Research On Physical Layer Security Methods Of COFDM System Based On Constellation Mapping And Puncture Technology

Physical layer security technology is a secure communications technology, which utilizes secure coding or otherwise to create differentiated channel, thereby increasing the secrecy capacity and reducing the security gap to achieve an absolute sense of secure.Under the traits of broadband and integration, physical layer security technology is an important means for solving the security problems of wireless communication and has become a hot research area in the field of information security.On the basis of introducing the Yarg-code mapping method in detail and applying it to LDPC-COFDM, a COFDM secure system based on the Yarg-code mapping (LDPC-Y-COFDM) is designed in this paper. Combined the puncture technology with LDPC-Y-COFDM, an improved COFDM secure system based on constellation puncture (LDPC-YP-COFDM) is proposed. System architectures and working principles of LDPC-Y-COFDM and LDPC-YP-COFDM are given respectively.The security gap of two secure systems and the influence of different parameters on the security gap are simulated and analyzed under the gaussian channel model and the multipath channel model respectively. According to the analysis results, recommendations for configuration parameters of the two secure systems are given respectively. Simulation results show that under both channel models, the security gap of LDPC-Y-COFDM and LDPC-YP-COFDM has dropped significantly. Especially under EVA, ETU, EPA multipath channel model, the security gap of the two secure systems decreases by 54%,54%,73% and 61%,61%,77% respectively. The results indicate that when the two secure systems are adopted in the actual communication environment, a slight quality degradation of wire-tap channel can force the eavesdropper' BER to exceed 0.4, thereby effectively realizing an absolute sense of secure communication.