Indoor VLC Research Articles

Performance Analysis of OIRS-Aided Indoor VLC Systems Under Dynamic Human Blockages and Random UE Orientation

Performance Analysis of OIRS-Aided Indoor VLC Systems Under Dynamic Human Blockages and Random UE Orientation

Physical Layer Security Based on 2-D Spatial Position Optimization of Relays in Reflected Indoor VLC System

Physical Layer Security Based on 2-D Spatial Position Optimization of Relays in Reflected Indoor VLC System

Solving the LEDs placement problem in indoor VLC system using a hybrid coronavirus herd immunity optimizer

Solving the LEDs placement problem in indoor VLC system using a hybrid coronavirus herd immunity optimizer

Efficient User-Centric AP Clustering Through Stable UE-AP Matching for Indoor VLC Systems

Efficient User-Centric AP Clustering Through Stable UE-AP Matching for Indoor VLC Systems

Neural Network-Based Optimization for SLIPT-Enabled Indoor VLC Systems With Energy Constraints

Neural Network-Based Optimization for SLIPT-Enabled Indoor VLC Systems With Energy Constraints

Resource allocation performance analysis and idle resource reallocation for FOV-limited indoor VLC networks

Visible light communication (VLC) networks based on multiple access points (APs) have gained significant attention in enhancing indoor communication coverage and transmission capacity. Since interference can significantly impact the quality of VLC links, this paper investigates and compares the performance of three resource allocation (RA) schemes based on the user equipment (UE) location to avoid interference under specific VLC deployments. Towards this end, we first derive statistical channel gain models in different overlap settings of coverage areas of optical APs according to the structural information, assuming that the UE distribution follows the Poisson point process (PPP) model. Then we derive the expressions for the performance metrics of the three RA schemes. Meanwhile, we construct a conflict graph to reveal potential interference relations and propose an idle resource reallocation policy (IRRP) in the case of low UE density. Finally, simulation results are provided to verify the correctness of derived expressions. It is shown that the performance of field-of-view (FOV)-limited VLC networks depends heavily on the RA schemes free of intercell interference (ICI). Without resource reallocation, more detailed resource division leads to worse system performance. With a user density of only 0.1UE/m2, the IRRP can even enhance the area spectral efficiency (ASE) of the proposed joint transmission (JT) scheme by 330% under linear deployment and 780% under hexagonal deployment, making the JT scheme the best among all relevant schemes in most situations.

A proposed preamble channel estimation scheme for flip FBMC-based indoor VLC systems

A proposed preamble channel estimation scheme for flip FBMC-based indoor VLC systems

Signal-Dependent Shot and Relative Intensity Noise in Channel Estimation of Laser Diode-based Indoor VLC Systems

Signal-Dependent Shot and Relative Intensity Noise in Channel Estimation of Laser Diode-based Indoor VLC Systems

Statistical channel modeling for indoor VLC communications based on channel measurements

Statistical channel modeling for indoor VLC communications based on channel measurements

Radio environment maps for indoor visible light communications aided by machine learning

VLC has been proposed as reliable high-capacity wireless optical communication system for indoor access networks. This technology comprises a high bandwidth unlicensed solution and has been suggested for ultra-reliable environments like hospitals. In this study, Machine Learning is used to investigate indoor wireless optical channels where ultra-reliable communications and signal coverage are required. Specifically, we assess the precision of different Decision Trees ML algorithms based on their mean absolute error metric in comparison to the anticipated simulated outcomes for optical channel estimation in various rooms that could be used in medical care. We demonstrate that Decision Trees models are capable of making fast and accurate predictions. It is shown that the Stack model is the most appropriate Decision Trees-based method, from the ones we studied, for predicting indoor VLC RSS values and constructing the corresponding REMs. These models are 300–65,000 times faster than traditional calculation methods, depending on the number of reflections bounces considered, and deliver accurate predictions, with less than 0.015 mean absolute percentage error, of the Radio Environment Map of a communication system that supports VLC. This is the first implementation of constructing optical REMs for Indoor VLC systems to the best knowledge of the authors.

Impact of the Refractive Index on the Achievable Rate of Liquid Crystal-Based Digital-RIS Indoor VLC Systems

In wireless networks, reconfigurable intelligent surfaces (RISs) have recently been proven to have a significant impact. The RIS has been incorporated into wireless communication systems to improve security, increase coverage, reduce interference, and improve transmission quality. Digital RIS (DRISs) have also proven to provide better reflection management. However, the impact of the DRIS intrinsic parameters on the system's achievable rate, has not yet been investigated. Due to their availability and easily reconfigurable properties, liquid crystals (LCs) appear as suitable materials for use in DRIS, specifically in optical communication systems. This paper analyzes the effect of the LC's refractive index on the achievable rate of LC-based DRIS indoor visible light communication systems. Based on a set of discrete phase shifts, required refractive indices have been evaluated. The reflected power and achievable rates are determined with respect to incoming light wavelengths at 510 nm, 550 nm, and 670 nm. According to the obtained numerical results, there is no linear relationship between refractive indices, corresponding transition coefficients, phase shifts, light power, and achievable rate.

