;next,using the cluster member vehicle to perceive information;then,the cluster head vehicle fuses the received information using a fusion algorithm;finally,the access network is selected according to the transmission requirements of the vehicle terminal service.Simulation results show that this algorithm is beneficial to balance the load of communication network,reduce the amount of data transmitted in the network,and improve the data transmission rate and system throughput.