Stable yellow light emission from lead-free copper halides single crystals for visible light communication

Yellow light-emitting diodes(LEDs) as soft light have attracted abundant attention in lithography room, museum and art gallery. However, the development of efficient yellow LEDs lags behind green and blue LEDs, and the available perovskites yellow LEDs suffer from the instability. Herein, a pressure-assisted cooling method is proposed to grow lead-free CsCu2I3single crystals, which possess uniform surface morphology and enhanced photoluminescence quantum yield(PLQY) stability, with only 10% PLQY losses after being stored in air after 5000 h.Then, the single crystals used for yellow LEDs without encapsulation exhibit a decent Correlated Color Temperature(CCT) of 4290 K, a Commission Internationale de l’Eclairage(CIE) coordinate of(0.38, 0.41), and an excellent 570-h operating stability under heating temperature of 100°C. Finally, the yellow LEDs facilitate the application in wireless visible light communication(VLC), which show a-3 dB bandwidth of 21.5 MHz and a high achievable data rate of 219.2 Mbps by using orthogonal frequency division multiplexing(OFDM) modulation with adaptive bit loading. The present work not only promotes the development of lead-free single crystals, but also inspires the potential of CsCu2I3in the field of yellow illumination and wireless VLC.

Modelling and Performance Analysis of Visible Light Communication System in Industrial Implementations

Visible light communication(VLC)has a paramount role in industrial implementations,especially for better energy efficiency,high speed-data rates,and low susceptibility to interference.However,since studies on VLC for industrial implementations are in scarcity,areas concerning illumination optimisation and communication performances demand further investigation.As such,this paper presents a new modelling of light fixture distribution for a warehouse model to provide acceptable illumination and communication performances.The proposed model was evaluated based on various semi-angles at half power(SAAHP)and different height levels for several parameters,including received power,signal to noise ratio(SNR),and bit error rate(BER).The results revealed improvement in terms of received power and SNR with 30 Mbps data rate.Various modulations were studied to improve the link quality,whereby better average BER values of 5.55×10^(−15) and 1.06×10^(−10) had been achieved with 4 PAM and 8 PPM,respectively.The simulation outcomes are indeed viable for the practical warehouse model.

Intelligent MRI Room Design Using Visible Light Communication with Range Augmentation

Radio waves and strong magneticfields are used by Magnetic Reso-nance Imaging(MRI)scanners to detect tumours,wounds and visualize detailed images of the human body.Wi-Fi and other medical devices placed in the MRI procedure room produces RF noise in MRI Images.The RF noise is the result of electromagnetic emissions produced by Wi-Fi and other medical devices that interfere with the operation of the MRI scanner.Existing techniques for RF noise mitigation involve RF shielding techniques which induce eddy currents that affect the MRI image quality.RF shielding techniques are complex and lead to RF leak-age.VLC(Visible light Communication)is an emerging and efficient technology to avoid RF interference near MRI scanners.Range augmentation with power conservation of the LED is a big challenge in existing VLC systems.The major objective of the proposed work is to develop an intelligent-MRI room design without RF interference using visible light communication and enhance the distance between VLC transmitter and VLC receiver.In this paper,it is proposed to implement VLC using On-Off keying modulation and enhance distance using large active area photodiodes with Automatic Gain Control Circuit(AGC)using software and hardware.The performance of the proposed intelligent MRI-VLC system is analyzed by calculating Bit Error Rate at an inclined distance of 50 cm away from line of sight of the LED.The Experimental results showed that the maximum distance achieved was 400 cm at Bit Error Rate(BER)of 1.5×10^(-5).

Optimizing Optical Attocells Positioning of Indoor Visible Light Communication System

Visible light communication(VLC),which is a prominent emerging solution that complements the radio frequency(RF)technology,exhibits the potential to meet the demands of fifth-generation(5G)and beyond technologies.The random movement of mobile terminals in the indoor environment is a challenge in the VLC system.The model of optical attocells has a critical role in the uniform distribution and the quality of communication links in terms of received power and signal-to-noise ratio(SNR).As such,the optical attocells positions were optimized in this study with a developed try and error(TE)algorithm.The optimized optical attocells were examined and compared with previous models.This novel approach had successfully increased minimum received power from−1.29 to−0.225 dBm,along with enhanced SNR performance by 2.06 dB.The bit error rate(BER)was reduced to 4.42×10−8 and 6.63×10−14 by utilizing OOK-NRZ and BPSK modulation techniques,respectively.The optimized attocells positions displayed better uniform distribution,as both received power and SNR performances improved by 0.45 and 0.026,respectively.As the results of the proposed model are optimal,it is suitable for standard office and room model applications.

