In this paper, a secured dual-hop confidential communication system is considered. In which, a source transmits secret information to the destination in the presence of an interferer and an eavesdropper. And, multiple relays provide cooperative diversity at the destination. The interferer, source and relays are equipped with single antenna whereas the destination and eavesdropper are equipped with multiple antennas. The maximum ratio combining (MRC) technique is used to get the best output SNR at the receiver. At the receiver, the expression of MRC combiner output SNR is derived using optimal weighting vector to protect the information from eavesdropping, so that the eavesdropper can't decipher the source message. Then, we derive the optimum secrecy capacity expression at the destination. The derived expressions and the numerical results show that there is an enhancement of secrecy capacity due to the strategy of optimization of the output SNR by weighting vector at the destination.
In this paper, a secured dual-hop confidential communication system is considered. In which, a source transmits secret information to the destination in the presence of an interferer and an eavesdropper. And, multiple relays provide cooperative diversity at the destination. The interferer, source and relays are equipped with single antenna whereas the destination and eavesdropper are equipped with multiple antennas. The maximum ratio combining (MRC) technique is used to get the best output SNR at the receiver. At the receiver, the expression of MRC combiner output SNR is derived using optimal weighting vector to protect the information from eavesdropping, so that the eavesdropper can't decipher the source message. Then, we derive the optimum secrecy capacity expression at the destination. The derived expressions and the numerical results show that there is an enhancement of secrecy capacity due to the strategy of optimization of the output SNR by weighting vector at the destination.
We consider a confidential communication system in which a source sends a confidential information to the destination in the presence of an eavesdropper. Multiple relays are used to provide cooperative diversity to the destination. The destination and the eavesdropper are equipped with multiple antennas while each relay and source are equipped with single antenna. We are interested to protect the transmitted information from eavesdropping and to find the effect of receive diversity on the secrecy capacity of the proposed model. We consider the maximal ratio combining (MRC) technique at the destination and derive the expression of combiner output signal-to-noise ratio (SNR) using optimum weighting vector so that the eavesdropper is unable to decode a single bit from the original massage. Finally, we derive the expression of optimum secrecy capacity in terms of the number of relays and the number of antennas at the destination. Our results show that the optimization of weighting vector at the receiver enhances secrecy capacity of a wiretap channel.
In this paper, a source communicates to the destination with the cooperation of a relay, in the presence of an eavesdropper. All the links undergo Rayleigh fading and perfect decoding at the relays is not considered. The secrecy outage probability expression is evaluated for a decode-and-forward (DF) dual-hop cooperative relay network, both with and without the presence of direct source to eavesdropper transmission link. The performance of the maximal ratio combining (MRC) and selection combining (SC) diversity at the eavesdropper is investigated. Asymptotic and diversity gain analysis for both the single relay and multi-relay system is obtained, when average SNRs of source-relay and relay-destination links are balanced or unbalanced. We have shown that the increase in target secrecy rate and eavesdropper channel quality significantly affects the outage performance of the system. We have investigated the outage probability of optimal relay selection scheme, when either full instantaneous channel state information (ICSI) or statistical channel state information (SCSI) of all the links is available and have shown that there is improvement in the secrecy performance with the increase in the number of relays.
We investigate the secrecy performance of dual-hop amplify-and-forward multi-antenna relaying systems over Rayleigh fading channels, considering the direct link between the source and the destination. In order to exploit the available direct link and the multiple antennas for secrecy improvement, different linear processing schemes at the relay and different diversity combining techniques at the destination are proposed, namely: 1) zero-forcing/maximal ratio combining (ZF/MRC); 2) ZF/selection combining (ZF/SC); 3) maximal ratio transmission/MRC (MRT/MRC); and 4) MRT/SC. For all these schemes, we present new closed-form approximations for the secrecy outage probability. Moreover, we investigate a benchmark scheme, i.e., cooperative jamming/ZF (CJ/ZF), where the secrecy outage probability is obtained in exact closed-form. In addition, we present asymptotic secrecy outage expressions for all the proposed schemes in the high signal-to-noise ratio (SNR) regime, in order to characterize key design parameters, such as secrecy diversity order and secrecy array gain. The outcomes of this paper can be summarized as follows: 1) MRT/MRC and MRT/SC achieve a full diversity order of M + 1, ZF/MRC and ZF/SC achieve a diversity order of M, while CJ/ZF only achieves unit diversity order, where M is the number of antennas at the relay; 2) ZF/MRC (ZF/SC) outperforms the corresponding MRT/MRC(MRT/SC) in the low SNR regime, while becomes inferior to the corresponding MRT/MRC (MRT/SC) in the high SNR; and 3) all the proposed schemes tend to outperform the CJ/ZF with moderate number of antennas, and linear processing schemes with MRC attain better performance than those with SC.
In this paper, the physical-layer security of a cooperative wireless system with multi-antenna full-duplex (FD) destination is examined. More specifically, we consider a cooperative transmission scenario in which a source communicates with a destination through a relay in the presence of an eavesdropper. In order to degrade the wiretap channel, the FD destination simultaneously transmits an interference signal towards the eavesdropper, while receiving information from the relay. A joint transmit and receive beamformer design is proposed to maximize the signal-to-interference-plus-noise ratio (SINR) at the destination, while guaranteeing that the SINR at the eavesdropper is below a certain threshold. We reformulate the optimization problem as a semidefinite relaxation problem in terms of a transmit beamforming matrix. To balance the performance and system complexity, we investigate suboptimum beamforming designs based on zero-forcing criterion. We derive exact closed-form expressions for the average secrecy rates of the proposed suboptimum designs. Our results reveal that optimum and suboptimum beamforming schemes along with friendly jamming significantly improve the secrecy performance. Moreover, simulation results demonstrate that the optimum scheme outperforms suboptimum schemes, especially in high transmit power regimes.
This paper studies the secrecy performance of an energy-harvesting relaying system in the presence of a dualuse source node and an eavesdropper.Specifically, the source has dual roles in the dual-hop communication: 1) to transmit confidential information in the first hop; 2) to generate jamming signal to interfere the eavesdropper in the second hop.Moreover, the multi-antenna relay deploys a power-splitting harvesting scheme to coordinate the information receiving and energy harvesting, and adopts maximal ratio combining technique to process the multiple copies of signals.Considering decode-andforward protocol and transmit antenna selection scheme, we derive an analytical expression for secrecy outage probability, and perform Monte Carlo simulation to validate the analysis.Analytical results show that the SOP performance with the dualuse source node can be effectively improved when the relaydestination channel does not have absolute advantage over the relay-eavesdropper channel.
In this paper, we consider a dual-hop amplify-and-forward (AF) multiple-input-multiple-output (MIMO) relay network, where the source, relay, and destination are each equipped with multiple antennas. The relay is untrusted if it is willing to forward the signal to the destination and, at the same time, acts as a potential eavesdropper to interpret the message from the source. Since there exists no direct link between the source and the destination, a positive secrecy rate cannot be obtained. Addressing this issue, we propose a joint destination-aided cooperative jamming and precoding at both the source and the relay scheme: joint source, relay, and destination precoding (JP). We target at maximizing the secrecy rate by jointly designing the source, relay, and destination precoding matrices and propose an alternating iterative optimization algorithm to tackle the nonconvex problem. Then, a comprehensive study on the asymptotic performance is conducted in a high signal-to-noise ratio (SNR) regime. In particular, we present simple closed-form expressions for the two key performance parameters in the asymptotic secrecy rate, i.e., the high-SNR slope and the high-SNR power offset. Finally, numerical results are conducted to demonstrate the validity of the proposed secure scheme and its performance analysis.