Research On The Physical Layer Security Transmission Scheme With Optimization Of Artificial Noise

The broadcasting characteristics of wireless channel make wireless communications vulnerable to security threats,and eavesdropping is one of the most important security issues.With the development of multi-antenna technology,signal processing technology and coding technology,it is possible to realize the secure transmission of information in the physical layer.Multi-antenna beamforming and artificial noise technology are important technical means to achieve the physical layer of security.This thesis studies physical layer security schemes with optimization of artificial noise.The main contents are as follows:1.A physical layer security scheme using beamforming technology and artificial noise is studied,which further takes the advantage of artificial noise for MISO systems without the eavesdropper's channel state information.Based on the transmitted symbols and channel coefficients,the transmitter determines whether or not the artificial noises are beneficial to the signal detection at the legitimate receiver.Then it designs beamforming vectors accordingly.By taking advantage of useful noise,the signal to noise ratio at the legitimate receiver is improved effectively while that at the illegal receiver remains unchanged.The rules of determining whether the artificial noise is beneficial or not in PSK modulation is given,and the corresponding bit error rate and secrecy rate are analyzed.The results demonstrate that the proposed scheme can improve the performance of the legal receiver and promote secrecy capacity.2.For the full duplex MIMO point-to-point two-way communication system with residual self-interference,the physical layer security transmission scheme with null space artificial noise is studied while the eavesdropper's channel state information is not available.First of all,the expression of the channel rate is given when the null-space artificial noise is used and the self-interference is considered.Second,a mathematical model to optimize the beamforming weights of message signal and the power of artificial noise is builded,which is an optimization problem with the constraint of the total transmission power and the legitimate target rate.Because the two legal nodes rely on each other's result to get their own result,this joint optimization problem can not be solved.By estimating and approximating the self interference noise's power in the optimization model,the joint optimization problem is transformed into two independent optimization problems which can be solved at each node.The covariance matrix of the signal are obtained,and the optimal allocation of the number of transmitting antennas and receiving antennas is analyzed.The simulation results show that the actual rate is very close to the target rate of theoretical optimization,which shows that the approximate treatment of the optimization model is appropriate,and a considerable secrecy rate can be obtained.