Visible Light Communication Networks Research Articles

Outage and Rate Analysis for Industrial Internet of Things in Multitier Visible Light Communication Networks Inside Finite 3-D Space

Outage and Rate Analysis for Industrial Internet of Things in Multitier Visible Light Communication Networks Inside Finite 3-D Space

Experimental validation of the appropriate channel model for an indoor Visible Light Communication system

Visible light communication (VLC) is a technology with significant potential to revolutionize indoor communication performance and satisfy the demands of fifth-generation (5G) and beyond technologies. To achieve an efficient VLC system that delivers optimal performance and coverage, it is imperative to create a reliable channel model. As a result, this research is centered around the evaluation of existing channel models for planning the VLC network coverage within indoor environments. The primary focus of this study is to enforce three types of channel models, Line of Sight (LoS), Nakagawa’s first reflection model, and the Spherical model through MATLAB simulations and obtain simulation results by varying the distance parameter. Furthermore, this research intends to implement a physical prototype representing a real-world scenario, and thereby determine the nearest channel model that aligns with the physical measurements obtained from the physical prototype.

The Latency Performance Analysis and Effective Relay Selection for Visible Light Networks.

In visible light communication (VLC), the precise latency evaluation of wireless access networks and the efficient forwarding strategy of core networks are the crux for end-to-end reliability provisioning. Leveraging martingale theory, an elegant latency-bounded reliability analysis framework is studied for the VLC network. Considering the characteristic that VLC links are easy to block, the martingale of the service process is constructed. Based on the time shift features, the martingale process related to latency is proposed for the VLC system, which models the influence of entanglement between aggregate arrivals and random service on latency. A stopping time event about latency is defined. Renting the stopping time theory, a tight upper bound of the unreliability with regard to latency is derived. In the core network, a dynamic forward backhaul framework is proposed, which uses the relay selection algorithm based on back-pressure theory to improve data transmission quality. The theoretical latency-bounded reliability matches the simulation results well, which verifies the effectiveness of the proposed analysis framework, and the proposed relay selection algorithm can also improve network performance under data-intensive transmission.

An Emergency Message Routing Protocol for Improved Congestion Management in Hybrid RF/VLC VANETs

Unexpected traffic incidents cause safety concerns and intense traffic congestion on crowded urban road networks. Vehicular ad-hoc network (VANET)-aided Intelligent Transport Systems (ITS) aim to mitigate these risks through timely dissemination of alert messages. However, conventional Radio frequency (RF) mobile ad-hoc routing protocols are ill-suited for dynamic VANET environments due to high mutual interference, packet collisions, high end-to-end delay from frequent route discoveries, and periodic beaconing requirements. Fortunately, the quickly emerging Visible Light Communications (VLC) provide complementary short-range connectivity with high bandwidth and low interference. This paper proposes an efficient adaptive routing protocol for emergency messages in dense VANET scenarios leveraging a hybrid RF/VLC system. When an incident or congestion happens, the source vehicle disseminates the information to the incoming vehicles as quickly as possible using a combination of VLC and RF communication networks. Multi-hop relays extend the connectivity if the direct links are blocked. The coverage area is partitioned into zones based on road segments, intersections, and traffic flows. The Road Side Units (RSU)s are intelligently assigned to zones and they analyze the historical traffic data to characterize each zone and decide a response strategy. We also propose a congestion detection scheme that utilizes traffic simulations to forecast the clearance times under different response strategies. The highest-scoring strategy is selected based on the predicted impacts on travel time, emissions, and driver stress levels. The proposed algorithm adaptively uses the selected strategy to proactively alleviate the predicted congestion through optimized routing and control. Overall, the protocol maximizes safety and efficiency during emergencies by leveraging the hybrid RF/VLC, incorporating real-time congestion forecasting and dynamic rerouting into the response strategies.

Channel-Independent Quantum Mapping-Substitution OFDM-Based Spatial Modulation for Physical-Layer Encryption in VLC Networks

