Polarization Filtering Based Physical-Layer Secure Transmission Scheme for Dual-Polarized Satellite Communication

In this paper, we propose a polarization filtering-based transmission scheme to enhance the physical layer security in the dual-polarized satellite communication. To prevent eavesdropping, this paper first divides the information sequence into two parts and modulates them independently. Subsequently, a pair of dual polarization states (PSs) is selected to carry the two modulated signals based on the designed selection rule. Last but not least, two polarized signals are added up and transmitted by the orthogonally dual-polarized antenna. Based on the assumption that the selection rule of the dual polarization states is synchronous among the legitimate users, the legitimate users can separate the two polarized signals by polarization filtering (PF). After that, the polarization match is performed to the two polarized signals, respectively. Then according to the demodulation rule, the information can be recovered. However, the eavesdropper does not know the PS selection rule and could not separate the two signals. Therefore, it is impossible for the eavesdropper to recover any useful information so that the security can be enhanced. In addition, the PSs of the signals will be changed due to the polarization dependent loss effect of the satellite channel, which leads to the PF performance degradation. To tackle this problem, a zero-forcing pre-filter is utilized at the receiver side. Finally, the security performance is validated by the theoretical analysis and simulation results in the dual-polarized satellite systems.