Secrecy performance in the near-field (NF) presents a compelling topic for sixth-generation (6G) wireless networks. In this paper, we investigate the physical layer security (PLS) of NF downlink networks serving a single legitimate user in the presence of an eavesdropper. To characterize the performance of the network, through the central limit theorem (CLT), the expected value of the eavesdropping channel statistics is derived for the downlink link in the case of Rayleigh fading. Furthermore, the performance of the proposed network is evaluated in terms of the secrecy outage probability (SOP). The closed-form expressions of the SOP and the floor of SOP under high signal-to-noise ratio (SNR) conditions are derived. We also contrast the impact of the number of antennas as well as the target secrecy rate on the overall secrecy performance of the considered network, and analyze the impact of the eavesdropper on the SOP of the considered network. We finally show that: The SOP of the system decreases with the increase of the transmit power, and finally converges to a fixed value. Our Monte Carlo simulations perfectly illustrate the analytical results.
Secrecy performance in the near-field (NF) presents a compelling topic for sixth-generation (6G) wireless networks. In this paper, we investigate the physical layer security (PLS) of NF downlink networks serving a single legitimate user in the presence of an eavesdropper. To characterize the performance of the network, through the central limit theorem (CLT), the expected value of the eavesdropping channel statistics is derived for the downlink link in the case of Rayleigh fading. Furthermore, the performance of the proposed network is evaluated in terms of the secrecy outage probability (SOP). The closed-form expressions of the SOP and the floor of SOP under high signal-to-noise ratio (SNR) conditions are derived. We also contrast the impact of the number of antennas as well as the target secrecy rate on the overall secrecy performance of the considered network, and analyze the impact of the eavesdropper on the SOP of the considered network. We finally show that: The SOP of the system decreases with the increase of the transmit power, and finally converges to a fixed value. Our Monte Carlo simulations perfectly illustrate the analytical results.
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.
As an effective way to enhance the physical layer security (PLS) for the broadcast channel (BC), regularized zero-forcing (RZF) precoding has attracted much attention. However, the reliability performance, i.e., secrecy outage probability (SOP), of RZF is not well investigated in the literature. In this paper, we characterize the secrecy performance of RZF precoding in the large multiple-input single-output (MISO) broadcast system. For this purpose, we first consider a central limit theorem (CLT) for the joint distribution of the users' signal-to-interference-plus-noise ratio (SINR) and the eavesdropper's (Eve's) signal-to-noise ratio (ESNR) by leveraging random matrix theory (RMT). The result is then utilized to obtain a closed-form approximation for the ergodic secrecy rate (ESR) and SOP of three typical scenarios: the case with only external Eves, the case with only internal Eves, and that with both. The derived results are then used to evaluate the percentage of users in secrecy outage and the required number of transmit antennas to achieve a positive secrecy rate. It is shown that, with equally-capable Eves, the secrecy loss caused by external Eves is higher than that caused by internal Eves. Numerical simulations validate the accuracy of the theoretical results.
The inherent openness of wireless networks exposes them to eavesdropping threats. In dense urban environments, signal propagation is frequently characterized by the keyhole effect, which causes channel rank deficiency and cascaded fading, challenging the assumptions of conventional multiple-input multiple-output (MIMO) physical layer security. This paper investigates the secrecy performance of MIMO multiple-antenna-eavesdropper (MIMOME) systems over keyhole channels with independent legitimate and eavesdropper links. We analyze the secrecy performance under three progressive scenarios: perfect CSI without artificial noise (AN), perfect CSI with AN-aided transmission, and practical imperfect CSI with AN. Specifically, we derive closed-form asymptotic expressions for the secrecy outage probability (SOP) and average secrecy rate (ASR) in the high signal-to-noise ratio (SNR) regime using Meijer G-functions and Gauss hypergeometric functions, from which the secrecy diversity order and secrecy array gain are explicitly extracted. The analytical results reveal that AN injection successfully restores the secrecy diversity order from zero to one, while imperfect CSI causes AN leakage that leads to ASR saturation and an SOP floor. The derived asymptotic expressions are verified by Monte Carlo simulations. Our findings provide theoretical guidelines by quantifying the trade-off between AN suppression capabilities and self-interference in cascaded fading environments.
The secrecy performance of wireless networks powered up by a dedicated power beacon (PB) is addressed in this work. Particularly, the closed-form expression of the secrecy outage probability (SOP) under the presence of multiple eavesdroppers is given. The considered networks are asymmetric since there are multiple eavesdroppers but only a single legitimate receiver. As a consequence, two wiretap schemes are employed, namely, non-colluding and colluding schemes, to take advantage of multiple eavesdroppers. To draw insights from the derived framework, the asymptotic framework of the SOP under the high transmit power regime is also provided. Next, Monte Carlo simulations are provided to validate the theoretical foundations of the proposed approach. Our findings show that by increasing the transmit power from −10 dB to 30 dB, the SOP ameliorates almost a thousand times. Additionally, the SOP is a monotonic decreasing function with a time-switching ratio. We also make comparisons with work in the literature in which the full-duplex relay is employed to help the legitimate link. Numerical results illustrate that the proposed network outperforms those described in the literature. Particularly, through reliance on the setup, the SOP under the proposed system is better than those of the literature by about twofold.
In this paper, we study uplink-downlink non-orthogonal multiple access (NOMA) systems by considering the secure performance at the physical layer. In the considered system model, the base station acts a relay to allow two users at the left side communicate with two users at the right side. By considering imperfect channel state information (CSI), the secure performance need be studied since an eavesdropper wants to overhear signals processed at the downlink. To provide secure performance metric, we derive exact expressions of secrecy outage probability (SOP) and and evaluating the impacts of main parameters on SOP metric. The important finding is that we can achieve the higher secrecy performance at high signal to noise ratio (SNR). Moreover, the numerical results demonstrate that the SOP tends to a constant at high SNR. Finally, our results show that the power allocation factors, target rates are main factors affecting to the secrecy performance of considered uplink-downlink NOMA systems.
With its capability to obtain a good tradeoff between complexity and performance, regularized zero-forcing (RZF) has been widely investigated to enhance the physical layer security. However, the associated reliability performance, i.e., secrecy outage probability (SOP), is not yet available in the literature. In this paper, we characterize the secrecy performance of RZF in the multi-user, downlink multiple-input single-output system. For this purpose, we first set up a central limit theorem for the joint distribution of users’ signal-to-interference-plus-noise ratio and eavesdropper’s signal-to-noise ratio by leveraging random matrix theory. The result is then utilized to obtain a closed-form approximation for the ergodic secrecy rate and SOP of three typical scenarios: the case with only external Eves, the case with only internal Eves, and that with both. The derived results are then used to evaluate the percentage of users in secrecy outage and the required number of transmit antennas to achieve a positive secrecy rate. It is shown that, with equally-capable Eves, the secrecy loss caused by external Eves is higher than that caused by internal Eves. Numerical simulations validate the accuracy of the theoretical results and demonstrate the advantage of RZF over other linear transmitters such as ZF.