Research On Technology Of Physical Layer Security In Scattering Channel

The scatter communication is widely used in military communication because of its strong anti-interference ability,strong ability to overcome obstacles and reliable propagation channel.The security of communication system is very important in military communication.In the original wireless communication,focusing on the analysis of the link layer and the above security technology,can not fully guarantee the security of the communication system.Therefore,people focus on the physical layer to ensure the safe and robust transmission of wireless signals by improving the security technology of the physical layer.Artificial noise method is an important method of physical layer security technology.The security capacity can be obtained through the different influence of artificial noise on legal users and eavesdropping users.Based on the communication system in tropospheric scattering channel,the physical layer security technology is studied in this paper.Firstly,the characteristics of scattering channel are analyzed,and SC-IFDM system with time-frequency frame is selected as communication system.And then,the physical layer security technology is studied.The main work includes: 1)The theoretical performance of the multiplicative noise safety scheme is analyzed.In this paper,the vector difference between the signal encrypted by multiplicative noise and the original signal is used as the equivalent noise,and the power ratio of the signal power to the equivalent noise is used as the SNR of the eavesdropping user.And then the performance of multiplicative noise safety scheme is analyzed theoretically.2)Based on different diversity schemes,an improved method for multiplicative noise security schemes is studied.Firstly,the diversity scheme in scatter communication is studied,and then the multiplicative artificial noise scheme based on different diversity schemes is studied.The results show that when multiplicative noise is added after transformation domain diversity,the SNR of the eavesdropping system reaching the maximum safety rate increases by about 6 dB.When two multiplicative noises are used in the transformation domain diversity scheme,and the safety rate is slightly higher than that of the multiplicative noises added only in the transformation domain.Studying the influence of different sequences on system security,the simulation results show that the system security performance of ZC sequence as multiplicative noise is better than the system security performance of chaotic sequence as multiplicative noise.3)The interference insertion encryption algorithm based on polarized MIMO system is studied.Polarized MIMO system can not only improve the transmission rate of the system,but also improve the anti-plaintext attack ability of the interference insertion security algorithm.The transmission signals in the polarized MIMO system are secondarily encrypted.That is,the interference signals and the effective signals are pre-coded while the interference signals are inserted,so that the two kinds of signals are fully combined.It achieves the purpose of enhancing security performance.At the same time the channel matrix is used as a default key,the signals are transmitted in the subchannel having a higher channel gain,and the interference signals are transmitted in the channel having a lower gain to maximize the energy of effective signals in the received signals.The results show that the security performance of the interference insertion encryption algorithm based on the polarized MIMO system is 8 dB better than that of the single antenna system,when the transmitting power is same.So the interference insertion encryption algorithm based on the polarized MIMO system effectively enhances the security of the eavesdropping system.