Optimal cooperative jamming (CJ) is studied for multiuser multiple-input multiple-output (MU-MIMO) broadcast channel to enhance the physical layer security with the help of a friendly jammer (FJ). We first derive a necessary and sufficient condition to achieve the asymptotically perfect security and propose an optimal CJ scheme to minimize the maximum signal-to-interference-plus-noise ratio (SINR) at the eavesdropper subject to a power constraint at the FJ. Then we derive an achievable lower bound of the eavesdropper's SINR and propose an asymptotically optimal CJ scheme achieving the lower bound. Numerical results demonstrate that the proposed schemes are effective.
Optimal cooperative jamming (CJ) is studied for multiuser multiple-input multiple-output (MU-MIMO) broadcast channel to enhance the physical layer security with the help of a friendly jammer (FJ). We first derive a necessary and sufficient condition to achieve the asymptotically perfect security and propose an optimal CJ scheme to minimize the maximum signal-to-interference-plus-noise ratio (SINR) at the eavesdropper subject to a power constraint at the FJ. Then we derive an achievable lower bound of the eavesdropper's SINR and propose an asymptotically optimal CJ scheme achieving the lower bound. Numerical results demonstrate that the proposed schemes are effective.
Cooperative jamming for multiuser multiple input multiple output (MIMO) broadcast channel is studied to enhance the physical layer security with the help of a friendly jammer. We assume the base station transmits multiple independent data streams to multiple legitimate users. During the transmission, however, there are multiple eavesdroppers with multiple antennas that have interests in the streams from the base station. In order to wiretap the desired streams, the eavesdroppers may collude or not, and maximize the signal-to-interference-plus-noise ratio (SINR) of the desired streams using receive beamforming. The optimal cooperative jammer is designed to keep the achieved SINR at eavesdroppers below a threshold to guarantee that the transmission from the base station to legitimate users is confidential. One main advantage of the proposed cooperative jamming scheme is that no modification is needed for the existing precoding schemes at the base station and decoding schemes at legitimate users. Thus, any existing practical precoding/decoding schemes for multiuser MIMO broadcast channel can be applied directly with the help of a friendly jammer using the proposed cooperative jamming.
A multiuser secure broadcast system is considered, where there are one multiantenna base station (BS), multiple single-antenna legitimate users, one multiantenna friendly jammer (FJ), and one multiantenna eavesdropper (Eve). We jointly design the optimal precoding matrix at the BS and the jamming covariance matrix at the FJ by minimizing the total transmit power of the BS and FJ under the signal-to-interference-plus-noise ratio constraints at the users and Eve. To solve this challenging problem, when the FJ has more antennas than the users and Eve, we first find the optimal structure of the jamming covariance matrix and, then, convert the problem into its equivalentconvexform. Also, we propose an iterative algorithm to jointly design the precoding and jamming covariance matrices in all scenarios. The solution obtained by this algorithm is shown to be asymptotically optimal when the FJ has more antennas than the users and Eve. Numerical results show that the proposed schemes considerably outperform the existing schemes.
Linear precoding and cooperative jamming for multiuser broadcast channel is studied to enhance the physical layer security. We consider the system where multiple independent data streams are transmitted from the base station to multiple legitimate users with the help of a friendly jammer. It is assumed that a normalized linear precoding matrix is given at the base station, whereas the power allocated to each user is to be determined. The problem is to jointly design the power allocation across different users for linear precoding and the cooperative jamming at the friendly jammer. The goal is to maximize a lower bound of the secrecy rate, provided that a minimum communication rate to the users is guaranteed. The optimal solution is obtained when the number of antennas at the friendly jammer is no less than the total number of antennas at the users and eavesdropper. Moreover, a suboptimal algorithm is proposed, which can be applied for all the scenarios. Numerical results demonstrate that the proposed schemes are effective for secure communications.
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.
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.
With the great-leap-forward development of Internet of Things (IoT), it is extremely important to study secure wireless transmission for IoT systems. A cooperative jamming (CJ) strategy has been extensively studied to enhance physical layer security in IoT systems. However, CJ's secrecy performance has not been well studied in the scenario of collusive eavesdroppers. In this paper, we propose a CJ scheme for IoT systems to fight against multiple passive and collusive eavesdroppers of unknown channel state information. Considering nodes with multi-antenna in an IoT system, we design beamforming vectors to maximize signal-to- interference-plus-noise ratio (SINR) of the wireless link from a controller (transmitter) to an actuator (receiver). Under the worst-case assumption that eavesdroppers can aggregate all signals to enhance their eavesdropping abilities, we derive the closed- form expressions of the secrecy outage probability (SOP) with and without CJ. In addition, we employ a strict mathematical asymptotic analysis to provide insights into the effects of various system parameters on the SOP. Numerical results verify that the CJ scheme can effectively prevent eavesdropping and the effects of system parameters on SOP is consistent with theoretical analytical results.