This paper studies the secure transmission problem of the artificial noise (AN) aided multiple-input single-output (MISO) system. Considering a practical assumption of worst-case scenario where the eavesdropper is passive and the noise at eavesdropper is arbitrarily small. The transmitter simultaneously transmits information-bearing signals and AN to the desired receiver and eavesdropper by multiple antennas. In this system, the exact closed-form expressions of outage probability (OP) and intercept probability (IP) which represent system reliability and security respectively are derived and the correctness of the derivation is proved by simulation. Next, the paper provides the security-reliability tradeoff (SRT) analysis of the system. It is found that the optimal power allocation between the information-bearing signal and AN to maximize SRT is different for different number of transmission antennas. Then, the SRT performance of the system is analyzed from the aspect of number of transmission antennas and signal-noise ratio (SNR) of the system under the condition of the optimal power allocation. It shows that the SRT performance can be better with the increasing number of the transmission antennas, which means a more secure and reliable communication transmission can be achieved. SRT will not keep enhancing when SNR reach a certain value which can provide valuable reference for setting the transmission power to avoid the waste of power.
This paper studies the secure transmission problem of the artificial noise (AN) aided multiple-input single-output (MISO) system. Considering a practical assumption of worst-case scenario where the eavesdropper is passive and the noise at eavesdropper is arbitrarily small. The transmitter simultaneously transmits information-bearing signals and AN to the desired receiver and eavesdropper by multiple antennas. In this system, the exact closed-form expressions of outage probability (OP) and intercept probability (IP) which represent system reliability and security respectively are derived and the correctness of the derivation is proved by simulation. Next, the paper provides the security-reliability tradeoff (SRT) analysis of the system. It is found that the optimal power allocation between the information-bearing signal and AN to maximize SRT is different for different number of transmission antennas. Then, the SRT performance of the system is analyzed from the aspect of number of transmission antennas and signal-noise ratio (SNR) of the system under the condition of the optimal power allocation. It shows that the SRT performance can be better with the increasing number of the transmission antennas, which means a more secure and reliable communication transmission can be achieved. SRT will not keep enhancing when SNR reach a certain value which can provide valuable reference for setting the transmission power to avoid the waste of power.
In this paper, we consider the artificial noise (AN) aided multiple-input single-output (MISO) secure systems in which a multi-antenna transmitter simultaneously transmits the combination of information-bearing signal and artificial noise to a single-antenna legitimate receiver and eavesdropper. At the transmitter front-ends, the signal and/or AN will be amplified by high-power amplifiers (HPAs) which however may work in a nonlinear region and introduce nonlinear distortion. We calculate the received signal-to-noise ratio (SNR) at legitimate receiver and eavesdropper under HPA nonlinearity, and derive the approximated closed-form expression of secrecy rate. Numerical results suggest that the approximated theoretical secrecy performance is very close to Monte Carlo simulations for relatively lower SNRs, and is severely degraded by the nonlinear distortion caused by HPAs as the transmit power increases. Moreover, we further provide a power allocation strategy between information-bearing signal and AN to alleviate the nonlinear distortion.
This paper studies the artificial noise (AN) aided beamforming design in the multiple-input, single-output, and multiple-eavesdropper wiretap channel from the perspective of secrecy outage. Unlike many existing works, which directly adopted the traditional null-space AN scheme, we start with a general assumption on the structure of the transmit signal, and seek to find the optimal structure by solving a secrecy outage probability (SOP) constrained secrecy rate maximization problem. By generalizing several existing conclusions regarding a single-antenna eavesdropper, we prove that the null-space AN scheme is indeed optimal for an arbitrary number of the eavesdropper’s antennas from the perspective of secrecy outage. Furthermore, the optimal power allocation between the information-bearing signal and the AN is found under both general conditions and the conservative assumption that the eavesdropper can be arbitrarily close to the transmitter or his receiver noise power can be arbitrarily low. It is also found that the increase in the eavesdropper’s antenna number is equivalent to requiring a smaller SOP under the conservative assumption. The results in this paper can help generalize existing design solutions for single-antenna eavesdroppers to multi-antenna eavesdroppers.
