In this paper, we investigate a cooperative jamming strategy combined with a null-steering beamforming technique (CJ-NB strategy) for physical-layer security. To evaluate the achievable secrecy rate, the source input distribution is assumed to be Gaussian, and the achievable secrecy rate can be formulated as an optimization problem for power allocation (PA). By solving the problem, an asymptotically optimal PA is obtained with an exactly closed-form expression. In addition, we provide an asymptotic analysis of the achievable secrecy rate. The asymptotic result shows that the achievable secrecy rate is linearly proportional to the signal-to-noise ratio, but it will become saturated when the number of jammers is high enough. Therefore, we then develop a simple and efficient jammer selection algorithm to find an appropriate jamming set to achieve almost the same performance, but significantly reduce the number of jammers used compared with all the jammers performing the CJ-NB strategy. Finally, we provide simulation results to support our analyses.
In this paper, we investigate a cooperative jamming strategy combined with a null-steering beamforming technique (CJ-NB strategy) for physical-layer security. To evaluate the achievable secrecy rate, the source input distribution is assumed to be Gaussian, and the achievable secrecy rate can be formulated as an optimization problem for power allocation (PA). By solving the problem, an asymptotically optimal PA is obtained with an exactly closed-form expression. In addition, we provide an asymptotic analysis of the achievable secrecy rate. The asymptotic result shows that the achievable secrecy rate is linearly proportional to the signal-to-noise ratio, but it will become saturated when the number of jammers is high enough. Therefore, we then develop a simple and efficient jammer selection algorithm to find an appropriate jamming set to achieve almost the same performance, but significantly reduce the number of jammers used compared with all the jammers performing the CJ-NB strategy. Finally, we provide simulation results to support our analyses.
In this paper, we propose power allocation (PA) and jammer selection schemes based on a cooperative jamming strategy combined with a null-steering beamforming technique (CJ-NB strategy) for physical-layer security. Using the CJ-NB strategy, we first present an asymptotic optimal PA scheme, obtained by solving an achievable secrecy rate maximization problem, and then provide the corresponding achievable secrecy rate analysis. The analysis results show that the maximum achievable secrecy rate will become asymptotically saturated if the number of jammers is large enough. To avoid waste in the use of jammers, we also provide two jammer selection schemes that can determine the minimum number of jammers necessary to achieve almost the same secrecy rate as using all jammers for the CJ-NB strategy with the asymptotic PA scheme. One has lower computational complexity, and the other achieves better performance in reducing the number of jammers used. Finally, simulation results are given to demonstrate the effectiveness of the proposed schemes.
This paper studies the secrecy rate maximization problem of a secure wireless communication system in the presence of multiple eavesdroppers. The security of the communication link is enhanced through cooperative jamming with the help of multiple jammers. First, a feasibility condition is derived to achieve a positive secrecy rate at the destination. Then, we solve the original secrecy rate maximization problem, which is not convex in terms of power allocation at the jammers. To circumvent this nonconvexity, the achievable secrecy rate is approximated for a given power allocation at the jammers, and the approximated problem is formulated into a geometric programming one. Based on this approximation, an iterative algorithm has been developed to obtain the optimal power allocation at the jammers. Next, we provide a bisection approach, based on 1-D search, to validate the optimality of the proposed algorithm. In addition, by assuming Rayleigh fading, the secrecy outage probability (SOP) of the proposed cooperative jamming scheme is analyzed. More specifically, a single-integral form expression for the SOP is derived for the most general case, as well as a closed-form expression for the special case of two cooperative jammers and one eavesdropper. Simulation results have been provided to validate the convergence and the optimality of the proposed algorithm, as well as the theoretical derivations of the presented SOP analysis.
This paper investigates cooperative security in wireless networks, where a source (Alice) intends to transmit a confidential message to a legitimate destination (Bob), with the help of a cooperative jammer (Charlie), coexisting with multiple passive eavesdroppers (Eves). In particular, by assuming knowledge of Bob's perfect channel state information (CSI) but only Eves’ statistical CSIs, secrecy beamforming with artificial noise (AN) is utilized for secure transmission, and cooperative jamming (CJ) is explored to further enhance secrecy. We first derive an accurate closed-form expression for the secrecy outage probability (SOP), and establish the condition under which positive secrecy rate is achievable. Then, we provide a secure transmit design for maximizing the SOP constrained secrecy rate. Moreover, based on a strict mathematical analysis, we characterize the impact of the main channel quality and the number of Eves on transmit design and secrecy performance. Specifically, optimal power allocation ratio between the information-bearing signal and the AN signal increases as the main channel quality improves, and decreases with the number of Eves. Numerical results confirm that our design achieves performance improvement in terms of both secrecy rate and secure energy efficiency, as compared to the approach without CJ.
Conventional physical layer (PHY) security assumes unencrypted transmissions, requiring zero information leakage to adversaries. By incorporating encryption, this constraint can be relaxed, enabling higher secure transmission rates while tolerating limited leakage. This paper investigates an encryption-aware power allocation strategy and achievable transmission rate of a Gaussian wiretap channel in the presence of multiple cooperative jammers. By analyzing the rate-equivocation region and the corresponding rate maximization problem, optimal cooperative jamming strategy that maximizes the encryption-aware secrecy capacity is first addressed. The encryption-aware rate maximization problem is then shown to be equivalent to a non-convex beamforming vector optimization under a non-linear constraint, which is explicitly solved. Our numerical results illustrate that by utilizing the prior knowledge of encryption, optimizing the power allocation among jamming nodes significantly enhances the achievable secrecy rates.
In this paper, we propose a two-phase cooperative transmission strategy using decode-and-forward (DF) relaying and cooperative null-steering beamforming (CN-SB) to overcome the multi-eavesdropper problem that reduces the secrecy capacity of wireless networks. First, two groups are built from all available relays-the jamming group and the cooperating group. Second, based on the proposed cooperative transmission strategy, we develop a new relay assignment and power allocation scheme to achieve a higher secrecy rate. Simulation results show that the secrecy rate of the proposed scheme linearly proportional to the signal-to-noise ratio (SNR), which is significantly larger than that of the scheme in which all relays perform CN-SB simultaneously in high SNR regions.
Cooperative jamming approach has been commonly used in the field of physical layer security to achieve a good secrecy rate of wireless networks. In this approach, the Gaussian noise signal sent by a friendly jammer can disrupt the reception of the eavesdropper, however, it may also interfere with the legitimate receiver. In this paper, we propose a novel approach, namely, information jamming, to go beyond the secrecy rate achieved by the traditional cooperative jamming approach in a multiple-input single-output (MISO) wiretap channel. We propose that a multi-antenna friendly jammer transmits the source message rather than Gaussian noise signal for simultaneously enhancing the signal strength at the legitimate receiver and canceling the received signal at the eavesdropper. In particular, we aim to maximize the achievable secrecy rate by optimizing the information jammer's beamforming vector. Though the optimization problem is non-convex, we successfully solve it optimally via a two-stage based numerical approach. To gain more useful analytical results, we also propose two suboptimal jamming schemes with low computation, by targeting at improving the legitimate reception and avoiding the eavesdropping, respectively. Finally, numerical results show that the proposed information jamming approach significantly helps go beyond the secrecy rate of the existing cooperative jamming approach, especially when the transmit power of the jammer is large enough.