Visible Light Communication Receiver Research Articles

Orientation-induced link-blocked receiver for MIMO visible light communication.

In this paper, we propose an orientation-induced link-blocked receiver (OLBR) to simultaneously reduce the correlation of the multiple-input multiple-output (MIMO) channels and avoid disruptive transmission in visible light communication (VLC) system. The idea of this paper is to combine the adjustable normal vector ideology of an angle diversity receiver with the channel correlation reduction of a link-blocked receiver. The proposed OLBR is designed to intentionally block specific links while enhancing other links between light-emitting diodes (LEDs) and photodiodes (PDs). Besides, the proposed receiver can perform well in many locations in the room whereas conventional receivers fail to receive signals from at least one LED due to unwanted line-of-sight (LOS) link blocking. Moreover, an algorithm is proposed to iteratively solve the optimization problem, taking the normal vectors of the PDs into consideration. The simulation results show that the proposed OLBR can achieve a performance gain in comparison with previous receiver design schemes for different scenarios, especially in the locations that are far from LEDs.

TRAFFIC LIGHT SYSTEMS MENGGUNAKAN VISIBLE LIGHT COMMUNICATION (VLC) SEBAGAI ALAT BANTU TUNANETRA UNTUK MENYEBERANG JALAN

The people with visual impairment have problems in mobility and orientation, especially in the outdoor environment. Recently, traffic lights systems, which is a facility where someone crosses do not support visually implaired people so they still need help from others in crossing the road. In this study, a system that integrates traffic lights is implemented using Visible Light Communication (VLC) technology, where the VLC transmitter is mounted on a traffic light, and the VLC receiver is installed as a wearable device that can be used with the audio information signal. The measurement is done by considering the use of color filters. The measurement results show that the transmitter system has been able to send signals with audio frequencies from 300 Hz to 4000 Hz. Besides that, receiving an information signal consisting of a audio signal from a transmitter mounted on a traffic light with a red, yellow and green color filter can be received by a VLC receiver that is placed on a visually impaired person of good quality with the signal voltage received above 4 Vpp, where the use of a yellow filter shows the best signal reception results with a voltage output of 5.00 Vpp at a frequency of 2400 Hz compared to other color filters.ABSTRAK: Penyandang tuna netra memiliki masalah dalam hal mobilitas dan orientasi, khususnya di lingkungan luar (outdoor). Pada sistem yang terdapat pada lampu lalu lintas (traffic light) yang merupakan fasilitas dimana seseorang menyebrang saat ini belum mendukung penyandang tuna netra, sehingga sampai saat ini masih membutuhkan bantuan orang lain dalam menyebrang jalan. Pada penelitian ini, sebuah sistem yang diintegrasikan pada lampu lalu lintas diimplementasikan menggunakan teknologi Visible Light Communication (VLC), dimana VLC transmitter dipasang pada lampu lalu lintas dan VLC receiver dipasang sebagai wearable device dengan sinyal informasi suara digunakan oleh penyandang tunanetra sehingga dapat menerima informasi mengenai kondisi lampu lalu lintas pada saat itu. Pengujian sistem dilakukan dengan mempertimbangkan penggunaan filter berwarna. Hasil pengukuran menunjukan bahwa sistem transmitter telah dapat mengirimkan sinyal dengan frekuensi suara dari 300 Hz sampai 4000 Hz. Disamping itu, penerimaan sinyal informasi berupa sinyal suara dari transmitter yang terpasang pada lampu lalu lintas dengan filter warna Merah, Kuning dan Hijau telah dapat diterima oleh receiver yang ditempatkan pada penyandang tuna netra dengan kualitas baik dengan tegangan sinyal yang diterima diatas 4 Vpp, dimana penggunaan filter warna kuning menunjukan hasil penerimaan sinyal yang paling baik dengan tegangan output 5,00 Vpp pada frekuensi 2400 Hz dibandingkan dibandingkan penggunaan filter warna lainnya

A SiPM-Based VLC Receiver for Gigabit Communication Using OOK Modulation

The growing demand for wireless communications services means that RF systems are increasingly unable to support user’s requirement. Consequently, there is a growing interest in using visible light communication (VLC), including interest in sensitive VLC receivers. Since they have the potential to detect single photons, silicon photomultipliers (SiPMs) could potentially be used to create the most sensitive possible VLC receivers. In this paper, results of experiments to determine the optimum bias voltage and dynamic range of an off-the-shelf SiPM are reported. Results are then presented which show that in 500 lux of ambient light this receiver supports data rates of more than 2 Gbps with a bit-error-rate (BER) of 10−3.