This paper studies the design of artificial-noise-aided (AN-aided) secure transmission in slow-fading multiple-input–single-output (MISO) channels. We consider the scenario where a multiantenna transmitter sends messages to a single-antenna legitimate receiver in the presence of multiple noncolluding single-antenna eavesdroppers. It is assumed that the transmitter possesses instantaneous channel state information (CSI) of the legitimate channel but only the statistics of the eavesdropper's channels. Instead of adopting the well-known adaptive and nonadaptive transmission schemes, we consider the newly proposed semiadaptive scheme, in which the communication rate is fixed, and the secrecy rate is adaptively adjusted according to the legitimate channel's CSI. Compared with the adaptive scheme, a major advantage of fixing the communication rate is that the codebook can be fixed, and thus, the encoder and decoder designs are both simplified. We consider a generalized AN-aided beamforming structure, which allows arbitrary beamforming direction. Specifically, we focus on the problem of maximizing the secrecy throughput on the premise of reliable and secure transmission. By solving this problem, the optimal beamforming direction, power-allocation parameters, and secrecy rate are derived in closed form, and the optimal communication rate is obtained numerically. Finally, simulation results are presented to show the performance of the semiadaptive scheme.
Physical layer security in wireless networks has received increasing attention in recent years. In this paper, we consider multiple-input single-output (MISO) fading wiretap channels, where the transmitter utilizes artificial noise-aided precoding (ANaP) transmission strategy to maximize the secrecy capacity of the channel. When the channel state information (CSI) of Eavesdropper's (Eve's) channel is known at Alice, we prove that the optimal ANaP strategy reduces to the conventional precoding strategy, i.e., all the transmit power should be allocated to the precoding of information signal. When the CSI of Eve's channel is unknown at Alice, we find that there exists an optimal power allocation ratio between the information signal and the artificial noise and that this power ratio depends on the number of antennas as well as the available transmit power at Alice. In particular, when the available transmit power at Alice increases or the number of antennas at Alice decreases, more power should be allocated to the artificial noise.
The problem of optimal power allocation between the information-bearing signal and the artificial noise (AN) signal is addressed in this letter to enhance the physical layer security of the multiple-input-single-output wiretap channel. Differing from the existing works concerning the secrecy rate maximization, this letter studies the problem of minimizing the secrecy outage probability given the secrecy rate, where the channel state information concerning the eavesdropper is modeled as quasi-static Rayleigh fading and only known statistically. After formulating the problem as an optimization problem of power allocation, we prove that the optimal solution can be conveniently obtained by using the method of bi-section search. Simulation results show that the proposed power allocation method is efficient and can enhance the physical layer security by reducing the secrecy outage probability.
We design a novel artificial-noise-aided secure ON-OFF transmission scheme in a wiretap channel. We consider a practical scenario, where the multi-antenna transmitter only obtains partial channel knowledge from the single-antenna receiver through limited training and feedback but has no channel knowledge about the single-antenna eavesdropper. In the design, we first propose a three-period block transmission protocol to capture the practical training and quantization features. We then characterize the statistics of the received signal-to-noise ratios at the receiver and the eavesdropper. Under the secrecy outage constraint, we exploit the ON-OFF scheme to perform secure transmission and derive a closed-form expression for the secrecy throughput. Moreover, we investigate the optimization problem of maximizing the secrecy throughput by proposing an iterative algorithm to determine the optimal power allocation between the information signal and artificial noise, as well as the optimal codeword transmission rate. Furthermore, we define the net secrecy throughput (NST), which takes the signaling overhead into account and address the problem of optimally allocating the block resource to the training and feedback overhead. Numerical results clearly demonstrate how the optimal signaling overhead changes with the number of transmit antennas, and there exists an optimal number of antennas that maximizes the NST.