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 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 study a multiuser uplink network consisting of one base station (BS), multiple users and one eavesdropper (E), where the users are intended to transmit their confidential messages to BS, while the eavesdropper attempts to tap their transmissions. To improve the transmission secrecy, we propose two friendly jammer selection-aided multiuser scheduling schemes, namely, the random jammer selection-aided multiuser scheduling (RJS-MUS) without knowing the eavesdropper's channel state information (CSI) and the optimal jammer selection-aided multiuser scheduling (OJS-MUS), where the CSIs of eavesdropper are available. For comparison purposes, the conventional non-jammer selection-aided multiuser scheduling (NJS-MUS) scheme is considered as a benchmark. We derive exact and asymptotic closed-form secrecy outage probability expressions for the conventional NJS-MUS as well as proposed RJS-MUS and OJS-MUS schemes. The numerical results show that the proposed RJS-MUS and OJS-MUS schemes with equal power allocation between the selected friendly jammer and scheduled user perform worse than the conventional NJS-MUS approach in terms of the secrecy outage probability in the low signal-to-noise ratio (SNR) region. As the SNR increases, the secrecy outage performance of RJS-MUS and OJS-MUS schemes substantially improves, which is, in turn, better than that of conventional NJS-MUS approach. Moreover, the secrecy advantage of RJS-MUS and OJS-MUS over NJS-MUS becomes more significant with an increasing SNR. Also, it is shown that for both the RJS-MUS and OJS-MUS schemes, a better secrecy performance can be achieved through an optimal power allocation (OPA) between the scheduled user and friendly jammer. In addition, the proposed RJS-MUS and OJS-MUS schemes with OPA strictly outperform the conventional NJS-MUS approach in terms of the secrecy outage probability.
We analyze and optimize the secrecy performance of artificial noise (AN) in multi-input single-output wiretap channels with multiple antennas at the transmitter and a single antenna at the receiver and the eavesdropper. We consider two transmission schemes: 1) an on-off transmission scheme with a constant secrecy rate for all transmission periods, and 2) an adaptive transmission scheme with a varying secrecy rate during each transmission period. For the on-off transmission scheme, an easy-to-compute expression is derived for the hybrid outage probability, which allows us to evaluate the transmission outage probability and the secrecy outage probability. For the adaptive transmission scheme where transmission outage does not occur, we derive a closed-form expression for the secrecy outage probability. Using these expressions, we determine the optimal power allocation between the information signal and the AN signal and also determine the optimal secrecy rate such that the effective secrecy throughput is maximized for both transmission schemes. We show that the maximum effective secrecy throughput requires more power to be allocated to the AN signal when the quality of the transmitter-receiver channel or the transmitter-eavesdropper channel improves. We also show that both transmission schemes achieve a higher maximum effective secrecy throughput while incurring a lower secrecy outage probability than existing schemes.
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 paper, we explore the physical-layer security of a multi-user wireless system that consists of multiple users intending to transmit to a base station (BS), while multiple eavesdroppers attempt to tap the user transmissions. We examine the employment of multi-user scheduling for improving the transmission security against eavesdropping and propose a multiuser scheduling scheme, which only requires the channel state information (CSI) of BS without the need of the passive eavesdroppers' CSI. We also consider the round-robin scheduling for comparison purposes. The closed-form secrecy outage probability expressions of the round-robin scheduling and proposed multiuser scheduling are derived over Rayleigh fading channels. Numerical results demonstrate that the proposed multi-user scheduling outperforms the round-robin scheduling in terms of the secrecy outage probability. As the number of users increases, the secrecy outage probability of round-robin scheduling keeps unchanged. By contrast, the secrecy outage performance of the proposed multi-user scheduling improves significantly with an increasing number of users.
Secrecy Outage Analysis of Multiuser Downlink Wiretap Networks With SECps Scheduling in Nakagami- m channel
In this letter, we investigate the security of multiuser downlink wiretap networks over Nakagami-m channel, where a base station (BS) serves NB legitimate users and is overheard by NE eavesdroppers. Specifically, to achieve a good tradeoff between the secrecy performance and number of user estimations, we introduce a threshold-based scheduling algorithm, termed switch-and-examine combining with post-examining selection (SECps). Moreover, we consider the practical scenario, where the channel state information (CSI) of the eavesdropper's channel is unavailable at the BS. Building on this, new exact and asymptotic closed-form expressions of the secrecy outage probability are derived for the considered network, which are valid for general systems with an arbitrary number of legitimate users, number of eavesdroppers, channel fading severity, and switching threshold. The findings suggest that with the switching threshold being carefully chosen, the considered SECps scheme achieves a comparable secrecy outage performance with regard to selection combining (SC) scheme while maintaining a lower number of user examinations.
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.