In this letter, we propose a user scheduling scheme, which enables non-scheduled users to generate artificial noise in order to enhance wireless security in a multiuser wiretap network, where there exist N users, a single desired receiver, and K eavesdroppers. Our proposed scheme can achieve the optimal multiuser diversity gain (i.e., log log N) by adopting appropriate threshold values for scheduling feedback, which is also able to significantly reduce signaling overhead. We mathematically prove the achievability based on the derivation of a secure user-scaling law. Simulation results demonstrate that the proposed scheme achieves a better average secrecy rate than the conventional scheme in a finite N case, even if both schemes obtain the same secure user-scaling law as N → ∞.
In this letter, we propose a user scheduling scheme, which enables non-scheduled users to generate artificial noise in order to enhance wireless security in a multiuser wiretap network, where there exist N users, a single desired receiver, and K eavesdroppers. Our proposed scheme can achieve the optimal multiuser diversity gain (i.e., log log N) by adopting appropriate threshold values for scheduling feedback, which is also able to significantly reduce signaling overhead. We mathematically prove the achievability based on the derivation of a secure user-scaling law. Simulation results demonstrate that the proposed scheme achieves a better average secrecy rate than the conventional scheme in a finite N case, even if both schemes obtain the same secure user-scaling law as N → ∞.
In this correspondence paper, we propose a secure user scheduling scheme, which selects a user for data transmission and an extra user for artificial noise generation in a multiuser single-input and multiple-output wiretap network. The proposed scheme does not require the instantaneous channel state information of the eavesdropper but effectively reduce the secrecy outage probability. Specifically, the secrecy outage probability of the proposed scheme is mathematically derived in closed form when we consider maximum-ratio combining at both desired receiver and eavesdropper. Through simulations, we verify our analytical results and investigate the effect of unknown location of the eavesdropper on the secrecy outage probability when we consider the notion of a secrecy protected zone.
In this paper, we investigate achievable secrecy sumrate in uplink multiuser networks where some base stations are compromised to operate as potential eavesdroppers. Due to the difficulty of analyzing the exact secrecy capacity region in multiuser networks, we focus on analyzing the secrecy sumrate scaling in terms of the number of transmitters based on multiuser diversity (MUD). We propose an opportunistic user scheduling scheme able to achieve optimal MUD gain in uplink multiuser networks whereNtransmitters (users), a single desired receiver (i.e., base station), andKpotential eavesdroppers (i.e., compromised base stations) are assumed. The proposed scheme enables multiuser transmissions in one scheduling time slot by employing orthogonal random beamforming at the receiver. In addition, the proposed scheme can fully exploit the degrees-of-freedom (DoF) gain when each transmitter is equipped with a single antenna, and base station and potential eavesdroppers are equipped withMantennas. The main results show that the proposed scheduling scheme achieves the optimal secrecy sum-rate scaling indicating that the achievable secrecy sum-rate scales asMlog (SNR log N) in a high signal-to-noise ratio (SNR) regime when a certain user scaling condition.
In this paper, we consider a multiuser downlink wiretap network consisting of one base station (BS) equipped with AA antennas, NB single-antenna legitimate users, and NE single-antenna eavesdroppers over Nakagami-m fading channels. In particular, we introduce a joint secure transmission scheme that adopts transmit antenna selection at the BS and explores threshold-based selection diversity scheduling over legitimate users to achieve a good secrecy performance while maintaining low implementation complexity. More specifically, in an effort to quantify the secrecy performance of the considered system, two practical scenarios are investigated, i.e.: in Scenario I, the eavesdropper's channel state information (CSI) is unavailable at the BS, and in Scenario II, the eavesdropper's CSI is available at the BS. For Scenario I, novel exact closed-form expressions for the secrecy outage probability are derived, which are valid for general networks with an arbitrary number of legitimate users, antenna configurations, number of eavesdroppers, and the switched threshold. For Scenario II, we take into account the ergodic secrecy rate as the principle performance metric, and derive novel exact closed-form expressions for the ergodic secrecy rate. In addition, we also provide simple and asymptotic expressions for secrecy outage probability and ergodic secrecy rate under two distinct cases, i.e.: in Case I, the legitimate user is located close to the BS, and in Case II, both the legitimate user and eavesdropper are located close to the BS. Our important findings reveal that the secrecy diversity order is AAmA and the slope of secrecy rate is one under Case I, while the secrecy diversity order and the slope of secrecy rate collapse to zero under Case II, where the secrecy performance floor occurs. Finally, when the switched threshold is carefully selected, the considered scheduling scheme outperforms other well-known existing schemes in terms of the secrecy performance and complexity tradeoff.
In this paper, we investigate two user scheduling algorithms (optimal user and threshold-based user scheduling algorithms) when we consider potential eavesdroppers in an uplink wiretap network. The optimal user scheduling (OUS) algorithm selects the user who has the maximum secrecy rate, based on channel feedback from all users. On the other hand, the threshold-based user scheduling (TUS) algorithm first considers the information leakage from the users to potential eavesdroppers and then selects the user among candidates who satisfy a threshold criterion on the information leakage. The OUS algorithm shows an optimal performance in terms of secrecy rate, but the TUS algorithm can achieve secrecy rate comparable with the OUS algorithm with reduced feedback overhead. For main contributions, we mathematically analyze the asymptotic behavior of the achievable secrecy rate of two scheduling algorithms when the signal-to-noise ratio (SNR) approaches to infinity. Further, we derive the approximated secrecy rate of the TUS algorithm and propose criteria to determine threshold values which maximize the achievable secrecy rate of the TUS algorithm. We verify our analytical results through simulations. We perform an extra simulation to investigate the effect of channel estimation error in the wiretap links on the average secrecy rate. Due to different scheduling principles in OUS and TUS schemes, the TUS scheme yields robustness against the channel estimation error in the wiretap links, compared with the OUS schemes.
This paper investigates physical layer security with opportunistic scheduling in a downlink wireless network with multiple asymmetrically located legitimate users (LUs) and eavesdroppers. We employ the cumulative distribution function (CDF)-based scheduling policy to guarantee fairness among LUs in arbitrary fading channels while exploiting multiuser diversity. Under this scheduling framework, the closed-form expressions for the secrecy throughput and secrecy outage probability are derived, illustrating the interplay among the system parameters such as the channel statistics and the number of LUs and eavesdroppers. In order to investigate the exploited multiuser diversity gain, the normalized secrecy throughput, i.e., the secrecy throughput for a given LU normalized by the probability of it being selected, is analyzed and is proved to achieve a double-logarithmic growth when the number of LUs in the network increases to infinity. In addition, we derive the secrecy diversity order through an asymptotic analysis of intercept probability and prove that the secrecy diversity order is equal to the number of LUs in the system, implying that full diversity is achieved by the CDF-based scheduling.
From the secrecy perspective, conventional cooperation communication is not always positive since it improves the link qualities of both the legitimate receiver and the eavesdropper node. To overcome this drawback, we propose an adaptive cooperation scheme, which activates the relay only when it has better secrecy capability than the source. This adaptive scheme is combined with secure user scheduling strategy to harvest the multiuser diversity (MUD) gain in the relay networks serving multiple sources. The results show that our scheme achieves a much higher secrecy capacity than alternatives. Meanwhile, the relay becomes less beneficial for a large number of sources.