In this paper, a 4-weighted-type fractional Fourier transform (4-WFRFT) technology is presented to enhance the physical layer security (PLS) performance in a system of multiple eavesdroppers. The average signal-to-noise ratio (SNR) of eavesdroppers is first derived. Based on the derived average SNR, closed-form expressions of average security capacity (ASC) and secrecy outage probability (SOP) are obtained by employing the 4-WFRFT technology. The numerical results demonstrate that: 1) when the number of eavesdroppers increases, the 4 -WFRFT technology can also obtain a higher secrecy capacity. 2) the ASC decreases first but finally keeps at a constant value as the number of eavesdroppers increases. Simulations verify our analysis and demonstrate the 4 -WFRFT technology can validly improve the PLS performance in the multiple eavesdroppers system.
In this paper, a 4-weighted-type fractional Fourier transform (4-WFRFT) technology is presented to enhance the physical layer security (PLS) performance in a system of multiple eavesdroppers. The average signal-to-noise ratio (SNR) of eavesdroppers is first derived. Based on the derived average SNR, closed-form expressions of average security capacity (ASC) and secrecy outage probability (SOP) are obtained by employing the 4-WFRFT technology. The numerical results demonstrate that: 1) when the number of eavesdroppers increases, the 4 -WFRFT technology can also obtain a higher secrecy capacity. 2) the ASC decreases first but finally keeps at a constant value as the number of eavesdroppers increases. Simulations verify our analysis and demonstrate the 4 -WFRFT technology can validly improve the PLS performance in the multiple eavesdroppers system.
In this paper, the integration of antenna selection(AS) and 4-weighted-type fractional Fourier transform (4-WFRFT) technologies into the multiple-input multiple-output (MIMO) system based channel correlation has been proposed to enhance the security performance of wireless communications, where the energy of transmitting signals is split into four portions by employing the 4-WFRFT technology. This is equivalent to introducing additional artificial noise at the eavesdropper. To characterize system performance, the channel correlation is first considered, then we propose a valid method to model the distribution of composite instantaneous signal-to-noise ratio (SNR) of eavesdropper as the tractable exponential distribution. Furthermore, we drive the close-form expressions for both the joint probability density function (PDF) of channel and the average SNR at the eavesdropper. Based on above results, we deduce the close-form expressions of average security capacity with AS and 4-WFRFT technologies. To obtain further insights, we also derive the theoretical expressions of secrecy outage probability. The analysis results show that AS and 4-WFRFT technologies exist to simultaneously increase the average security capacity and then decrease the secrecy outage probability. The numerical results illustrate that: 1) 4-WFRF technology can validly eliminate the impact of channel correlation due to introducing the artificial noise; 2) the secrecy performance of system can be improved remarkably by employing AS and 4-WFRFT technologies.
In this paper, 4-weighted-type fractional Fourier transform (4-WFRFT) technology is introduced into Multiple-input multiple-output (MIMO) correlated Rayleigh fading channel to enhance physical layer security (PLS) significantly. The MIMO correlated Rayleigh fading channel is built first, and then 4-WFRFT is introduced into correlated channel model while transmitter and receiver share transform order but eavesdropper cannot acquire the exact transform order, so there is estimate error at eavesdropper. In MIMO correlated channel while using 4-WFRFT, the signal-to-noise ratio (SNR) of receiver and eavesdropper are derived, then the average secrecy capacity (ASC) is derived, at last the simulation results are analyzed. It can be concluded that when the estimate error is not zero, 4-WFRFT technology can reduce the SNR of eavesdropper while the SNR of receiver is unaffected, so 4-WFRFT can increase ASC significantly. When estimate error is within [0, 1], the greater the estimate error is, the greater ASC is, but not the case within [1], [2]. But when the estimate error is zero, it means eavesdropper acquire the transform order shared by transmitter and receiver, 4-WFRFT cannot achieve the purpose of enhancing PLS.