Indoor amplify-and-forward power-line and visible light communication channel model based on a semi-hidden Markov model

In this paper, the channel model of a multicarrier, indoor amplify-and-forward (AF) hybrid power-line communication (PLC) and visible light communication (VLC) channel is demonstrated. Measurements are obtained from different positions between the VLC transmitter and receiver in an indoor testbed with the aid of software-defined radios. Using the obtained measurements, channel models are derived using a semi-hidden Markov model (SHMM) with the aid of a Fritchman channel state representation model. The Baum-Welch algorithm is then used to re-estimate and validate the derived models. Results presented show the error-free run distribution in the hybrid channel and the probability of error from the obtained measurements. The re-estimated probability of error (P¯e) of each measured indoor scenario is also seen to match the corresponding measured Pe, showing the validity of the derived SHMM models.

Light follower systems for visually impaired using visible light communication

Visual impairment is the condition of someone who has a disorder or an obstacle in their vision. In this research, the implementation of light follower systems for visually impaired using visible light is proposed. This system can enable visually impaired people to determine orientation and support mobility, especially in an indoor situation, using visible light. The prototype of the visually impaired pathway was made as visible light communication (VLC) transmitter consisting of a 12 V power supply, light emitting diode (LED), MPEG-1 Layer-3 (MP3), and band pass filter (BPF) filter circuit. The VLC receiver is made a prototype of a blind stick consisting of a photodiode, amplifier, buzzer, timer, and 9 V battery. The measurement of this system uses acrylic and color filters with system accuracy taking into account the angle and conditions when the fluorescent lights are turned on and off. This result showed the system could transmit audio signals at a frequency of 3000 Hz. Furthermore, the comparison results showed that the quality of measurements without using a filter is better than using a filter. The output voltage value without using a filter with an angle of 700 degree is 7.19 Vp-p, meanwhile using a filter with an angle of 700 degree is 6.48 Vp-p.

Hardware Architectures of Visible Light Communication Transmitter and Receiver for Beacon-based Indoor Positioning Systems

High-speed applications of Visible Light Communications have been presented recently in which response times of photodiode-based VLC receivers are critical points. Typical VLC receiver routines, such as soft-decoding of run-length limited (RLL) codes and FEC codes was purely processed on embedded firmware, and potentially cause bottleneck at the receiver. To speed up the performance of receivers, ASIC-based VLC receiver could be the solution. Unfortunately, recent works on soft-decoding of RLL and FEC have shown that they are bulky and time-consuming computations. This causes hardware implementation of VLC receivers becomes heavy and unrealistic. In this paper, we introduce a compact Polar-code-based VLC receivers. in which flicker mitigation of the system can be guaranteed even without RLL codes. In particular, we utilized the centralized bit-probability distribution of a pre-scrambler and a Polar encoder to create a non-RLL flicker mitigation solution. At the receiver, a 3-bit soft-decision filter was implemented to analyze signals received from the VLC channel to extract log-likelihood ratio (LLR) values and feed them to the Polar decoder. Therefore, the proposed receiver could exploit the soft-decoding of the Polar decoder to improve the error-correction performance of the system. Due to the non-RLL characteristic, the receiver has a preeminent code-rate and a reduced complexity compared with RLL-based receivers. We present the proposed VLC receiver along with a novel very-large-scale integration (VLSI) architecture, and a synthesis of our design using FPGA/ASIC synthesis tools.

