In Rayleigh fading channels, to enhance the secrecy performance of wireless communication systems and efficiently disturb the interception of eavesdroppers, the multiple-antenna source node utilizes the artificial noise aided precoding (ANP) strategy with imperfect channel state information to emit the confidential information and the artificial noise simultaneously. Besides, the two-antenna decode-and-forward relay node applies the full-duplex (FD) relaying protocol, and the destination node which contains multiple antennas adopts the maximum ratio combining technique. Taking into account the existence of self-interference at the relay, the closed-form expression of approximate ergodic achievable secrecy rate (EASR) for any value of antenna number and that of exact EASR in the case of large-scale antenna array are derived, respectively. To extract more distinct insights from the considered system and hence obtain some simple and meaningful conclusions, the asymptotic performance analyses in two different asymptotic cases are studied. The numerical simulations validate the correctness of our theoretical derivation and analysis, which indicates that the ANP scheme combined with the FD relaying can achieve considerable secrecy performance.
In Rayleigh fading channels, to enhance the secrecy performance of wireless communication systems and efficiently disturb the interception of eavesdroppers, the multiple-antenna source node utilizes the artificial noise aided precoding (ANP) strategy with imperfect channel state information to emit the confidential information and the artificial noise simultaneously. Besides, the two-antenna decode-and-forward relay node applies the full-duplex (FD) relaying protocol, and the destination node which contains multiple antennas adopts the maximum ratio combining technique. Taking into account the existence of self-interference at the relay, the closed-form expression of approximate ergodic achievable secrecy rate (EASR) for any value of antenna number and that of exact EASR in the case of large-scale antenna array are derived, respectively. To extract more distinct insights from the considered system and hence obtain some simple and meaningful conclusions, the asymptotic performance analyses in two different asymptotic cases are studied. The numerical simulations validate the correctness of our theoretical derivation and analysis, which indicates that the ANP scheme combined with the FD relaying can achieve considerable secrecy performance.
In Rayleigh fading channels, we investigate the secrecy performance of a full-duplex relay secure transmission system. To improve the secrecy capacity of the system and efficiently interfere the interception of the eavesdropper, the multiple-antenna source applies the artificial noise aided precoding (ANP) scheme to broadcast the intended signal and the artificial noise simultaneously, and the decode-and-forward relay operates in full- duplex mode. To improve the received signal-to-noise ratio (SNR), the multiple-antenna destination applies maximum ratio combining (MRC) strategy. In the presence of self-interference at the relay, the approximate closed-form expression of ergodic achievable secrecy rate (EASR) for any values of antenna number and the exact closed-form expression of EASR for large-scale antennas array were derived respectively. Both the theoretical analysis and numerical simulations show that the ANP combined with full-duplex scheme can achieve considerable secrecy performance gain.
Considering existing eavesdroppers, this paper analyzes the secrecy outage probability (SOP) of the full-duplex (FD) relaying network with imperfect channel state information (CSI), where the decode-and-forward relay protocol is adopted. To enhance the physical-layer security, two relay selection schemes are proposed. The first scheme uses the maximum-minimum principle to select the optimal relay. The other selection scheme is based on partial signal-to-interference-plus-noise ratio. Then, the tight closed-form approximations of the SOP are obtained for three special CSI cases, respectively. Moreover, based on these approximated results, the effects of some system parameters are analyzed for the SOP of the relay system, including the CSI error, the number of relays, the signal-to-noise ratio (SNR) of the eavesdropper, and the residual self-interference caused by the FD model. The numerical results show that at low SNR of the eavesdropper, residual self-interference has a significantly impact on SOP, while at high SNR of the eavesdropper, this effect is negligible. In addition, the SOP of FD model is always superior to the half-duplex (HD) model when the number of relays changes.
