This paper studies the problem of secure dual-hop AF network in the presence of eavesdropper. We study the secrecy performance of partial relay selection with outdated channel state information (CSI). We propose a system secrecy where two sources and destination simultaneously transmit the legitimate and the jamming signal respectively. The selected relay forwards the combined signal to the legitimate receiver and the eavesdropper. We derive a closed-form expression for lower bound on the ergodic secrecy capacity (ESC) under different assumptions of the eavesdropper channel gains. We verify that the system performance is degraded as the correlation coefficient decreases. Simulation results are considered to verify the exactness of the proposed mathematical analysis.
This paper studies the problem of secure dual-hop AF network in the presence of eavesdropper. We study the secrecy performance of partial relay selection with outdated channel state information (CSI). We propose a system secrecy where two sources and destination simultaneously transmit the legitimate and the jamming signal respectively. The selected relay forwards the combined signal to the legitimate receiver and the eavesdropper. We derive a closed-form expression for lower bound on the ergodic secrecy capacity (ESC) under different assumptions of the eavesdropper channel gains. We verify that the system performance is degraded as the correlation coefficient decreases. Simulation results are considered to verify the exactness of the proposed mathematical analysis.
This paper studies cooperative transmission for securing a two‐hop network where the eavesdropper can wiretap the relay channels. With outdated channel state information (CSI), we propose an opportunistic relaying with destination‐based jamming scheme, where one relay is chosen to forward the confidential signal and the destination sends jamming signal to confuse the eavesdropper. To reveal the capability of the proposed scheme in improving the system secrecy, we investigate the two common performance metrics under different assumptions on the eavesdropper CSI. First, lower bound on the ergodic secrecy capacity (ESC) is derived assuming perfect knowledge of the eavesdropper channel gains. We, then, extend our results to the scenario where only the legitimate channel gain is known. Here, lower bound on the secrecy outage probability (SOP) is obtained. To further improve the utility of the destination, under total power constraint, a power allocation between data signal and jamming noise is considered. Both the analysis and simulation results indicate that the system performance is significantly improved in terms of both ESC and SOP when the jamming power at the destination is adjusted according to the selected relay position. We verify that, with outdated CSI, the secrecy performance of opportunistic relaying is severely degraded.
This paper studies the secrecy performance of an untrusted amplify-and-forward relaying network where both the relaying and the direct links are used to convey the source's information. Since relays act as eavesdroppers, a source-based jamming technique is proposed to keep the source's message secret from these helper nodes. We analyze the secrecy capacity of partial relay selection based on outdated channel state information. The study is conducted analytically by deriving the lower-bound expression for the ergodic secrecy capacity (ESC). We demonstrate through the simulation results the tightness of the derived bound. The use of the direct link is shown to improve the secrecy performance of the proposed scheme. In this case, we found that ESC performance with maximum ratio combining at the destination is better than that with selection combining. The system performance worsens as the correlation coefficient decreases. Furthermore, the maximum of ESC is achieved when relays are in the middle between the source and the destination with equal power allocation between the information and the jamming signals at the source.
In this paper, we study secure outdated-channel-state-information amplify-and-forward (SO-CSI-AF) relaying network using partial relay selection method. The best relay node is chosen based on the maximum instantaneous signal-to-noise ratio (SNR) of the first hop. We analyze a system with one source, multiple untrusted relays and one destination, where the relays act as eavesdroppers and a source-assisted-jamming technique is adopted. The jamming signal is transmitted by the source node to convey the information signal. We provide a closed-form expression for ergodic secrecy capacity considering Rayleigh fading channels. The accuracy of our proposed analysis is well demonstrated by simulation results. Moreover, we compare partial relay selection with reactive relay selection in secure untrusted relay networks. We obtain that our proposed system provides better performance especially when the relay is placed closer to the destination.
This paper investigates secure cooperative transmissions in a dual-hop MIMO relay system using a combined transmit antenna selection (TAS) and maximal-ratio combining (MRC) scheme over the Nakagami-m fading channels, where an adaptive decode-and-forward relaying protocol and an multi-antenna eavesdropper are considered. Due to the feedback delay, channel state information (CSI) for TAS might be outdated at both the source and the relay. To evaluate the secrecy performance of the TAS/MRC scheme and the impacts of outdated CSI, the closed-form expressions for the metrics of exact ergodic secrecy rate and exact secrecy outage probability are derived under both perfect and outdated CSI conditions in a channel feedback error model. In order to explicitly reveal the behaviors of the secrecy performance in high signal-to-noise ratio regime, asymptotic expressions for both the metrics are further derived. As validated by simulation results, analytically numerical results demonstrate that outdated the CSI always results in a loss in the secrecy performance, but the loss can be recovered by increasing the number of antennas at legitimate receivers. Furthermore, the outdated CSI yields a reduced secrecy diversity order, whereas only the perfect CSI leads to the full secrecy diversity order.
In this paper, the secrecy of a dual-hop unmanned aerial vehicle-based wireless communication system, in the presence of mobility and imperfect channel state information (CSI), is investigated. The system consists of a decode-and-forward relay connecting a source and destination node. The transmission is performed under the presence of two eavesdroppers aiming to intercept independently the source-relay and source-destination communication channels. It is assumed that the transmitters are equipped with one transmit antenna, while the receivers have multiple receive antennas. Based on the statistical properties of the per-hop signal-to-noise ratio (SNR), a closed-form formula for the network’s secrecy intercept probability (IP) is derived, in terms of the main system and channel parameters. The results correlate the impact of such parameters on the secrecy level of the system, where the latter can be enhanced by increasing the number of antennas at the legitimate receivers and the average SNRs of the legitimate links. Furthermore, it is shown that as the CSI imperfection level, nodes’ speed, delay, and carrier frequency increase, the system’s secrecy degrades. All the derived results are verified through Monte Carlo simulations.
We evaluate the upper bound, lower bound and an approximate expression for secrecy outage probability of a dual hop Amplify-and-forward (AF) relay system when the single cooperating relay among the relays is selected without the knowledge of eavesdropper's instantaneous channel state information (CSI). This situation arises when eavesdropper is not a legitimate node, or being a trusted node, it acts maliciously and does not share its instantaneous CSI. We also obtain the tighter bounds in high signal-to-noise ratio (SNR) of the source to relay links and in high SNR of the relay to destination links. We show that when the SNR of the source to relay links tends to zero, it becomes the bottle neck for secure communication, and the secrecy outage tends to 1. We show that the approximate expression follows the simulated outage closely and the outage decreases with an increase in the number of relays and increases with an increase in the required secrecy rate.