A novel threshold‐based scheduling scheme for multiuser downlink wiretap networks is addressed, which consist of a base station (BS), multiple legitimate users and multiple eavesdroppers. Particularly, the active scenario is concentrated, where BS has access to the channel state information for the eavesdropper's channel. In doing so, new exact and asymptotic closed‐form expressions for the ergodic secrecy capacity are derived for multiuser downlink networks using switch‐and‐examine combining with post‐selection scheduling at legitimate users and maximum ratio combining at the eavesdroppers. Moreover, the high signal‐to‐noise ratio slope and power offset are also given to explicitly characterise the impact of main link and wiretap link on the ergodic secrecy capacity. Simulation results show the effect of key parameters such as the number of legitimate users and eavesdroppers, switching threshold on the secrecy performance of the considered wiretap network.
A novel threshold‐based scheduling scheme for multiuser downlink wiretap networks is addressed, which consist of a base station (BS), multiple legitimate users and multiple eavesdroppers. Particularly, the active scenario is concentrated, where BS has access to the channel state information for the eavesdropper's channel. In doing so, new exact and asymptotic closed‐form expressions for the ergodic secrecy capacity are derived for multiuser downlink networks using switch‐and‐examine combining with post‐selection scheduling at legitimate users and maximum ratio combining at the eavesdroppers. Moreover, the high signal‐to‐noise ratio slope and power offset are also given to explicitly characterise the impact of main link and wiretap link on the ergodic secrecy capacity. Simulation results show the effect of key parameters such as the number of legitimate users and eavesdroppers, switching threshold on the secrecy performance of the considered wiretap network.
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.
Secure Multiuser Scheduling in Downlink Dual-Hop Regenerative Relay Networks Over Nakagami- m Fading Channels
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 eavesdropper's channel state information (CSI), i.e., Scenario I, where the eavesdropper's CSI is not available at the relay, and Scenario II, where the eavesdropper's 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.
In this letter, we study on-off opportunistic beamforming for the multiuser downlink channel with a passive eavesdropper. Two opportunistic scheduling schemes exploiting multiuser diversity are investigated which require limited feedback of the effective signal-to-noise ratio (SNR) from the legitimate users. For the two scheduling schemes, we derive new closed-form expressions for the ergodic secrecy rate with on-off beamforming over Rayleigh fading channels. Numerical results are provided to verify our analytical results and illustrate the impact of multiuser diversity on the secrecy performance.
Abstract We investigate the secrecy performance of cellular multiuser two‐way relay networks, where the bidirectional information exchange between a multiantenna base station (BS), and several users can be accomplished with the assistance of decode‐and‐forward relay(s) in the presence of a multiantenna passive eavesdropper. We employ low‐complexity antenna selection strategy at the BS coupled with user scheduling for maximizing the end‐to‐end signal‐to‐noise ratios (SNRs). To enhance the wiretap probability, the eavesdropper applies a maximal ratio combining technique to combine the received signals. Under such considerations, in the single‐relay scenario, we deduce the exact closed‐form secrecy outage probability (SOP) expression under Rayleigh fading channels. For more insights into the system secrecy diversity order, we derive the closed‐form asymptotic SOP expressions at high SNR based on the quality of the main and wiretap links. In the multirelay scenario, we formulate an opportunistic relay selection strategy, followed by its impact on the SOP performance in the presence of Rayleigh channels. To show the impact of multiple relays on the secrecy diversity order, we derive the asymptotic SOP expressions in the high SNR regime depending on the quality of the main and wiretap links. It is shown from the asymptotic SOP expressions under both single‐relay and multirelay scenarios that the secrecy diversity order reduces to zero in the high SNR regime, regardless of number of antennas, number of users, and number of relays. Our results also reveal that the SOP performance diminishes with an increased number of eavesdropper antennas. Numerical and simulation results verify our derived analytical findings.
In this paper, we consider the problem of secure communication in multiuser downlink wiretap networks where there exist a base-station (BS) equipped with multiple antennas, multiple legitimate receivers and a passive eavesdropper. The transmitter simultaneously transmits an information signal and artificial noise (AN) separately to the intended receivers and the eavesdropper, in which way, the secrecy rate at the eavesdropper can be seriously degraded without thinking about it location. Different schemes are studied about the power allocation of the multiple antennas in the BS, namely the average power allocation scheme and the Water-filling scheme. And in the average power allocation scheme, Zero-forcing (ZF) pre-coding scheme is used at the BS to eliminate the internal interference of all the security users. We obtain an analytical closed form expression of an achievable ergodic secrecy rate and use it as the objective function to optimize the power allocation rate between the information signal and the AN in the two schemes.