To provide reliable connectivity in recent and future wireless communication systems, it is necessary to deploy several relay nodes. Further, a full-duplex (FD) technique has been in the spotlight since it can significantly improve spectral efficiency, and thus recent studies in relaying networks have considered FD relays. In relaying networks, confidentiality between the source and destination nodes from the relay node should be carefully kept since the relay node cannot be fully trusted, so calleduntrustedrelay node. To this end, in this paper, we consider physical-layer security taking into account an untrusted FD relay node. We investigate a secure relaying protocol against the untrusted relay node where the destination generates artificial noise to prevent the untrusted relay from decoding the source information. We derive the analytical expression of the lower bound of the ergodic secrecy rate (Rˉ). We find two main factors affecting the secrecy performance: residual self-interference (RSI) at the FD-available nodes (i.e., relay and destination), and outdated channel state information (CSI) at the destination. Thereafter, we evaluate their effects onRˉand suggest the algorithm to find the sub-optimal artificial noise power level at the destination for maximizingRˉ. Through simulations, we have verified our mathematical derivation and shown that our secure relaying protocol can achieve near-optimal secrecy performance. Numerical results imply that the artificial noise power level should be carefully considered when the channel is severely outdated and RSI is irresistible.
We assume a full-duplex (FD) cooperative network subject to hostile attacks and undergoing composite fading channels. We focus on two scenarios: a) the transmitter has full CSI, for which we derive closed-form expressions for the average secrecy rate; and b) the transmitter only knows the CSI of the legitimate nodes, for which we obtain closed-form expressions for the secrecy outage probability. We show that secure FD relaying is feasible, even under strong self-interference and in the presence of sophisticated multiple antenna eavesdropper.
In this article, a new relay-aided secure communication system is investigated, where a transmitter sends signals to a destination via an amplify-and-forward (AF) relay in the presence of an eavesdropper. We consider a general system configuration, where the source, relay, destination, and eavesdropper are all equipped with multiple antennas. In the practical scenarios of unknown eavesdropper's channel state information (CSI) and uncertainty of the eavesdropper's location, we aim to maximize the expected value of the system secrecy rate over the presumed distribution of the eavesdropper's channels, by exploiting the artificial noise (AN) transmitted by the source and relay nodes. The system design issue is formulated as a nonconvex stochastic optimization problem with a source transmission power constraint and a nonconvex relay transmission power constraint. A novel computational method is proposed to solve this challenging problem. The new method is developed based on an exact penalty function method together with a parallel stochastic decomposition algorithm. Numerical simulations are performed to study the effectiveness of the proposed scheme at various locations of the eavesdropper. Simulation results show that for most cases, secure communication can be achieved without the CSI knowledge of eavesdropper's channels, and the achievable secrecy rate follows the trend of a benchmark system where the eavesdropper's full CSI is available. In particular, the achievable system secrecy rate increases with the number of antennas at the legitimate users. Moreover, the optimal power allocated for the transmission of the AN increases with the system signal-to-noise ratio. The proposed computational method achieves a higher system secrecy rate than a conventional penalty function based approach.
This paper investigates the ergodic achievable secrecy rate (EASR) of multiple-antenna amplify-and-forward relay systems, where one eavesdropper can wiretap the relay. To reveal the capability of the multiple-antenna relay in improving the secrecy performance, we derive new tight closed-form expressions of the EASR for three secure transmission schemes: artificial noise aided precoding (ANP), destination based jamming (DBJ) and eigen-beamforming (EB). We also derive the lower bounds of the EASR for ANP and DBJ with a large antenna array at the relay, and investigate their corresponding asymptotic performance in the high SNR and low SNR regimes to show valuable intrinsic insights as well. Based on the asymptotic analysis, we optimally allocate the power to the information signal and the artificial noise. Both the analysis and simulation results indicate that, in the moderate-to-high SNR regime, ANP achieves considerable performance gain over DBJ and EB, while in the low SNR regime, EB outperforms the other two schemes with equal power allocation. As SNR grows large, the EASR of EB approaches a constant independent of the first hop channel. Moreover, in the high SNR regime, it is optimal to allocate around half of total power to artificial noise for ANP and most of the power to artificial noise for DBJ.