In this paper, a novel secure image signal transmission scheme was proposed in wireless systems, in which the poly-polarization filtering and the orthogonal matrix (PPF-OM) were combined to protect the image signal and eliminate the polarization dependent loss (PDL) at the same time, which was caused by the non-ideal wireless channel. This scheme divided the image information sequence into two parts in order to modulate and reshape the results into symbol matrices with the same size. Then, two sets of polarization states (PSs) and orthogonal matrices (OMs) were designed to process the symbols in order to enhance information protection and eliminate the PDL. Legitimate users were able to apply the shared PSs and OMs, step by step, so the information could be recovered. However, for eavesdroppers, the received signals were random symbols that were difficult to demodulate. Then, the bit error rate and the secrecy rate were derived to evaluate the performance of the PPF-OM scheme. Finally, the simulations demonstrated the superior performance of the PPF-OM scheme for enhancing the information security and eliminating the PDL.
In this paper, a novel secure image signal transmission scheme was proposed in wireless systems, in which the poly-polarization filtering and the orthogonal matrix (PPF-OM) were combined to protect the image signal and eliminate the polarization dependent loss (PDL) at the same time, which was caused by the non-ideal wireless channel. This scheme divided the image information sequence into two parts in order to modulate and reshape the results into symbol matrices with the same size. Then, two sets of polarization states (PSs) and orthogonal matrices (OMs) were designed to process the symbols in order to enhance information protection and eliminate the PDL. Legitimate users were able to apply the shared PSs and OMs, step by step, so the information could be recovered. However, for eavesdroppers, the received signals were random symbols that were difficult to demodulate. Then, the bit error rate and the secrecy rate were derived to evaluate the performance of the PPF-OM scheme. Finally, the simulations demonstrated the superior performance of the PPF-OM scheme for enhancing the information security and eliminating the PDL.
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.
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.
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.
Wireless communication security can be enhanced by leveraging the characteristics of the physical (PHY) layer, where discriminatory scrambling can be employed at the symbol level to either improve the signal quality of the legitimate receiver or degrade that of the eavesdroppers. However, in the presence of multiple passive eavesdroppers with more antennas than the transmitter, the transmitted signals can still be reliably separated from random disturbances. To mitigate this challenge, we propose a two-dimensional vectorized secure transmission scheme. Unlike existing transmission schemes (where the same data symbol is sent over each antenna with a predesigned complex weight at a time), in the proposed scheme, a sequence of data symbols in a predefined order (named symbol vector) is first pre-superposed through pre-coding with a random complex matrix prior to been sent as a vector in parallel over each transmitting antenna at a time. As a result, physical randomness of the legitimate channel is introduced into the received signals at passive eavesdroppers in the pre-coding procedure. Moreover, to ensure that transmitted data symbols can be recovered in the right order, each symbol vector is sent repeatedly, according to the principle of maximum entropy. To ensure the intended receiver can recover the transmitted symbol vector, the random pre-coding matrices are selected such that a linear constraint imposed by the CSI of the legitimate channel is satisfied. In addition, an extended maximum likelihood (ML) detection method is developed for the desired receiver while the random pre-coding matrices are not required to be transmitted. We then analyze its security based on the signal detection theory to demonstrate that the intended receiver can recover the transmitted symbol vectors while the eavesdroppers are not capable of doing so. We also evaluate the performance of the proposed scheme to demonstrate its effectiveness.
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.