Visible Light Communication Transceiver Research Articles

Design of PAM-8 VLC Transceiver System Employing Neural Network-Based FFE and Post-Equalization

Wireless communication technology adopting electromagnetic waves in an unlicensed spectrum, such as visible light, for communication has attracted wide research efforts. Visible light communication (VLC) utilizes visible light as a communication medium to transmit signals but faces a limited communication bandwidth and low data rate, which is caused by the intrinsic characteristics of LEDs. This paper first studies a mathematical model of limited bandwidth and its effect on transmitted signals and then analyzes the free space and underwater channel loss. With the theoretical analysis, a VLC transceiver system is presented for solving bandwidth limitation by utilizing a pulse-amplitude modulation-8 (PAM-8) scheme and a hybrid equalization method. The proposed hybrid equalization combined a passive equalizer, a neural network (NN)-based feed-forward equalization (FFE), and a radial basis function neural network (RBF-NN). The feasibility of this VLC system was verified through a co-simulation platform with both free-space and underwater channels. Compared with a VLC system adopting a deep neural network (DNN)-based post-equalization method, the proposed VLC system could achieve a data rate of 3.6 Gbps with a bit error rate (BER) of 3.8 × 10−3 over a 3 m free-space channel. The RBF-NN achieved a reduced training time of 10 min, which was 86.7% lower than the conventional DNN-based post-equalization method.

Design and verification of SoC for OFDM-based visible light communication transceiver systems and integration with off-the-shelf analog front-end

In this paper, a System-on-Chip (SoC) design for Orthogonally Frequency Division Multiplexing (OFDM)-based Visible Light Communication (VLC) transceiver is presented. The VLC transceiver system comprises the physical (PHY) layer and analog front-end (AFE). The OFDM modulation was implemented in the PHY layer. We design the SoC-based PHY layer using the “reuse methodology”. In this methodology, the Intellectual Property (IP) cores do not necessarily need to be created from scratch as it can be obtained from a 3rd party. Using this methodology, it can increase our productivity during the designing process. This methodology is suitable for developing an OFDM system, especially in VLC system, that requires high complexity blocks. When the IP cores are not available from the 3rd party, they can be designed from scratch. We design the IP cores with the AXI4 protocol standard which is widely used in SoC design. Later, the OFDM system IP cores are integrated by using the AXI4-Stream protocol. In addition, the dual-core ARM Cortex-A9 processor is integrated into the OFDM system IP cores using the AXI4-Lite protocol. The transmitter (TX) and receiver (RX) applications run on Linux OS (Xilinux) can access the OFDM system IP cores with the memory–mapped I/O method. To guarantee the successful design, we have tested our SoC design with the off-the-shelf AFE transceiver integration in a real setting. The analog part for this work was created by available commercially components. Three modulation types were selected for the field test, i.e., BPSK, QPSK, and QAM-16. The maximum data rates of VLC system also have been investigated in a real-time as a proof of concept of the proposed SoC architecture.

A Manchester-OOK Visible Light Communication System for Patient Monitoring in Intensive Care Units

Visible Light Communication (VLC) is an interesting solution in Intensive Care (IC) medical environments to, among others, prevent the spread of emerging diseases. This work presents the design of a low-cost and stable VLC transceiver system in addition to practical characterizations and experimental performance evaluations for application in IC environments. The application focuses on the transmission of Manchester-based on-off keying signals, in a proof-of-concept apparatus that makes use of the Eye Opening Penalty (EOP) metric to illustrate a comprehensive picture of the potentials of the evaluated VLC system. Parameters such as Light-Emitting Diode (LED) bias current, modulation frequency, line-of-sight link distance, and signal pattern were analyzed here. Experimental results show an outstanding behavior considering an LED bias current of 400 mA, a signal frequency of 1 MHz and a VLC transmission link length of 2.5 m. To validate our system, vital parameters as heart rate, oxygen saturation, pulse rate, respiration rate, temperature and non-intrusive blood pressure signals were transmitted for VLC links of 1.5, 5 and 15 m, which were received by a multi-parameter monitor, with EOP values of 0.89, 0.96 and 2.67 dB, respectively.

