Research On Physical Layer Security Transmission Technology In Full Duplex Relay System

With the rapid development of wireless communication technology, people pay more attention to the security of wireless communication while paying attention to the communication speed. Because physical layer security technology takes full advantage of the wireless channel's own characteristics, it can not rely on the upper security mechanism, and from the bottom of the communication protocol to achieve the safe transmission of information, and other security communication technology can be very compatible. As one of the key technologies of wireless communication network, relay transmission technology has the characteristics of significantly increasing the throughput of wireless communication and expanding network coverage. At the same time, full duplex technology enables both communication in the same slot and the same frequency band to work, to overcome the shortcomings of half duplex technology,making the use of spectrum resources more flexible. Therefore, in the more complex physical layer security transmission model, considering the advantages of full-duplex relay technology, it is of great practical significance and application value to study the physical layer security transmission technology of full-duplex relay system.In this thesis, the full duplex relay physical layer security transmission technology is studied in detail,and the contributions include the following three aspects.Firstly, the full duplex single-relay physical layer security transmission model is studied. In this model, a full duplex hybrid relaying-and-jamming scheme is proposed to introduce the full duplex relay technology, while the relay node transmits the desired signal and the jamming signal. The destination node can extract the original desired signal from the received information from the relay node while eliminating the jamming signal, while the eavesdropping node can not decode the desired signal and reduce the eavesdropper's performance. Finally, the achievable secrecy rate of the system is deduced, and the optimal power allocation scheme is obtained by the power allocation of the original desired signal and the jamming signal.Secondly, in the physical layer security model of full duplex multi-relay system,the full duplex technology is introduced into the model of cooperative relay selection.In this scheme,a modified duplex relay selection scheme is proposed, which utilizes the advantages of half duplex and full duplex. When two duplex modes are selected among the multiple relay nodes,selecting the relay node as the optimal relay selection results,which make the achievable secrecy rate reach to the maximum value. The achievable secrecy rate and secrecy outage probability of the hybrid duplex relay scheme are deduced. The simulation shows the advantage of the modified duplex relay selection scheme.Thirdly, in the multi-user full duplex relay system physical layer security model,combined with full duplex technology and random weight coding, a full duplex relay random weight scheme is proposed. In this scheme,the relay node works in full duplex mode, and uses random weight code to process the received signal. It can interfere the eavesdropper nodes without affecting the destination nodes. Finally, the achievable secrecy rate of the full duplex relay random weight scheme is deduced. The simulation shows that the full duplex relay random weight scheme improves the security performance of the system.