Research On Optimal Relay Selection Algorithm For Physical Layer Security In Vehicle Communication Network

With the continuous development of connected car technology,vehicle to vehicle(V2V)application scenarios have been continuously designed and developed.In the process of wireless network communication,signal fading and communication security have been the focus of research.In order to reduce signal fading,in the traditional communication process,MIMO technology can be used to increase the transmit power and increase the number of transmitting and receiving antennas to combat wireless signal fading.However,relative to these methods,in the communication process of the in-vehicle communication network,increasing the transmission power will increase the load of the in-vehicle system,and the MIMO technology cannot be completely applied due to the physical size limitation of the in-vehicle communication equipment.In order to ensure the safe transmission of signals,the traditional method is to continuously improve the encryption method.This method may reduce the transmission of effective information and affect the transmission efficiency.Therefore,this paper considers how to solve the problems of wireless signal fading and communication security in the V2 V communication process from the physical layer in the communication model.It is necessary to ensure both communication quality and communication security.Based on the consideration of the above problems,in the light of the problem of signal fading,this article compares the two relay transmission methods,and the method chosen is to select a repeater in the cooperative network to amplify and forward the signal quality.Based on the complex communication environment of the vehicle when it is moving,the fading of the channel is more consistent with the Nakagami-m distribution,and the expression of the channel capacity under this environment is derived accordingly.On the issue of communication security,this paper considers the effect of eavesdroppers on the channel capacity between two transmission nodes at the physical level,proposes a secure channel capacity,and gives an expression formula.Based on the above research,the problem of relay selection strategy must be solved.This paper uses reinforcement learning knowledge to model the relay selection process,simplify the Markov model based on the established model,and determine the state set,action set,probability set and reward.Considering the influence of the distance between communication nodes on the selection of relay nodes,this paper presents two shortest communication link algorithms to determine the probability set of relay selection.This article uses secure channel capacity as a measure of communication quality,but because the sum of the secure channel capacity of each communication link does not have any practical significance,this article uses the total communication link information processing time as a value function of strategy selection.The value of the value function is compared to find the optimal relay selection.The model is verified by experiments.First,it is concluded that as the communication distance increases,the channel capacity and the secure channel capacity decrease.Secondly,according to the Markov Decision Process(MDP),by comparing the value of the value function in the selection strategy,the optimal relay selection is obtained,and the transmission route with the best communication quality is obtained.Finally,the data is compared and analyzed.The optimal relay selection can increase the effective information transmission distance between the fleets.Under the condition of equal distances,when only the safety channel capacity is considered,the optimal selection of multiple relays can enhance communication quality and communication security.