A simplified approach for single carrier visible light communication transceiver using off-the-shelf components

Over the past decades, the demand for high-speed data transmission has grown exponentially, necessitating broadband technology integration to satisfy the emerging data-hungry society. This concern has engendered the proposition of a simplified optical wireless transceiver module using off-the-shelf electronic devices. According to the transistor to transistor logic levels, the transmitter module was made up of a single negative-positive-negative (NPN) transistor operated as a switch to drive an off-the-shelf 12V 5W light-emitting diode (LED). In contrast, the receiver was made up of a photodetector (solar) module for photons detection and back-conversion to electrical signals. The received signal was passed through a four-stage amplification process to remove the ambient noise and retrieve the data signal. The last transceiver module was demonstrated using personal computers. It was observed to perform at different optimum points consistent with exposure to fluorescent light, daytime, and night-time operations consequent upon the induced ambient light interference at data rates constrained by the communication device interface.

A 75-Mb/s RGB PAM-4 Visible Light Communication Transceiver System With Pre- and Post-Equalization

Visible light communication (VLC) technology employing light-emitting diodes (LEDs) as light sources has the advantages of using the license-free spectrum, being power and cost-efficient and having high security. However, common LED devices have the limitations of narrow bandwidths, nonlinear optical and frequency responses over different bias current levels, which cause inter-symbol interference and signal distortion, especially under high order modulation schemes with large current swings. In view of this, a compact PAM-4 VLC transceiver system employing a white LED as the light source with pre- and post-equalization is proposed. The white LED consists of a red, a green and a blue LED unit (RGB LED). Controlled by 3-bit thermometer codes, three separate drivers with feed-forward equalizers (FFEs) drive the RGB LED units to produce the PAM-4 optical signal. The driving currents from the three drivers with FFEs can be calibrated using digital and analog tunings to eliminate the differences in optical and frequency responses of the RGB LED units. A cascaded continuous-time linear equalizer (CTLE) is used at the receiver side as post-equalization to compensate for the narrow bandwidth of LED units. Based on experimental results, the proposed RGB PAM-4 VLC system can improve the highest achievable data rate by 1.67 times from 28 to 75 Mb/s using the pre- and post-equalization scheme.

Design of Ethernet-VLC Data Conversion System Based on FPGA

Visible light communication (VLC) has attracted people's attention due to its wide range of spectrum resources and good privacy in recent year. But research on visible light communication is mostly focused on LED materials, transfer protocol, transmission rates, etc. Lack of research that connect the visible light communications with existing communications methods. In this paper, we propose an Ethernet-visible data conversion system based on FPGA, including Ethernet interface logic, bit-width conversion logic, data buffer logic, and visible light communication transceiver logic. The proposed system achieves Ethernet and visible light access, and realizes 1000Mbps Ethernet data and 625Mbps visible light data conversion. Through buffer control, Ethernet data can be completely and reliably transmitted from high speed to low speed. By defining the structure of visible light communication frame and adding data self-recovery mechanism, data transmission has higher stability on the path of visible light. The feasibility of the system is proved by actual measurements.

A Deep Learning Approach to Universal Binary Visible Light Communication Transceiver

This paper studies a deep learning (DL) framework for the design of binary modulated visible light communication (VLC) transceiver with universal dimming support. The dimming control for the optical binary signal boils down to a combinatorial codebook design so that the average Hamming weight of binary codewords matches with arbitrary dimming target. An unsupervised DL technique is employed for obtaining a neural network to replace the encoder-decoder pair that recovers the message from the optically transmitted signal. In such a task, a novel stochastic binarization method is developed to generate the set of binary codewords from continuous-valued neural network outputs. For universal support of arbitrary dimming target, the DL-based VLC transceiver is trained with multiple dimming constraints, which turns out to be a constrained training optimization that is very challenging to handle with existing DL methods. We develop a new training algorithm that addresses the dimming constraints through a dual formulation of the optimization. Based on the developed algorithm, the resulting VLC transceiver can be optimized via the end-to-end training procedure. Numerical results verify that the proposed codebook outperforms theoretically best constant weight codebooks under various VLC setups.

