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.

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.

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.

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.

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.

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).

接收机朝向随机的NOMA-VLC系统性能

在可见光通信(visible light communication, VLC)系统中,针对用户位置、接收机朝向对视距(line of sight, LOS)链路影响严重,以及实时准确的信道状态信息(channel state information, CSI)反馈需求而导致的整体计算复杂性问题,对用户位置和接收机朝向随机的下行VLC系统性能进行了研究,并利用非正交多址接入(non-orthogonal multiple access, NOMA)技术提高频谱利用率。根据用户位置以及接收机朝向模型建立的室内VLC系统一般框架,推导了中断概率以及遍历和速率解析表达式。在此基础上,进一步提出了不同的NOMA调度机制及用户反馈策略,以提高系统性能、降低链路开销。最后,通过蒙特卡洛仿真验证了解析结果的正确性。仿真结果表明,用户位置和接收机朝向会严重影响VLC系统性能,且对于任意NOMA调度机制,同时反馈距离和朝向信息比只反馈距离信息更具优越性。

基于STM32的VLC字符传输系统

对可见光通信字符传输系统进行了改进。与基于51单片机的可见光通信系统相比,改进后的基于STM32的VLC字符传输系统具有更小的发射板体积和接收板体积,可以支持更高速率和更多的功能。系统链路采用定向式视距信道、光强度调制-直接检测技术,通过对白光LED的高速调制,利用功能较全面的串口调试软件观察了PC机间的LED可见光通信。实验结果表明,系统在PC机间能够实现中英文字符的高速单工数据通信。

VLC-WiFi异构网络QoS感知的跨层动态资源分配

VLC-WiFi异构网络已经成为广受欢迎的短距离无线通信方式之一。然而,有限的频谱资源导致VLC-WiFi异构网络容量难以满足井喷式增长的用户数据带宽需求。该文结合物理层的动态链路传输性能以及媒体访问控制层的队列缓冲延迟性能,定义链路传输性能和链路服务质量(QoS)感知等级评估公式,根据用户数据包QoS需求,设计QoS感知的跨层动态资源分配(QoS-CLDRA)方法,并引入非正交多址接入的用户匹配与功率分配策略,进一步提升系统的吞吐量。仿真结果表明:所提方法能够有效提升系统吞吐量和降低缓冲队列长度。

VLC网络中兼顾QoS和公平性的协作子载波与功率分配算法

针对目前可见光通信(visible light communication,VLC)中干扰管理算法存在的问题,提出了一种兼顾服务质量(quality of service,QoS)和公平性的协作子载波和功率分配算法。将终端公平度与QoS的乘积作为优先级因子,每轮优先级因子最高的终端获得协作接入点(access point,AP)分配的子载波,并且采用基于图论的advanced-BFM(advanced-backward-forward marking)算法进行协作子载波分配;为了充分利用每个AP的发送功率,避免由于终端所处位置引起的信道质量差异影响,提出了基于改进注水思想的3步优化功率分配算法,进一步最大程度提高终端QoS与公平性,最大化和速率。通过模拟仿真可得,与代表性文献比较,提出的干扰管理与功率分配方案明显提升了网络公平性、平均QoS、频谱效率和能效。

基于三维正交频分复用的可见光通信系统研究

为解决调制带宽受限和频率选择性衰落问题,提出了一种基于三维正交频分复用(3D-OFDM)的可见光通信系统,通过三维星座映射,该系统增加了相邻星座点间的最小欧式距离(MED),从而降低了系统的误码率。针对接收机的硬判决易受到可见光信道非线性效应和采样频偏干扰的问题,提出了一种基于K均值聚类解调的三维星座解映射方法。结果表明,在误码率为3.8e-3时,与采用16QAM和8QAM调制的2D-OFDM系统相比,所提出的16ary与8ary的3D-OFDM,分别能够实现3 dB和5 dB的信噪比增益;此外,所提出的3D-OFDM系统在峰均功率比(PAPR)方面也有优势,分别降低了0.3 dB和0.4 dB。所提出的3D-OFDM可见光通信系统具有更优的误码性能。

