In this paper, we study the impact of correlated fading on the secrecy performance of multiple decode-and-forward (DF) relaying with outdated relay selection. It is assumed that the information transmission, assisted by N DF relays from the source to the destination, can be overheard by an eavesdropper. Particularly, we consider the realistic scenario where the eavesdropper's and the main channels are correlated. In order to enhance the network security, the best relay is selected among N available DF relays to assist the secure transmission. Due to the time-varying channel environments, we note that the selected relay may be outdated. In order to study the impact of both channel correlation and outdated relay selection on the secrecy performance, we first derive an analytical expression for the secrecy outage probability (SOP). Also, we derive the asymptotic expression for the SOP in the high main-to-eavesdropper ratio regime. Numerical results are provided to demonstrate the correctness of our analytical expressions.
This paper quantifies the impact of correlated fading on secure communication of multiple amplify-and-forward (AF) relaying networks. In such a network, the base station (BS) is equipped with multiple antennas and communicates with the destination through multiple AF relays, while the message from the relays can be overheard by an eavesdropper. We focus on the practical communication scenario, where the main and eavesdropper's channels are correlated. In order to enhance the transmission security, transmit antenna selection is performed at the BS, and the best relay is chosen according to the full- or partial-relay selection criterion, which relies on the dual-hop relay channels or the second-hop relay channels, respectively. For these criteria, we study the impact of correlated fading on the network secrecy performance, by deriving an analytical approximation for the secrecy outage probability and an asymptotic expression for the high main-to-eavesdropper ratio. From these results, it is concluded that the channel correlation is always beneficial to the secrecy performance of full relay selection. However, it deteriorates the secrecy performance if partial-relay selection is used, when the number of antennas at the BS is less than the number of relays.
This paper proposes relay selection to increase the physical layer security in multiuser cooperative relay networks with multiple amplify-and-forward relays, in the presence of multiple eavesdroppers. To strengthen the network security against eavesdropping attack, we present three criteria to select the best relay and user pair. Specifically, criteria I and II study the received signal-to-noise ratio (SNR) at the receivers, and perform the selection by maximizing the SNR ratio of the user to the eavesdroppers. To this end, criterion I relies on both the main and eavesdropper links, while criterion II relies on the main links only. Criterion III is the standard max-min selection criterion, which maximizes the minimum of the dual-hop channel gains of main links. For the three selection criteria, we examine the system secrecy performance by deriving the analytical expressions for the secrecy outage probability. We also derive the asymptotic analysis for the secrecy outage probability with high main-to-eavesdropper ratio. From the asymptotic analysis, an interesting observation is reached: for each criterion, the system diversity order is equivalent to the number of relays regardless of the number of users and eavesdroppers.
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.
We study the secrecy outage probability of the amplify-and-forward (AF) relaying protocol, which consists of one source, one destination, multiple relays, and multiple eavesdroppers. In this system, the aim is to transmit the confidential messages from a source to a destination via the selected relay in presence of eavesdroppers. Moreover, partial relay selection scheme is utilized for relay selection based on outdated channel state information where only neighboring channel information (source-relays) is available and passive eavesdroppers are considered where a transmitter does not have any knowledge of eavesdroppers’ channels. Specifically, we offer the exact secrecy outage probability of the proposed system in a one-integral form as well as providing the asymptotic secrecy outage probability in a closed-form. Numerical examples are given to verify our provided analytical results for different system conditions.
Abstract We investigate the secrecy performance of cellular multiuser two‐way relay networks, where the bidirectional information exchange between a multiantenna base station (BS), and several users can be accomplished with the assistance of decode‐and‐forward relay(s) in the presence of a multiantenna passive eavesdropper. We employ low‐complexity antenna selection strategy at the BS coupled with user scheduling for maximizing the end‐to‐end signal‐to‐noise ratios (SNRs). To enhance the wiretap probability, the eavesdropper applies a maximal ratio combining technique to combine the received signals. Under such considerations, in the single‐relay scenario, we deduce the exact closed‐form secrecy outage probability (SOP) expression under Rayleigh fading channels. For more insights into the system secrecy diversity order, we derive the closed‐form asymptotic SOP expressions at high SNR based on the quality of the main and wiretap links. In the multirelay scenario, we formulate an opportunistic relay selection strategy, followed by its impact on the SOP performance in the presence of Rayleigh channels. To show the impact of multiple relays on the secrecy diversity order, we derive the asymptotic SOP expressions in the high SNR regime depending on the quality of the main and wiretap links. It is shown from the asymptotic SOP expressions under both single‐relay and multirelay scenarios that the secrecy diversity order reduces to zero in the high SNR regime, regardless of number of antennas, number of users, and number of relays. Our results also reveal that the SOP performance diminishes with an increased number of eavesdropper antennas. Numerical and simulation results verify our derived analytical findings.