Analog network coding aided multiuser visible light communication networks using optical CDMA

A novel architecture of a visible light communication (VLC) network that can provide bidirectional transmission for multiple users is proposed in this paper. Multiple users can exchange data asynchronously and simultaneously thanks to the use of analog network coding (ANC) and optical code division multiple access (OCDMA) with the support of a coordinator, which plays a role as a relay node. We derive the mathematical expressions for bit error rate (BER) and network throughput of an indoor VLC network with multiple users located in a room and one coordinator mounted on the ceiling. Many physical layer impairments are considered in our analysis, including shot noise, thermal noise, multiuser interference (MUI), and optical beat noise. BER and throughput performance are investigated versus the transmitted optical power, the number of users, and the VLC transceiver’s parameters. The numerical results obtained in this paper will provide useful information for designing the indoor multiuser VLC networks.

Design and optimization of VLC based small-world data centers

The visible light communication (VLC) has the potential to provide dense and fast connectivity at low cost. In this paper, we propose a novel VLC enabled Wireless Small-World Data Center (WSWDC). It employs VLC links to achieve a fully wireless data center network (DCN) across racks for the first time. The using of VLC links eliminates hierarchical switches and inter-rack cables, and thus reducing hardware investment, as well as maintenance cost. More precisely, to simplify the configuration and control operations, we propose three DCN design rationales: (1) fully-wireless, all inter-rack links are wireless; (2) easy-deployable, it is not necessary to change the existing infrastructure inside data center; (3) plug-and-play, no extra centralized control operations are required. Previous proposals, however, cannot achieve the three rationales simultaneously. To this end, we first use regular VLC links to interconnect racks as a regular grid DCN and optimize the rack placement to shorten the average path length and the network diameter. To further exploiting the benefits of VLC links, a few random VLC links are carefully introduced to update the wireless grid DCN as a wireless small-world DCN. To avoid the potential interference among VLC links, we deploy VLC transceivers at different heights on the top of each rack. In this way, VLC links would not interfere with others at each height level. Moreover, we design a greedy but efficient routing method for any pair of racks using their identifiers as inputs. Comprehensive evaluation results indicate that our WSWDC exhibits good topological properties and network performance.

Binary signaling design for visible light communication: a deep learning framework.

This paper develops a deep learning framework for the design of on-off keying (OOK) based binary signaling transceiver in dimmable visible light communication (VLC) systems. The dimming support for the OOK optical signal is achieved by adjusting the number of ones in a binary codeword, which boils down to a combinatorial design problem for the codebook of a constant weight code (CWC) over signal-dependent noise channels. To tackle this challenge, we employ an autoencoder (AE) approach to learn a neural network of the encoder-decoder pair that reconstructs the output identical to an input. In addition, optical channel layers and binarization techniques are introduced to reflect the physical and discrete nature of the OOK-based VLC systems. The VLC transceiver is designed and optimized via the end-to-end training procedure for the AE. Numerical results verify that the proposed transceiver performs better than baseline CWC schemes.

Deep learning based transceiver design for multi-colored VLC systems.