The traditional information security based on cryptosystem is seriously threatened due to the exponential growth of computing capacity. In order to improve for the upper cryptosystem security, the secure transmission at the physical layer is introduced into the wireless communication system. However, considering the openness of wireless channel, the performance analysis of security wireless communication systems has become a hot issue in recent years. Due to the existence of the upper layer cryptosystem being cracked and the openness of wireless channel security problems, the Multiple-Input Multiple-Output (MIMO) technology increases the difference between channels, the development of its rich spatial degrees of freedom can greatly improve the channel capacity and achieve the purpose of enhancing the Physical layer security (PLS); On this basis, Weighted Type Fractional Fourier Transform (WFrFT) technology rotates and splits the constellation points of signals, it is equivalent to increasing the artificial noise to enhance the PLS. The Average security capacity is an important index to measure the PLS, Therefore, this paper deduces the Average security capacity in MIMO scenario and gives a specific closed expression when considering the channel correlation. By analyzing the expression, the increase of the number of MIMO antennas will improve the Average security capacity. When the estimated bias is 1 in 4-WFRFT, the Average security capacity will be significantly improved; the Average security capacity will reach the maximum value, thus enhancing the PLS.
In this paper, weighted fractional Fourier transform (WFRFT) is employed to safeguard the physical layer (PHY) security of wireless communications. By leveraging the features of WFRFT, we propose a PHY security modulation scheme, which significantly degrades the equivalent signal-to-noise ratio (SNR) of the unauthorized receiver while imposing no impact on the legitimate receiver. With the proposed scheme, a robust nonzero secrecy capacity can be guaranteed. Moreover, the proposed scheme can conceal the actual modulation paradigms to prevent malicious signal detection, due to the variation in signal characteristics. A higher order statistics (HOS) based classifier is used to investigate the anti- recognition performance. Meanwhile, the secrecy performance of the proposed scheme is evaluated in terms of both secrecy capacity and average bit error rate (BER) by numerical simulations. Finally, as a proof-of-concept, an all-digital field programmable gate array (FPGA) based prototype system is developed to validate the practicability of the proposed scheme.
In this paper, the secrecy performance of the physical layer security (PLS) of the hybrid free-space optical/radio frequency (FSO/RF) communication system is analyzed. The transmission protocol of the considered system is performed under the eavesdropper's attempt to overhear the RF link between the transmitter and legitimate receiver of the hybrid system. The FSO link is characterized by Málaga-M distribution while the RF links are modeled by Nakagami-m distribution. The two practical eavesdropping modes considered in this paper include: colluding and non-colluding. Exact closed-form expressions for the system's secrecy outage probability (SOP), the asymptotic of the SOP (SOP∞), the probability of strictly positive secrecy capacity (SPSC), the average secrecy capacity (ASC), and the asymptotic of the ASC (ASC∞), are specifically derived under the influence of both eavesdropper modes. Our derived analytical expressions present an efficient tool to investigate the impact of some channel parameters on the secrecy performance, namely the fading severity of the RF links, atmospheric turbulence severity, pointing error of the FSO link, number of eavesdroppers, and the power of the eavesdropper links. The results show that the increase of the eavesdroppers' number under both modes profoundly degrades the considered system secrecy performance. The accuracy of the numerical results obtained is validated by Monte-Carlo simulations.
This paper proposes a Weighted fractional Fourier transform (WFRFT) based cooperation scheme to improve PHY layer security against eavesdropping in wireless communications. Rather than dissipating valuable transmission power to jam the eavesdropper, by leveraging the features of WFRFT, the information bearing signal can create “Artificial Noise” effect at the eavesdropper while imposing no effect on the legitimate receiver. Specifically, the proposed WFRFT based cooperation is performed in a two-phase manner, whereby the source first broadcasts its message to the intermediate nodes which then perform WFRFT operation to relay the message to the destination, with the objective of boosting the secrecy rate of the source-destination pair. Simulation results are provided, which demonstrate that the WFRFT-based user cooperation scheme can acehieve a significant performance gain, in terms of secrecy ergodic capacity, compared with conventional security-oriented user cooperation schemes.