Improve uniformity for an indoor visible light communication system

Visible light communication (VLC) is an alternative technology to the radio frequency (RF) for different applications in the indoor and outdoor environments, it could be utilized for illumination and communication simultaneously, and it offers several advantages over contemporary RF technologies such as low power consumption, free license, large bandwidth, and being friendly to the environment. In this paper, an indoor VLC system uniformity improvement in terms of high received power, signal‐to‐noise ratio (SNR), and bit rate, with RMS delay spread reduction, is proposed. It features a novel model that utilizes a 13‐optical attocells configuration on the ceiling. Moreover, proposed model was evaluated at different semi‐angle at half power. The average received power and SNR were improved to 2.85 dBm and 75.5 dB, while achieved received power and SNR levels at the center of the room were 4.92 dBm and 79.5 dB, respectively. A minimum average RMS delay spread of 0.4749 nanoseconds is obtained, while the highest average bit rate calculated is 211 Mb/s. The proposed model provides a better communication quality and meets illumination standards requirements.     

Location-adaptive transmission for indoor visible light communication

A location-adaptive transmission scheme for indoor visible light communication (VLC) system is proposed in this paper. In this scheme, the symbol error rate (SER) of less than 10^-3 should be guaranteed. And the scheme is realized by the variable multilevel pulse-position modulation (MPPM), where the transmitters adaptively adjust the number of time slots n in the MPPM symbol according to the position of the receiver. The purpose of our scheme is to achieve the best data rate in the indoor different locations. The results show that the location-adaptive transmission scheme based on the variable MPPM is superior in the indoor VLC system.     

基于OCDMA的改进型室内可见光无线局域网分析

在原有的室内可见光无线通信网络结构的基础上,提出将用户终端适配器光源改为激光。用激光通信实现系统的上行链路,采用可见光通信与激光通信相结合的方式实现室内无线局域网,并基于光码分多址(OCDMA)技术,用光正交码(OOC)作为地址码对信号进行编码。仿真结果表明,改进后的系统误码率明显降低,能较好地满足通信的需求。     

Training sequence based channel estimation for indoor visible light communication system

Channel estimation is a key technology in indoor wireless visible light communications(VLCs).Using the training sequence(TS),this paper investigates the channel estimation in indoor wireless visible light communications.Based on the propagation and signal modulation characteristics of visible light,a link model for the indoor wireless visible light communications is established.Using the model,three channel estimation methods,i.e.,the correlation method,the least square(LS) method and the minimum mean square error(MMSE) method,are proposed.Moreover,the performances of the proposed three methods are evaluated by computer simulation.The results show that the performance of the correlation method is the worst,the LS method is suitable for higher signal to noise ratio(SNR),and the MMSE method obtains the best performance at the expense of highest complexity.     

MIMO室内可见光通信系统的同步方法研究

提出了一种适用于MIMO室内可见光通信系统的优化帧同步方法。阐述了优化方法的同步原理,给出了系统同步方法设计和优化方案同步流程。实验仿真结果表明,基于MIMO的多通道优化同步方法在牺牲有限同步建立时间的情况下,能大幅度降低漏同步概率,显著提高系统同步效率。     

Optimal LED deployment for mobile indoor visible light communication system: Performance analysis

The maximization of the system performance in a typical indoor visible light communication system is a major challenge while minimizing the overall resources for the deployment. The intelligent smart lighting systems can be optimized to reduce the requirement of various resources without compromising on the system performance. In this paper, we investigate the optimization of the light emitting diode (LED) resources within an indoor room scenario using a most efficient stochastic optimization technique-Hyper-heuristics evolutionary algorithm (HypEA). The performance of the communication system has been measured in terms of average area outage ratio, computational efficiency and mobility area analysis. The performance of the HypEA has been compared against the most experimented algorithm-Particle swarm optimization (PSO). The detailed investigation and analysis shows that HypEA is computationally more efficient and is able to achieve full mobility with almost 12.5 percent fewer resources as compared to PSO.     

