Physical Layer Security Transmission Technology In Wireless Multicast System

Compared with unicast communication,multicast communication has the advantages of low delay and high efficiency,so it is widely used in daily life and work.With the application and development of multicast technology,the improvement of the security performance of multicast systems has become the focus of current research.In the multicast system,since the keyless physical layer security does not require users to perform complex authentication and key management through multiple interactions,it has many advantages such as low complexity and low delay.It is of great significance to study as a supplementary or alternative mechanism of traditional security technology.Based on the security of keyless physical layer,this thesis studies the information security transmission technology of multicast system from the two directions of signal processing and channel coding.The specific work is as follows.Firstly,this thesis studies and analyzes some theories,security technologies and corresponding security evaluation standards of physical layer security,which provides a theoretical foundation for subsequent research on information security transmission technology in multicast systems.Then,the downlink security transmission problem of multi-cell multicast system is studied from the direction of signal processing.When multiple cells reuse the same frequency band and there are eavesdropping users in the local cell,a beamforming method for multi-cell cooperative multicast communication is proposed.The method suppresses the interference between cells by coordinating beamforming between the base stations of each cell,and makes the beam with greater interference avoid legal users as much as possible,thereby improving the security capacity of the multicast system and maximizing the security of the local cell rate and the multicast rate of neighbor cells.Finally,the effectiveness of the proposed algorithm is verified by simulation.At the last,from the perspective of channel coding,the secure channel coding scheme in multicast system is studied.When the security capacity of the system is not zero,the smaller the security gap,the easier it is to realize the secure transmission of information.Therefore,On the basis of the most used jamming matrix technology,this thesis proposes a scramble coding technology based on partial information coupling to further reduce the security gap and improve the security performance of the multicast system.And it is proved by simulation that the proposed scheme can reduce the safety gap by 14.59% based on the disturbance matrix technology.Finally,on the basis of the proposed scheme,two improvement measures are proposed to further reduce the safety gap and enhance the safety performance of the system.