Comparative Characterization of Indoor VLC and MMW Communications via Ray Tracing Simulations

Comparative Characterization of Indoor VLC and MMW Communications via Ray Tracing Simulations

Dual Channel Indoor VLC System Using PDM Scheme: An Investigation

Dual Channel Indoor VLC System Using PDM Scheme: An Investigation

An Effective Spatial Modulation Based Scheme for Indoor VLC Systems

We propose an enhanced spatial modulation (SM)-based scheme for indoor visible light communication systems. This scheme enhances the achievable throughput of conventional SM schemes by transmitting higher order complex modulation symbol, which is decomposed into three different parts. These parts carry the amplitude, phase, and quadrant components of the complex symbol, which are then represented by unipolar pulse amplitude modulation (PAM) symbols. Superposition coding is exploited to allocate a fraction of the total power to each part before they are all multiplexed and transmitted simultaneously, exploiting the entire available bandwidth. At the receiver, a two-step decoding process is proposed to decode the active light emitting diode index before the complex symbol is retrieved. It is shown that at higher spectral efficiency values, the proposed modulation scheme outperforms conventional SM schemes with PAM symbols in terms of average symbol error rate (ASER), and hence, enhancing the system throughput. Furthermore, since the performance of the proposed modulation scheme is sensitive to the power allocation factors, we formulated an ASER optimization problem and propose a sub-optimal solution using successive convex programming (SCP). Notably, the proposed algorithm converges after only few iterations, whilst the performance with the optimized power allocation coefficients outperforms both random and fixed power allocation.

Experimental performance evaluation of real-time image transmission in indoor VLC environment

Experimental performance evaluation of real-time image transmission in indoor VLC environment

Quantitative analysis of different LED lamp configurations in indoor VLC system

SummaryIn this article, an indoor environment of 5 × 5 × 3 m3 dimensions is considered and a total of nine LED lamps are installed at the ceiling in a symmetrical pattern. The inter‐spatial separation between LED lamps is varied to achieve the dual purpose of lighting and communication services. The multipath channel impulse response for distinct receiver locations is also calculated under line‐of‐sight (LOS) and non‐line‐of‐sight (NLOS) channel conditions. Several performance parameters, that is, illumination uniformity, received power fluctuations, root‐mean‐delay spread (RMDS), are evaluated to estimate the performance of the proposed system. The results show that spatial separation of 1.5 m between the LED lamps outperforms the other considered spatial separations, and the error‐free data transmission rate for the proposed system comes out to be about 40 Mbps across the entire receiver plane. Furthermore, an RGB image is transmitted at 40 Mbps and the received image quality is estimated in terms of image quality parameter, that is, structure similarity index (SSIM) over the receiver plane. The results outlined that the received image shows 100% similarity with the transmitted image, and thus, the proposed system can be effectively deployed in practical indoor environments.

Novel handover scheme for indoor VLC systems

Managing mobility in visible light communication systems is one of the main encounters that requires to be tackled. In this paper, we propose subcarrier multiplexing tones as control signals for handover in visible light communication systems. These control tone signals are unmodulated signals, and each light unit is given a unique unmodulated control signal. One light unit is used to send the data to the user, which is the best light unit. At a receiver side, band pass filters are used to separate subcarrier multiplexing tones. This enables receiver to connect with all light units via subcarrier multiplexing tones. The carrier to noise ratio of each control tone signal is estimated at the receiver, which leads to make the receiver connects with the light unit that offers the best connection during its mobility.

Indoor Wavelet OFDM VLC-MIMO System: Performance Evaluation

Both light emitting diode (LED) characteristics for illumination and communication simultaneously have made visible light communication-orthogonal frequency division multiplexing (VLC-OFDM) a strong competitive to radio frequency (RF). In this juncture, to improve signal to noise ratio (SNR) and coverage contour, the wavelet-OFDM is suggested for indoor VLC systems. In this paper, a wavelet VLC-OFDM is proposed for imaging multiple-input multiple-output (MIMO) systems. The proposed wavelet-OFDM is exploited for a hybrid space-frequency domain pre-equalization technique instead of the traditional fast Fourier transform (FFT)-OFDM technique. The Meyer filter is selected and employed in the proposed technique. A comparable achievement is elaborated for several numbers of channels to achieve the enhanced performance in terms of bit rate and coverage contour. In addition, a useful comparison is executed between our wavelet VLC-OFDM and the traditional FFT-OFDM for a hybrid space-frequency domain pre-equalization technique. The simulation results emphasize the superiority point of wavelet VLC-OFDM MIMO system by improving the coverage contour by ~20% over the traditional OFDM at a 10−3 bit error rate (BER) target. Hence, the proposed technique can be potentially executed in indoor VLC-MIMO systems.

Hard link-switching scheme using pre-scanning for indoor VLC networks

VLC has been accepted as a potential technology for deployment in indoor wireless networks in 5G. Use of efficient link switching scheme among VLC access points is critical in indoor environment to provide seamless connectivity to mobile users. This paper proposes a User Device (UD) based intermittent link switching based on hard link switching. This method is highly suitable for the indoor scenario where most of the fixtures and furniture remains unchanged. A Coordinator is employed in this method, that stores this information, thus, user is not required to search for the best transmitter when RSS is reduced to a threshold value as in conventional methods which cause substantial delay in switching process. Here, coordinator predicts the user position and allots best possible source for that position based on pre-scanned database and transfer the link to new source while releasing the old one by the time user reached that particular position. This method reduces the substantial delay time that occurs in switching process applied in conventional hard link switching. Simulation results show that the proposed scheme for indoor VLC System achieves the dual purpose of adequate illumination and mobility to user in considered indoor scenario.

An enhanced indoor visible light communication physical‐layer security scheme for 5G networks: Survey, security challenges, and channel analysis secrecy performance

SummaryVisible 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.