| The incremental number of mobile terminals and the explosive growth of users' traffic demands have impelled the network operators to look for any alternatives to overcome the scarcity of wireless spectrum resources.Device-to-Device(D2D)communication has been proposed as a key technology in 5G networks to improve the utilization of wireless spectrum and enhance the data rate experience of mobile users.However,compared with the traditional cellular communication,D2 D terminals can communicate directly without the help of base station(BS).Therefore,the D2 D pairs may have a high probability of suffering from the security issue.This indicates that the D2 D link should be well designed for the sake of security threats.Recently,the problems of physical layer security(PLS)of D2 D communication are largely modeled by point-to-point network.In real scenarios,the distribution of eavesdroppers(Eves)is uncertain and the network may be attacked in anywhere and anytime.By leveraging stochastic geometry,we can model the both D2 D nodes and the Eves by Poisson point processes(PPP),which exactly reflects the practical network conditions.This thesis mainly concentrates on the security performance of D2 D communication system.We consider a random network in which the users and Eves are distributed as the independent homogeneous Poisson point processes(HPPP).To improve the security performance under different wiretap circumstances,we propose the corresponding secrecy enhancement techniques.Finally,based on stochastic geometry,we derived the expressions of secrecy probability of D2 D communication.Simulations are conducted to verify the results of our proposed schemes.The main content and contributions of this thesis can be summarized as follows:1.Considering the passive wiretapping environment,we assume that the random distributed Eves cannot collude with each other,and they only receive the secret messages separately from the D2 D transmitter.1)In single cell network,we derive the coverage probabilities of cellular user(CU)and D2 D user(DU),respectively,as well as the secrecy probability of DU.To improve the reliability of CU and the security of DU,we propose a novel concept of guard region for both CU link and DU link.Simulations confirm that the significant impacts of our proposed joint guard region on the security performance of D2 D communication;2)In multi-cell network,the effects of the intra-cell interference on the coverage probability of CU and DU and the secrecy probability of DU are characterized.To improve the secrecy transmission performance of D2 D links,we propose a threshold-based access control scheme for D2 D link.Then we derive the expression of effective security throughput(EST)of D2 D link.The simulation validate that the scheme can achieve higher EST when the number of D2 D transmitter is larger enough.What's more,when only take the access threshold into consider,the maximization of EST can be realized under the premise of achieving CU connected reliability.2.Considering the active wiretapping environment,we assume that the random distributed Eves can collude and share their observations in a central Eve for decryption.1)For the aforementioned multi-cell network,we derive the secrecy transmission capacity of D2 D link.We find that the colluding Eve deteriorate the secure communication of DU compared with the non-colluding Eve.2)To well understand the D2 D security performance where the Eves are colluding,we consider the case of Single Transmitter Multiple Receivers Multiple Eves(STMRME).The distance between the legitimate receiver and D2 D transmitter is sorted in ascending order.Then we derive the secrecy outage probability of D2 D link and analyze the influence of D2 D receivers' location on D2 D security.Furthermore,because of colluding Eves on security,we propose a cooperative reception scheme for the D2 D receivers.In the end,the simulation results prove that the scheme can improve the security of D2 D link in the active wiretapping environment. |
PDF Full Text Request