High-speed visible light communication based on micro-LED:A technology with wide applications in next generation communication

The evolution of next-generation cellular networks is aimed at creating faster,more reliable solutions.Both the next-generation 6G network and the metaverse require high transmission speeds.Visible light communication(VLC)is deemed an important ancillary technology to wireless communication.It has shown potential for a wide range of applications in next-generation communication.Micro light-emitting diodes(μLEDs)are ideal light sources for high-speed VLC,owing to their high modulation bandwidths.In this review,an overview ofμLEDs for VLC is presented.Methods to improve the modulation bandwidth are discussed in terms of epitaxy optimization,crystal orientation,and active region structure.Moreover,electroluminescent white LEDs,photoluminescent white LEDs based on phosphor or quantum-dot color conversion,andμLED-based detectors for VLC are introduced.Finally,the latest high-speed VLC applications and the application prospects of VLC in 6G are introduced,including underwater VLC and artificial intelligence-based VLC systems.

Separate Least Mean Square Based Equalizer with Joint Optimization for Multi-CAP Visible Light Communication

Visible light communication(VLC) is expected to be a potential candidate of the key technologies in the sixth generation(6G) wireless communication system to support Internet of Things(IoT) applications. In this work, a separate least mean square(S-LMS) equalizer is proposed to compensate lowpass frequency response in VLC system. Joint optimization is employed to realize the proposed S-LMS equalizer with pre-part and post-part by introducing Lagrangian. For verification, the performance of VLC system based on multi-band carrier-less amplitude and phase(m-CAP) modulation with S-LMS equalizer is investigated and compared with that without equalizer,with LMS equalizer and with recursive least squares(RLS)-Volterra equalizer. Results indicate the proposed equalizer shows significant improved bit error ratio(BER) performance under the same conditions. Compared to the RLS-Volterra equalizer, SLMS equalizer achieves better performance under low data rate or high signal noise ratio(SNR) conditions with obviously lower computational complexity.

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.

Advances and prospects in visible light communications

Visible light communication （VLC） is an emerging technology in optical wireless communication （OWC） that has attracted worldwide research in recent years. VLC can combine communication and illumina- tion together, which could be applied in many application scenarios such as visible light communication local area networks （VLANs）, indoor localization, and intelligent lighting. In recent years, pioneering and significant work have been made in the field of VLC. In this paper, an overview of the recent progress in VLC is presented. We also demonstrate our recent experiment results including bidirectional 100 Mbit/s VLAN or Li-Fi system based on 00K modulation without blue filter. The VLC systems that we proposed are good solutions for high-speed VLC application systems with low-cost and low-complexity. VLC technology shows a bright future due to its inherent advantages, shortage of RF spectra and ever increasing popularity of white LEDs.

High-speed phosphorescent white LED visible light communications without utilizing a blue filter

We experimentally demonstrate a high-speed phosphorescent white light emitting diode （LED） visible light communication （VLC） system without utilizing an optical blue filter. Here, the white light response is equalized by using the proposed analog equalizers. The 3 dB bandwidth of the VLC link could be extended from 3 to 132 MHz, which allows 330 Mbit/s non-return-to-zero on-off keying （NRZ-OOK） data transmission with a bit error ratio （BER） of 7,2 × 10^-10 and 672 Mbit/s 64-quadrature amplitude modulation （64-QAM） data transmission with a BER of 3.2 × 10^-3. These resultant BERs are less than the forward error correction （FEC） limit of 3.8× 10^-3. The VLC link distance is 1 m using a single 1 W LED. The transmitter and receiver modules are integrated to a compact size. Furthermore, the relationships between the signal performance and illumination level or optical power are investigated and analyzed.

