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, 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.
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, 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, 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.
Physical layer security is an important method to improve the secrecy performance of wireless communication systems. In this paper, we analyze the effect of employing channel correlation to improve security performance in multiple-input multiple-output (MIMO) scenario with antenna selection (AS) scheme. We first derive the analytical expressions of average secrecy capacity (ASC) and secrecy outage probability (SOP) by the first order Marcum Q function. Then, the asymptotic expressions of ASC and SOP in two specific scenarios are further derived. The correctness of analytical and asymptotic expressions is verified by Monte Carlo simulations. The conclusions suggest that the analytical expressions of ASC and SOP are related to the product of transmitting and receiving antennas; increasing the number of antennas is beneficial to ASC and SOP. Besides, when the target rate is set at a low level, strong channel correlation is bad for ASC, but is beneficial to SOP.
In this paper, we analyze the impact of the antenna correlation on the secrecy of multiple-input multiple-output (MIMO) wiretap channels with multiple eavesdroppers, where transmit antenna selection (TAS) and maximal-ratio combining (MRC) are employed at the transmitter, receiver and eavesdroppers, respectively. For the practical passive eavesdropping, we first develop new and closed general formulas for the secrecy outage probability and the probability of non-zero secrecy capacity to characterize the effect of spatial correlation, and results prove that the enhanced security performance can be achieved when multiple antennas are provided at the transmitter. We then explore how spatial correlation affects the asymptotic secrecy outage probability, and the secrecy diversity order is revealed. Based on these, the results show that when the average SNR of the main channel is relatively low, higher antenna correlation is more perfect to the secrecy. When the average SNR of the main channel is relatively high, higher antenna correlation is more destructive to the secrecy.
Transmit antenna selection (TAS) is an emerging technology in physical layer security. To provide new insights into the achievable secrecy performance of TAS in practical communication systems, this paper investigates the average secrecy rate (ASR) and secrecy outage probability (SOP) under practical modulation schemes in TAS aided multiple-input multiple-output multiple-antenna eavesdropper (MIMOME) wiretap channels over Rayleigh fading. Particularly, this research concentrates more on the square M-ary quadrature amplitude modulation (M-QAM). Furthermore, in the considered MIMOME channel, a single antenna is selected to transmit the secret message, and selection combining (SC) or maximal-ratio combining (MRC) is utilized at the legitimate receiver and the eavesdropper. Based on this system model, novel expressions for the ASR and SOP are formulated to characterize the secrecy performance of the finite-alphabet driven MIMOME channel. Besides exact analysis, an asymptotic analysis is performed using the considered performance metrics in high signal-to-noise ratio (SNR) regime. Theoretical analyses suggest that the asymptotic ASR and SOP converge to finite constants in high SNR regime due to the discrete constellation constraint, and we find that the asymptotic behaviour of discrete inputs differs from that of Gaussian inputs. Furthermore, we derive concise expressions to characterize the rate of convergence (ROC) of the ASR and SOP, respectively. To unveil more system design insights, we discuss the relationship between the ROC and several important system parameters such as the antenna number and the modulation order.