基于导频的室内可见光自适应OFDM通信系统信道估计

使用自适应OFDM技术改善可见光通信系统性能,需要以准确的信道估计为前提。研究可见光自适应OFDM通信系统的基于导频的信道估计方法,引入射频通信中常用的LMS方法,与可见光信道基于LS的估计方法进行了比较,并对其特性进行了分析,仿真实验结果表明,采用LMS估计方法在BER为10-3水平时,SNR优于LS估计方法2 dB,LMS信道估计方法信道跟踪能力较强,比LS法抗干扰。     

白光LED室内可见光通信的关键技术

可见光通信是一项新兴基于白光LED的无线光通信技术,具有发射功率高、不占用无线电频谱、无电磁干扰、无电磁辐射和节约能源等优点,能够同时实现照明和通信的双重功能.阐述了可见光通信技术的发展动态,介绍基于白光LED的室内可见光通信系统,并对提高系统整体性能的若干关键技术进行了研究讨论,为白光LED室内可见光通信系统进一步研究提供依据.     

LED室内可见光语音通信系统设计及实现

LED灯作为主要的新型照明工具,因其较高的灵敏度,可用于光通信系统中。为了研究与验证LED室内可见光语音通信系统的接收性能与传输距离,参照红外通信的信道模型,融入反射光的影响因素,在使用室内标准照明的光发射功率下,采用多径叠加网格算法,计算桌面各接收点接收信号功率等参量的分布,并设计与实现了LED可见光语音单向通信系统的收发电路。结果表明,当LED灯的发射功率大于2W、信号物理层通信速率不高于1Mbit/s的情况下,系统能够满足信号接收功率与接收信噪比的实际通信要求,并能够实现10m距离内的信号无失真解码与清晰收听。这一结果对LED可见光通信系统进一步的研究与应用有一定的价值。     

室内可见光通信光功率分布的实验研究

室内可见光通信技术是基于白光LED（发光二极管）照明光源的无线光通信技术,在机场、医院等严格限制电磁干扰的场合可替代射频通信,应用前景广阔。鉴于室内可见光在传输过程中墙壁反射引起的多径效应对信号传输质量的影响,本文在4.0m×4.0m×2.8m的房间内测量了室内可见光系统光源的光功率分布,结果表明光源的光信号经墙壁反射,会造成严重的多径效应,从而产生码间干扰。本文对室内可见光功率分布的仿真研究进行了实验验证,实验结果与理论仿真研究基本吻合。     

基于LED阵列的可视信道室内可见光通信系统设计

随着固态光源的发展,大功率LED已被广泛应用到照明中。将照明功能与通信功能结合的室内可见光通信系统将有广泛的应用前景。为了满足室内照明和通信要求,通过使用大功率LED构成阵列,设计发射端、接收端,接口模块,构建了基于强度调制及直接检测方法的全双工可见光通信系统。并对系统信道模型进行分析,对单向链路实际光强分布及其可靠通信范围进行实际测量。实验证明该系统的可行性和可靠性。     

基于MIMO-OFDM的室内可见光通信降噪研究

解决阴影效应和多径效应一直是研究可见光通信系统的关键.提出利用MIMO(Multi Input Multi Output)技术扩大通信过程中信号传输的信道容量,配合LED的高强度光线,实现室内光照的大面积覆盖和抗阴影能力.而OFDM(Orthogonal Frequency Division Multiplexing)...     

我国室内可见光通信现状及发展趋势

利用LED光源的快速调制特性,可实现照明和通信一体的室内可见光通信(VLC).针对系统容量提升和多径干扰的消除问题,提出一种采用空时编码的多输入多输出(MIMO)系统结构的VLC方案.     

