Research On Physical Layer Secure Transmission For Wireless Cooperative Networks

In recent years,the continuous development of wireless communication technology has brought great convenience to people's work and life.However,due to the openness of the wireless channel,information is vulnerable to eavesdropping and interference by illegal users during the transmission process.Generally,information security is guaranteed by a high-level encryption system.But with the increasingly powerful operational ability of computers,the traditional encryption system can hardly meet the current security requirements of wireless communication networks.In recent years,physical layer security technology makes it difficult for eavesdroppers to decode correctly by using the characteristics of the wireless channel itself,thereby ensuring the secure transmission of information,which is considered to be a potential security technology.In the physical layer security field,cooperative relaying is often used.It can not only expand the network coverage and increase the data transmission rate,but also improve the security performance of the wireless communication network.It has become one of the current research hotspots in wireless communication technology.Therefore,this article starts with the communication security problem of the cooperative relay network and studies its secure transmission schemes.The main work is as follows:The secure transmission schemes of cooperative relay network with untrusted relay is studied.Aiming at the scenario where there are both untrusted relays and eavesdroppers in the cooperative relay networks,three physical layer security transmission schemes were studied respectively,namely cooperative interference scheme,two-way relay scheme and successive relaying(SR)scheme.First,a network model of the cooperative interference scheme is established.By setting the interference node to send artificial interference signals to reduce the signal-to-noise ratio of the untrusted relay and the eavesdropper,and the closed-form expression of the system secrecy outage probability(SOP)is derived.The simulation results show that,compared with the non-interference scheme,the cooperative interference scheme can effectively improve the security performance of the system.Secondly,the network model of the two-way relay scheme is given,and two source nodes are used to send information to the relay at the same time,so that the signals of both parties interfere with each other at the eavesdropper,thereby improving the security performance,and theoretical analysis and simulation verification are carried out.Simulation shows that the security performance of the two-way relay scheme is better than the cooperative interference scheme.Finally,the SR scheme is modeled,and the source node information is forwarded by two untrusted relays in turn to generate inter-relay interference to reduce the signal-to-noise ratio of untrusted relays.On this basis,theoretical analysis and simulation verification are carried out.The simulation compares the impact of the three schemes on the system performance.The results show that the SR scheme has the best security performance among the three schemes.The secure transmission scheme of the cooperative relay network with trusted relay is studied.A new physical layer security transmission scheme is proposed for a SR network with multiple eavesdroppers and multiple relays.First,in the design of the SR scheme,the relayed signal is used to interfere with the eavesdropping of the confidential signal of this time slot by the eavesdropper,and at the same time,the inter-relay interference is eliminated at the destination node,thereby improving the security performance of the entire system.Secondly,in the process of selecting relays,aiming at minimizing the average SOP of the system in T transmission time slots,the method of selecting the best relay node is given.Finally,the closed-form expression of the average SOP that can be obtained by this secure transmission scheme is derived.The simulation results verify the correctness of the closed-form expression of the SOP,and show that the proposed scheme can significantly reduce the system SOP compared with the traditional relay cooperation schemes and the method of only one relay selection.