This paper studies the secrecy sum-rate in multi-user multiple-input single-output (MU-MISO) broadcast visible light communication (VLC) systems with confidential messages. The well-known Zero-Forcing (ZF) precoding is utilized to ensure confidentiality among users. Different from radio frequency (RF) counterpart, input data signals of VLC systems are amplitude constrained. This fundamental difference makes the derivation of the secrecy capacity more complex. In this study, we investigate a lower bound on the secrecy sum-rate of all users, which is valid in high signal-to-noise ratio (SNR) regime. The secrecy sum-rate is derived for two scenarios: known and unknown eavesdropper's channel state information (CSI) at the transmitter.
This paper studies the secrecy sum-rate in multi-user multiple-input single-output (MU-MISO) broadcast visible light communication (VLC) systems with confidential messages. The well-known Zero-Forcing (ZF) precoding is utilized to ensure confidentiality among users. Different from radio frequency (RF) counterpart, input data signals of VLC systems are amplitude constrained. This fundamental difference makes the derivation of the secrecy capacity more complex. In this study, we investigate a lower bound on the secrecy sum-rate of all users, which is valid in high signal-to-noise ratio (SNR) regime. The secrecy sum-rate is derived for two scenarios: known and unknown eavesdropper's channel state information (CSI) at the transmitter.
We investigate in this paper the achievable secrecy sum-rate of the multiple-input single-output (MISO) visible light communication (VLC) broadcast Gaussian channel with confidential messages. We consider a system model comprising (K +1) nodes: a transmitter (Alice) equipped with N fixtures of LEDs and K (K ≤ N) spatially dispersed users, each equipped with a single photo-diode (PD). The channel is modeled as deterministic and real-valued, subject to amplitude and power constraints, through which Alice wants to transmit in one channel use K confidential messages. We propose a new precoding scheme based on the eigenvalues of the pencils of the different K MISO VLC channels in order to maximize the achievable secrecy sum-rate of the overall system. The motivation behind this scheme is based on the fact that the optimal precoding scheme maximizing the achievable secrecy rate of the single user MISO VLC wiretap channel is expressed through the eigenvector associated to the largest eigenvalue of the wiretap channel's pencil. We investigate both cases, namely, when the locations of users are known, i.e., perfect channel state information (CSI) is available to Alice, or unknown, i.e., imperfect CSI. Furthermore, we adopt the truncated generalized normal (TGN) distribution as input signaling. We present several examples which demonstrate the substantial improvements in the secrecy sum-rates achieved by the proposed techniques compared to those achieved by zero-forcing (ZF) precoding.
We study, in this paper, the secrecy performance of a multi-user (MU) multiple-input single-output visible light communication broadcast channel with confidential messages. The underlying system model comprises K +1 nodes: a transmitter (Alice) equipped with N fixtures of LEDs and K spatially dispersed users, each equipped with a single photo-diode. The MU channel is modeled as deterministic and real-valued and assumed to be perfectly known to Alice, since all users are assumed to be active. We consider typical secrecy performance measures, namely, the max-min fairness, the harmonic mean, the proportional fairness, and the weighted fairness. For each performance measure, we derive an achievable secrecy rate for the system as a function of the precoding matrix. As such, we propose algorithms that yield the best precoding matrix for the derived secrecy rates, where we analyze their convergence and computational complexity. In contrast, what has been considered in the literature so far is zero-forcing (ZF) precoding, which is suboptimal. We present several numerical examples through which we demonstrate the substantial improvements in the secrecy performance achieved by the proposed techniques compared with those achieved by the conventional ZF. However, this comes at a slight increase in the complexity of the proposed techniques compared with ZF.
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.
We study the secrecy capacity of the multiple- input single-output (MISO) Gaussian wiretap visible light communication (VLC) channel. We study a typical VLC scenario with one transmitter, one legitimate receiver, and one eavesdropper. Specifically, we compute the achievable secrecy rate for various input signaling distributions, including the truncated generalized normal (TGN) and uniform distributions. The transmitter is equipped with multiple light sources, while the legitimate and unauthorized receivers are each equipped with a single photodetector. We analyze the achievable secrecy rates via transmit beamforming and artificial noise. In addition, both zero-forcing beamforming and robust beamforming are considered. In the former case, the location of the eavesdropper is assumed to be known, whereas in the latter case, the location of the eavesdropper is unknown. Our numerical results show that the secrecy rate achieved by the TGN distribution is significantly improved as compared to those achieved by the truncated Gaussian and uniform distributions, for both zero-forcing beamforming and robust beamforming. We also derive an upper bound on the achievable secrecy capacity that we used to assess the closeness of the achievable secrecy rates to the derived bound.
This paper considers secure transmission over the visible light communication (VLC) channel by the means of physical-layer security techniques. In particular, we consider achievable secrecy rates of the multiple-input, single-output (MISO) wiretap VLC channel. The VLC channel is modeled as a deterministic and real-valued Gaussian channel subject to amplitude constraints. We utilize null-steering and artificial noise strategies to achieve positive secrecy rates when the eavesdropper's channel state information (CSI) is perfectly known and entirely unknown to the transmitter, respectively. In both scenarios, the legitimate receiver's CSI is available to the transmitter. We numerically evaluate achievable secrecy rates under typical VLC scenarios and show that simple precoding techniques can significantly improve the confidentiality of VLC links.
Recent developments in visible light communications (VLC) have focused on enhancing its security and privacy. This paper studies the physical layer security in VLC networks with multiple users when there is a single wiretap eavesdropper. In particular, our aim is to design the optimal artificial noise (AN)-aided precoding scheme to improve the secrecy performance in terms of legitimate users and eavesdropper’s signal-to-interference-plus-noise ratios (SINRs). The purpose of our AN-aided precoding design is to ensure a fairness of the legitimate users’ SINRs while impairing the quality of eavesdropper’s channel as much as possible. Depending on the availability of the eavesdropper’s channel state information (CSI) at the transmitters, there are generally two design strategies. When the eavesdropper’s CSI is unknown to the transmitters (i.e., passive eavesdropper), the AN is constructed to be orthogonal to the users’ aggregate channel matrix. In case the eavesdropper’s CSI is available (i.e., active eavesdropper), the AN design strategy is to keep the SINR of the eavesdropper below a certain predefined threshold. Aside from the general design, we also study a specific design with the zero-forcing (ZF) technique and compare its performance with that of the general design. In both designs, numerical results show that significant gaps between users’ and eavesdropper’s SINR can always be achieved, thus guaranteeing a high secrecy performance. It is also observed that while the general design outperforms the ZF one in terms of the users’ SINRs, it does not result in lower eavesdropper’s SINRs compared to the ZF design, especially in the low transmit power region.