We investigate the impact of eavesdropping on the secrecy outage performance of dual-hop amplify-and-forward networks with a single untrusted relay, in which cooperative jamming technique is employed at the destination to realize positive secrecy rate. Under Nakagami-m fading channels, we derive tight closed-form and asymptotic expressions for the lower and upper bounds of the secrecy outage probability (SOP). Our results explicitly show that a secrecy diversity order of min(m1, m2/2) in terms of the SOP is achieved, where m1and m2are the respective integer fading parameters of the source-relay and relay-destination links. Afterwards, we propose an asymptotically optimal power allocation (OPA) scheme that minimizes the SOP. Numerical and simulation results show that the proposed OPA offers significant improvement on the SOP performance, especially in the case of m1> m2/2.
Impact of Relay’s Eavesdropping on Untrusted Amplify-and-Forward Networks Over Nakagami- m Fading
We investigate the impact of eavesdropping on the secrecy outage performance of dual-hop amplify-and-forward networks with a single untrusted relay, in which cooperative jamming technique is employed at the destination to realize positive secrecy rate. Under Nakagami-m fading channels, we derive tight closed-form and asymptotic expressions for the lower and upper bounds of the secrecy outage probability (SOP). Our results explicitly show that a secrecy diversity order of min(m1, m2/2) in terms of the SOP is achieved, where m1and m2are the respective integer fading parameters of the source-relay and relay-destination links. Afterwards, we propose an asymptotically optimal power allocation (OPA) scheme that minimizes the SOP. Numerical and simulation results show that the proposed OPA offers significant improvement on the SOP performance, especially in the case of m1> m2/2.
In this paper, we investigate the secrecy performance of a dual-hop cooperative untrusted relay network. In this network, a source node communicates with the destination node via an untrusted fixed-gain amplify-and-forward (AF) relay node. We use destination-assisted jamming so as to keep the source and destination nodes information confidential from the relay node. Under this scenario, we derive the exact secrecy outage probability (SOP) expression, tight approximate SOP expression, and asymptotic SOP expression in the high signal-to-noise ratio regime under Nakagami-m fading channels. The analysis studied in this paper can be applicable to any AF relaying systems for fixed relay gain, and two scenarios to calculate the fixed gain are compared in terms of SOP performance. Finally, the numerical and simulation studies corroborate our analytical findings.
The authors investigate the secrecy performance of a cooperative relaying network, wherein a fixed source communicates with a fixed destination via an amplify‐and‐forward mobile relay in the presence of a passive mobile eavesdropper. They assume that the source‐to‐relay channel and relay‐to‐destination channel experience Nakagami‐ m fading, whereas relay‐to‐eavesdropper link follows double Nakagami‐ m fading. Under such a mixed fading environment, they derive the novel tight closed‐form expressions for the secrecy outage probability (SOP), probability of non‐zero secrecy capacity, and intercept probability of the considered system. They also deduce the asymptotic secrecy outage and intercept probability expressions in the high signal‐to‐noise ratio regime to highlight the impact of fading parameters and channel conditions on the secrecy diversity order. It is shown that the system can achieve secrecy diversity order of min( ) in terms of SOP, and in terms of intercept probability, where and represent the fading severity parameters between source and relay and between relay and destination, respectively. They also formulate and investigate analytically two optimisation problems, namely, optimal relay location with fixed power allocation and optimal power allocation with fixed relay location, to minimise the system SOP. They verify analytical findings via numerical and simulation results.
In this paper, the secrecy outage performance of a three-node amplify-and-forward relay network with an untrustworthy relay is investigated. To enable a secure transmission, we consider a destination-based jamming technique to prevent the relay from successfully decoding the secret messages between the source and the destination. In addition, the relay is assumed to be an energy-constrained device, thus being first energized by the source in order to be able to retransmit the information to the destination. In doing so, a time switching-based simultaneous wireless information and power transfer scheme is used. A closed-form asymptotic expression for the secrecy outage probability is derived in order to obtain a tight approximation at medium-to-high signal-to-noise ratio. The accuracy of the performed analysis is corroborated by Monte Carlo simulations through different illustrative cases. Numerical results show the impact of key system parameters on the secrecy performance, such as the time allocation factor between the energy harvesting and information transmission phases, the power allocation factor between source and destination for cooperative jamming, and the relay position, so as to provide insights on the design criteria for energy efficient and secure networks.
In this paper, we investigate the performance of cooperative amplify-and-forward (AF) multi-relay networks with relay selection strategy over independent and identically distributed (i.i.d.) Nakagami-m fading channels. In this system we study multiuser cooperative relaying to have a secure transmission from source to destination, since transmitted information may be wiretapped by multiple eavesdroppers. The secrecy outage probability is derived in closed-form using signal-to-noise-ratio statistics, while a useful expression is presented for the asymptotically low outage regime. Our results explicitly demonstrate significant improvement of the secrecy outage probability in the multi-relay scenario.
Abstract—In this paper, the problem of secure transmission in two-hop amplify-and-forward (AF) systems with an untrusted relay is investigated. To prevent the untrusted relay from intercepting the source message and to achieve positive secrecy rate, the destination-based cooperative jamming (DBCJ) technique is used. In this method the destination sends an intended jamming signal to the relay. This jamming signal helps protecting the source message from being captured reliably at the untrusted relay, while the destination cancels itself intended jamming signal. The optimal power allocation (OPA) technique is considered for the presented system. It is observed that the objective function is a quasiconcave function at high signal-to-noise-ratio (SNR) regimes. Based on this OPA technique, we study the ergodic secrecy rate (ESR) and the secrecy outage probability (SOP) of the system when the source and relay are equipped with a single antenna while the destination is equipped with largescale antenna arrays (LSA). Using the achieved closed-form expressions, one can evaluate the performance of the secure system easily and fast and also, they provide significant insight for system design. Finally, simulation results indicate the accuracy of the derived expressions.
Secure Multiuser Scheduling in Downlink Dual-Hop Regenerative Relay Networks Over Nakagami- m Fading Channels
In this paper, we investigate the secrecy performance of multiuser dual-hop relay networks where a base station (BS) communicates with multiple legitimate users through the assistance of a trustful regenerative relay in the presence of multiple eavesdroppers. In particular, the maximal ratio transmission scheme is exploited at the BS and a threshold-based multiuser scheduling scheme is employed over the legitimate users, while concerning the imperfect decoding at the regenerative relay. To evaluate the secrecy performance of the considered system, two practical situations are addressed based on the availability of eavesdropper's channel state information (CSI), i.e., Scenario I, where the eavesdropper's CSI is not available at the relay, and Scenario II, where the eavesdropper's CSI is available at the relay. For both the scenarios, we further consider two eavesdropping modes, i.e., colluding eavesdropping and non-colluding eavesdropping. For Scenario I, new exact and asymptotic closed-form expressions for the secrecy outage probability (SOP) are derived. For Scenario II, we derive new exact and asymptotic closed-form expressions for the ergodic secrecy rate (ESR). The asymptotic SOPs demonstrate that the secrecy diversity order is independent of the number of legitimate users NB and eavesdroppers NE, the number of antennas equipped at eavesdroppers AE, as well as the fading factor of the wiretap channel mE. Furthermore, we also determine the secrecy multiplexing gain and the power cost to explicitly quantify the impact of the legitimate channel and wiretap channel on the ESR. Our findings demonstrate that increasing the switching threshold, the number of antennas at the BS, and the number of legitimate users has a positive impact on secrecy performance.