We investigate the secrecy outage probability (SOP) of a downlink wiretap network consisting of a single legitimate base station (BS), multiple legitimate mobile stations (MSs), and multiple potential eavesdroppers (EVEs), where each EVE randomly attempts to overhear the data transmission with a certain probability. In particular, we consider an opportunistic feedback (OF) strategy in which each legitimate MS feeds their channel gain back to the BS for data reception only when its gain is greater than a certain threshold. We analyze a closed-form expression of the SOP under this strategy. As our main result, we demonstrate that the SOP of the OF strategy approaches that of the full feedback strategy as the number of legitimate MSs becomes large. It is worth noting that, for the first time, we mathematically characterize the SOP in this practical wiretap network setting having multiple potential EVEs.
We investigate the secrecy outage probability (SOP) of a downlink wiretap network consisting of a single legitimate base station (BS), multiple legitimate mobile stations (MSs), and multiple potential eavesdroppers (EVEs), where each EVE randomly attempts to overhear the data transmission with a certain probability. In particular, we consider an opportunistic feedback (OF) strategy in which each legitimate MS feeds their channel gain back to the BS for data reception only when its gain is greater than a certain threshold. We analyze a closed-form expression of the SOP under this strategy. As our main result, we demonstrate that the SOP of the OF strategy approaches that of the full feedback strategy as the number of legitimate MSs becomes large. It is worth noting that, for the first time, we mathematically characterize the SOP in this practical wiretap network setting having multiple potential EVEs.
Recently, wireless security has been highlighted as one of the most important techniques for 6G mobile communication systems. Many researchers have tried to improve the Physical-Layer Security (PLS) performance such as Secrecy Outage Probability (SOP) and Secrecy Energy-Efficiency (SEE). The SOP indicates the outage probability that the data transmission between legitimate devices does not guarantee a certain reliability level, and the SEE is defined as the ratio between the achievable secrecy-rate and the consumed transmit power. In this paper, we consider a Multi-User Multi-Input Single-Output (MU-MISO) downlink cellular network where a legitimate Base Station (BS) equipped with multiple transmit antennas sends secure information to multiple legitimate Mobile Stations (MSs), and multiple potential eavesdroppers (EVEs) equipped with a single receive antenna try to eavesdrop on this information. Each potential EVE tries to intercept the secure information, i.e., the private message, from the legitimate BS to legitimate MSs with a certain eavesdropping probability. To securely receive the private information, each legitimate MS feeds back its effective channel gain to the legitimate BS only when the effective channel gain is higher than a certain threshold, i.e., the legitimate MSs adopt an Opportunistic Feedback (OF) strategy. In such eavesdropping channels, both SOP and SEE are analyzed as performance measures of PLS and their closed-form expressions are derived mathematically. Based on the analytical results, it is shown that the SOP of the OF strategy approaches that of a Full Feedback (FF) strategy as the number of legitimate MSs or the number of antennas at the BS increases. Furthermore, the trade-off between SOP and SEE as a function of the channel feedback threshold in the OF strategy is investigated. The analytical results and related observations are verified by numerical simulations.
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.
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.
The secrecy outage performance of multi-antenna downlink wiretap networks with scan-and-wait (SWC) combining scheme is analyzed, where there exists a single-antenna base station communicating with a multi-antenna legitimate user in the presence of a multi-antenna eavesdropper. A new general closed-form expression of secrecy outage probability is derived to quantify the secrecy performance, and the asymptotic secrecy outage probability is also provided to gain further insights to the secrecy performance. Numerical results are presented to validate the theoretical analysis and demonstrate the impact of key system parameters on the secrecy performance.
In this letter, we study the interacting effects of the exclusion zone and eavesdropper colluding strategy on the secrecy performance of multiple-antenna transmission system. In particular, a base station (BS) applies random beamforming and user scheduling to enhance the legitimate user channel while multiple eavesdroppers try, either individually or jointly, to overhear the transmitted signal. We derive the closed-form expressions of secrecy outage probability (SOP) of the system with and without exclusion zone under different colluding strategies. Through selected numerical examples, we develop the design guideline on the size of the exclusion zone for a target security level subject to eavesdroppers' density and colluding strategy.
In this paper, we propose two opportunistic scheduling algorithms for uplink wiretap networks with multiple legitimate users (LUs) and eavesdroppers. Different from the existing works on scheduling algorithms with secrecy considerations, we focus on the practical scenario where LUs experience diverse path-loss to the base station (BS). Hence, both secrecy throughput and fairness among LUs are crucial design considerations. In the proposed scheduling algorithms, the feedback information generated by each LU is designed to reduce the probability that the LU is selected by the BS when the eavesdroppers overhear much information. It is proved that fairness among LUs can be achieved in arbitrary fading channels. In order to investigate the efficiency of our proposed scheduling algorithms, the normalized secrecy throughput, i.e., the secrecy throughput for a given LU normalized by the probability of it being selected, is analyzed and proved to achieve double-logarithmic growth when the number of LUs in the network increases to infinity.