Physical-layer encryption has lately been highlighted as a promising security approach for visible light communications (VLC). Orthogonal frequency-division multiplexing (OFDM) is the main structural entity of multiple-carrier modulation in most modern communication systems, including vehicle ad hoc networks, 5G systems, and the Internet of Things. The integration of OFDM and spatial modulation (SM) can improve the capacity of low-complication VLC systems. Two common methods have been proposed for OFDM-based SM schemes: frequency-domain SM (FD-SM) and time-domain SM (TD-SM). TD-SM supports higher spectral efficiency than FD-SM with low complication. In this paper, we propose a physical-layer encryption method, referred to as channel-independent quantum mapping-substitution (CIQMS) TD-SM, for enhancing VLC's confidentiality. The random properties of the input data are used for generating dynamic cypher keys that are updated for each frame using hashing and stream cypher methods. The proposed approach performs four encryption operations: quantum noise stream cypher, substitution of radiated data symbols mapping, substitution of light-emitting-diode information mapping, and polarity encryption of time-domain OFDM subcarriers. The findings show that our CIQMS method provides a considerably higher secrecy rate than channel-dependent methods proposed in the literature. Also, it provides high robustness against both authorized and non-authorized eavesdroppers. In addition to that, the results show that the CIQMS method provides high confidentiality against several attacks, e.g., statistical attacks, chosen-/known-plaintexts, and brute-force attacks.

Visible light communication and WiFi hybrid networks based on dynamic resource allocation algorithm

Visible light communication and WiFi hybrid networks based on dynamic resource allocation algorithm

Homology Theory-Based Coverage Hole Localization and Area Estimation for Visible Light Communication Networks

Homology Theory-Based Coverage Hole Localization and Area Estimation for Visible Light Communication Networks

Low-Latency Network Slicing for VLC-Based Industrial Internet of Things: Superframe Duration Minimization and Delay Violation Probability Analysis

Visible light communication (VLC) is promising for the future application in industrial internet of things (IIoT) due to limited inter-user interference from directional transmission, which can provide a good guarantee for the delay and reliability of communication. In this work, we consider the model of a downlink indoor VLC network covered by multiple lighting emitting diodes (LEDs). We reduce the delay violation probability via minimizing the superframe duration, and analyze the delay violation probability based on the optimized superframe duration. We analyze the delay violation probability using stochastic network calculus (SNC). More specifically, we propose a low-complexity resource slicing scheme, and exploit LED layout characteristics to minimize the superframe duration. Then, assuming that the users are uniformly distributed in each served area, we obtain the achievable rate distribution for each served area. Our results show that the proposed resource slicing scheme yields a shorter superframe duration than random scheme and the delay violation probability increases with traffic arrival rate, LED spacing and the coverage radius.

Improved physical layer secrecy fairness in a realistic indoor NOMA VLC network under users’ mobility

This paper investigates the improvement of the secrecy rate fairness in a cellular non-orthogonal multiple access (NOMA) visible light communication (VLC) network. We formulate the users’ secrecy rate by taking into account the users (legitimate and illegitimate) mobility according to the random way-point (RWP) model. We propose an optimization problem to maximize the minimum secrecy rate for two legitimate users per cell, and then we generalize it for an arbitrary number of users. Moreover, utilizing secrecy considerations, we customize two well-known power allocation methods of fixed power allocation (FPA) and gain ratio power allocation (GRPA) as benchmarks for comparison of the proposed maximization power allocation method. Our numerical results demonstrate the superiority of the proposed power allocation algorithm compared with FPA and GRPA methods. Moreover, for the higher number of users, our results indicate the advantages of the proposed algorithm over modified FPA and GRPA methods. Finally, we investigate the effect of the optical receiver’s field of view fluctuations on the performance of the VLC network.

SLIPT-Enabled Multi-LED MU-MISO VLC Networks: Joint Beamforming and DC Bias Optimization

This paper studies a simultaneous lightwave information and power transfer (SLIPT)-enabled multi-user (MU) multiple input single output (MISO) visible light communication (VLC) network, where multiple user equipments (UEs) are simultaneously allowed to receive information by the photodiode (PD) and harvest energy by the solar panel, respectively. To improve the system spectral efficiency, an achievable sum rate maximization problem is formulated subject to the minimum energy harvesting (EH) requirement of each UE, the total transmit power constraint of the LEDs and the dimming control constraint of the LEDs, by jointly optimizing the beamforming vector and the direct current (DC) bias vector of the LEDs. To be general, the practical non-linear EH model and the information capacity model of the VLC channel are adopted. To solve the non-convex optimization problem, the objective function is equivalently transformed at first by using the epigraph reformulation, and then the transformed problem is relaxed with the semi-definite relaxation (SDR) method. Based on this, an iterative algorithm is designed to approximately obtain the maximal achievable sum rate based on the successive convex approximation (SCA). Simulation results indicate that there exists a non-trivial trade-off between the achievable sum rate and the harvested energy, and that DC bias vector dominates the amount of the harvested energy compared with the beamforming vector. Besides, for a given relatively high EH requirement, the achievable sum rate increases with the increment of the dimming level, especially for relatively small dimming level. Once the dimming level is larger than a specific value, with the increment of the dimming level, more transmit power will be allocated for illumination, resulting in the decrement of the achievable sum rate.

