Abstract To a large extent, the physical layer security (PLS) performance of a visible light communication (VLC) system is affected by light source radiation characteristics. Previous works are limited to well‐known Lambertian beam configurations, which fail to support flexible coordinated coverage. Unlike existing works, this article proposes one secrecy capacity (SC) enhancement scheme based on asymmetric non‐Lambertian optical beam cooperation. Without loss of generality, this article presents a numerical analysis of coordinated and non‐coordinated PLS performance in a typical indoor application scenario. Compared with a non‐coordinated benchmark, the numerical results illustrate that the proposed cooperation‐based scheme could induce about 0.88 bps/Hz average SC gain without a transmission power increase. Therefore, non‐Lambertian beam cooperation could be viewed as one promising secure VLC performance enhancement technology.
Abstract To a large extent, the physical layer security (PLS) performance of a visible light communication (VLC) system is affected by light source radiation characteristics. Previous works are limited to well‐known Lambertian beam configurations, which fail to support flexible coordinated coverage. Unlike existing works, this article proposes one secrecy capacity (SC) enhancement scheme based on asymmetric non‐Lambertian optical beam cooperation. Without loss of generality, this article presents a numerical analysis of coordinated and non‐coordinated PLS performance in a typical indoor application scenario. Compared with a non‐coordinated benchmark, the numerical results illustrate that the proposed cooperation‐based scheme could induce about 0.88 bps/Hz average SC gain without a transmission power increase. Therefore, non‐Lambertian beam cooperation could be viewed as one promising secure VLC performance enhancement technology.
Visible light communications (VLC) techniques are viewed as promising candidates for the upcoming B5G&6G mobile wireless networks. Due to the broadcast nature of VLC channel, physical layer security (PLS) techniques have been considered and explored to improve the confidentiality of VLC transmission. Nevertheless, almost all current designs focus on application scenarios including sufficient transmitters and fail to match the scenarios with limited, even just two transmitters. For addressing this challenge, in this article, multiple optical beam switching scheme is proposed. Unlike conventional Lambertian beam based technique paradigm, the given scheme tentatively utilize two asymmetry non-Lambertian beams to configure each VLC transmitter. Numerical results show that, for the typical center legitimate receiver, compared with about 0.92 bps/Hz average secrecy capacity (SC) of the conventional Lambertian beam configuration, up to 5.55 bps/Hz average SC gain is acquired through the proposed beam switching scheme. Moreover, this potential gain will be enhanced to about 5.86 bps/Hz when three candidate non-Lambertian beams are available for each transmitter.
Due to the broadcast nature of visible light communications (VLC) channel, physical layer security (PLS) techniques have been considered to improve the transmission confidentiality of VLC links. However, almost all current schemes merely work with multiple distributed transmitters and fail to serve the scenarios with centralized transmitters, even single transmitter. For addressing this issue, in this work, the dynamic inclined optical beam-based PLS enhancement scheme is proposed. Unlike conventional Lambertian beam-based technique paradigm, the above scheme utilizes the commercially available typical non-Lambertian beams to form the secure VLC links. Numerical results show that, compared with the conventional static Lambertian configuration, up to 5.52 bps/Hz average secrecy capacity gain could be derived via the proposed dynamic scheme using two inclined candidate beams. Moreover, this potential gain will be further elevated to about 6.63 bps/Hz when up to four candidate beams are available at the transmitter.
Summary Visible light communication (VLC) is considered to be a great replacement or complement to existing radio frequency networks to provide the future fifth‐generation (5G) wireless technology with higher data rates for indoor connectivity, which alleviates the traffic demand. Therefore, many issues emerged regarding the security in 5G networks as human safety is at risk. This work presents a comprehensive study on the physical‐layer security (PLS) and solutions in 5G networks, specifically, the security of VLC technology as one of the core PLS solutions for 5G future wireless networks. Furthermore, VLC threats and PLS solutions are extensively investigated. Based on our study, we propose a new indoor VLC secure model to enhance the secrecy performance in VLC networks using a combination of multiple PLS techniques to achieve this aim as beamforming, secure communication zones, and friendly jamming. The simulation results with respect to the received optical power and signal‐to‐noise ratio (SNR) prove that the proposed indoor VLC model can improve the secrecy performance. As the user's SNR exceeded 100 dB and optical received power reached 15 mW, the malicious user's SNR barely reached 30 dB with a 4‐μW received power outside the target zone increasing his interference level. Finally, future research directions in VLC security are outlined to encourage future research.
