Design And Research Of LDPC-COFDM Security System Based On Scrambling Matrix

With the development of wireless communication technology in the direction of broadband and the integration,the facing security threats is becoming more and more serious.The traditional link layer security mechanism can not fundamentally protect the security of wireless communication systems.Therefore the physical layer security,especially how to reduce the security gap has become a focus of research at the present stage.Based on the principle and the key technology of LDPC-COFDM system,this paper presents the baseband model and simulation model of LDPC-COFDM system for studying the security gap of the system.On this basis,through the design of information scrambling matrix,Yarg code mapping method and excellent LDPC encoding and decoding method,an LDPC-COFDM security system based on scrambling matrix(SC-LDPC-COFDM system)is proposed.The simulation results show that the SNR cost of SC-LDPC-COFDM system designed in this paper is less than 0.5dB.When the number of decoding iterations is 10 times and the security level is 0.4,the security gap is 0.95dB in the AWGN channel,1.5dB in the EVA multipath channel,1.7dB in the ETU multipath channel,and 5dB in the EVA multipath channel.The scheme can adapt to different LDPC code length,constellation mapping mode and subcarrier number.The security result of this scheme is close to the practical level.