This paper presents a deep-learning (DL) based approach to the design of multi-colored visible light communication (VLC) systems where RGB light-emitting diode (LED) lamps accomplish multi-dimensional color modulation under color and illuminance requirements. It is aimed to identify a pair of multi-color modulation transmitter and receiver leading to efficient symbol recovery performance. To this end, an autoencoder (AE), an unsupervised deep learning technique, is adopted to train the end-to-end symbol recovery process that includes the VLC transceiver pair and a channel layer characterizing the optical channel along with additional LED intensity control features. As a result, the VLC transmitter and receiver are jointly designed and optimized. Intensive numerical results demonstrate that the learned VLC system outperforms existing techniques in terms of the average symbol error probability. This framework sheds light on the viability of DL techniques in the optical communication system design.

Min‐Max‐MSE Transceiver Design for MU‐MIMO VLC System

This paper considers a multiuser (MU) multiple‐input multiple‐output (MIMO) visible light communication (VLC) system with broadcast channels. Due to the simultaneous transmission of the different source data to the receivers covered with the light rays, the interuser interference (IUI) may degrade the system performance. We strive to suppress the IUI by minimizing the maximum mean square errors (MSE) under the assumption of the perfect knowledge of channel state information (CSI). However, since the CSI may not be perfectly known in practice, a robust design is required against the channel uncertainties. Additionally, the nonnegativity and the limited linear range of the optical signals have been taken into account in the VLC transceiver designs. Simulation results validate that the proposed min‐max‐MSE approach can provide fair transmission, compared with the minimization of sum‐MSE approach. Furthermore, it is demonstrated that the robust scheme is capable of providing robustness and gaining a considerable bit error rate (BER) performance.

Consumer LED lamp with ODAC technology for high-speed visible light communications

Optical digital-to-analog converters (ODACs) were recently proposed to mitigate the non-linear characteristic of light emitting diodes (LEDs) and to simplify the transceiver in optical wireless communication systems. This paper describes the implementation and performance of an ODAC lamp built with commercial phosphor coated LEDs. It is shown to have sufficient performance to cope with data-rates compatible with those recommended for Ultra HD quality internet download speed (25Mbps), despite the very low bandwidth of these LEDs. Also, the structure of a low-cost and high-speed OFDM-based Visible Light Communication transceiver, based on commercial LEDs and off-the-shelf components, is presented. This solution does not require D/A conversion or complex LED driving circuitry in the transmitter, which are usually seen as limiting factors to the deployment of high-speed VLC systems in the consumer LED lighting market.

OCDMA and OSTBC based VLC transceiver design using NI cDAQ

Visible light communication (VLC) is a novel technology especially for short-range data communication. IEEE has standardized VLC for 5G systems as a means to short-range wireless communication. In this paper, a complete state-of-the-art VLC software-defined radio is designed using NI cDAQ components tools developed in LabVIEW/MATLAB. The main objectives in designing a VLC transceiver are the suitable envelope for driving LEDs (transmitters) and a high data rate. The current work makes use of optical code division multiple access mainly to achieve the said objectives. It is shown through comparison with existing system that the proposed system is computationally less expensive and provides improved data rate. Finally, simulation programs are also developed and the proposed system is compared with the existing system in terms of bit error rate.

위치기반서비스 제공을 위한 휴대기기용 가시광통신 송수신기 구현

위치기반서비스 제공을 위한 휴대기기용 가시광통신 송수신기 구현

Designing of an Indoor Visible Light Communication Transceiver for Data Transmission using White LED

Abstract: In this paper, a prototype of full-duplex indoor Visible Light Communication (VLC) transceiver is designed to demonstrate an optical wireless system based on Universal Serial Bus (USB) port for data transmissions using white Light Emitting Diode (LED). Based on VLC technology, the designed system consists of transmitters and receivers can achieve data rate of 161.2 Kbps error free at the distance of 92 cm between two computers for real-time text and image transmission over indoor environment. Experiment results show that for text transmission, symbol error rate (SER) does not vary data rate at some transmission distances, whereas for image transmission, minimum square error (MSE) and peak signal to noise ratio (PSNR) indicate that the received image and transmitted image were almost similar.

