Orthogonal vector based transmission method for security enhancement and PDL elimination in dual-polarized wireless communications

Abstract

In this paper, we propose an orthogonal vector based transmission method to enhance the transmission security and eliminate the polarization dependent loss (PDL) effect in wireless communications. In the proposed method, the information is modulated into symbols with polarization state modulation technique. Then, two polarization signal vectors are reshaped into two matrices and each column of them is multiplied by an unique vector selected from an orthogonal matrix, which results into several matrices. After that, for each polarization, all matrices are added up into a mixed matrix and then, reshaped into a vector for transmission. To enhance the transmission security, the weighted fractional Fourier transform (WFRFT) technique is designed to process the mixed matrices before reshaping into vectors. For legitimate users, the received signals could be reshaped into matrices with right size and the inverse-WFRFT is operated to the matrices with right WFRFT orders. Moreover, the same orthogonal vectors are used to process the signal matrix in the right sequence to recover original signals. As orthogonal vectors are different for two polarizations, there is no mutual interferences in two recovered polarization signals, thus, the PDL effect is naturally eliminated. In addition, the signals are also difficult to crack. Finally, simulation results demonstrate the superior performance of the proposed method in enhancing the transmission security and eliminating the PDL effect.