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。     

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。     

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.     

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。     

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.     

基于MIMO室内可见光通信系统最大化保密速率分析

可见光通信(VLC)物理层安全研究对于VLC的商用化和普及有着重要的作用.以一个多输入多输出(MIMO)室内VLC系统为模型,先分别推导了窃听者串通和非串通情况下的保密容量下限表达式并进行分析对比,然后针对非串通情况提出了一种最优的波束赋形方案来最大化保密速率,最后进行了数值仿真.仿真结果表明:非串通情况下的保密容量优...     

室内可见光蜂窝网络信道特性研究

基于可见光通信(VLC)技 术的LED蜂窝网络,设想作为第5代移动通信技术在室内应用的主要备选方式之一,得到越来 越多的关注。本 文采用广义光线追踪算法对符合蜂窝布局的室内可见光信道特性进行研究,分析了不同LED 发光角度条件 下信道冲击响应、路径损耗和信道时延等信道特性。随着LED半功率角从30°增大到60°, 系统路径损耗 与信道时延也整体增大,其中总体路径损耗变化范围为32～36.5dB ,信道时延的变化范围为0.4～1.5ns。     

Compressed sensing channel estimation for STBC‐SM based hybrid MIMO‐OFDM system for visible light communication

This paper presents the idea of sparse channel estimation using compressed sensing (CS) method for space–time block coding (STBC), and spatially multiplexing (SM) derived hybrid multiple‐input multiple‐output (MIMO) Asymmetrically clipped optical‐orthogonal frequency division multiplexing (ACO‐OFDM) optical wireless communication system. This hybrid system accounts multiplexing gain of SM and diversity gain of STBC technique. We present a new variant of sparsity adaptive matching pursuit (SaMP) algorithm called dynamic step‐size SaMP (DSS‐SaMP) algorithm. It makes use of the inherent and implicit structure of SaMP, along with dynamic adaptivity of step‐size feature which is compatible with the energy of the input signal, thus the name dynamic step size. Existing CS‐based recovery algorithms like orthogonal matching pursuit, SaMP, adaptive step‐size SaMP, and proposed DSS‐SaMP were compared for hybrid MIMO‐ACO‐OFDM visible light communication system. The performance analysis is demonstrated through simulation results with respect to bit error rate, symbol error rate, mean square error, computational complexity, and peak‐to‐average power ratio. Simulation results show that the proposed technique gives improved performance and lesser computational complexity in comparison with conventional estimation algorithms.     

基于非正交多址的室内可见光通信系统性能优化方法

室内可见光通信(Visible Light Communication, VLC)系统常用的非对称限幅光OFDM(Asymmetrically Clipped Optical Orthogonal Frequency Division Multiplexing, ACO-OFDM)与直流偏置光OFDM(DC-biased Optical OFDM, DCO-OFDM)采用加循环前缀、信道均衡和载波复用等方法解决信道干扰及多用户复用问题,但均以牺牲有效性为代价。非正交多址(Non-orthogonal Multiple Access, NOMA)通过功率域复用提高频谱利用率,利用串行干扰消除(Successive Interference Cancelling, SIC)进行多用户信号处理,有效兼顾可靠性与有效性。将NOMA应用于室内可见光系统,建立基于NOMA-DCO-OFDM的可见光信号传输及信道增益模型。通过功率域多用户信道差异计算信道增益,进行功率分配实现功率域复用,提高系统容量和通信速率;利用SIC按功率分配算法对用户逐一解调,减弱信道干扰,提高可靠性。通过理论分析和仿真实验验证表明:该系统的通信速率达到6.8×107 bit·s?1,且合速率受用户数量的影响不显著。2用户下,误码率(Bit Error Rate, BER)为10?4时用户1有5.2 dB左右的性能提升,用户2有2.3 dB左右的性能提升,通信可靠性也明显提高。     

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。     

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.     

基于改进粒子群算法的室内可见光通信系统灯源布局

针对传统室内可见光通信(VLC)系统中光源分布的不均匀性导致的通信盲区和通信质量不平稳等问题,提出一种位置和灯源参数联合优化的方法.该方法在不改变传统布局的总功率前提下进行发光二极管(LED)阵列的重新分配,其次遍历搜寻各LED阵列的最优位置,最后运用改进的粒子群优化(PS0)算法对各LED阵列中的参数进行优化.仿真结...     

Indoor multisource channel characteristic for visible light communication

In this paper, we present a wavelength depended ray-tracing algorithm to model the indoor multisource channel impulse response for visible light communication （VLC）. We compare the multipath loss difference between multisource and unisource channel. We also analyze the root mean square （RMS） delay spread and average time delay of three typical wavelengths as VLC holds a wide spectrum from 380 nm to 780 nm, the spectral reflectance of walls is wavelength-dependent. And the result shows that the blue light emitting diode （LED） owns a larger communication bandwidth than other wavelengths in the room with plastic walls. Also, the path loss of three different wavelengths is compared.     

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)...     

An improved Park timing synchronization combined with PN sequence for DCO-OFDM based visible light communication system

This paper presents a new method for timing synchronization of direct current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) visible light communication (VLC) system. This improved method combines the modified Park’s synchronization method with the pseudo-noise (PN) sequence. The synchronization performance of the proposed method is analyzed in details and compared with that of three traditional methods in DCO-OFDM system. It is demonstrated that the improved method can obtain only one narrow and accurate timing point, which increases the synchronization performance of DCO-OFDM VLC system. Furthermore, the simulated results reveal that the new method has higher timing accuracy and resolution than other conventional methods for different signal noise ratios (SNRs) and fast Fourier transform (FFT) block sizes. To further investigate the performance of time metric, experiment is employed and the results show that the proposed method outperforms the other methods.     

基于PWC编码的mCAP可见光通信系统实验

针对可见光通信(VLC)系统中发光二极管(LED)有限的调制带宽,提出了 一种多带无载波幅度相位(mCAP)调制与成对编码(PWC)结合的混合方案.该方案中PWC技术将高频子带与低频子带进行配对和交织来有效克服信噪比(SNR)不平衡问题.通过实验验证,给出了在子带数分别为2、3、4和5的情况下PWC编码对应的最佳旋转角...     

基于MIMO的可见光通信系统研究

可见光通信是利用LED发出的可见光传输信息的,可见光通信兼顾照明和通信,同时LED具备发光强度高、耗能低、无电磁干扰,有着巨大的发展潜力。文章指出,将MIMO技术应用于可见光通信系统,合理地对LED进行布局,可提升系统的可靠性。同时文章研究了可见光通信系统中的调制技术,比较了几种常见的调制技术,分析了各自的优缺点。