Physical-layer-based security aims at ensuring the reliability of communication and preventing eavesdropping by taking advantage of the physical layer's characteristics rather than the data encryption in upper layer. Cooperation is a way to achieve this goal with many benefits for wireless communication. In particular, the cooperation scheme called decode-and-forward (DF) is discussed in this paper and our objective is to design each cooperating node's beamforming factor for maximum achievable secrecy rate. Considering that individual power constraint is more reasonable than total power constraint and to set noise power levels at the destination and the eavesdropper different is more practical than the same, we get the whole optimization problem which is unconvex. With the help of perfect global channel state information (CSI), the problem is solved through a way where convex optimization and one-dimensional search are combined together. And strict proofs are presented for this method. Numerical results of the obtained maximum achievable secrecy rate show that the proposed design can significantly improve the security performance of wireless systems compared to directly transmission.
Physical-layer-based security aims at ensuring the reliability of communication and preventing eavesdropping by taking advantage of the physical layer's characteristics rather than the data encryption in upper layer. Cooperation is a way to achieve this goal with many benefits for wireless communication. In particular, the cooperation scheme called decode-and-forward (DF) is discussed in this paper and our objective is to design each cooperating node's beamforming factor for maximum achievable secrecy rate. Considering that individual power constraint is more reasonable than total power constraint and to set noise power levels at the destination and the eavesdropper different is more practical than the same, we get the whole optimization problem which is unconvex. With the help of perfect global channel state information (CSI), the problem is solved through a way where convex optimization and one-dimensional search are combined together. And strict proofs are presented for this method. Numerical results of the obtained maximum achievable secrecy rate show that the proposed design can significantly improve the security performance of wireless systems compared to directly transmission.
Physical-layer-based security aims at ensuring the reliability of communication and preventing eavesdropping by taking advantage of the physical layer's characteristics rather than the data encryption in upper layer. Cooperation is a way to achieve this goal with many benefits for wireless communication. In particular, the cooperation scheme called decode-and-forward (DF) is discussed in this paper and our objective is to design the beamforming weight of each cooperating node which is one antenna equipped for maximum achievable secrecy rate. Considering that individual power constraint is more reasonable than total power constraint and to set noise power levels at the destination and the eavesdropper different is more practical than the same, we get the whole optimization problem which is unconvex. With the help of perfect global channel state information (CSI), the problem is solved through a way where convex optimization and one-dimensional search are combined together. And strict proofs are presented for this method. Then zero-forcing (ZF) based simplification and extension to cope with multi-antenna case are discussed. Numerical results show that the proposed design can significantly improve the security performance of wireless systems.
Physical (PHY) layer security approaches for wireless communications can prevent eavesdropping without upper layer data encryption. However, they are hampered by wireless channel conditions: absent feedback, they are typically feasible only when the source-destination channel is better than the source-eavesdropper channel. Node cooperation is a means to overcome this challenge and improve the performance of secure wireless communications. This paper addresses secure communications of one source-destination pair with the help of multiple cooperating relays in the presence of one or more eavesdroppers. Three cooperative schemes are considered: decode-and-forward (DF), amplify-and-forward (AF), and cooperative jamming (CJ). For these schemes, the relays transmit a weighted version of a reencoded noise-free message signal (for DF), a received noisy source signal (for AF), or a common jamming signal (for CJ). Novel system designs are proposed, consisting of the determination of relay weights and the allocation of transmit power, that maximize the achievable secrecy rate subject to a transmit power constraint, or, minimize the transmit power subject to a secrecy rate constraint. For DF in the presence of one eavesdropper, closed-form optimal solutions are derived for the relay weights. For other problems, since the optimal relay weights are difficult to obtain, several criteria are considered leading to suboptimal but simple solutions, i.e., the complete nulling of the message signals at all eavesdroppers (for DF and AF), or the complete nulling of jamming signal at the destination (for CJ). Based on the designed relay weights, for DF in the presence of multiple eavesdroppers, and for CJ in the presence of one eavesdropper, the optimal power allocation is obtained in closed-form; in all other cases the optimal power allocation is obtained via iterative algorithms. Numerical evaluation of the obtained secrecy rate and transmit power results show that the proposed design can significantly improve the performance of secure wireless communications.
In this paper, the case of one source-destination pair with the help of multiple cooperating nodes in the presence of one eavesdropper was considered to improve the performance of secure wireless communications.A novel cooperative scheme decode-and-forward plus cooperative jamming(DFCJ) was proposed.In this scheme, the relay nodes transmit a weighted version of the source signals plus a common weighted jamming signal to confound the eavesdropper.For DFCJ, the optimal power allocation is obtained in closed-form in the condition of the complete nulling of jamming signals at the destination subject to a secrecy rate constraint.The numerical evaluation of the transmit power and the obtained secrecy rate results shows that the proposed scheme can significantly improve the performance of wireless physical layer security, as compared to the decodeand-forward(DF) scheme.
The feasibility of physical-layer-based security approaches for wireless communications in the presence of one or more eavesdroppers is hampered by channel conditions. In this paper, cooperation is investigated as an approach to overcome this problem and improve the performance of secure communications. In particular, a decode-and-forward (DF) based cooperative protocol is considered, and the objective is to design the system for secrecy capacity maximization or transmit power minimization. System design for the DF-based cooperative protocol is first studied by assuming the availability of global channel state information (CSI). For the case of one eavesdropper, an iterative scheme is proposed to obtain the optimal solution for the problem of transmit power minimization. For the case of multiple eavesdroppers, the problem of secrecy capacity maximization or transmit power minimization is in general intractable. Suboptimal system design is proposed by adding an additional constraint, i.e., the complete nulling of signals at all eavesdroppers, which yields simple closed-form solutions for the aforementioned two problems. Then, the impact of imperfect CSI of eavesdroppers on system design is studied, in which the ergodic secrecy capacity is of interest.
We employed node cooperation in a cooperative wireless network to achieve physical layer- based security. The case of a source-destination pair that works with the assistance of multiple cooperating nodes in the presence of an eavesdropper was considered in this study to improve the performance of secure wireless communications. A novel cooperative scheme, called the decode-and-forward plus cooperative jamming (DFCJ), was proposed. In this scheme, relay nodes transmit a weighted version of the source signals plus a common weighted jamming signal to confound the eavesdropper. The novel system design was proposed to determine cooperative node weights and transmit power allocation. In DFCJ, a closed-form solution is obtained to minimize the total transmit power that is subjected to a secrecy rate constraint under complete nulling of jamming signals at the destination. The results of the numerical evaluation of the transmit power and the obtained secrecy rate show that the proposed scheme can significantly improve the performance of wireless physical layer security compared with the original decode-and-forward scheme.
In a cooperative wireless network, we exploited node cooperation for achieving physical layer based security. In this paper, the case of one source-destination pair with the help of multiple cooperating nodes(relay nodes and jamming nodes) in the presence of one eavesdropper was considered to improve the performance of secure wireless communications. A novel cooperative scheme joint decode-and-forward and cooperative jamming(JDFCJ) was proposed. In this scheme, the relay nodes transmit a weighted version of the source signals and the jamming nodes just transmit a common weighted jamming signal to confound the eavesdropper. The novel system design is proposed to minimize the transmit power subject to a secrecy rate constraint. For JDFCJ, the optimal power allocation is obtained in closed-form in the condition of the complete nulling of jamming signals at the destination. The numerical evaluation of the transmit power results shows that the proposed scheme can significantly improve the performance of secure wireless communications, as compared to the DF scheme.