Coalition Formation Game-Based Secure And Efficient Clustering Communications In Vehicular Cyber-Physical Systems

Apparently,the urban traffic safety and congestion issues are increasingly serious due to the popularization of automobiles and driverless cars.A Vehicular Ad-hoc Network(VANETs),a typical application in traffic of Mobile Ad-hoc Networks(MANETs),plays an important role in assisting driving,security warning and traffic monitoring.The dynamics of nodes in VANETs may lead to frequent network topology changing.Yet,the existing communication models,schemes and strategies in Ad-hoc Networks cannot be directly used in VANETs because of the above typical characteristics.In order to address these challenges,the clustering network topology can be applied by taking advantage of the layout of the roadside.That is,the movement of vehicles in VANETs is more regular than that of nodes in other ad hoc networks due to the layout of the roadside.Therefore,the clustering structure is a convenient and efficient communication mechanism which conforms to the typical characteristics of VANETs.Although clustering schemes have already been studied in the past,most of them only concern the scenario of a highway or closed lanes.When it comes to crossroads in an urban scenario,however,the previous schemes have not been considered comprehensively and may lead to worse performance(e.g.,the degradation of communication quality).In order to prevent the degraded clustering performance in crossroads caused by changing direction,high node density and high bandwidth requirements,this thesis deeply studied the characteristics of VANETs and clustering mechanism and proposed a coalition-based clustering strategy.We also present a reputation-based incentive and penalty mechanism to stop selfish nodes from entering clusters.The specific work is as follows:1.In this paper,a coalition-based clustering strategy is proposed.In the proposed strategy,the coalition utility is formulated by the relative velocity,relative position and the bandwidth availability ratio of vehicles among the cluster.Employing the coalition utility,the vehicles are denoted as the nodes that make the decision whether to switch to a new coalition or stay in the current coalition.In order to balance the stability and efficiency of the clustering structure,we design a CG-SECC algorithm.In the algorithm,the node with the highest bandwidth and reaching the stable threshold can be elected as a cluster head node.Through which,we could make full use of the bandwidth provided by cluster heads.Besides,we also propose two criteria in terms of bandwidth requirement and mobility in clustering maintenance.These two criteria are used to reduce the number of nodes in the directed head list,computational complexity and the network delay.Numerical simulation results show that our strategy takes on a better performance for the tradeoff between the stability and efficiency of clustering communication.2.For the system model proposed in this thesis,we analyze the security model of crossroads scene and study the behavior of malicious nodes.Thus,we also present a reputation-based incentive and penalty mechanism to stop the selfish nodes from entering clusters.Specifically,the mechanism contains two aspects.On the one hand,it can avoid the nodes that are unwilling to serve as a head due to the heavy tasks on communication and management;on the other hand,it may reduce the possibility that cluster members make black deed to benefit from networks.A case study demonstrates that the proposed incentive and penalty mechanism can play an important role in discovering and removing malicious nodes.