Security and privacy are major concerns in any wireless communication system. Physical layer security is an information-theoretic perspective which overcomes any limitations of traditional security algorithms. Cooperative jamming is a security scheme in which a jamming signal degrades the eavesdropper-channel but does not affect the channel of the intended receiver, thus allowing transmission of confidential messages. This paper considers a hybrid combination of an uncoordinated jamming approach, called local nulling, and transmit beamforming, showing an increased secrecy rate performance. The scheme is analyzed under different conditions including the case of increased number of eavesdropper antennas.
Security and privacy are major concerns in any wireless communication system. Physical layer security is an information-theoretic perspective which overcomes any limitations of traditional security algorithms. Cooperative jamming is a security scheme in which a jamming signal degrades the eavesdropper-channel but does not affect the channel of the intended receiver, thus allowing transmission of confidential messages. This paper considers a hybrid combination of an uncoordinated jamming approach, called local nulling, and transmit beamforming, showing an increased secrecy rate performance. The scheme is analyzed under different conditions including the case of increased number of eavesdropper antennas.
The broadcast nature of wireless communications makes the propagation medium vulnerable to security attacks such as eavesdropping and jamming from adversarial or unauthorized users. Applying physical layer secrecy approaches will enable the exchange of confidential messages over a wireless medium in the presence of unauthorized eavesdroppers, without using any secret keys. However, physical layer security approaches are typically feasible only when the source-eavesdropper channel is weaker than the source-destination channel. Cooperative jamming can be used to overcome this challenge and increase the secrecy rate. In this paper, the security of two-phase relaying system with multiple intermediate nodes and in the presence of an eavesdropper is investigated. To enhance the system secrecy rate, a joint cooperative beamforming and jamming combined with relay and jammer selections is proposed. In phase I, the source node broadcasts a signal to relays while three intermediate nodes (which act as jammers) help the source node by transmitting random jamming signals to confuse the eavesdropper. Since the friendly (cooperative) jammers create interference for both the intended relays and the eavesdropper, optimal beamforming is applied such that no interference is caused at two preselected desired relays (that are going to receive the confidential massage in phase I). In phase II, two preselected relays transmit the source message with beamforming coefficients such that the received signal at the eavesdropper is completely nulled out. Our goal in this paper is to minimize the received SNR at the eavesdropper while increasing it at the destination as much as possible by applying different methods such as cooperative beamforming, cooperative jamming and relay selection. To avoid operational complexity, we consider the minimum number of intermediate nodes that are necessary without losing the performance. Numerical results demonstrate the advantage of our proposed scheme compared with the scheme with no cooperative jamming.
1A wireless communication network is considered, consisting of a source, a destination and an eavesdropper, each equipped with a single antenna. The communication is assisted by multiple multi-antenna helpers, which independently transmit jamming noise to confound the eavesdropper. The optimal structure of the jamming noise that maximizes the secrecy rate is derived. A suboptimal solution that results in nulling at the legitimate receiver is also considered. Unlike the optimal solution, which requires global channel information, the suboptimal solution requires local channel information only, i.e., each helper needs to know only its own channel to the destination. Although the nulling solution results in lower secrecy rate as compared to the optimal solution, simulations show that the difference is rather small, with the inexpensive and easy to implement nulling scheme performing near optimal.
To improve the information-theoretic security of two-way wireless cooperative communication systems, we propose in this study a hybrid relaying and jamming mechanism based on multi-node cooperative beamforming to enhance the security of the physical layer transmission of information. The basic concept is that in the cooperative transmission phase, some intermediate nodes adopt distributed beamforming to help the transmitter send messages to legitimate users and simultaneously others jam the eavesdropper, which can significantly improve the security performance of the system in the broadcast phase. Two different cooperative beamforming schemes are proposed with and without the instantaneous channel state information (CSI) of the eavesdropper. We show that optimizing both the schemes requires the mathematical solving of one or a series of second-order convex cone programming (SOCP) problems, which can be executed by efficiently using the interior point method. Simulation and comparisons show that our proposed hybrid relaying, jamming mechanism and beamforming approaches significantly increase the security sum rate of the two source terminals and outperform both the relays-only and jammers-only mechanisms when the number of intermediate nodes is relatively large.
