In this paper, we study the secrecy performance of cooperative single carrier system with the kth-best user selection scheme in Rayleigh fading channels. Assuming perfect decoding at the relay, we choose the legitimate user with the kth-best instantaneous signal-to-noise ratio (SNR) among Q users to receive the forwarded messages, which are intercepted at a passive eavesdropper simultaneously. To accurately assess the secrecy performance of the system, we derive exact closed-form expressions of secrecy outage probability and the probability of nonzero secrecy capacity to evaluate the impact of key parameters on the secrecy performance. Moreover, the asymptotic analysis is also performed to demonstrate that the secrecy diversity order is determined by both the number of channel taps and the index of the selected user. Finally, simulation results are provided to verify the correctness of the derived closed-form as well as asymptotic expressions.
In this paper, we study the secrecy performance of cooperative single carrier system with the kth-best user selection scheme in Rayleigh fading channels. Assuming perfect decoding at the relay, we choose the legitimate user with the kth-best instantaneous signal-to-noise ratio (SNR) among Q users to receive the forwarded messages, which are intercepted at a passive eavesdropper simultaneously. To accurately assess the secrecy performance of the system, we derive exact closed-form expressions of secrecy outage probability and the probability of nonzero secrecy capacity to evaluate the impact of key parameters on the secrecy performance. Moreover, the asymptotic analysis is also performed to demonstrate that the secrecy diversity order is determined by both the number of channel taps and the index of the selected user. Finally, simulation results are provided to verify the correctness of the derived closed-form as well as asymptotic expressions.
In this paper, the impact of multiple active eavesdroppers on cooperative single carrier systems with multiple relays and multiple destinations is examined. To achieve the secrecy diversity gains in the form of opportunistic selection, a two-stage scheme is proposed for joint relay and destination selection, in which, after the selection of the relay with the minimum effective maximum signal-to-noise ratio (SNR) to a cluster of eavesdroppers, the destination that has the maximum SNR from the chosen relay is selected. To accurately assess the secrecy performance, exact and asymptotic expressions are obtained in closed form for several security metrics, including the secrecy outage probability, probability of nonzero secrecy rate, and ergodic secrecy rate in frequency selective fading. Based on the asymptotic analysis, key design parameters, such as secrecy diversity gain, secrecy array gain, secrecy multiplexing gain, and power cost, are characterized, from which new insights are drawn. In addition, it is concluded that secrecy performance limits occur when the average received power at the eavesdropper is proportional to the counterpart at the destination. In particular, for the secrecy outage probability, it is confirmed that the secrecy diversity gain collapses to zero with outage floor, whereas for the ergodic secrecy rate, it is confirmed that its slope collapses to zero with capacity ceiling.
In this paper, the impact of multiple eavesdroppers on cooperative single carrier systems with multiple relays and multiple destinations is examined. To achieve the secrecy diversity gains in the form of opportunistic selection, a two-stage scheme is proposed for joint relay and destination selection, in which, after the selection of the relay with the minimum effective maximum signal-to-noise ratio (SNR) to a cluster of eavesdroppers, the destination that has the maximum SNR from the chosen relay is selected. In order to accurately assess the secrecy performance, the exact and asymptotic expressions are obtained in closed-form for the ergodic secrecy rate in frequency selective fading. Based on the asymptotic analysis, key design parameters such as multiplexing gain, and power cost are characterized, from which new insights are drawn. Moreover, it is concluded that capacity ceiling occurs when the average received power at the eavesdropper is proportional to the counterpart at the destination.
In this paper, we investigate the secrecy performance of cellular multiuser two-way decode-and-forward (DF) relay networks with physical-layer security constraints, wherein a multiantenna base station (BS) communicates bidirectionally with several single-antenna mobile stations (MSs) via single-antenna DF relay in the presence of a single-antenna eavesdropper. We employ antenna selection (AS) transmission scheme at the BS with MS scheduling. Specifically, we derive the closed-form expression for the secrecy outage probability (SOP) of the considered system under independent and identically distributed (i.i.d.) Rayleigh fading channels. To gain more insights into the system secrecy diversity order, we analyze the asymptotic secrecy outage behavior in the high signal-to-noise ratio (SNR) regime. Our results reveal that the SOP saturates in the medium-to-high SNR regime, and reduces the secrecy diversity order to zero. Finally, the numerical and simulation corroborate our theoretical and analytical findings.
In this paper, we investigate the secrecy performance of multiuser dual-hop relay networks where a base station (BS) communicates with multiple legitimate users via the assistance of a trustful regenerative relay in the presence of multiple eavesdroppers. In particular, the maximal ratio transmission (MRT) 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. Furthermore, we consider the passive eavesdropper scenario and non-colluding eavesdropping mode. In order to quantify the secrecy performance of the considered system, the new exact closed-form expression for the secrecy outage probability is derived. In addition, conducive and simple high SNR approximation for the secrecy outage probability is also presented, which capacitates further insights into the impact of key system parameters on secrecy performance. Numerical results are provided to verify our theoretical analyses and illustrate the impact of key system parameters on the secrecy outage performance.
We investigate the secrecy performance of a multiuser diversity scheme for an interference-limited wireless network with a base station (BS), N legitimate users, and an eavesdropper in the presence of a single dominant interferer. Assuming interference dominates noise power at the eavesdropper and at each legitimate user's receiver, the BS transmits information to the legitimate user with the kth best (highest) signal-tointerference ratio. We derive a closed-form expression for the secrecy outage probability for an arbitrary N and an asymptotic expression for a fixed k and large N. Furthermore, we derive a closed form asymptotic expression for the ergodic secrecy capacity of the kth best user and shows that it scales like O (log(N)) for a fixed k and large N.
In this paper, we present a comprehensive investigation on the secrecy performance of opportunistic relay selection systems employing the decode-and-forward protocol over Rayleigh fading channels. Considering a practical setting where direct link between the source node (Alice) and the destination node (Bob) is available, we study the secrecy performance of three different diversity combining schemes, namely, maximum ratio combining (MRC), distributed selection combining (DSC), and distributed switch-and-stay combining (DSSC). Throughout the analysis, we consider two different scenarios based on the availability of the eavesdropper's channel state information (CSI), i.e., Scenario A, where the eavesdropper's CSI is not available at Alice and the relay, and Scenario B, where Alice and the relay have knowledge about the eavesdropper's CSI. For Scenario A, we derive exact closed-form expressions for secrecy outage probability and simple asymptotic approximations for the secrecy outage probability, which enable the characterization of the achievable secrecy diversity order and coding gains. For Scenario B, we derive closed-form expressions for the achievable secrecy rates. For both scenarios, we investigate the impact of feedback delay (outdated CSI) on the secrecy performance wherein exact and asymptotic secrecy outage probability and closed-form expressions of the secrecy achievable rates are obtained. Our analytical findings suggest that both the MRC and DSC schemes achieve the maximum diversity order of K+1 where K is the number of relays. In addition, the feedback delay has a significant impact on the achievable secrecy performance by reducing the achievable diversity order to two.