Visible Light Communication System Design and Link Budget Analysis

This paper presents, for the first time, a systematic approach to visible light communication (VLC) transceiver design based on an analytical optical wireless link budget study. To obtain the signal-to-noise ratio at the receiver, the received signal power is predicted by modeling the transmitted optical power and the channel path loss, while the input-referred noise is estimated by characterizing the noise contribution from each of the receiver building blocks. Based on the targeted bit error rate (BER) and communication distance, a VLC transceiver using discrete components and a fully integrated CMOS VLC transmitter compliant with the IEEE 802.15.7 Standard have been designed and tested. Experimental results show that the measured BER agrees well with the proposed model for both the systems, validating our design approach and the link budget analysis.

조명 및 무선통신이 동시에 가능한 가시광 송수신기에 관한 연구

본 연구는 조명 및 무선통신이 동시에 가능한 가시광 송수신기에 대해 가시광 통신 본연의 가시성, 무선 통신의 사용 편의성 그리고 고속의 통신 속도를 고려해 edge-emitting laser diode와 silicon photo diode를 기반으로한 고속 가시광 무선 송수신기를 구현하였다. 제안된 가시광 무선 송수신기는 120Mbit/s의 고속에서 양방향 전송이 가능하도록 설계되었으며 이때 발생하는 누화(crosstalk)를 방지하기 위한 방법으로 shielding 방식을 적용해 가시광 송수신기의 성능을 실험적으로 측정 분석하였다. 또 수신기의 시야각 확대를 위한 방법으로는 새로운 구조의 광학적 antenna를 적용해 광학적 antenna가 없는 두 개의 송수신기 사이의 전송링크 특성과 광학적 antenna를 사용한 두 개의 송수신기 사이의 전송링크 특성을 2차원 평면상에서 전송거리, 적용범위 그리고 기울임 정도를 변화시켜 실험과 시뮬레이션을 통해 그 성능을 비교 분석하였다. We investigated the performance of a visible light communication (VLC) transceiver applicable to both of illumination and wireless communication. we considered the visibility of VLC, the easy connection for wireless communication and high-speed transmission and implemented VLC transceiver based on edge-emitting laser diode and silicon photodiode. The proposed VLC transceiver is designated to operate in a full duplex mode at high speed of 120 Mbit/s. The shielding method that is employed as a means to reduce the light cross coupling effect inside the VLC transceiver is proposed and its performance is experimentally measured. We also applied optical antenna to have the larger angle of field of view (FOV) to novel structure of VLC transceiver and examined and analyzed their bit error rate performance, photometric result with respect to the transmission distance, the coverage range and the tilt degree as transmission link characteristic between two transceivers without optical antenna and with optical antenna.

Performance evaluation of visible-light transceiver for peripheral interface

We examine the practicability of the visible-light communication (VLC) transceiver for bidirectional high-speed and short-range communications. A visible-light peripheral interface could be a novel approach, visualizing the veiled security feature of light by employing visible lights as communication media beyond its intended applications, such as illumination and display. The proposed VLC transceivers are implemented with edge-an emitting laser diode and a silicon photodiode, which is primarily designed to operate in a full duplex mode at 120 Mbit/s. The shielding method that is employed to reduce the light cross-coupling effect inside the VLC transceiver is proposed and experimentally investigated. The bit error rate performance of the proposed VLC transceiver is examined with respect to the transmission distance and the coverage.

Visible light communication systems for optical video transmission

This article describes an optical wireless system based on visible light communication (VLC), which allows a video broadcasting to reach a bit rate of 1 Mbps, although this system can also be used for low-speed sensor interconnections. The main advantages of this technology are the robustness against EM interference, safety for human eye, and security against undesired network access. In this article, we present the electronic structure of a low-cost VLC transceiver, the modulation process and the Ethernet interface that has been implemented in each AP (access point). Finally, some conclusions are drawn. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 1572–1576, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.25236