A Wireless Physical Layer Security Enhancement Method Based On Cooperative Interference In Public Transportation

This thesis studies cooperative jamming(CJ)based security enhancement technology of physical layer inside public transportation.Physical layer security technology makes use of the inherent physical characteristics of wireless channel,and some signal processing technologies,such as antenna configuration,relay selection,cooperative jamming,etc.,to create difference between the legitimate channel and the wire-tap channel,which makes it impossible for eavesdroppers to interpret secret information and thus improves the security performance of wireless communication system.Beamforming and CJ are two important technologies to achieve secure communication in physical layer.The simulation result shows that,on the basis of beamforming,the security performance of communication system can be effectively improved by adding CJ.Therefore,in order to improve the confidentiality of downlink communication between the base station(BS)and the destination user in the vehicle and prevent secret information from being intercepted by the eavesdropper in the same carriage,we adopt joint beamforming and CJ method to achieve this goal.While the BS uses beamforming technology to send confidential information to the destination user,multiple cooperative nodes in the same carriage transmit artificial noise to interfere with the eavesdropper.The cooperative nodes used in the CJ are composed of two parts,one is the fixed jamming equipment in the vehicle,the other is acted by legitimate users.This not only guarantees the basic secure communication in the worst-case scenario,but also causes great interference to the eavesdropper to improve the security performance.Since mobile jammers consume their limited energy to transmit the interference signals,energy compensation is provided through energy harvesting technology.In addition,in order to compensate for the contribution of legitimate users as cooperative nodes to secure communication,we use energy collection technology to compensate them.In this thesis,we design the physical layer security transmission schemes for both ideal and actual situations.Ideally,the eavesdropper is known to the BS and the CSI of all channels can be acquired accurately.In this case,in order to obtain the best security and power performance,we propose B-CJ-SRM and B-CJ-TPM schemes respectively.Then,we propose low complexity schemes LC-B-CJ-SRM and LC-B-CJ-TPM to obtain sub-optimal security and power performance.The simulation results show that the security and power performance of the proposed schemes are better than zero-forcing method and QoSD method.The actual situation refers to the eavesdropper is unknown to the BS which cause it is mistaken for one of the cooperatives nodes by the BS,and the obtained CSI of the main channel and the wire-tap channel are imperfect because of channel estimation error.In this case,in order to maximize the expectation of secrecy rate,we use two-level optimization method to achieve this goal.The simulation results show that the security performance of the proposed scheme is better than that of zero forcing method.