In this letter, we propose a tag selection scheme to enhance the security transmission in a passive backscatter communication system with multiple tags and one eavesdropper, and analyze the secrecy outage probability (SOP). In particular, considering a practical non-linear energy harvesting model, we first determine the optimal dynamic reflection coefficient to maximize the power of the backscattered signal while satisfying the energy-causality constraint of tags, and then select the tag that can maximize the instantaneous secrecy capacity. The closed-form analytical expression of the SOP corresponding to the proposed tag selection scheme over the independent but not necessarily identically distributed Rayleigh fading channels is derived and the diversity gain is analyzed. Numerical simulations corroborate the theoretical analysis and exhibit the superior performance of the proposed scheme compared to other schemes.
In this letter, we propose a tag selection scheme to enhance the security transmission in a passive backscatter communication system with multiple tags and one eavesdropper, and analyze the secrecy outage probability (SOP). In particular, considering a practical non-linear energy harvesting model, we first determine the optimal dynamic reflection coefficient to maximize the power of the backscattered signal while satisfying the energy-causality constraint of tags, and then select the tag that can maximize the instantaneous secrecy capacity. The closed-form analytical expression of the SOP corresponding to the proposed tag selection scheme over the independent but not necessarily identically distributed Rayleigh fading channels is derived and the diversity gain is analyzed. Numerical simulations corroborate the theoretical analysis and exhibit the superior performance of the proposed scheme compared to other schemes.
In this letter, we investigate a multi-tag backscatter communication system in the presence of an eavesdropper. In order to strengthen transmission security, the optimal tag is chosen among N tags. We consider a practical backscatter communication scenario, where channel correlation between the forward and backscatter links may exist and we study its impact on the system's security. Specifically, we derive an analytical expression for the secrecy outage probability (SOP). Moreover, in order to gain more insights for the system design, we obtain an asymptotic closed-form expression for the SOP over correlated Rayleigh fading channels. Finally, simulations are performed to validate the theoretical analysis.
This paper studies the secrecy outage performance (SOP) of an energy-harvesting multi-backscatter-device (BD) network in the presence of a passive eavesdropper. A dedicated radio-frequency source illuminates multiple BDs employing power splitting (PS), and the BD with the strongest source-to-BD channel is opportunistically selected for confidential backscatter transmission. Unlike conventional secure backscatter communication models that assume an always-active BD, we explicitly impose a practical circuit-activation constraint requiring the selected BD to harvest sufficient energy before transmission. Consequently, the selected source-to-BD channel jointly determines circuit availability and the strengths of the legitimate and wiretap cascaded links. A tractable analytical framework for the SOP is developed by accounting for activation failure, secrecy-rate outage, opportunistic selection, PS, and Rayleigh fading. Since the activation constraint yields a non-zero lower integration bound, we derive a finite-sum approximation using the binomial expansion and Gaussian -Chebyshev quadrature. We further obtain a high-signal-to-noise-ratio expression that reveals a non-zero secrecy outage floor caused by the proportional scaling of the legitimate and eavesdropping links. Monte Carlo simulations validate the analysis and show that increasing the number of candidate BDs improves secrecy performance, particularly in energy-limited regimes, but with diminishing returns. The results also reveal the trade-off between circuit activation and backscattered-signal strength and quantify the effects of the activation threshold, PS coefficient, and channel conditions on secrecy performance. Keywords: Energy harvesting, backscatter communication, physical layer security, secrecy outage probability, power splitting
In this paper, we consider an active eavesdropping scenario in a cooperative system consisting of a source, a destination, and an active eavesdropper with multiple decode-and-forward relays. Considering an existing assumption in which an eavesdropper is also a part of network, a proactive relay selection by the eavesdropper is proposed. The best relay which maximizes the eavesdropping rate is selected by the eavesdropper. A relay selection scheme is also proposed to improve the secrecy of the system by minimizing the eavesdropping rate. Performances of these schemes are compared with two passive eavesdropping scenarios in which the eavesdropper performs selection and maximal ratio combining on the relayed links. A realistic channel model with independent non-identical links between nodes and direct links from the source to both the destination and eavesdropper are assumed. Closed- form expressions for the secrecy outage probability (SOP) of these schemes in Rayleigh fading channel are obtained. It is shown that the relay selection by the proactive eavesdropper is most detrimental to the system as not only the SOP increases with the increase in the number of relays, but its diversity also remains unchanged.
In this paper, the secrecy outage probability (SOP) for the proposed secure decode-and-forward (DF) cooperative networks with non-linear energy harvester is investigated. The energy-constrained relays are considered and the harvested energy is described using a practical non-linear energy harvesting model, whose non-linear property is depicted by a piecewise linear model. On the premise of the harvested power satisfying its own consumption, the optimal dynamic power splitting (PS) factor is designed to maximize the power of the transmitted signal at relays. Then the relay that can maximize the secrecy capacity is selected to convey the information through relay selection scheme. The analytical results of the SOP for the proposed network with practice non-linear energy harvester are derived. The numerical results verify the theoretical analysis and show the superior performance compared to other counterparts under the different parameters.
This paper studies the secrecy rate maximization problem of a secure wireless communication system in the presence of multiple eavesdroppers. The security of the communication link is enhanced through cooperative jamming with the help of multiple jammers. First, a feasibility condition is derived to achieve a positive secrecy rate at the destination. Then, we solve the original secrecy rate maximization problem, which is not convex in terms of power allocation at the jammers. To circumvent this nonconvexity, the achievable secrecy rate is approximated for a given power allocation at the jammers, and the approximated problem is formulated into a geometric programming one. Based on this approximation, an iterative algorithm has been developed to obtain the optimal power allocation at the jammers. Next, we provide a bisection approach, based on 1-D search, to validate the optimality of the proposed algorithm. In addition, by assuming Rayleigh fading, the secrecy outage probability (SOP) of the proposed cooperative jamming scheme is analyzed. More specifically, a single-integral form expression for the SOP is derived for the most general case, as well as a closed-form expression for the special case of two cooperative jammers and one eavesdropper. Simulation results have been provided to validate the convergence and the optimality of the proposed algorithm, as well as the theoretical derivations of the presented SOP analysis.
For cooperative systems, in which an eavesdropper overhears source information through relays' transmission, an optimal relay selection (ORS) scheme has recently been proposed to improve the system secrecy performance. In this letter, we evaluate the secrecy outage probability (SOP) of the ORS scheme with an amplify-and-forward system over independent and non-identically distributed Rayleigh fading. More specifically, we derive a tight approximation on the SOP. Thereafter, by analyzing asymptotic behaviour of the derived approximation, novel insights are revealed. The derivations are confirmed through Monte Carlo simulations.