Research On Physical Layer Security In Multi-Antenna Communication System

In recent years,due to the rapid development of wireless communication technologies and mobile terminal technologies,the demand for high-speed data services has exploded,and wireless communication for the purpose of enhancing the security of information transmission has become a hot research topic.The physical layer security technology based on information theory,as an important direction in the field of information security,has also received more and more attention.With the wide application of multi-antenna technology in communication systems,it is very promising to study the physical layer security in multi-antenna systems.Therefore,this paper will focus on this part of the content,including the following two parts:Firstly,this thesis simply introduces a physical layer security transmission scheme based on Alamouti code.This scheme uses Alamouti code to encode confidential information,and sends artificial noise to resist eavesdropping,which can realize the secure transmission of system information.On this basis,this paper introduces the physical layer security transmission scheme for joint antenna selection,that is,the step of selecting the best two antennas from multiple transmit antennas before signal transmission.Through Matlab simulation,the performances of the two security schemes are compared.The simulation results show that antenna selection can further increase the legal channel capacity,thereby obtaining higher security capacity and enhancing system security.Secondly,this thesis proposes a physical layer secure transmission scheme based on Orthogonal Space-Time Block Code(OSTBC).This scheme makes use of OSTBC's full set gain to improve the transmission quality of the legal channel,and utilizes zero-space Artificial Noise technology to resist eavesdropping,which can enhance system security performance,but there is a deficiency in transmission rate loss.In order to overcome this defect,an improved physical layer security transmission scheme based on constellation rotation Quasi-Orthogonal Space-Time Block Code(QOSTBC)is proposed.The improved scheme uses the constellation rotation QOSTBC to encode confidential information and can realize full-rate transmission of information.In addition,the simulation results show that the security performance of the improved scheme outperforms the OSTBC-based physical layer security transmission scheme under all signal-to-noise ratio conditions.Therefore,the physical layer security transmission scheme based on constellation rotation QOSTBC is more suitable for multi-antenna communication systems.