Robust Power Allocation for Integrated Visible Light Positioning and Communication Networks

Integrated visible light positioning and communication (VLPC), capable of combining advantages of visible light communications (VLC) and visible light positioning (VLP), is a promising key technology for the future Internet of Things. In VLPC networks, positioning and communications are inherently coupled, which has not been sufficiently explored in the literature. We propose a robust power allocation scheme for integrated VLPC Networks by exploiting the intrinsic relationship between positioning and communications. Specifically, we derive explicit relationships between random positioning errors, following both a Gaussian distribution and an arbitrary distribution, and channel state information errors. Then, we minimize the Cramer-Rao lower bound (CRLB) of positioning errors, subject to the rate outage constraint and the power constraints, which is a chance-constrained optimization problem and generally computationally intractable. To circumvent the nonconvex challenge, we conservatively transform the chance constraints to deterministic forms by using the Bernstein-type inequality and the conditional value-at-risk for the Gaussian and arbitrary distributed positioning errors, respectively, and then approximate them as convex semidefinite programs. Finally, simulation results verify the robustness and effectiveness of our proposed integrated VLPC design schemes.

The Performance Comparison of SC-PPM Receiver Models

Visible light communication (VLC) technology has arisen as promising candidate to solve the critical challenges of wireless communication networks. In particular, the evolving explosion in use of internet services requiring high bandwidth will soon become a great potential problem among the service provider. Meanwhile, this paper describes a physical layer solution to provide data transmission in the VLC networks. In the paper, it is aim to examine the performance comparison of SC-PPM (Subcarrier Pulse Position Modulation) demodulator schemes. It is considered three receiver techniques to assemble the demodulator techniques to SC-PPM receiver system. Firstly, the traditional PPM (T-PPM) demodulator has been applied on the SC-4PPM receiver system to estimate the slot that includes high frequency signal that is referred to as subcarrier signal. To successfully detect the bits by using traditional PPM receiver, it must be known the dimming level of received SC-4PPM signal. This is a serious problem to ensure data transmission in the real-time VLC systems due to challenge of providing the variable dimming level knowledge at the receiver side. In another receiver model that is referred to as PD (Peak Detector), it is aim to detect peak values of slot with high frequency signal. The disadvantage of this system is that BER (Bit Error Rate) performance depends the difference between peak and bottom values of subcarrier filled slot. Hence, second method is improved to achieve the similar BER performance at all dimming levels between 12.5% and 87.5%. This receiver model is called as IPD in the paper. In brief, it is reported for the first time, it has been employed the PD and the IPD algorithms for the SC-PPM receiver schemes. In addition to this, it is given a theoretical framework for both the traditional PPM and the improved receiver schemes in VLC-SC-PPM schemes. Moreover, it has been investigated how the SC-PPM receiver schemes are affected by brightness level.

Threefold layered optical wireless network: illumination, communication, and positioning.

Visible light communication (VLC) technology has traditionally emerged as a complementary solution to radio frequency, due to its huge available bandwidth and high data rates. Relying on visible spectrum, VLC allows both illumination and communication, thus representing a green technology with reduced energy impact. However, VLC can also be exploited for localization, and thanks to its huge bandwidth it can reach very high accuracy (i.e., <0.1 m). In this paper, we deal with a VLC network intended as a fully integrated indoor system providing at the same time both illumination, communication, and positioning tasks. Three different optimization problems are presented, aiming to seek for the minimum number of white LEDs that can achieve different constraints of illumination, data rate, and localization accuracy. Different types of LEDs are considered, according to which tasks they are intended to pursue. We consider traditional white LEDs aiming to provide illumination, communication, and positioning; otherwise, we distinguish between devices designed for localization-only and communication-only. Such distinction results in different optimization problems, and related solutions, as confirmed through extensive simulation results.

