Polarization state modulation(PM) It is known that satellite communication signals are easy to eavesdrop and how to realize secure transmission is the key problem. This paper proposes a secure transmission scheme based on the polarized constellation rotation and the weighted fractional Fourier transform. Firstly, the pseudo-random sequence is used to process the phase of the two components of polarization signals to make them change randomly, and the constellation points will randomly rotate around the horizontal polarization axis in the Poincare sphere. Then two polarization signals are processed by WFRFT with different orders separately to further distort the polarization constellation. In this manner, the constellation points will be randomly distributed in, on and outside the sphere improve the transmission security. In addition, with the proposed, it is difficult for the eavesdropper to accurately recover the WFRFT parameters and when there are errors in the cracked WFRFT parameters, self-interferences occur in the recovered signals, which causes a decrease in the SNR of the signals received by the eavesdropper. In this way, it also obtains a positive secrecy capacity to ensure the transmission security. Finally, the performance of the proposed scheme is verified from three aspects: polarization constellation distortion, security capacity and the bit error rate performance.
Polarization state modulation(PM) It is known that satellite communication signals are easy to eavesdrop and how to realize secure transmission is the key problem. This paper proposes a secure transmission scheme based on the polarized constellation rotation and the weighted fractional Fourier transform. Firstly, the pseudo-random sequence is used to process the phase of the two components of polarization signals to make them change randomly, and the constellation points will randomly rotate around the horizontal polarization axis in the Poincare sphere. Then two polarization signals are processed by WFRFT with different orders separately to further distort the polarization constellation. In this manner, the constellation points will be randomly distributed in, on and outside the sphere improve the transmission security. In addition, with the proposed, it is difficult for the eavesdropper to accurately recover the WFRFT parameters and when there are errors in the cracked WFRFT parameters, self-interferences occur in the recovered signals, which causes a decrease in the SNR of the signals received by the eavesdropper. In this way, it also obtains a positive secrecy capacity to ensure the transmission security. Finally, the performance of the proposed scheme is verified from three aspects: polarization constellation distortion, security capacity and the bit error rate performance.
In this paper, a novel transmission scheme based on constellation rotation and weighted fractional Fourier transform (WFRFT) is proposed to enhance the physical-layer security in polarization modulation (PM)-based dual-polarized satellite communications. Typically, by appropriately selecting the WFRFT order, the distribution of the signals processed by WFRFT can be close to Gaussian, which makes them difficult to be detected by eavesdroppers. However, once the signals are captured, it is possible for eavesdroppers to recover the information through the WFRFT order scanning method. To overcome this problem, in the proposed scheme, the constellation points are randomly rotated before the WFRFT operation, making it almost impossible to crack the WFRFT order. In this manner, the constellations are distorted, which is difficult for the eavesdropper to demodulate the signals accurately. Furthermore, a robust nonzero secrecy capacity is guaranteed. In addition, the impairment to the PM from the polarization-dependent loss effect is discussed, and a zero-forcing prefilter is applied at the receiver side to mitigate this adverse effect. Finally, the security performance of the proposed scheme is evaluated in terms of the average secrecy capacity and symbol error rate by numerical simulations in dual-polarized satellite communications.
In this paper, a transmission scheme based on polarization filtering and weighted fractional Fourier transform (PF-WFRFT) is proposed to enhance the transmission security in wireless communications. Indeed, the distribution of the transmit signals processed by WFRFT can be close to Gaussian, which can significantly improve the low detection probability. However, through scanning the WFRFT order with small step size, an eavesdropper can restore a regular constellation and crack the information. To overcome the problem, in the PF-WFRFT scheme, two polarized signals with mutually orthogonal polarization state are utilized to convey the information, which are processed by WFRFT separately and added up linearly before being transmitted by dual-polarized antennas. In this manner, even by scanning the WFRFT order, recovered signals are composite ones, which make the WFRFT order and the signals’ PSs difficult to crack, thus improving the security. In addition, the polarization-dependent loss (PDL) effect on the proposed scheme is discussed and a proprocessing matrix based on the channel information is constructed to eliminate this effect. Finally, numerical results are given to demonstrate the security performance of the proposed scheme in wireless communications.
A weighted fractional Fourier transform (WFRFT) based on channel state information (CSI), aiming to safeguard the physical (PHY) layer security of wireless communication system, is proposed. With the proposed scheme, WFRFT is first applied to satellite communications such that the transmitted signal is distorted and can only be neutralized by inverse‐WFRFT with the same parameter. Moreover, by exploiting the physical properties of wireless channels, the CSI matrix is transformed as a secret key. In addition, by adding phase rotation (PR) factors to each branch of the WFRFT system, a new unitary matrix with the encryption properties is constructed, and hence, the satellite communications secrecy is reliably guaranteed due to the variation in signal characteristics. Finally, the efficacy of the security enhancement is evaluated in terms of the average bit error rate (BER) and the secrecy capacity. Simulation results show that the proposed encryption method can make the detection and demodulation more difficult for the eavesdropper.
In this paper, a dual-polarized phased array based polarization state modulation method is proposed to enhance the physical-layer security in millimeter-wave (mm-wave) communication systems. Indeed, we utilize two polarized beams to transmit the two components of the polarized signal, respectively. By randomly selecting the transmitting antennas, both the amplitude and the phase of two beams vary randomly in undesired directions, which lead to the PM constellation structure distortion in side lobes, thus the transmission security is enhanced since the symbol error rate increases at the eavesdropper side. To enhance the security performance when the eavesdropper is close to the legitimate receiver and located in main beam, the artificial noise based on the orthogonal vector approach is inserted randomly between two polarized beams, which can further distort the constellation structure in undesired directions and improve the secrecy capacity in main beam as well. Finally, theoretical analysis and simulation results demonstrate the proposed method can improve the transmission security in mm-wave communication systems.
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.
In this letter, we investigate secure communication for the downlink rate-splitting multiple access (RSMA) system by integrating both the spatial domain and weighted fractional Fourier transform (WFRFT) signal domain to enhance its physical layer security (PLS) performance. To counter the external passive eavesdropper, we propose an RSMA-CM-WFRFT scheme to promote the dual use of the common message (CM), thereby improving the secrecy rate of both common and private messages. Specifically, the common message is encoded based on WFRFT, enabling all received power of legitimate users for signal reconstruction, while introducing inter-component interference at the eavesdropper. Furthermore, the inevitable serial interference caused by the WFRFT-encoded CM sequence overlays onto the private message (PM), thus enhancing its security. To counter internal eavesdroppers, we propose an RSMA-PM-WFRFT scheme to achieve parallel encryption by encoding the private message of different users into different WFRFT domains. Additionally, we formulate and solve a non-convex optimization problem aimed at minimizing the required power under both security and reliability constraints. Numerical results demonstrate the superior performance of the two proposed schemes.