Research On Group Based Vertical Handoff Algorithm In Vehicle Heterogeneous Networks

Intelligent Transportation System(ITS)has been put forward for many years,but the research situation is not enough to meet the current practical application of the vehicle network environment and user demands.At the same time,the slow construction process of vehicle communication network and the more closed existing car communication system only apply to highway billing,vehicle identification and other purposes,its use function and application scenarios are limited.Therefore,the next generation of vehicle communication network based on the information security interworking to study the communication between vehicles to vehicles,vehicles to base stations or access points have important practical significance.When the vehicle as a mobile access point of the network,its high-speed mobility will lead to deterioration of network structure stability.At the same time,vehicle movement is restricted by roads and traffic signals,especially in urban environments.So vehicles tend to operate in groups,and such mobile characteristics are not fully considered when the vehicle is connected to the network.In addition,the traditional single-terminal design of the network access mechanism exist the network competition issues.Terminal convergence and selfishness can lead to a large number of terminals simultaneously access the better quality of service network,and then lead to a series of network side and terminal side of the problem.In this thesis,the problem of vehicle mobility management and network selection access in vehicle communication network is analyzed deeply.Based on the group study,the vertical handoff strategy for vehicle heterogeneous network is proposed and the related improvement algorithm is put forward.The main contents of this thesis include:1.According to the characteristics of vehicular ad hoc networks,a clustering algorithm suitable for vehicular ad hoc networks is improved.The algorithm expands the concept of spatial dependency according to the vehicle moving characteristic,and obtains the group relation value among the vehicles by predicting the moving trajectory of the vehicle as the measure of the clustering.The simulation results show that the proposed algorithm can effectively adapt to the vehicle network environment and complete the clustering by predicting the moving trajectory of vehicles and considering the relative mobility between vehicles.Under the changes of network scale in the scene it can still maintain a more stable number of groups and lower group cost.2.As the lots of vehicle terminals may lead to network congestion problems when accessing to the networks,based on the existing research,this thesis improves the vehicle group handoff algorithm which is suitable for vehicular heterogeneous network.Firstly,the vehicle users in the group are divided according to their traffic priority.Secondly,the group members at the same priority are assigned to different handoff slots under the handoff blocking rate constraints,thus avoiding the situation where a large number of group members selecting the same network and make it congestion.The simulation results show that the algorithm can ensure that the group members choose different network access and improve the utilization rate of the network resources under the condition of satisfying the different member's service requirements.