Information theoretic security has recently emerged as an effective physical layer approach to provide secure communications. The outage performance of such a secrecy communication system is considered in this paper, since it is an important criterion to measure whether users' predefined quality of service can be met. Provided that the legitimate receiver and eavesdropper have the same noise power, many existing secure schemes cannot achieve outage probability approaching zero, regardless of how large the transmission power is. By introducing cooperative transmission into secrecy communication systems, it will be shown here that outage probability approaching zero can be achieved. In particular, scenarios with single-antenna nodes and multiple-antenna nodes will both be addressed, and the optimal design of beamforming/precoding will be investigated. Explicit expressions of the achievable outage probability and diversity-multiplexing tradeoff will be developed to demonstrate the performance of the proposed cooperative secure transmission schemes, and numerical results are presented.
Information theoretic security has recently emerged as an effective physical layer approach to provide secure communications. The outage performance of such a secrecy communication system is considered in this paper, since it is an important criterion to measure whether users' predefined quality of service can be met. Provided that the legitimate receiver and eavesdropper have the same noise power, many existing secure schemes cannot achieve outage probability approaching zero, regardless of how large the transmission power is. By introducing cooperative transmission into secrecy communication systems, it will be shown here that outage probability approaching zero can be achieved. In particular, scenarios with single-antenna nodes and multiple-antenna nodes will both be addressed, and the optimal design of beamforming/precoding will be investigated. Explicit expressions of the achievable outage probability and diversity-multiplexing tradeoff will be developed to demonstrate the performance of the proposed cooperative secure transmission schemes, and numerical results are presented.
This paper investigates secure multi-antenna transmission in slow fading channels without the eavesdropper's channel state information. The use of multiple transmit antennas enables the transmitter to strengthen the signal reception at the intended receiver while simultaneously confusing the eavesdropper by delivering artificial noise. A recently developed secrecy outage formulation, which can separately measure the quality of service and the level of security, is used to characterize the security performance. We show that an arbitrarily low secrecy outage probability cannot be achieved by adding more transmit antennas alone without optimizing other system parameters. To facilitate the practical system design, we present an on-off transmission scheme with optimal artificial noise power allocation, which minimizes the secrecy outage probability whilst guaranteeing a minimum required quality of service.
The growing demand for wireless communications systems makes security an important and difficult design task. Therefore, in this thesis we approached different studies at physical layer security considering different scenarios of partial secrecy requirements, multiple antennas and finite blocklenghts. With respect to the partial secrecy regime, we evaluate the secure energy efficiency (SEE) of a cooperative network subject to partial secrecy requirements, implemented through a fractional equivocation parameter θ ϵ (0, 1] that allows partial secrecy when θ < 1. We assume that only the channel state information (CSI) of the legitimate channel is available, while the CSI with respect to the eavesdropper is unknown. Then, we propose a CSI-Aided Decode-and-Forward (DF) scheme, in which the transmitter uses the available CSI in order to choose between direct and cooperative paths. Moreover, the relay employs either Repetition Coding (CSI-RC), i.e., source and relay use the same codebook, or Parallel Coding (CSI-PC), when different codebooks are used. By resorting to the Dinkelbach algorithm, we propose a joint power allocation scheme, which also optimizes θ to maximize the SEE. Our schemes are compared with the traditional DF, Amplify-and-Forward (AF), and Cooperative Jamming (CJ). Extending the previous analysis, we also study the SEE in a cooperative scenario where all nodes are equipped with multiple antennas. Moreover, we employ secrecy rate and power allocation at Alice and at the relay in order to maximize the SEE, subjected to a constraint in terms of a minimal required secrecy outage probability. Considering this MIMO scenario in which only the CSI with respect to the legitimate nodes is available at Alice, we compare the Artificial-Noise (AN) scheme with CSI-Aided Decode-and-Forward (CSI-DF). Lastly, considering a more restrictive scenario with respect to the CSI, but more realistic, in which the legitimate transmitter has no knowledge of the instantaneous channel state information with respect to neither the legitimate receiver nor the eavesdropper, we investigate the secure throughput in a delay-critical scenario, such as in some applications of machine-to-machine communications, so that users communicate with a finite blocklength. In this approach, the performance of direct and selective decode-and-forward cooperative communication strategies are compared.
Physical layer security has attracted tremendous attention in recent years. This paper proposes a novel transmit antenna selection and cooperative communication design to enhance physical layer security. The proposed scheme is brought up in order to take full advantage of macro diversity, so that security performance can be enhanced to some extent. Specifically, we consider the scenario which contains two cooperative transmitters, one legitimate receiver and one eavesdropper. We first illustrate the proposed scheme, under which we derive the expressions of the probability density function of the signal-to-noise ratio at the receivers. We then derive the exact expression of secrecy outage probability. Following that, the cooperation method, which refers to the optimal power allocation strategy between the two transmitters is raised. Numerical simulation results show that compared with traditional TAS method without cooperation, the proposed scheme achieves better 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.
As Internet of Things (IoT) has boomed in recent years, many security issues have also been exposed. Focusing on physical layer security in wireless Internet of Things network communication, a series of security methods have been widely studied. Nevertheless, cooperative jamming methods in physical layer security to fight against collusive eavesdroppers have not been thoroughly studied yet. In this article, we study a cooperative-jamming-based physical layer secure transmission scheme for Internet of Things wireless networks in the presence of collusive eavesdroppers. We design a cooperative jamming strategy without knowing the channel state information of eavesdroppers. Considering the cooperation of multiple nodes with multiple antennas, this strategy can maximize the signal-to-interference-plus-noise ratio at an actuator (legitimate receiver). Meanwhile, the generated cooperative jamming signals can reduce the signal-to-interference-plus-noise ratio at eavesdroppers. To explore the theoretical security performance of our strategy, we perform a secrecy outage probability analysis and an asymptotic analysis. In the cases of cooperative jamming and without cooperative jamming, the closed-form expressions of the secrecy outage probability are deduced, and the influence of system parameters on the secrecy outage probability becomes more intuitive through a strict mathematical asymptotic behavior analysis. In addition, considering the energy limitation of Internet of Things devices, we propose a power allocation algorithm to minimize the total transmission power given the security requirements. The numerical results show the effectiveness of our schemes and are consistent with the theoretical analysis.
In this paper, we consider a secrecy relaying communication scenario where all nodes are equipped with multiple antennas. An eavesdropper has the access to the global channel state information (CSI), and all the other nodes only know the CSI not associated with the eavesdropper. A new secrecy transmission protocol is proposed, where the concept of interference alignment is combined with cooperative jamming to ensure that artificial noise from transmitters can be aligned at the destination, but not at the eavesdropper due to the randomness of wireless channels. Analytical results, such as ergodic secrecy rate and outage probability, are developed, from which more insightful understanding of the proposed protocol, such as multiplexing and diversity gains, can be obtained. A few special cases, where outage probability cannot be decreased to zero regardless of SNR, are also discussed. Simulation results are provided to demonstrate the performance of the proposed secrecy transmission protocol.