In this paper the cooperation of beam-forming and artificial noise (AN) in two-hop amplify-and- forward (AF) relaying system is proposed to enhance the security. we consider a half duplex AF relaying network with a multi-antenna source node and a destination in the presence of a passive eavesdropper.Since channel state information (CSI) of the eavesdropper is unknown, the AN transmitted by the source in the first phase and by the relays in the second phase is in all directions except the legitimate node one. As such two scenarios are considered here,: i) when all the relays amplify and forward the information source signal ii) when only the best relay is selected to amplify and forward the information source signal. The beam-former weights and the power allocation are obtained by solving an optimization problem. Results reveal that the proposed system can provide considerable improvements in terms of secrecy rate. It is also found that increasing the AN power, relative to the information signal power, will further improve the secrecy rate.
In this paper the cooperation of beam-forming and artificial noise (AN) in two-hop amplify-and- forward (AF) relaying system is proposed to enhance the security. we consider a half duplex AF relaying network with a multi-antenna source node and a destination in the presence of a passive eavesdropper.Since channel state information (CSI) of the eavesdropper is unknown, the AN transmitted by the source in the first phase and by the relays in the second phase is in all directions except the legitimate node one. As such two scenarios are considered here,: i) when all the relays amplify and forward the information source signal ii) when only the best relay is selected to amplify and forward the information source signal. The beam-former weights and the power allocation are obtained by solving an optimization problem. Results reveal that the proposed system can provide considerable improvements in terms of secrecy rate. It is also found that increasing the AN power, relative to the information signal power, will further improve the secrecy rate.
In this paper, we propose a destination-assisted jamming and beamforming (DAJB) scheme for physical layer security in a one-way cooperative amplify-and-forward (AF) relay communication system. The system model consists of one source, one destination, one eavesdropper, and N relay nodes, with the individual power constraint of each relay node and the destination-assisted jamming node as well as unknown instantaneous channel state information (CSI) of the eavesdropper. Due to the half-duplex constraint of the relay nodes, there are two phases in our proposed DAJB scheme. In the first phase, the source node broadcasts information signal and all N relay nodes listen simultaneously. In the meantime, the destination node transmits the jamming signal to confuse the potential eavesdropper. In the second phase, all N relay nodes amplify and forward the received signals, covered by the artificial noise (AN), to the destination using the distributed beamforming technology. The optimal beamformer weights and power allocation are obtained by solving the second-order convex cone programming (SOCP) together with a linear programming (LP) problem. Furthermore, the performance of the DAJB scheme is analyzed in terms of the achievable secrecy rate. Compared with the scheme that selects a relay node as the jammer, we obtain larger power gain to achieve higher secrecy rates. Finally, the simulation results verify that the DAJB scheme greatly improves the secrecy rate of a one-way cooperative AF relay communication system.
The idea of multiuser (nodes) cooperation is an efficient way to improve the physical-layer security of a wireless transmission in the presence of passive eavesdroppers. However, due to the half-duplex constraint of the practical transceivers, two phases are required for one round of data transmission, which grants the eavesdroppers two opportunities to wiretap the information. Therefore, protecting the data transmissions in both phases is critical. Toward this end, we propose a joint cooperative beamforming, jamming, and power-allocation scheme to enhance the security of an amplify-and-forward (AF) cooperative relay network in this paper. Different from the existing works assuming that the source node always uses its total power, we show that the secrecy rate is a quasi-concave function of the power of the source node so that allocating its total power may not be optimal. The beamformer design and power optimization problem can be solved by a bisection method together with a generalized eigenvalue decomposition, which has a semiclosed form and is computationally very convenient. Simulations show that the joint scheme greatly improves the security.
Cooperative relaying and cooperative jamming have been used to improve the secrecy of wireless networks. In this paper, Artificial Noise (AN) based secrecy enhancement of a dual-hop wireless network consisting of ‘n’ amplify-and-forward (AF) relays in the presence of a passive eavesdropper (E) is studied. A practical setting where direct links exist between source-destination (S-D) and source-eavesdropper (S-E) is considered. The source allocates some of its available power to transmit AN in order to confuse the eavesdropper and thereby degrades its channel. The optimum power allocation factor (a) and maximum secrecy rate are estimated analytically and by simulation. The performance is evaluated based on secrecy rate (Rs) and bit error rate (BER); for the case of randomly distributed relays and for any eavesdropper location. Numerical results show the improvement of the proposed cooperative scheme over other schemes.
Securing the wireless transmissions in the physical layer is a new perspective of security. In a wireless relay system, cooperative beamforming and jamming are two efficient schemes to improve the physical-layer security in the presence of passive eavesdroppers. However, in most works these two techniques are used in phase II of the cooperative transmission, which leaves the phase I out of protection. In this paper, we propose a joint cooperative beamforming and jamming scheme to enhance the security of a cooperative relay network, where a part of intermediate nodes adopt distributed beamforming while others jam the eavesdropper, simultaneously, such that both phases are secured. Since the instantaneous channel state information (CSI) of the eavesdropper may not be known, we propose a cooperative artificial noise transmission based secrecy strategy, subjected to the individual power constraint of each node. The beamformer weights and power allocation can be obtained by solving a second-order convex cone programming (SOCP) together with a linear programming problem. Simulations show the joint scheme greatly improves the security.
In this letter, we propose a novel scheme to improve physical layer security for amplify-and-forward (AF) relay networks with two-hop information leakage. Unlike traditional joint cooperative beamforming (CB) and cooperative jamming (CJ) design, where mere artificial noise (AN) is exploited by the jammers to degrade eavesdroppers' channels, in our proposed scheme, the jammers send AN along with the confidential signal to simultaneously confuse the eavesdroppers and enhance the quality of received signals at the destination. In particular, the CB vectors and AN covariance matrix are jointly optimized for the relays and jammers under individual power constraints. By decoupling this resultant design problem, suboptimal solutions are obtained using the semidefinite relaxation technique. Simulation results are also provided to demonstrate that the proposed scheme has an obvious advantage in enhancing the secrecy rate.
In this paper, we investigate secrecy communications in two-hop wireless relaying networks which consist of one source, one amplify-and-forward (AF) relay, one legitimate destination, and one eavesdropper. To prevent the eavesdropper from intercepting the source message, we make the destination send the intended noise to the AF relay during the first phase. This is referred to as cooperative jamming. According to the channel information at the destination, we address two types of jamming power allocation; (i) rate-optimal power allocation and (ii) outage-optimal power allocation. More specifically, without the instantaneous channel knowledge for the eavesdropper side, the outage probability of the secrecy rate is minimized with respect to the intended noise power level. We show that the outage-optimal allocation gives almost the same outage probability as the rateoptimal one. In addition, the jamming power consumption can be significantly reduced compared to the fixed and rate-optimal power allocation methods.