移动场景下高速可见光通信系统硬件电路设计

针对移动场景下高速可见光通信中存在信号衰减快与系统带宽受限问题,创新设计了能够实现高速、稳定可见光通信系统的自适应均衡硬件电路。首先,从自适应控制接收信号衰减角度,提出一种面向移动可见光通信的自适应增益电路设计方案。其次,从补偿通信系统频响衰减角度,设计了一种模拟预均衡与后均衡电路。最后,基于所设计的电路搭建了可见光通信硬件测试平台。实验结果表明,将自适应均衡电路应用于可见光通信系统中,可以有效提高通信速率,还可有效克服移动过程中信号衰减与中断问题。

Enhancements of SDR-Based FPGA System for V2X-VLC Communications

This pilot study focuses on a real measurements and enhancements of a software defined radio-based system for vehicle-to everything visible light communication(SDR-V2X-VLC).The presented system is based on a novel adaptive optimization of the feed-forward software defined equalization(FFSDE)methods of the least mean squares(LMS),normalized LMS(NLMS)and QR decomposition-based recursive least squares(QR-RLS)algorithms.Individual parameters of adaptive equalizations are adjusted in real-time to reach the best possible results.Experiments were carried out on a conventional LED Octavia III taillight drafted directly from production line and universal software radio peripherals(USRP)from National Instruments.The transmitting/receiving elements used multistate quadrature amplitude modulation(M-QAM)implemented in LabVIEW programming environment.Experimental results were verified based on bit error ratio(BER),error vector magnitude(EVM)and modulation error ratio(MER).Experimental results of the pilot study unambiguously confirmed the effectiveness of the proposed solution(longer effective communication range,higher immunity to interference,deployment of higher state QAM modulation formats,higher transmission speeds etc.),as the adaptive equalization significantly improved BER,MER and EVM parameters.The best results were achieved using the QR-RLS algorithm.The results measured on deployed QR-RLS algorithm had significantly better Eb/N0(improved by approx.20 dB)and BER values(difference by up to two orders of magnitude).

基于均衡电路的可见光通信系统带宽拓展方案

为了有效提高LED可见光通信系统的传输带宽,设计了一种基于均衡电路的带宽拓展方案。该方案在发射端加入具有谐振效应的预均衡电路,在接收端加入具有高通特性的后均衡电路。通过电路仿真设计后,搭建了可见光通信系统,对电路进行测试。

可见光通信系统的后均衡电路设计

结合ADS仿真软件工具,设计了一款π型均衡器。根据可见光通信接收系统的响应曲线,采用双级联π型均衡器作为后均衡。经过与电路仿真软件结果对比,验证了π型均衡器设计的可靠性,测试了π型均衡器在后均衡电路上对提高LED调制带宽的可行性。

白光LED煤矿工作面可见光通信调制技术研究

介绍了煤矿工作面可见光通信系统总体结构;研究了煤矿工作面可见光通信关键技术,包括载波调制技术、调制驱动电路设计以及调制带宽,得出兼顾带宽和发光效率的白光LED是理想的可见光通信系统光源。

200 Mb/s visible optical wireless transmission based on NRZ–OOK modulation of phosphorescent white LED and a pre-emphasis circuit

We present a high-speed visible light communication （VLC） link that uses a commercially available phos- phorescent white light-emitting diode （LED）. Such devices have few megahertz bandwidth due to the slow response of phosphorescent component, which severely limit the transmission data rate of VLC system. We propose a simple pre-emphasis circuit. With blue-filtering and the pre-emphasis circuit, the bandwidth of VLC system can be enhanced from 3 to 77.6 MHz, which allows non-return-to-zero on-off-keying （NRZ- OOK） data transmission up to 200 Mb/s with the bit error ratio of 5.3 × 10-7 which is below 10-6. The VLC link operates at the room illumination level of -1000 lx at 1.1 m range using a single 1 W white LED.

高速可见光通信硬件预均衡技术研究进展

基于发光二极管(LED)的可见光通信(VLC)技术能够实现照明和数据通信的双重功能,成为近年来无线通信的研究热点之一。目前商用LED较小的调制带宽在很大程度上制约了高速VLC系统的快速发展。为了解决这一问题,提出了通过硬件预均衡技术拓宽VLC系统的-3dB调制带宽的方法,有效提高VLC系统传输速率;分析总结了近年来国内外应用于高速VLC系统中硬件预均衡技术的发展脉络和应用现状,并对比分析了不同预均衡方案的均衡控制策略、均衡电路结构以及均衡效果;对均衡技术的发展趋势提出建议,为今后高速VLC技术的研究提供参考。