LED Modulation Characteristics in a Visible-Light Communication System

This paper conducts a research on modulation characteristics of blue light-emitting diodes (LEDs) used in a visible-light communication (VLC) system. Through analysis of the modulation characteristics of LEDs with different emitting sizes, we find that there is a similar linear relationship between LED’s 3dB bandwidth and the operation current density. This experiment also shows that high series resistance is one major issue that limits our LED's modulation speed. To further improve the LED bandwidth, the resistance can be reduced by optimizing device layout as well as reducing material bulk resistance. Clearly, this study provides an approach to increase the modulation bandwidth of GaN-based LEDs for VLC systems.

Symbol Error Rate Performance Analysis of Non-Orthogonal Multiple Access for Visible Light Communications

Non-orthogonal multiple access(NOMA) is considered as one of promising radio access techniques for visible light communications(VLC) in next-generation wireless communications systems.In order to provide theoretical support for designing VLC-NOMA,we derive its analytic expressions for the symbol error rate(SER).Specifically,NOMA is first incorporated with appropriate VLC to establish a VLC-NOMA framework.Afterwards,mathematical expressions of the SER for the VLC-NOMA are developed.Moreover,numerical results are provided carefully to demonstrate that the proposed VLC-NOMA scheme outperforms than state-of-the-art orthogonal frequency division multiple access(OFDMA) one in terms of SER performance.Finally,relationships between the SER performance and the number of users,power allocation coefficient and semi-angle are well investigated,which can give us a scientific guide to devise the VLC-NOMA system for achieving better SER performance.

Design and Analysis of Traffic Information Transmission System Based on Visible Light Communication

Visible Light Communication( VLC) based on LED is a new wireless communication technology with high response rate and good modulation characteristics in the wavelengths of 380- 780 nm. Compared with conventional methods,the waveband of VLC is harmless to human and safe to communication because of no magnetism radiation. An audio information transmission system using LED traffic lights is presented based on VLC technology. The system is consisted of transmitting terminal,receiving terminal and communication channel. Some experiments were made under real communication environment. The experimental results showed that the traffic information transmission system works steadily with good communication quality and achieves the purpose of transmitting audio information through LED traffic lights,with a data transfer rate up to 250 kbps over a distance of 5 meters.

Demonstration of a low‐complexity memory‐polynomial‐aided neural network equalizer for CAP visible‐light communication with superluminescent diode

Visible-light communication(VLC)stands as a promising component of the future communication network by providing high-capacity,low-latency,and high-security wireless communication.Superluminescent diode(SLD)is proposed as a new light emitter in the VLC system due to its properties of droop-free emission,high optical power density,and low speckle-noise.In this paper,we analyze a VLC system based on SLD,demonstrating effective implementation of carrierless amplitude and phase modulation(CAP).We create a low-complexity memory-polynomial-aided neural network(MPANN)to replace the traditional finite impulse response(FIR)post-equalization filters of CAP,leading to significant mitigation of the linear and nonlinear distortion of the VLC channel.The MPANN shows a gain in Q factor of up to 2.7 dB higher than other equalizers,and more than four times lower complexity than a standard deep neural network(DNN),hence,the proposed MPANN opens a pathway for the next generation of robust and efficient neural network equalizers in VLC.We experimentally demonstrate a proof-of-concept 2.95-Gbit/s transmission using MPANN-aided CAP with 16-quadrature amplitude modulation(16-QAM)through a 30-cm channel based on the 442-nm blue SLD emitter.

High Capacity Data Rate System:Review of Visible Light Communications Technology

Wireless communications have become an integral part of global convergence as global connectedness has gradually become dependent on its efficient deployment.The need for"more-broadband"techniques in relation to the ever increasing growth rate of the data hungry society now necessitates novel techniques for the high-speed data transmission.While advancements have been made in this regard,the projection of having an eventual Internet of everything (IoE) deployment will result in an unimaginable transmission data rate requirement as huge data traffic will be conveyed per time within the communications network,which will require a capacity upgrade of the existing infrastructure.Visible light communications (VLCs),as an integral part of optical wireless communications (OWCs),have been reviewed in this article,having the capacity to extend the achievable data rate requirement of the wireless communications network.The technologies,techniques,and best practices have been presented alongside technology integration for the seamless high capacity wireless broadband deployment.

