Physical Layer Security Of Vehicular Networks With Cooperative Strategies

As an important part of the intelligent transportation system,vehicular networks can provide drivers and passengers with more comfortable and convenient services.However,the security threats on data exchanges over vehicular networks have become increasingly severe.Different from traditional cryptographic techniques,physical layer security under the information-theoretic security model can be used to ensure the security of exchanging privacy data over the wireless channel under the assumption that no computational restrictions are placed on the eavesdropper,i.e.,as long as the data transmission rate does not exceed the secrecy capacity of the channel,no eavesdropper can obtain any data information.Cooperative strategy is an effective method to improve the secrecy performance of the system in the physical layer.Therefore,aiming at the requirements of secure communication between vehicles in vehicular networks,this paper proposes two different cooperative strategies,namely cooperative jamming and cooperative relaying,and studies their impact on the physical layer security of vehicular networks.The main indicators to measure the performance of physical layer security(PLS)are secrecy capacity,average secrecy capacity(ASC)and secrecy outage probability(SOP).The secrecy capacity is the maximum of the secrecy transmission rate.The greater the secrecy capacity is,the stronger the secure communication capability of the system is.The secrecy outage probability reflects the probability of successful secure communication.The smaller the secrecy outage probability is,the greater the probability of successful secure communication is.Therefore,numerical estimation of secrecy capacity,average secrecy capacity and secrecy outage probability is an important research direction in physical layer security,which is significant for the networking design of vehicular networks.The main contributions of this paper are as follows:1)The cooperative jamming strategy in vehicular networks has been proposed.Under this cooperative jamming strategy,the average secrecy capacity(ASC)and the secrecy outage probability(SOP)have been studied.First,in order to improve the secrecy performance of vehicular networks,the cooperative jamming vehicle transmits the jamming signal to prevent the eavesdropping vehicle from eavesdropping the secret data transmission.This jamming signal does not prevent the destination vehicle from receiving secret data.Second,based on the Rayleigh fading channel model,the SOP and the ASC of the considered system are given and their closed-form expressions are derived by mathematical methods.These closed-form expressions can not only calculate the exact value of the SOP and the ASC rather than conducting a large number of simulations,but also reveals the relationships between SOP/ASC and various parameters of the system.Third,the definition of the optimal jamming vehicle has been given.Furthermore,the(optimal)jamming vehicle selection scheme has been proposed and the probability of the existence of the optimal jamming vehicle has been analyzed.Fourth,in order to maximize the secrecy capacity,the optimal power allocation between the source vehicle and the jamming vehicle has been analyzed.Finally,the simulation results validate the correctness of the analysis and verify the advantage of the proposed cooperative jamming strategy and the optimal power allocation.The influence of the main parameter of the system on the secrecy performance can be observed by the simulation results and the numerical results,which can provide helpful guideline for the practical scenario.2)Based on the cooperative relaying,the physical layer security of vehicular networks has been studied in the presence of the location-uncertain eavesdropper.First,the eavesdropping vehicle captures the secret data transmitted by the source vehicle,the source vehicle communicates with the destination vehicle via not only the direct link but also the indirect link with the help of an amplify-andforward relay vehicle.Second,the eavesdropping vehicle usually hide its exact position,so the impact of the eavesdropper’s uncertain location on the secrecy performance has been studied.Third,based on the double-Rayleigh fading channel model,the ASC of the considered system has been given and its approximate analytical expression has been derived by some mathematical method.Fourth,the validity of the analysis has been verified by the Monte-Carlo simulations and the numerical results.Furthermore,the impact of the eavesdropper’s uncertain location and the relay’s location on the ASC has been illustrated by the simulations and the numerical results.