Exploiting Blockage in VLC Networks Through User Rotations

Visible Light Communication (VLC) has attracted significant attention over the past decade. Although numerous research studies have been performed to improve the data rate of VLC links, an important fact has been largely neglected: human bodies that host VLC receivers could block their Line-of-Sight (LOS) downlinks , and thus, degrade the system performance greatly. In this paper, we propose a system that can significantly improve the robustness for VLC networks by avoiding performance degradation due to blockage. A novel user-in-the-loop mechanism is designed in which users (including human bodies and VLC receivers) are guided by the network to rotate themselves to improve the system performance and the individual user experience. Both our simulation and experimental results demonstrate that the proposed user-in-the-loop mechanism can improve the system throughput and user fairness on average by 48% and 14%, respectively. For individual users, the average gain in throughput can reach up to 135%. Furthermore, to make the system more practical, two lightweight heuristics are designed and implemented which can achieve similar gains while reducing the computational complexity by 99%.

Intelligent and Practical Deep Learning Aided Positioning Design for Visible Light Communication Receivers

Visible light positioning (VLP) systems can achieve high positioning precision. However, they are not compatible with visible light communication (VLC) systems. They require special positioning modules and could not reuse functional communication modules, while requiring more than two light emitting diodes (LEDs) to be deployed at user ends. In order to address the issues of weak compatibility and high complexity of VLP, we present a novel position estimation deep neural network (PE-DNN) and propose to add a PE-DNN aided module at the VLC receivers. The proposed module firstly learns features of the VLC channel from received pilot signals implicitly, then it can estimate receivers’ 2-dimension positions intelligently with a single LED. Accordingly, VLC systems can simultaneously provide positioning and information transmission services with only one LED and one photodiode (PD), thus the compatibility and the practicality are greatly improved. Simulation results show that the proposed system achieves a centimeter-level positioning accuracy, and can provide intelligent and practical positioning services for the users.

P.507 Visual activity monitoring and social attention in autism spectrum disorder: effect of context and age

Using solar cell (or photovoltaic cell) for visible light communication (VLC) is attractive. Apart from acting as a VLC receiver (Rx), the solar cell can provide energy harvesting. This can be used in self-powered smart devices, particularly in the emerging “Internet of Things (IoT)” networks. Here, we propose and demonstrate for the first time using pre-distortion pulse-amplitude-modulation (PAM)-4 signal and parallel resistance circuit to enhance the transmission performance of solar cell Rx based VLC. Pre-distortion is a simple non-adaptive equalization technique that can significantly mitigate the slow charging and discharging of the solar cell. The equivalent circuit model of the solar cell and the operation of using parallel resistance to increase the bandwidth of the solar cell are discussed. By using the proposed schemes, the experimental results show that the data rate of the solar cell Rx based VLC can increase from 20 kbit/s to 1.25 Mbit/s (about 60 times) with the bit error-rate (BER) satisfying the 7% forward error correction (FEC) limit.

Performance of Location-Based Equalization for OFDM Indoor Visible Light Communications

In indoor visible light communication (VLC) systems, multiple optical transmitters and reflections will result in a dispersive multi-path channel. We propose a location-based equalization (LBE) method for indoor VLC using orthogonal frequency division multiplexing. With LBE, the location information of a VLC receiver, particularly in terms of coordinates, is utilized for channel estimation. The estimated channel parameters can be further used in a variety of ways for real-time mitigation of multi-path effects induced by a dispersive channel. As a result, the channel distortion can be predictable and thus VLC becomes a smart location-based value-added service. With different implementation schemes, extensive numerical simulations and comparisons are carried out to verify the feasibility of LBE. Results show that LBE can effectively improve system bit error rate (BER) performance at different indoor locations. Even in the presence of location error, link shadowing, or receiver tilt, the LBE design, especially based on only a line-of-sight channel, still shows good robustness, which can achieve reliable transmission quality with BER < 10−3 at various locations. With LBE, the horizontal and vertical tolerance against location error can be 0.28 m and 0.1 m, respectively, while the tolerance angle against receiver tilt is basically no less than 30°.

