Research On Physical Layer Secure Transmission Technology Of Multi-antenna NOMA System

With the rapid development of wireless communication,we are gradually entering an intelligent society.At the same time,the rapid growth of smart terminals leads to the lack of the wireless spectrum resources,so how to use the limited spectrum resources to meet people's higher demand for communication services has become an urgent problem to be solved.Non-orthogonal multiple access(NOMA)technology opens up a new dimension to superimpose and transmit different user information in the power domain,ensuring better performance gain while improving spectral efficiency,and has become a research hot spot of the fifth generation(5G)mobile communication.Nevertheless,the NOMA communication system also faces severe security problems due to the openness of the wireless channel.In view of the above reasons,this paper will give priority to the physical layer security transmission technology of non-orthogonal multiple access communication systems,analyze and simulate the transmission performance of the system according to different communication scenarios combined with multi-antenna technology.The main results of this paper are summarized as follows:For the multi-input single-output non-orthogonal multiple access(MISO-NOMA)system,this paper analyzes the secrecy performance of users and systems in two different communication scenarios.Firstly,combined with antenna selection(TAS)technology,the secrecy outage probability of users and systems in the MISO-NOMA system under independent channel is studied.Then,which is different from the ideal assumption of the independent channel in the past,this paper takes the correlation between the main channel and the eavesdropping channel in the MISO-NOMA system into consideration for the first time,and deduces the closed expression of the secrecy outage probability of the near user and the far user in the correlated channel.The simulation results show that the TAS technology can effectively improve the secrecy performance of users and systems in both independent channel and correlated channel situations,and verify the rationality and correctness of theoretical derivation.For the NOMA relay system,this paper first discusses whether there is a direct link between the eavesdropper and the base station,and the closed expressions of users and systems secrecy outage probability in two cases are derived.Then,which is different from the previous assumptions based on perfect channel state information(CSI),this paper combines TAS technology for the first time in this system to analyze the users and systems secrecy performance in the case where the sender can only obtain outdated CSI.We consider a suboptimal antenna selection scheme in the system,the closed expression of the secrecy outage probability of the users and the systems under the scheme is derived.Finally,the influence of the direct link between the eavesdropper and the base station on the secrecy performance of the system is analyzed.The influence of different delays and the number of antennas on the secrecy performance of the system is analyzed.The rationality and correctness of the proposed antenna selection scheme and its theoretical derivation are verified.