In this work, physical layer secure transmission of a cooperative wireless communication system over a three-phase amplify-and-forward (AF) two-way relaying channels is studied. A cooperative jamming and multi-antenna relay beamforming scheme that improves physical layer security of the system is proposed. Specifically, it is suggested that in the first and second timeslots when the legitimate users transmit alternatively, a jamming signal can be transmitted by the legitimate party that is not transmitting information-bearing signals This scheme, compared with the approach using a dedicated jammer, achieves a similar jamming effect with reduced complexity. In the third time slot of the protocol, the relay uses two beamforming matrices to process the bidirectional information signals. The jamming signal components at the relay are projected onto the null space of the legitimate relay-destination channels such that they do not affect legitimate communications. Through joint optimization, the sum throughput of the legitimate communication is maximized. In the numerical examples, the proposed scheme is shown to improve the system's secrecy transmission performance.
Physical layer security is a promising technique for information security. In multi-antenna systems, secure transmission designs are of crucial importance for physical layer security. In this thesis, our research focuses on the secure transmission designs for jamming signal aided multi-antenna systems. We first investigate robust secure transmission designs for a cooperative jamming aided multiple-input-single-output (MISO) system. Two scenarios are considered: (a) eavesdroppers' channel state information (ECSI) is available and (b) ECSI is unavailable. In scenario (a), a quality-of-service (QoS)-based design is considered to minimize the worst case signal-to-interference-and-noise ratio at the eavesdroppers. A secrecy rate based design is also studied. In scenario (b), a QoS-based design is considered to maximize the power of jamming signals, and the secrecy rate based design is not applicable. We propose an algorithm for each design problem through semidefinite relaxation. Our analysis shows that, even though the beamforming scheme in our designs is fixed as single stream beamforming, this does not cause any loss of optimality. We further consider secure transmission designs for a simultaneous wireless information and power transfer enabled MISO heterogeneous cellular network. In the considered system, all base stations (BSs) send confidential messages to information receivers and energy signals to energy receivers (ERs). BSs collaboratively utilize the energy signals as jamming signals to cripple ERs' interceptions. We propose a sum logarithmic secrecy rate maximization design problem. To tackle the design problem, we propose a semidefinite relaxation and successive convex approximation based centralized secure transmission design algorithm. Moreover, an alternating direction method of multipliers based distributed secure transmission design is also proposed. Simulation results demonstrate the effectiveness of the proposed algorithms. Secure transmission is designed for a cooperative jamming aided MISO non-orthogonal multiple access system. We consider an outage constrained secure transmission design problem under the assumption that only statistical ECSI is available. In the design problem, the minimum probabilistic secrecy rate is maximized. Based on 0-norm and the path-following approach, we develop an algorithm to find a solution to the design problem. Simulation results demonstrate that the secrecy outage probability can be guaranteed through the proposed secure transmission design algorithm.
This paper addresses enhancing the physical layer security of a downlink non-orthogonal multiple access systems. The proposed scheme consists of a base station, multiple legitimate users, and an eavesdropper. In each transmission slot, the base station communicates with two paired users, under the malicious attempts of the eavesdropper to intercept the information messages. In order to impair the eavesdropper's channel without affecting the legitimate paired users, a jamming signal is injected into the system by means of null-steering beamforming. In null-steering precoding, the jamming signal is directed toward the malicious node while being suppressed in the legitimate users' directions. Null-steering jamming is exploited in two different mainstreams, namely, self-cooperative and nonself-cooperative jamming. In the self-cooperative strategy, the base station implements the null-steering beamformer to transmit the jamming signal during the information exchange with the legitimate users, whereas in the nonself-cooperative jamming scheme, idle legitimate users (helpers) utilize the harvested energy in the first phase to transmit the jamming signal toward the eavesdropper in the second phase during the base station communication with the legitimate users. The outage behavior in the two considered scenarios is investigated, and the secrecy outage probability for both paired users is derived and provided in closed-form expressions. Numerical simulations are performed to validate the derived analytical results and to compare the two considered strategies secrecy performance. Comparisons yield that self-cooperative jamming has better outage behavior unless the number of helpers in the system is large enough.