This paper proposes a novel usage of zero-forcing beamforming (ZFB) for secure transmission in multiple-input single-output (MISO) wiretap channels. When using ZFB for secure transmission, the difficulty lies in the legitimate transmitter (Alice) hardly knowing the channel to eavesdroppers (Eves). The knowledge of the channel to Eves is essential when Alice builds a ZFB precoder that could eliminate the information leakage to Eves. To overcome this difficulty, this paper introduces a torch node that is assumed to be close to an Eve and helps Alice to estimate the channel to the Eve though the estimation is prone to errors. An exact secrecy outage probability (SOP) of the proposed ZFB with torch nodes as well as its asymptotic analysis is provided in this paper. Due to the channel estimation errors, a torch node is not always beneficial to reducing SOP. For a typical problem with a single Eve, a sub-optimal threshold that supports the usage of a torch node is provided in close-form. Numerical results show that the proposed ZFB with torch nodes significantly improves SOP.
This paper proposes a novel usage of zero-forcing beamforming (ZFB) for secure transmission in multiple-input single-output (MISO) wiretap channels. When using ZFB for secure transmission, the difficulty lies in the legitimate transmitter (Alice) hardly knowing the channel to eavesdroppers (Eves). The knowledge of the channel to Eves is essential when Alice builds a ZFB precoder that could eliminate the information leakage to Eves. To overcome this difficulty, this paper introduces a torch node that is assumed to be close to an Eve and helps Alice to estimate the channel to the Eve though the estimation is prone to errors. An exact secrecy outage probability (SOP) of the proposed ZFB with torch nodes as well as its asymptotic analysis is provided in this paper. Due to the channel estimation errors, a torch node is not always beneficial to reducing SOP. For a typical problem with a single Eve, a sub-optimal threshold that supports the usage of a torch node is provided in close-form. Numerical results show that the proposed ZFB with torch nodes significantly improves SOP.
In this paper, we present secure communication system with torch nodes. With a channel state information (CSI) between source and eavesdropper, a Alice null the received signal for eavesdropper with zero forcing beamforming (ZFB). But the CSI between source and eavesdropper is hard to achieve in secure communication. In this work, we propose the torch node in secure communication. The torch is assist node for secure communication that only report the CSI between source and the torch node. And we consider that the CSI of the torch node and some of eavesdroppers that close to torch node has a correlation. With this assumption, the Alice improve the secure outage with the CSI from the torch node. The study show that when transmit antennas of source is many then torch node bring the transmit power gain.
As an effective way to enhance the physical layer security (PLS) for the broadcast channel (BC), regularized zero-forcing (RZF) precoding has attracted much attention. However, the reliability performance, i.e., secrecy outage probability (SOP), of RZF is not well investigated in the literature. In this paper, we characterize the secrecy performance of RZF precoding in the large multiple-input single-output (MISO) broadcast system. For this purpose, we first consider a central limit theorem (CLT) for the joint distribution of the users' signal-to-interference-plus-noise ratio (SINR) and the eavesdropper's (Eve's) signal-to-noise ratio (ESNR) by leveraging random matrix theory (RMT). The result is then utilized to obtain a closed-form approximation for the ergodic secrecy rate (ESR) and SOP of three typical scenarios: the case with only external Eves, the case with only internal Eves, and that with both. The derived results are then used to evaluate the percentage of users in secrecy outage and the required number of transmit antennas to achieve a positive secrecy rate. It is shown that, with equally-capable Eves, the secrecy loss caused by external Eves is higher than that caused by internal Eves. Numerical simulations validate the accuracy of the theoretical results.
In this paper, we analyze the secrecy performance of multi-antenna cognitive wiretap network, where the secondary transmitter (Alice) communicates with the secondary receiver (Bob) in the presence of an eavesdropper (Eve). Specifically, we investigate the cases of maximal-ratio combining (MRC) with half-duplex (HD) and selection combining/Zero forcing beamforming (SC/ZFB) scheme with full-duplex (FD) operation, respectively. Assuming the Rayleigh fading, closed-form expressions for the secrecy outage probability of cognitive wiretap channels with MRC and SC/ZFB are derived. Furthermore, we provide simple asymptotic approximations for the secrecy outage probability and find that both schemes achieve full diversity. In addition, simulation results reveal that MRC outperforms SC/ZBF in the low interference threshold regime, while the opposite holds in the high interference threshold regime.
In this paper, the secrecy outage performance of a multiple-input single-output (MISO) wiretap channel is investigated. Different from previous works, we assume that the legitimate transmitter employs maximal-ratio transmission (MRT) beamforming scheme with outdated channel state information (CSI) of the main channel. A closed-form expression for the secrecy outage probability is derived, from which an asymptotic secrecy analysis is carried out. Furthermore, a closed-form expression for the probability of non-zero secrecy rate is derived. Our results are corroborated by Monte Carlo simulations and show that full diversity gain cannot be realized in the presence of outdated CSI. In addition, the MRT scheme is analytically compared with a transmit antenna selection scheme and the secrecy outage improvement is quantified.
With its capability to obtain a good tradeoff between complexity and performance, regularized zero-forcing (RZF) has been widely investigated to enhance the physical layer security. However, the associated reliability performance, i.e., secrecy outage probability (SOP), is not yet available in the literature. In this paper, we characterize the secrecy performance of RZF in the multi-user, downlink multiple-input single-output system. For this purpose, we first set up a central limit theorem for the joint distribution of users’ signal-to-interference-plus-noise ratio and eavesdropper’s signal-to-noise ratio by leveraging random matrix theory. The result is then utilized to obtain a closed-form approximation for the ergodic secrecy rate and SOP of three typical scenarios: the case with only external Eves, the case with only internal Eves, and that with both. The derived results are then used to evaluate the percentage of users in secrecy outage and the required number of transmit antennas to achieve a positive secrecy rate. It is shown that, with equally-capable Eves, the secrecy loss caused by external Eves is higher than that caused by internal Eves. Numerical simulations validate the accuracy of the theoretical results and demonstrate the advantage of RZF over other linear transmitters such as ZF.
In this letter, we aim to achieve secure communication for a multiple-input single-output (MISO) wiretap channel in the presence of multiple non-colluding eavesdroppers. It is assumed that the eavesdroppers' channels are unavailable to the transmitter, and artificial noise (AN) is used to provide masked beamforming for degrading the eavesdroppers' channels. First, we derive the secrecy rate outage probability for the masked beamforming system and then the optimal power allocation between data and AN is obtained in closed form for minimizing the secrecy rate outage probability under a total power constraint. The effects of the number of transmit antennas, the transmit power, and the target secrecy rate on the optimal power allocation parameter are characterized. Numerical results are presented to show the performance of our proposed power allocation scheme.