Research On Application-value-awareness Cross-layer MAC Game Methods In VANETs

Under the background of the rapid development of the global intelligent connected vehicle industry,the research on the technology of Vehicular Ad hoc Networks(VANETs)is of great significance to promote the development of automobile connections.In most applications of VANETs,delay is often an important attribute to be considered.Especially in the case of high-speed vehicle movement,the application has more stringent requirements for medium access delay.However,even if the security-related information is transmitted in the reserved channel,when the vehicle density is high and the wireless channel is close to saturation,the medium access method in the existing protocol cannot guarantee the medium access delay,and the delay may increase infinitely,that is,the message cannot be guaranteed to be transmitted in an effective time.It is necessary to improve performance and efficiency of medium access to ensure that messages are successfully transmitted within the time limit determined by packet delay requirements.Therefore,this paper uses game theory to design a competition model of medium access control(MAC)layer based on application value to distinguish message priority of different nodes in VANETs.Through the continuous game of each node’s strategy,the optimal strategy will reach an equilibrium,and each node accesses the medium according to its channel access probability,making the channel relatively better utilized.Firstly,in order to reflect the different value of each vehicle in application,we introduce a new notion of a weight factor(e.g.,the distance between vehicles,and the role of each vehicle)in a medium access game to distinguish the priority of different vehicles in channel competition.And we propose a game model to adjust each nodes channel access probability in the vehicular environment based on the weight factors of vehicles.We also provide instances of relevant applications by using the distance between vehicles and a vehicle’s role.Then,we analyze the incomplete information game in which each node cannot acquire the previous channel access probabilities of other nodes.Moreover,we construct a distributed algorithm based on the medium access game model and demonstrate that the game can converge to a unique and stable equilibrium under certain conditions.Finally,the two instances are implemented in a series of comparative experiments and their performances under saturated conditions are tested.Compared with MAC competition algorithm without considering vehicle weight,it is proved that the performance of the algorithm can be improved to a certain extent.In addition,to ensure that the messages in delay-sensitive applications of each node can be sent in time,we propose the concept of packet value(i.e.,the value of a conveyed packet),and correlate it with the waiting time of a packet determined by the delay of each concerned message.Subsequently,we design an inter-vehicle cooperative game model considering the global optimal utility of the vehicles.Next,we theoretically prove the existence of an equilibrium using a Markov decision process(MDP)and provide a concrete approach to obtain the channel access probability of a node according to the Bellman-type fixed-point equation.Finally,the channel performance is analyzed according to the results of partial observable MDP.