Optical Wireless Communications

The optical spectrum can serve as a good spectrum resource for wideband wireless communications. The advantages of optical wireless communications （OWC） mainly lie in two aspects： the potential large transmission bandwidth due to the high-frequency carrier, and thecommunication security due to no radio-frequency radiation. Thus OWC can be applied in the seenarios where the radio silence is required or the radio frequency radiation may cause explosions, for example in the battle field or some special ar- eas in the storehouses.

Study of Wireless Sensor Network Based on Optical Communication:Research Challenges and Current Results

With the rapid developments of commercial demands,a majority of ad­vanced researches have been investigated for the applications of underwa­ter wireless sensor(WSN)networks.Recently optical communication has been considered for underwater wireless sensor network.An experimental set-up for testing optical communication underwater has been provided and designed in present papers to maximize the energy coupled from these displacements to the transduction mechanism that converts the mechanical energy into electrical.The true case has been considered by measuring dif­fuse attenuation coefficients in different seas.One stand out potential opti­cal communication method,Visible Light Communication(VLC)has been talked and several communication methods are compared from many points of view,for example attenuation in salt water.The evaluation of modula­tion techniques for underwater wireless optical communications has been displayed,and further how the data collection and storage with an under­water WSN is introduced.In this paper current researches for an(UWSN)based on optical communication are studied,in particular the potential VLC method and comparisons of VLC with other optical communication approaches.Underwater challenges would be analyzed by comparing a sort of communication methods,applied in underwater.Future work will be de­veloped at last.

Automotive Visible-Light Communication: Alternative Devices and Systems

Continuous advancements in visible-light communication(VLC)technology have paved the way for future high-capacity communication links that can simultaneously provide data transmission and illumination.VLC is being accepted as a potential complementary technology in 5G networks,and standardization efforts through IEEE 802.15.7 are on their way.Today,vehicular networking applications have become increasingly complex with tight power and performance requirements.Consequently,devices and systems that can meet diverse vehicular networking applications are in great demand.In this article,we discuss three alternatives for vehicular networking applications in(1)LED–photodiode-based active VLC,(2)VLC with a multicamera array receiver,and(3)passive VLC based on decoding information from optical backscatter.We also present our recent experimental and modeling work using our camera-based and passive VLC prototype implementations.

VLC-Based Indoor Positioning Algorithm Combined with OFDM and Particle Filter

Visible light communications(VLC) have recently attracted a growing interest and can be a potential solution to realize indoor positioning,however,the performance of existing indoor positioning system is limited by multipath distortion inside a room.In order to combat the effect of multipath distortion,this paper proposes an LED-based indoor positioning algorithm combined with hybrid OFDM(HOFDM),in which asymmetrically clipped optical OFDM(ACOOFDM) is transmitted on the odd subcarriers while using pulse amplitude modulated discrete multitone(PAM-DMT) to modulate the imaginary part of each even subcarrier.In this scheme,we take a combined approach where a received-signal-strength(RSS) technique is employed to determine the location of the receiver and realize the 3-D positioning by Trust-region-based positioning.Moreover,a particle filter is used to further improve the positioning accuracy.Results confirm that this proposed positioning algorithm can achieve high accuracy even with multipath distortion,and the algorithm has better performance when combined with particle filter.

The Design of VLC-PLC System for Substation Inspection

A kind of integrated network architecture visible light communication (VLC) and power line communication (PLC) is put forward. This architecture is low cost and easy to implement which overcomes the shortcoming of the traditional network architecture. Furthermore, the VLC-PLC integration technology is applied to typical power grid business scene, which is substation intelligent inspection. The business process of master station platform is analyzed. During the intelligent inspection, the VLC-PLC system provides voice communication for on-site inspection personnel and management personnel, and position service. The system can ensure the safety and security of power production.