Abstract For visible light communication (VLC), the light signals are transmitted without optical fibers or any sort of wave-guiding. Due to the inherent broadcast nature, physical-layer security emerges as a promising method to protect information delivery from eavesdropping. As for the secrecy capacity of VLC channel, there exist two features. In one way, the limited optical power makes the common capacity expressions in radio-frequency (RF) communication unapplicable for VLC. In another way, several correlated geometrical parameters directly alters the Lambertian model of indoor VLC channel, which gives the secrecy capacity more meanings. However, the issue considering both aspects has not been studied recently. In this paper, from the practical scenarios, we extract a typical geometrical model to reveal the mobility principles of the legitimate receiver and the eavesdroppers. Then, we character two typical distributions of the geometrical parameter. Correspondingly, we derive the upper and lower bounds on the average secrecy capacity, which have the closed forms. Finally, simulation results show that our upper and lower bounds are tight at high optical signal-to-noise rates (OSNRs). Moreover, the geometrical features of VLC systems and distribution parameters of the receiver mobility are effectively reveal by the bounds.
Visible light communication (VLC) is a new enabling communication technology that exploits illumination devices, mostly high-brightness light-emitting diodes (LEDs), to establish high-speed short-range wireless communication links. VLC is a promising technology that has gained significant interest in the last decade due to its high data rates and low cost of deployment. Although VLC systems are less susceptible to eavesdropping than RF systems since light does not penetrate through walls, they become as vulnerable as their radio-frequency (RF) counterparts when their nodes are deployed in public areas and/or when there are large windows. Thus, security for VLC systems is as important as it is for RF systems. Security in wireless communication systems may be enhanced by introducing physical layer security (PLS) techniques. In fact, PLS has been applied to a wide range of RF applications in an effort to improve the overall security by complementing existing cryptography-based security techniques. The potential of PLS stems from its ability of leveraging features of the surrounding environments via sophisticated encoding techniques at the physical layer. Indeed, PLS schemes can be applied in the same spirit to VLC systems. \n \nThere exist many specificities that characterize VLC systems, leading to major differences compared to RF systems. Specifically, VLC channels are quasi-static and real valued channels, which seemingly simplify the application of PLS techniques. However, due to the limited dynamic range of the LEDs, VLC systems impose an amplitude constraint on the channel input, which makes unbounded inputs not admissible. As a result, the performance of PLS schemes must be revised in the VLC context due to its different operating constraints. \n \nWe propose in this thesis enhancing the secrecy performance of VLC systems through PLS techniques. Firstly, we consider the degraded single-input single-output (SISO) VLC system. We derive achievable secrecy rates using continuous and discrete input distributions and we demonstrate the substantial improvement in the secrecy performance by using discrete distributions. Secondly, we consider the multiple-input single-output (MISO) VLC systems. We consider at first the case of randomly located eavesdroppers, in which we develop an associated achievable secrecy rate and we develop a beamforming-based precoding scheme that enhances the secrecy performance of this class of systems. In the second part, we consider the multi-user (MU) MISO broadcast system with confidential messages and we develop linear precoding schemes that enhance typical secrecy performance measures, including the max-min fairness and the weighted fairness. Finally, we consider the multiple-input multiple-output (MIMO) VLC system. We derive achievable secrecy rates using continuous and discrete distributions and we develop linear precoding schemes that improve its secrecy performance.
In the indoor scenario, visible light communications (VLC) is regarded as one of the most promising candidates for future wireless communications. Recently, the physical layer security for indoor VLC has drawn considerable attention. In this paper, the secrecy capacity of indoor VLC is analyzed. Initially, an VLC system with a transmitter, a legitimate receiver, and an eavesdropper is established. In the system, the nonnegativity, the peak optical intensity constraint and the dimmable average optical intensity constraint are considered. Based on the principle of information theory, the closed-form expressions of the upper and the lower bounds on the secrecy capacity are derived, respectively. Numerical results show that the upper and the lower bounds on secrecy capacity are very tight, which verify the accuracy of the derived closed-form expressions.