| Non-orthogonal multiple access(NOMA)technology has the advantages of high throughput,low transmission delay,high frequency spectral efficiency,and is a potential key enabling technology in 5G and B5 G communication systems.However,due to the openness and broadcasting of wireless communication and the successive elimination and decoding mechanism of NOMA technology,its information transmission process is more vulnerable to malicious attacks such as eavesdropping and replay,which partially restricts the wide application of NOMA technology.Therefore,it is of great significance to study the secure transmission of NOMA system for ensuring the security of the next generation wireless communication system.Based on game theory,this thesis studies the physical layer security transmission of NOMA communication system.Specifically,aiming at the two typical scenarios of single paired users and multiple paired users in the NOMA communication system,this thesis studies the selection of security strategies for legitimate communicators to improve the system’s secure communication rate and resist external eavesdropping.In the single paired users scenario,the non-cooperative confrontation between the legitimate communicator and the eavesdropper is studied based on the zero-sum game.In the multiple paired users scenario,based on the coalition game,this thesis focuses on the cooperation behavior of the legitimate communicators.The main research results of this thesis are as follows:(1)Aiming at the problem of confrontation between legitimate communicators and external eavesdroppers in the single paired users NOMA communication scenario,two typical physical layer security design schemes,artificial signal assistance and relay assistance,are considered.A two-person zero-sum game model describing the non-cooperative confrontation behavior between legitimate communicators and eavesdroppers around the secrecy rate is proposed.The strategy and benefits of legitimate communicators and eavesdroppers are analyzed,and the existence condition of Nash equilibrium is proved,The pure strategy Nash equilibrium and mixed strategy Nash equilibrium under the two schemes are solved and analyzed respectively.The simulation results show that both schemes improve the security rate of the system and the physical layer secrecy performance of the NOMA system,it provides some enlightenment for the design of secure NOMA downlink transmission,and has certain reference value for the selection of legitimate communication strategies.(2)Aiming at the internal cooperation problem of legitimate communicators in order to counter external eavesdropping in the multiple paired users NOMA communication scenario,a coalition game model based on the pairing and cooperation behavior between legitimate users is proposed to maximize the total secrecy rate of the system.The original user pairing problem is transformed into a coalition game problem with non-transferable utility.The expression of the optimal power distribution coefficient between legitimate users is given through theoretical analysis,and a closed form of globally optimal user matching scheme is obtained.The simulation results show that the total security rate of the system is maximized. |
