Bangning Zhang

Secure Multiuser Scheduling in Downlink Dual-Hop Regenerative Relay Networks Over Nakagami-

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 eavesdroppers channel state information (CSI), i.e., Scenario I, where the eavesdroppers CSI is not available at the relay, and Scenario II, where the eavesdroppers 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.

m

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 eavesdroppers channel state information (CSI) is unavailable at the BS, and in Scenario II, the eavesdroppers 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.

Fading Channels

In this paper, we investigate the physical layer security for amplify-and-forward relay networks with simultaneous wireless information and power transfer. Specifically, by considering the dual-functional desired receiver, which is capable of decoding information and energy harvesting (EH), and assuming that only imperfect eavesdroppers’ channel state information can be attained, we propose a joint robust cooperative beamforming, artificial noise, and power splitting scheme. We formulate the relay power minimization problem under both the secrecy rate constraint and the EH constraint, which is non-convex and hard to tackle. To tackle this problem, we propose a two-level optimization approach, which involves 1-D search and the semi-definite relaxation. In addition, we testify that the SDR can obtain the rank-one optimal solution. Simulation results show that the proposed robust scheme achieves better secrecy performance than other schemes.

Physical Layer Security With Threshold-Based Multiuser Scheduling in Multi-Antenna Wireless Networks

In this paper, we investigate the secure transmission in wireless sensor networks (WSNs) consisting of one multiple-antenna base station (BS), multiple single-antenna legitimate users, one single-antenna eavesdropper and one multiple-antenna cooperative jammer. In an effort to reduce the scheduling complexity and extend the battery lifetime of the sensor nodes, the switch-and-stay combining (SSC) scheduling scheme is exploited over the sensor nodes. Meanwhile, transmit antenna selection (TAS) is employed at the BS and cooperative jamming (CJ) is adopted at the jammer node, aiming at achieving a satisfactory secrecy performance. Moreover, depending on whether the jammer node has the global channel state information (CSI) of both the legitimate channel and the eavesdropper’s channel, it explores a zero-forcing beamforming (ZFB) scheme or a null-space artificial noise (NAN) scheme to confound the eavesdropper while avoiding the interference to the legitimate user. Building on this, we propose two novel hybrid secure transmission schemes, termed TAS-SSC-ZFB and TAS-SSC-NAN, for WSNs. We then derive the exact closed-form expressions for the secrecy outage probability and the effective secrecy throughput of both schemes to characterize the secrecy performance. Using these closed-form expressions, we further determine the optimal switching threshold and obtain the optimal power allocation factor between the BS and jammer node for both schemes to minimize the secrecy outage probability, while the optimal secrecy rate is decided to maximize the effective secrecy throughput for both schemes. Numerical results are provided to verify the theoretical analysis and illustrate the impact of key system parameters on the secrecy performance.

Joint Robust Design for Secure AF Relay Networks With SWIPT

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 eavesdroppers 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.

Secure Multiuser Communications in Wireless Sensor Networks with TAS and Cooperative Jamming

This paper investigates the secure transmit design of a cooperative hybrid satellite-terrestrial relay network (HSTRN). Assuming that amplify-and-forward (AF) protocol is adapted at terrestrial relays, and global channel state information (CSI) is known, we propose two schemes through jointly optimizing the relay beamforming vector and the covariance matrix of artificial noise (AN) to maximize the secrecy rate. In the first scheme, our design is based on secrecy rate maximization and optimal solution is obtained by following the idea of two-level optimization which is composed of one-dimensional search technique and semidefinite relaxation (SDR) technique. In the second scheme, to reduce the computation, we assume that there is no information leakage to all eavesdroppers, and the solution of this problem is obtained by solving one semidefinite programing (SDP) only with SDR. Numerical results are provided to demonstrate the performance of different designs and the benefit of AN.

Secrecy Outage Analysis of Multiuser Downlink Wiretap Networks With SECps Scheduling in Nakagami-

The hardware impairments of physical transceivers that create distortions degrade the performance of satellite relay communication. In this paper, we investigate the impact of hardware impairments on both the outage performance and the instantaneous capacity of dual-hop decode-and-forward (DF) satellite-relay network. Specifically, the exact closed-form expression for the outage probability of the system and the analytical expression for the instantaneous capacity of the system are derived over shadowed Rician fading channel, which provide fast means to evaluate the impact of hardware impairments. Moreover, the results reveal that the outage floor and the capacity upper bound appear when the hardware impairments exist. In addition, simulation results are given to show the correctness of the analytical results.

m

Space information networks are proposed to broaden the observation area and realize continuous information acquisition using satellites and high-altitude platform stations. Space information networks are able to enhance detection and transmission capabilities compared to the current single Earth observation satellite. The satellite–terrestrial network is an important component of the space information networks. Hence, the major contribution of this article is to propose a new transmitted link selection scheme in a satellite–terrestrial network. Switch-and-stay combining scheme is used by destination to have a trade-off between the complexity and efficiency. The satellite, terrestrial relays, and destination user are influenced by hardware impairments, respectively. The closed-form expressions for the outage probability and throughput are derived. In order to analyze the system performance at high signal-to-noise rate, the asymptotic expressions for the system performance are also derived to give a special view on the impact of hardware impairments on the considered network. What is more, numerical results are derived to verify the correctness of our analytical results.

channel

In this letter, we investigate the outage constrained robust secure design in multiple-input multiple-output simultaneous wireless information and power transfer systems, where the energy receivers (ERs) may eavesdrop the confidential information sent to the desired receivers (DRs). Specifically, we propose a joint design of the precoding matrix and the power splitting (PS) ratios at the DRs to maximize the total harvested energy at the DRs, under the outage secrecy rate constraints at the DRs and the outage harvested energy constraints at the ERs. To solve the formulated non-convex maximize the sum of non-linear functions problem, we decouple the original problem into two sub-problems and propose an alternating optimization algorithm, wherein large deviation inequality and successive convex approximation are used to handle these sub-problems. Finally, numerical results are provided to validate our proposed algorithm.

Joint beamforming and jamming design for secure cooperative hybrid satellite-terrestrial relay network

In this letter, the effect of hardware impairments on two-way satellite-terrestrial hybrid relay networks is analyzed. The terrestrial relay is considered as a two-way relay, which can transmit signals to both the satellite source and the mobile source simultaneously. Specifically, the closed-form expression, the asymptotic expression at high signal-to-noise rates and the throughput for the considered system are derived. The expressions show that the impairments greatly affect the system performance and system performance will be worse when the impairment level is larger. In addition, numerical results are provided to show the correctness of the analytical results.