基于VLC+WiFi协同的室内异构无线接入网络

针对基于VLC与WiFi协同的室内异构无线接入网络进行研究,提出了一种改进的组网结构及切换策略,改进方案的基本思想是使用可见光下行通信,使用WiFi进行上下行通信,当下行链路可见光通信中断时,切换使用WiFi进行通信。提出了典型的应用场景,并结合典型的VLC及WiFi信号源,计算和分析了信号覆盖和功率分布。

GSSK⁃VLC系统中基于SVM的LED选择算法

为了有效降低室内基于广义空移键控(Generalized Space Shift Keying,GSSK)调制技术的可见光通信(Visible Light Communications,VLC)系统LED选择算法的复杂度,提高系统的LED选择速度,提出了一种基于支持向量机(Support Vector Machine,SVM)的机器学习低复杂度高效率LED选择算法.通过将室内GSSK⁃VLC系统的LED选择等价建模为多分类的机器学习问题,利用核SVM构建LED选择的最优化问题,通过对偶理论,获得原问题的二次凸规划对偶问题,从而高效的获取SVM的最优分类参数.最后,通过学习训练获得的最优分类参数实现对任意给定用户信道信息的在线天线选择.通过计算机仿真和复杂度分析,与传统的LED选择算法相比,本文提出的算法能够在实现在线LED选择的同时保持低误码率(Bit Error Ratio,BER)性能,表明了该算法的有效性.

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.

基于译码转发的PLC-VLC/RF混合传输系统中断性能分析

针对译码转发(Decode and Forward,DF)协议下室内电力线通信(Power Line Communication,PLC)-可见光通信(Visible Light Communication,VLC)/射频(Radio Frequency,RF)的混合传输系统,考虑接收端采用最大比合并(Maximal Ratio Combining,MRC)和选择合并(Selection Combining,SC)两种方案,并分析这两种方案下的系统中断性能。首先,在考虑路径损耗、信道衰落和用户随机分布的情况下,分别给出MRC和SC两种方案的输出信噪比表达式。接着,推导出这两种方案下系统的中断概率闭合表达式。最后,利用计算机仿真验证理论分析的正确性,分析不同参数对系统中断性能的影响,从而为PLC-VLC/RF混合传输系统的实际应用提供理论依据。

An indoor positioning system for mobile target tracking based on VLC and IMU fusion

An indoor positioning system( IPS) is designed to realize positioning and tracking of mobile targets,by taking advantages of both the visible light communication( VLC) and inertial measurement unit( IMU). The platform of the IPS is designed,which consists of the light-emitting diode( LED)based transmitter,the receiver and the positioning server. To reduce the impact caused by measurement errors,both inertial sensing data and the received signal strength( RSS) from the VLC are calibrated. Then,a practical propagation model is established to obtain the distance between the transmitter and the receiver from the RSS measurements. Furthermore,a hybrid positioning algorithm is proposed by using the adaptive Kalman filter( AKF) and the weighted least squares( WLS)trilateration to estimate the positions of the mobile targets.Experimental results show that the developed IPS using the proposed hybrid positioning algorithm can extend the localization area of VLC,mitigate the IMU drifts and improve the positioning accuracy of mobile targets.

基于FPGA实现的自适应OFDM VLC仿真系统

采用现场可编程门阵列（FPGA）技术搭建了一个自适应正交频分复用（OFDM）可见光通信（VLC）仿真系统。该系统实现了自适应高阶OFDM调制和高速数据速率传输,正交振幅调制（QAM）的调制阶数M有16、64、256、1024四种方式,数据传输速率为16.8～42.0Mb/s。

基于VLC技术的车辆安全预警系统

针对车辆间传统灯语交流方式沟通不便、不安全的现状,设计了一种基于可见光通信(VLC)技术的车辆安全预警系统。该系统以DSP处理器为核心,利用可见光进行通信,以LED作为信号的发射源,用强度不同表征信号,并将其加载到LED发光器件上,通过LED灯的明暗闪烁来传递所需要的信息;App音频输入后经DSP处理器处理将音频信号转换为电信号,并将其加载到LED灯上实现信号发送;指定方向的车辆在收到光信号后,经过处理器处理后最终以音频信号的形式表达,发送方车辆所要传达的信息。试验证明,该装置操作简单方便,信息传送快速、高效,能达到预期的安全预警目的,在现有汽车和未来无人驾驶汽车的安全领域有较高的市场推广价值。