The design of a cooperative protocol relying on both cooperative relaying and jamming in order to provide security at the physical layer of wireless communications is considered in this paper. We suppose that pair of nodes is assisted by a number of helpers in their communication, which either relay information or cause harmful interference to an eavesdropper, at both stages of the relaying protocol. Instead of maximizing the secrecy capacity, a signal-to-noise ratio based approach is taken. Solutions for the optimal weights used at each protocol and stage are sought along with the optimal power distribution. To solve this problem, tools from semi-definite and geometric programming are utilized, and an iterative algorithm is proposed. Simulations show noticeable gains (up to 50dB) compared to the non-cooperative case.
The design of a cooperative protocol relying on both cooperative relaying and jamming in order to provide security at the physical layer of wireless communications is considered in this paper. We suppose that pair of nodes is assisted by a number of helpers in their communication, which either relay information or cause harmful interference to an eavesdropper, at both stages of the relaying protocol. Instead of maximizing the secrecy capacity, a signal-to-noise ratio based approach is taken. Solutions for the optimal weights used at each protocol and stage are sought along with the optimal power distribution. To solve this problem, tools from semi-definite and geometric programming are utilized, and an iterative algorithm is proposed. Simulations show noticeable gains (up to 50dB) compared to the non-cooperative case.
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.
Cooperative relaying and jamming are two efficient schemes to improve the physical-layer security of a wireless transmission in the presence of an eavesdropper. In this paper, we propose a hybrid cooperative relaying and jamming mechanism to enhance the security of a two-way relay network, where some intermediate nodes adopt distributed beamforming to improve the channel quality to legitimate terminals and others jam the eavesdropper, simultaneously. Subjected to the more practical per-node power constraint of each cooperative node, we propose a secrecy scheme to maximize the secrecy sum rate of the two terminals. It is shown that the problem can be transformed into a semi-definite programming (SDP) problem with an additional rank-1 constraint. We then propose a penalty function method and an iterative algorithm to solve such a problem efficiently, instead of the popular semi-definite relaxation (SDR) and randomization technique in the previous literature. Simulations show that the proposed hybrid schemes greatly improve the security of the two-way relay networks.
Exploiting the idea of cooperative communications is an efficient way to improve the physical-layer security of a wireless transmission in the presence of passive eavesdroppers. In this paper, we propose a hybrid cooperative relaying and jamming scheme to enhance the security of a two-way relay network, where some intermediate nodes help to relay the signal to the legitimate terminals via distributed beamforming and the others jam the eavesdropper simultaneously. In such a way, both two cooperative phases of the data transmission are protected. Subjected to the more practical per-node power constraint of each node and without the channel state information (CSI) of the eavesdropper, we propose a scheme to enhance the secrecy of the two terminals. It is shown that the problem can be transformed into a semidefinite programming (SDP) problem with an additional rank-1 constraint. We then develop a penalty function method and an iterative algorithm to solve such a problem efficiently, instead of the popular semi-definite relaxation (SDR) and randomization techniques proposed in the previous literatures. Simulations show that the proposed hybrid scheme greatly improves the security of the two-way relay networks.
We consider a cooperative wireless network in the presence of one or more eavesdroppers, and exploit node cooperation for achieving physical (PHY) layer based security. Two different cooperation schemes are considered. In the first scheme, cooperating nodes retransmit a weighted version of the source signal in a decode-and-forward (DF) fashion. In the second scheme, referred to as cooperative jamming (CJ), while the source is transmitting, cooperating nodes transmit weighted noise to confound the eavesdropper. We investigate two objectives: i) maximization of the achievable secrecy rate subject to a total power constraint and ii) minimization of the total power transmit power under a secrecy rate constraint. For the first design objective, we obtain the exact solution for the DF scheme for the case of a single or multiple eavasdroppers, while for the CJ scheme with a single eavesdropper we reduce the multivariate problem to a problem of one variable. For the second design objective, existing work introduces additional constraints in order to reduce the degree of difficulty, thus resulting in suboptimal solutions. Our work raises those constraints, and obtains either an analytical solution for the DF scheme with a single eavesdropper, or reduces the multivariate problem to a problem of one variable for the CJ scheme with a single eavesdropper. Numerical results are presented to illustrate the proposed results and compare them to existing work.
The feasibility of physical layer security approach for communication in the presence of one or more eavesdroppers. In the previous scheme, the one-way cooperative networks can be used for transferring information from source to destination. At present this technique is implemented without the eavesdroppers and it becomes ineffective due to sometimes attackers can hack the file. In future this work is carried out in two-way cooperative networks using two-stage cooperative protocol and the objective is to design the system for secrecy capacity maximization or transmit power minimization. The information can be divided into two halves then transferred into intermediate nodes and then merge the files to the destination. By implementing two-stage cooperative protocol will maximize the secrecy capacity in the presence of eavesdroppers by selecting relay and jamming nodes.
Cooperative jamming is an approach that has been recently proposed for improving physical layer based security for wireless networks in the presence of an eavesdropper. While the source transmits its message to its destination, a relay node transmits a jamming signal to create interference at the eavesdropper. In this paper, a scenario in which the relay is equipped with multiple antennas is considered. A novel system design is proposed for determining the antenna weights and transmit power of source and relay, so that the system secrecy rate is maximized subject to a total transmit power constraint, or, the transmit power is minimized subject to a secrecy rate constraint. Since the optimal solutions to these problems are difficult to obtain, suboptimal closed-form solutions are proposed that introduce an additional constraint, i.e., the complete nulling of jamming signal at the destination.