20.231 Gbit/s tricolor red/green/blue laser diode based bidirectional signal remodulation visible-light communication system

We propose and experimentally demonstrate a recorded 1-m bidirectional 20.231-Gbit/s tricolor R/G/B laser diode(LD) based visible-light communication(VLC) system supporting signal remodulation. In the signal remodulation system, an LD source is not needed at the client side. The client reuses the downstream signal sent from the central office(CO) and remodulates it to produce the upstream signal. As the LD sources are located at the CO, the laser wavelength and temperature managements at the cost-sensitive client side are not needed.This is the first demonstration, to our knowledge, of a >20 Gbit∕s data rate tricolor R/G/B VLC signal transmission supporting upstream remodulation.

光无线通信技术与下一代超宽带家庭接入网

本文描述了一种新的光接入技术一光无线通信技术。简要分析了室外、室内光无线通信技术发展面临的挑战。重点讨论了室内光无线通信在下一代超宽带家庭接入网中实现的方案。最后,介绍了室内光无线通信近期的发展及未来发展的方向。

Towards 10 Gb/s orthogonal frequency division multiplexing-based visible light communication using a GaN violet micro-LED

Visible light communication(VLC)is a promising solution to the increasing demands for wireless connectivity.Gallium nitride micro-sized light emitting diodes(micro-LEDs)are strong candidates for VLC due to their high bandwidths.Segmented violet micro-LEDs are reported in this work with electrical-to-optical bandwidths up to 655 MHz.An orthogonal frequency division multiplexing-based VLC system with adaptive bit and energy loading is demonstrated,and a data transmission rate of 11.95 Gb/s is achieved with a violet micro-LED,when the nonlinear distortion of the micro-LED is the dominant noise source of the VLC system.A record 7.91 Gb/s data transmission rate is reported below the forward error correction threshold using a single pixel of the segmented array when all the noise sources of the VLC system are present.

MISO visible light communication system utilizing hybrid post-equalizer aided pre-convergence of STBC decoding

In this Letter, we propose a modified hybrid linear and nonlinear post-equalizer to aid pre-convergence of space–time block coding（STBC） decoding in the formulated multiple-input-single-output（MISO） visible light communication（VLC） model. Meanwhile, we present a channel estimation algorithm, as the existing method is suboptimal. Experiments demonstrate that a data rate of 1 Gbit/s is easily achieved in 1.3 m indoor free space transmission with the bit error rate（BER） limited to 3.8 × 10^-3. Correspondingly, the Q factor can be improved to 3.13 d B compared to the pure linear equalizer case.

6G Mobile Network Requirements and Technical Feasibility Study

The sixth generation(6G)mobile network is envisaged to be commercially deployed around 2030,which will profoundly change people's lifestyles and accelerate the digitalization of society.To ensure that the requirements of 6G can be achieved,it is essential to establish a set of key performance indicators(KPIs).This paper comprehensively assesses the KPIs not only from the service requirements but also from the technical feasibility points of view.Specifically,theoretical derivations of KPIs have been clarified,and numerical evaluations have been conducted with reasonable technical assumptions.Evaluation results show that some KPIs defined from the service requirements can be improved through advanced technologies while some are still challenging for practical implementations,such as Tbps-level peak data rate and 0.1 ms user plane latency.In addition,it is also necessary to comply with multiple KPIs for some cases.Furthermore,based on the technical analysis,the potential enabling technologies are outlined and foreseeable implementation challenges as well as possible solutions are presented,which promotes a more reasonable design for 6G mobile network.

Indoor gigabit 2×2 imaging multiple-input–multiple-output visible light communication

We propose and experimentally demonstrate a 2 x 2 imaging multiple-input-multiple-output （MIMO） Ny quist single carrier visible light communication （VLC） system based on spectral efficient 64/32-ary quadrature amplitude modulation, as well as pre- and post-equalizations. Two commercially available red-green- blue light-emitting diodes （LEDs） with 3 dB bandwidth of I0 MHz and two avalanche photodiodes with 3 dB bandwidth of i00 MHz are employed. Due to the limited experiment condition, three different colors/ wavelengths are transmitted separately. The achieved data rates of red, green, and blue LED chips are 1.5 , 1.25, and 1.25 Gb/s, respectively. The resulting bit error ratios are below the 7% pre-forward error correction limit of 3.8 × 10-3 after 75 cm indoor transmission. To the best of our knowledge, this is the first experimental investigation of imaging MIMO system, and it is the highest data rate ever achieved in MIMO VLC system.