Semipolar () InGaN/GaN micro-photodetector for gigabit-per-second visible light communication

This paper investigated the use of semipolar InGaN/GaN multiple quantum well based micro-photodetectors (μPDs) as the optical receiver for visible light communication (VLC). The fabricated semipolar μPDs exhibited a low dark current of 1.6 pA at −10 V, a responsivity of 0.191 A W−1, and a −3 dB modulation bandwidth of 347 MHz. A high data rate of up to 1.55 Gbit s−1 was achievable by utilizing the extended bandwidth of more than −10 dB, and based on a straight-forward non-return-to-zero on–off keying modulation scheme. This development demonstrated the feasibility of wavelength-selective detection scheme using semipolar μPD for high-data-capacity VLC systems.

Deep Reinforcement Learning-Enabled Secure Visible Light Communication Against Eavesdropping

The inherent broadcast characteristics of the visible light communication (VLC) channel makes VLC downlinks susceptible to unauthorized terminals in many actual VLC scenarios, such as offices and shopping centers. This paper considers a multiple-input-single-output (MISO) VLC scenario with multiple light fixtures acting as the transmitter, a VLC receiver as the legitimate user, and an eavesdropper attempting to intercept the undisclosed information. To improve the confidentiality of VLC links, a physical-layer anti-eavesdropping framework is proposed to obscure the unauthorized eavesdroppers and diminishes their capability of inferring the information through smart beamforming over the MISO VLC wiretap channel. To cope with the intractable problem of finding the theoretically optimal solution of the secrecy rate and utility for the MISO VLC wiretapping channel, a reinforcement learning (RL)-based VLC beamforming control scheme is proposed to achieve the optimal beamforming policy against the eavesdropper. Furthermore, a deep RL-based VLC beamforming control scheme is proposed to handle the curse of dimensionality for both observation space and action space and avoid the quantization error of the RL-based algorithm. Simulation results show that the proposed learning-based VLC beamforming control schemes can significantly decrease the bit error rate of the legitimate receiver and increase the secrecy rate and utility of the anti-eavesdropping MISO VLC system, compared with the benchmark strategy.

The Future Prospects for SiPM-Based Receivers for Visible Light Communications

A silicon photomultiplier (SiPM) could be used to create visible light communications receivers whose sensitivity is determined by shot-noise. However, its finite output pulse width will limit its bandwidth and its recovery time, and dark count rate could limit its sensitivity. In this paper, a method of accurately determining the signal levels needed to transmit data in a shot-noise limited system using pulse-amplitude modulation is described. In addition, a method of estimating the additional power needed to use equalisation to overcome inter-symbol interference caused by the finite output pulse width of SiPMs is described. The best way to achieve more than 1 Gb/s with this type of receiver and how to select the best available SiPM as a receiver are then discussed.

Dynamic FOV visible light communications receiver for dense optical networks

This study explores how the field-of-view (FOV) of a visible light communications (VLCs) receiver can be manipulated to realise the best signal-to-noise ratio (SNR) while supporting device mobility and optimal access point (AP) selection. The authors propose a dynamic FOV receiver that changes its aperture according to receiver velocity, location, and device orientation. The D-FOV technique is evaluated through modelling, analysis, and experimentation in an indoor environment comprised of 15 VLC APs. The proposed approach is also realised as an algorithm that is studied through analysis and simulation. The results of the study indicate the efficacy of the approach including a 3X increase in predicted SNR over static FOV approaches based on measured received signal strength in the testbed. Additionally, the collected data reveal that D-FOV increases effectiveness in the presence of noise. Finally, the study describes the tradeoffs among the number of VLC sources, FOV, user device velocity, and SNR as a performance metric.

Fully integrated receiver for free-space visible light communication

Fully integrated receiver for free-space visible light communication

Optimal and Robust Power Allocation for Visible Light Positioning Systems Under Illumination Constraints

The problem of optimal power allocation among light emitting diode (LED) transmitters in a visible light positioning system is considered for the purpose of improving localization performance of visible light communication (VLC) receivers. Specifically, the aim is to minimize the Cramer-Rao lower bound (CRLB) on the localization error of a VLC receiver by optimizing LED transmission powers in the presence of practical constraints, such as individual and total power limitations and illuminance constraints. The formulated optimization problem is shown to be convex and thus can efficiently be solved via standard tools. We also investigate the case of imperfect knowledge of localization parameters and develop robust power allocation algorithms by taking into account both overall system uncertainty and individual parameter uncertainties related to the location and orientation of the VLC receiver. In addition, we address the total power minimization problem under predefined accuracy requirements to obtain the most energy-efficient power allocation vector for a given CRLB level. Numerical results illustrate the improvements in localization performance achieved by employing the proposed optimal and robust power allocation strategies over the conventional uniform and non-robust approaches.