Energy Efficiency in Secure VLC Networks With SLIPT

This letter focuses on maximizing the energy efficiency (EE) for secure visible light communication (VLC) network with simultaneous lightwave information and power transfer (SLIPT) by optimizing the beamforming vectors and direct current (DC) bias under the constraints of the minimal rate requirement, the secure transmission requirement, the minimal energy harvesting (EH) requirement, and total power budget at the transmitters. To solve the non-convex optimization problem, we present a dual-layer iterative algorithm based on Dinkelbach’s and successive convex approximation (SCA) methods. An efficient algorithm is also designed to find a good initial point to accelerate the convergence. Simulation results show three typical phenomena: (1) the EE first remains unchanged and then decreases with the increasing EH requirement; (2) compared with the traditional sum-rate maximization design, our proposed approach achieves notable EE performance gain under the secure constraints; (3) the number of the authorized receivers, as well as the number of the unauthorized receivers, imposes significant impact on the EE performance.

R-AP's position-domain model for an RO-receiver and AP placement strategy for an uninterrupted link between the robotic arm and AP in the VLC network.

In the visible light communication (VLC) network, the optical link between the robotic arm and the access point (AP) is easily interrupted due to the random orientation of the receiver on the robotic arm. First, based on the VLC channel model, a position-domain model of reliable AP (R-AP) for a random-orientation receiver (RO-receiver) is proposed. The channel gain of the VLC link between the receiver and the R-AP is non-zero. The tilt-angle range of the RO-receiver is [0,π]. Given the field of view (FOV) angle and the orientation of the receiver, the R-AP's position domain of the receiver can be obtained by this model. Then, based on the R-AP's position-domain model for the RO-receiver, a novel AP placement strategy is proposed. Under this AP placement strategy, the number of R-APs for the RO-receiver is not less than 1, thereby effectively avoiding link interruption caused by the random orientation of receivers. Finally, it is proved by the Monte Carlo method that, under the AP placement strategy proposed in this paper, the VLC link of the receiver on the robotic arm can remain uninterrupted during the movement of the robotic arm.

Preface

With great, successful, and prestigious history of ICETAC, the 2022 3rd International Conference on Electrical Technology and Automatic Control (ICETAC 2022) not only sets a solid foundation but also has the potential to be even greater than ever before. The conference took place in Macau, China during December 2nd-4th, 2022 in the form of virtual conference.ICETAC 2022 provided an international cooperation and exchange platform for experts and scholars in related fields, and promoted the scientific and academic information interchange among all the participants and the industrialization cooperation of academic achievements in Electrical Technology and Automatic Control. It is not only an exceptional academic conference, but also a great platform to discover new perspective, and inspire new thinking.During the conference, we had about 100 participations both as speakers and participants, including researchers, industrial experts, professionals, etc. To make this conference on schedule, we had a three-part plenary including a keynote speech delivered by three resources persons from different parts of China and other countries. All the keynote speakers have delivered expertise lectures by imparting the latest findings from their respective research domains. Among them, Assoc. Prof. Lisu Yu from Nanchang University, China addressed a keynote speech on A Novel Multiple Access Scheme for Visible Light Communication Networks in 6G. He provided an overview and outlook on the application of sparse code multiple access (SCMA) for 6G wireless communication systems, which is an emerging disruptive non-orthogonal multiple access (NOMA) scheme for the enabling of massive connectivity and proposed to apply SCMA to a massively distributed access system whose architecture is based on fiber-based visible light communication, ultra-dense networks, and NOMA. Under this framework, he considered the interactions between optical fronthauls and wireless access links, and he also outlined a number of promising directions associated with SCMA. It was a wonderful opportunity for all the participants to interact with the experts and specialists to get their advice or suggestions.The proceedings of ICETAC 2022 contain quantities of excellent papers grouped by topics. All submissions were performed double blind review to check their quality of content, level of innovation, significance, originality and legibility, covering but not limited to the following topics: Electric Vehicle Technology, Intelligent Control System, Automation and Instrumentation, Motors and Electrical Appliances, Fault Detection, etc.We would like to express our gratitude to all the participants for their fruitful work and excellent contribution to ICETAC 2022. Especially, we appreciate the enormous work of the editorial board and reviewers in the preparation of this volume. Also, our special thanks and appreciation go to the Journal of Physics: Conference Series. Hopefully, all participants and other interested readers can benefit scientifically from the proceedings and find it rewarding in the process.The Committee of ICETAC 2022List of Committee member is available in this Pdf.

