Visible light communication (VLC) has emerged as a promising candidate to complement and enhance the performance of the existing radio frequency (RF) networks in indoor environments. Due to the broadcast nature of both RF and VLC channels, improving the transmission confidentiality is a requirement in practical wireless networks. Physical-layer security has emerged to provide a first line of defense against eavesdropping attacks. In this paper, we study the physical layer security problem of a hybrid RF/VLC system. First, we formulate the minimization problem of the consumed electrical power in the hybrid RF/VLC network while satisfying the user's required secrecy rate. Then, we propose a zero forcing beamforming strategy and a minimum power allocation algorithm. Simulations results show that the proposed power allocation and beamforming algorithms outperform the benchmark algorithms in terms of the average consumed electrical power in various indoor scenarios.
Visible light communication (VLC) has emerged as a promising candidate to complement and enhance the performance of the existing radio frequency (RF) networks in indoor environments. Due to the broadcast nature of both RF and VLC channels, improving the transmission confidentiality is a requirement in practical wireless networks. Physical-layer security has emerged to provide a first line of defense against eavesdropping attacks. In this paper, we study the physical layer security problem of a hybrid RF/VLC system. First, we formulate the minimization problem of the consumed electrical power in the hybrid RF/VLC network while satisfying the user's required secrecy rate. Then, we propose a zero forcing beamforming strategy and a minimum power allocation algorithm. Simulations results show that the proposed power allocation and beamforming algorithms outperform the benchmark algorithms in terms of the average consumed electrical power in various indoor scenarios.
The broadcast nature of wireless networks makes them vulnerable to eavesdropping attacks; therefore, physical layer security (PLS) becomes essential to protect the signal at the physical layer. In this paper, we investigate PLS aspects in terms of the secrecy capacity (SC) in hybrid radio frequency (RF)/visible light communication (VLC) networks. First, we design RF-and VLC-based beamforming vectors to maximize the achievable SC. Moreover, using these vectors, we solve the power minimization problem satisfying the required SC. The results provide useful insights into how the eavesdropper's location affects the power consumption profile. Finally, the results reveal that the performance of the VLC network in terms of the consumed power per bits/s/Hz is more efficient than the RF one.
Recently, the hybrid radio frequency (RF)/ visible light communication (VLC) network has been widely studied due to the advantages of high data transmission and no interference between the two networks. Taking the physical layer security (PLS) into account, most work on hybrid RF/VLC network focused on single user. However, many practical scenarios require hybrid network to serve multiple users (MU). Thus, in this paper, we make a study on the PLS of MU hybrid RF/VLC network where the messages to each of the users must be kept confidential from the other and also from the external eavesdropper. To enhance the secrecy performance of the hybrid network, we propose a zero forcing (ZF) beamforming strategy to ensure that the information of each legitimate user can not be received by other users and the eavesdropper. A sum secrecy rate (SSR) optimization problem is formulated under the ZF constraint and the constraint of the power transmitted from the VLC and the RF access point. To reduce the complexity of the original problem, we decouple it into two successive sub-problems and solve them via convex optimization theory and matrix theory. Simulation results show that a positive SSR can always be achieved, and the SSR of the MU hybrid RF/VLC network is superior to that of the standalone RF and VLC networks.
In this paper, we study physical layer security (PLS) aspects of a hybrid radio frequency (RF)/visible light communication (VLC) system with multiple decode-and-forward relaying nodes equipped with friendly jamming capabilities. We first propose a novel joint relay–jammer selection algorithm to enhance the secrecy performance of the network. Next, we obtain beamforming vectors and the minimal power values, which satisfy the required secrecy threshold. Our simulation results show that the proposed hybrid RF/VLC scheme obtains higher secrecy capacity compared to the standalone VLC and RF technologies. Finally, we proved the proposed technique to be an eavesdropping-resilient PLS solution.
Integrating visible light communication (VLC) and radio-frequency (RF) networks can improve the performance of communication systems in terms of coverage and data rates. However, adding RF links to VLC networks weakens the secrecy performance due to the broadcast and ubiquitous nature of RF links. This paper studies the physical layer security (PLS) in cooperative non-orthogonal multiple access (CoNOMA) hybrid VLC/RF systems. Consider a VLC system, where two entrusted users close to a VLC access point (AP) help an out-of-coverage legitimate user using RF signals in the presence of an eavesdropper. The AP transmits data to both entrusted users and the legitimate user using the principle of NOMA, where the entrusted users harvest energy from the received light intensity, decode the legitimate user's message, forward it using a RF link, and then decode their messages. It is required to maximize the secrecy rate at the legitimate user under quality-of-service (QoS) constraints using beamforming and DC-bias and power allocation. Different solutions are proposed for both active and passive eavesdropper cases, using semidefinite relaxation, zero-forcing, beamforming, and jamming. Numerical results compare between the different proposed approaches and show how the proposed approaches contribute in improving the secrecy performance of the proposed model.
In this paper, we consider the secrecy of a hybrid radio frequency (RF)/visible light communication (VLC) system equipped with decode-and-forward relaying. We develop physical layer security algorithms that mitigate eavesdropping on both RF and VLC networks based on zero-forcing beamforming techniques. We evaluate the system performance in terms of secrecy capacity (SC) and outage probability (OP) for two network scenarios, namely non-cooperative (NCPS) and cooperative power saving (CPS) models. The NCPS case assumes fixed power at both source and relay while the CPS case assumes total average power shared between the source and relay. Our objective is to find the minimum power that satisfies a specific SC for both cases. Our simulation results show that CPS policy achieves higher SC and maintain lower OP compared with the NCPS one for the same amount of power. We also show that, for both cases, the hybrid RF/VLC network can improve SC compared with standalone RF or VLC networks.
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.