Design and Implementation of a Long Range Indoor VLC System using PWM

Visible Light Communications (VLC) is currently considered one of the most promising Optical Wireless Communications (OWC) for commercial applications, due to the widespread deployment of Light Emitting Diodes (LEDs) for energy efficiency, durability and low cost. With the ability to provide several THz of bandwidth, VLC is expected to co-exist with legacy and future Radio Frequency (RF) media as a reliable solution to the rapid demand of high-speed wireless communication. VLC is challenged by two main drawbacks: ambient light interference and the transmission range. To overcome these drawbacks, we propose a tuned VLC Analog Front-End (AFE) using simple and low-cost electronic circuity. The proposed VLC receiver architecture consists of a transimpedance amplifier, a fourth order Multiple Feed Back (MFB) band pass filter and a comparator. Experimental results demonstrated that by employing the proposed front-end the VLC transmission range could be extended up to 4.7 m by using Pulse Width Modulation (PWM). Moreover, the proposed system showed robustness against ambient light interference under the indoor scenario.

Low Rate VLC Receiver Design Using NCP302 Voltage Detector for IoT/IoL Connected Smart Homes

The Internet of Things (IoT) and Visible Light Communication (VLC) is opening up new services in lighting industry by integrating sensory network features in addition to standard illumination functionality. In this progressive developments, the next generation lighting devices for smart homes are capable to sense the environmental conditions and transfer the captured data through lights to gateway controller to access remotely. The smart home environmental sensor information’s are few kbps only so VLC systems need to built-in with low rate light connectivity to transfer data to the gateway. To provide error free communication, the quality of a received light signal is important to be considered when designing an VLC receiver. Therefore, this paper proposes the design of robust low rate IoL receiver design using NCP302 voltage detector for micro controller to adapt the IoT/IoL front end module for system integration. To evaluate the proposed system performance, the Arduino UNO based IoT/IoL controller designed with lighting, sensors and lights connectivity interfaces. The experimental result shows that the robust interference rejection is feasible on proposed VOL receiver and possible to have an error-free communication up to 10 kbps at a low SNR using OOK modulation.

On the Use of the Intrinsic Ripple of a Buck Converter for Visible Light Communication in LED Drivers

In this paper, we present the analysis of a novel technique to implement visible light communication (VLC) into light emitting diode (LED) drivers with minimum hardware requirements and efficacy degradation. It uses a synchronous buck converter as a circuit for a dual-purpose LED driver for illumination and VLC. The role of the converter is to regulate the average current via the duty cycle value for lighting purposes and to modulate digital data through the phase of its ripple waveform. In this technique, the phase of the pulsewidth modulator acts as an independent variable to modulate the ripple waveform for a binary phase-shift keying modulation and does not affect lighting regulation. Thus, the transmission of wireless digital data uses the remaining ac content present in the waveform of the ripple. By detecting the phase of the ripple, a VLC receiver can decode the data sent by the transmitter. Finally, our experimental results show that the efficacy of the LED is not affected by the value of the ripple when operating outside its nonlinear region, along with minimum global efficacy degradation when compared with a standard synchronous buck converter with the same parameters and no VLC capabilities.

Noise and Bandwidth in Operational Amplifiers for Conventional TIAs used in Visible Light Communication

Trans-impedance amplifiers play an essential role in the physical layer of visible light communication systems. They are applied in the first stage of a visible light communication receiver. This short paper is a follow-up from a previous study about the bandwidth and noise of Op-Amp based trans-impedance amplifier as used in visible light communication systems through two approaches: calculation and simulation. The results of both calculation and simulation are then compared through several scenarios. In this study, the &lt;em&gt;Orozco &lt;/em&gt;approach is used as a fundamental reference in calculating the trans-impedance amplifier’s bandwidth and noise. Whereas for simulation, we used TINATM-SPICE®.