Random-blockage model and adaptive feedback strategy of CSI for an indoor VLC network

This paper investigates the feedback period of channel state information (CSI) considering random blockage for an indoor visible light communication (VLC) network. First, a random-blockage model (RBM) for the indoor VLC network was built. Through the RBM, a closed expression for the dynamic blockage and self-blockage probability were obtained. Based on the statistical method and RBM, a coherence distance model (CDM) under random blockage was established. Through the CDM, the weighted coherence distance of channel gain for user equipment at any position can be obtained under a specific distribution density of blockers. Based on the CDM, an adaptive feedback strategy for CSI was proposed, thus realizing the timely feedback of CSI under random blockage. Finally, the effectiveness of the above RBM and CDM was verified via simulation. The value obtained by Monte Carlo simulation is consistent with the theoretical value obtained by the RBM. Compared with the fixed-period feedback strategy, the adaptive feedback strategy was able to achieve compromise between improving channel reliability and reducing feedback overhead. The average interrupted time ratio and the average mean square error between the recovered channel gain and the actual channel gain were significantly reduced.

Convolutional-neural-network-based versus vision-transformer-based SNR estimation for visible light communication networks.

Visible light communication (VLC) has emerged as a promising technology for future sixth-generation (6 G) communications. Estimating and predicting the impairments, such as turbulence and free space signal scattering, can help to construct flexible and adaptive VLC networks. However, the monitoring of impairments of VLC is still in its infancy. In this Letter, we experimentally demonstrate a deep-neural-network-based signal-to-noise ratio (SNR) estimation scheme for VLC networks. A vision transformer (ViT) is first utilized and compared with the conventional scheme based on a convolutional neural network (CNN). Experimental results show that the ViT-based scheme exhibits robust performance in SNR estimation for VLC networks compared to the CNN-based scheme. Specifically, the ViT-based scheme can achieve accuracies of 76%, 63.33%, 45.33%, and 37.67% for 2-quadrature amplitude modulation (2QAM), 4QAM, 8QAM, and 16QAM, respectively, against 65%, 57.67%, 41.67%, and 34.33% for the CNN-based scheme. Additionally, data augmentation has been employed for achieving enhanced SNR estimation accuracies of 95%, 79.67%, 58.33%, and 50.33% for 2QAM, 4QAM, 8QAM, and 16QAM, respectively. The effect of the SNR step size of a contour stellar image dataset on the SNR estimation accuracy is also studied.

Game Theory Based Delta-OMA Scheme for VLC Networks

This paper proposes a delta-orthogonal multiple access (D-OMA) scheme-based visible light communications (VLC) network to enhance spectral efficiency and massive connectivity in the indoor environment. The D-OMA scheme is an advanced version of the non-orthogonal multiple access (NOMA) scheme. D-OMA allows the partial overlapping of the in-band NOMA clusters to achieve the benefits of a massive in-band NOMA scheme with low power consumption and less complexity. In this work, the massive in-band NOMA scheme is used as a special case of the proposed D-OMA scheme. Game theory is employed for the user grouping mechanism, which enhances the sum rate of the proposed network. Closed-form expressions for the bit error rate (BER) and outage probability of the proposed network are derived. Further, downlink transmission power optimization is performed using Karush-Kuhn Tucker (KKT) conditions to improve the outage performance of the proposed D-OMA VLC network. The presented numerical results show the effect of optical filter gain and field of view (FoV) in indoor communication. Further, it is noted that the BER performance of the D-OMA scheme outperforms the massive in-band NOMA scheme due to the cluster sizes which control the interference in the D-OMA scheme. Moreover, the sum rate of the proposed network is significantly improved using the preference relation algorithm (PRA) compared to the random NOMA scheme.

Successive Light Interference Cancellation and Allocation (SLICA) Algorithm for Indoor VLC System: A Backbone for 6G Network

This paper considers a successive light interference cancellation and allocation algorithm (SLICA) practicing interference cancellation for an indoor visible light communication (VLC) system based on successive interference cancellation (SIC) technique. The interference among users is cancelled with the help of the proposed approach to reduce computational complexity. VLC has become the cornerstone of intelligence in the current scenario. The data services allocated to the users are demand based and rely on their channel conditions. The data is allocated to user by modulating light waves via illuminated LEDs. The receiving end has photodiode installed in it to recover back the data. Better performance rate is achieved with lesser interference with the proposed approach. To guarantee good (quality-of service) QoS, considerable simulations are carried out considering real- time scenario which further demonstrates the high level performance of the proposed approach over conventional approach. Based on the analysis, the SINR and interference level is demonstrated for the conventional and the proposed approach and there is a hike in the performance rate of SINR and interference level of about 20 – 30 % with the applied proposed approach. The prior motto of this study is to enhance the system throughput and improve per user average performance rate and reducing the complexity of the system. This contributes to the total efficiency of the optical indoor VLC network. Our proposed algorithm will provide a strong backbone for the 6G deployment.