Full duplex(FD)technology can improve the spectral efficiency of relay cooperative wireless systems and device to device(D2D)systems,and is currently a research hotspot in wireless communication.When the distance between D2 D users is relatively long,relay assistance is needed to achieve communication between D2 D users,and FD technology can further improve its spectral efficiency.However,the broadcasting characteristics of FD relay systems and D2 D systems make them susceptible to malicious eavesdropping,posing a physical layer security threat.The use of artificial noise interference,transmit antenna selection(TAS),and other technologies can enhance their physical layer security performance.This thesis intends to study them.Aiming at the security information transmission issue of untrusted relays as potential eavesdropping nodes,a physical layer security model for FD untrusted relay system using TAS was proposed,and an analytical expression of average secrecy rate was derived.The numerical calculation and simulation results show that increasing the number of transmitting antennas at the source node and receiving antennas at the destination node can improve the security performance of the FD untrusted relay system;The higher the efficiency of self interference cancellation,the better the security performance of the FD untrusted relay system.A physical layer security model for FD untrusted relay system was proposed for the Nakagami fading channel,in which the source node sends artificial noise to interfere with eavesdroppers.The expression for its average secrecy rate was derived.The numerical and simulation results indicate that the higher the efficiency of self interference cancellation,the better the security performance of the FD untrusted relay system on the Nakagami fading channel.The larger the channel fading parameters,the better the security performance of the FD untrusted relay system.Aiming at the issue of secure information transmission for cellular users under outdated channel state information(CSI),physical layer security models of D2 D systems with artificial noise interference by FD relays in passive and active eavesdropping scenarios were proposed.The ergodic capacity expression for D2 D users was derived,as well as the precise expressions for the probability of non-zero secrecy capacity,secure outage probability,and asymptotic secure outage probability of cellular users in two eavesdropping scenarios.The numerical calculation and simulation results show that the more transmitting antennas in the base station and the more interference antennas in the relay,both can improve the security performance of cellular users in the D2 D system;The smaller the normalized delay of cellular links or interference eavesdropping links,the better the security performance of cellular users in D2 D systems;Increasing the number of antennas used for cooperative forwarding in relays can improve the ergodic capacity performance of D2 D users;and that the smaller the normalized delay of the D2 D link,the better the ergodic capacity performance of D2 D users. |