室内可见光通信LED布局研究与性能分析

发光二极管(LED)的布局对于维持接收平面上光功率分布的稳定起着重要的作用,针对现有矩形LED布局接收功率分布存在盲区,影响可见光通信系统的性能的问题,文章根据照度均方差最小原则,设计了一种LED的圆形布局方案.通过对接收光功率分布、信噪比的分布进行仿真,研究了圆形布局和矩形布局方案.结果表明,在LED数量相同的情况下...     

室内可见光通信APD 探测电路的设计与实现

室内可见光无线通信技术是随着白光LED 照明技术的发展而兴起的无线光通信技术。在分析目前的可见光通信技术基础上,针对室内可见光通信系统的应用需求,设计了雪崩光电二极管(APD)探测电路组件。首先阐述了APD 探测电路的工作原理,其次详细设计并分析了系统各组成部分的电路结构及其功能,最后对所设计的用于室内可见光通信接收子系统的探测组件进行了相关实验测试。实验结果表明:设计有效可行,APD 探测电路具有增益高、带宽宽、温控可靠、稳定性好等优点,对室内可见光通信系统有很好的应用价值,为室内可见光通信系统进一步研究提供依据。     

可见光通信的自动导航系统设计

设计了一套利用可见光通信的自动导航系统。通过分析室内可见光信道模型,设计了可见光定位导航系统的发射模块和接收模块。系统在获取了停车位置信息后,通过光电二极管驱动电路将信息发出,光信号传感器模块接收可见光信号;信号经过解调、滤波后由显示屏显示,同时语音系统播报位置信息,利用贝叶斯相位中心偏置天线（Bayesian Information Criterions Displaced Phase Center Antenna,BDPCA）聚类算法计算出最佳导航路径,从而实现自动导航的目的。测试结果表明,该系统可满足目标的精准定位功能,在搭建的1m×1m×1m 验证实验中,系统的最大定位误差为 7.90 cm ,平均定位误差为 4.85 cm ,降低了26%,最佳导航路径距离更短,所需时间降低了20%,系统有较高的工作效率。     

Design of an optical receiving antenna with high gain and large field of view for indoor visible light communication

In order to meet the requirements of the high gain and wide field of view (FOV) for indoor visible light communication (VLC) system, a new optical receiving system is proposed, which integrates a Fresnel lens with a hemispherical lens. The effects of the two lenses’ spacing and the radius of the hemispherical lens on the optical gain at different FOV are investigated. As the FOV increases, the designed antenna displays enhanced reception performance compared with the traditional receiving optical antenna. The optical gain of the designed antenna is 6.88 in the condition of FOV of 40°. To further verify the rationality of the designed antenna, a model of VLC system is established based on the designed antenna in a room with a size of 5 m×5 m×3 m. The results show that the received average power using the designed antenna increases by 22.81 dBm, and the average signal to noise ratio (SNR) is 2.3 times of that without any optical antenna. The designed antenna is promising for the application in indoor VLC systems.     

TDOA-based indoor positioning using visible light

In this paper, we propose an indoor positioning system in which the visible light radiated from LEDs is used to locate the position of receiver. Compared to current indoor positioning systems using LED light, our system has the advantages of simple implementation, low cost, and high accuracy. In our system, a single photo diode receives pilot signals from LED panels on the ceiling. Then, the time differences of arrival of these pilot signals are used to estimate the position of the receiver. The system can be employed easily because it does not require embedding any ID to the pilot signal. In the paper, the estimation accuracy of the proposed system is analyzed through the simulation. The causes of estimation error are analyzed, and the estimation accuracy of the system in various conditions is shown by simulations.     

基于自适应OFDM的室内可见光通信系统性能研究

为了提高室内可见光通信(VLC)系统性能并充分利用信道带宽资源,将OFDM与自适应技术结合应用于VLC系统中.讨论了系统反馈途径的实现方法,在室内空间环境建模的基础上,对自适应OFDM通信系统的吞吐量和误码率进行了Matlab仿真和分析.