Bidirectional Visible Light Communication Research Articles

The Role of Bidirectional VLC Systems in Low-Latency 6G Vehicular Networks and Comparison with IEEE802.11p and LTE/5G C-V2X.

In this paper, we present very recent results regarding the latency characterization of a novel bidirectional visible light communication (VLC) system for vehicular applications, which could be relevant in intelligent transportation system (ITS) safety applications, such as the assisted and automated braking of cars and motorbikes in critical situations. The VLC system has been implemented using real motorbike head- and tail-lights with distances up to 27 m in a realistic outdoor scenario. We performed a detailed statistical analysis of the observed error distribution in the communication process, assessing the most probable statistical values of expected latency depending on the observed packet error rate (PER). A minimum attainable observed round-trip latency of 2.5 ms was measured. Using our dataset, we have also estimated the probability to receive correctly a message with a specific average latency for a target PER, and we compare it to the ultra-reliable low-latency (URLL) 5G communications service. In addition, a mobility model is implemented to compare the VLC and radio frequency (RF) technologies (IEEE802.11p, LTE, 5G) to support an automated braking systems for vehicles in urban platooning.

Bidirectional Vehicle-to-Vehicle Communication System Based on VLC: Outdoor Tests and Performance Analysis

Intelligent Transportation Systems (ITS) aim at integration of innovative technologies in next-generation vehicles in order to increase the safety and efficiency standards of vehicular traffic fluxes. Although many sensors are currently available in modern cars, mutual data exchange between vehicles in real-time will be crucial in future smart vehicles, but this domain, and in particular bidirectional Vehicle-to-Vehicle (V2V) through Visible Light Communications (VLC), remain relatively unexplored yet. In this paper we present a system for bidirectional data transmission between vehicles through VLC. Specifically, we implement for the first time a bidirectional VLC link using real motorcycle headlights (HL) and rear lights (RL), and we provide a characterization of transmission performances under direct sunlight conditions in an outdoor scenario for realistic distances (up to 30 m) and relative positions between two vehicles. The performance of the VLC system has been evaluated in terms of Signal-to-Noise (SNR) maps and Packet Error Rate (PER), measured in various configurations and for different baudrates (28 kBaud / 57 kBaud). Our result show that a bidirectional error-free communication is possible between two consecutive vehicles for distances up to 12 m, whilst successful transmission could be observed up to 21 m. Finally, we compare our bidirectional intensity and PER data in realistic ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">flat</i> ) configuration against the predictions of a physical model which considers non-ideal orientations of the receiver stage through a novel, simple technique that could also be exploited in different VLC implementations. A very good agreement between the experimental data set and the model is found on the whole measurements grid.

A dynamic handover scheme based on bidirectional VLC channel in multi-user attocell networks

Light fidelity (LiFi) would be a potential optical wireless communications technology for future mixed-spectrum 5G/6G indoor attocell network, which uses light-emitting diodes based as an optical antenna and offers Gbits capacity. For this scenario, a dynamic handover scheme based on bidirectional visible light communications (VLC) channel is proposed, which uses the uplink light sources to characterize terminal’s movement status for the mobility and make the handover decision in contrast to the unidirectional links. The uplink reference signal received power and the movement state are examined, and the created algorithm is executed in the bidirectional VLC test bed. The experimental results show that the proposed method will reduce the terminal’s handover rate by up to 45% and increase the optical network throughput by up to 26% at the experimental data rate compared with the skipping handover scheme for indoor LiFi network.

Asymmetrical bidirectional VLC based on beam homogenizer OAM generation technology.

An asymmetric bidirectional visible light communication (B-VLC) system is presented in this Letter. It combines beam homogenizers with a spatial light modulator (SLM) to implement the orbital angular momentum (OAM) generation technology at a terminal user for uplink data transmission. The major advantage of the proposed approach is that multiple OAM modes can be arbitrarily generated simultaneously by a single SLM. The uplink transmission capacity can also be significantly improved by multiplexing more generated OAM channels. For the proof of concept, an asymmetric B-VLC based on the OAM generation technology for uplink transmission at a distance of nearly 2 m has been implemented. The baseband modulation schemes, including on-off keying (OOK) and quadrature phase-shift keying, were also implemented to validate the transmission performance. The experimental results show that the downlink transmission capacity of up to 2.2 Gbit/s can be achieved using an S-polarization beam. In comparison, the uplink transmission capacity can also be significantly enhanced by using P-polarization through multiplexing four OAM channels, each with a maximum transmission rate of up to 800 Mbit/s. The bit error rates (BERs) of both uplink and downlink transmissions were all under the forward error correction limit (BER=3×10-3).

Design and Demonstration of a TDD-Based Central-Coordinated Resource-Reserved Multiple Access (CRMA) Scheme for Bidirectional VLC Networking

The sharply growing demand for increased transmission capacity and bandwidth in last meter and last mile access networks together with the commercialization of fifth generation (5G) wireless systems has been opening up new opportunities for non-radio frequency (RF)-based wireless technologies. Visible light communications (VLC) technology is a potential candidate for access networking in 5G, which offers a higher spectral efficiency than RF-based Femtocell networks by three orders of magnitude. This paper proposes an all wireless optical bidirectional VLC multiple access scheme for pure VLC network access points in terminals. Centralized coordination is adopted to reduce the system complexity. And reservation of resource is introduced to guarantee collision avoidance during data frame transmission. The proposed multiple access scheme introduces special system parameters to achieve the balance of system throughput and access latency. The feasibility of the proposed scheme is verified by both theoretical analysis and experimental investigation. We show that the proposed scheme is suitable for a bidirectional pure VLC access network and can be used as a supplement in the IEEE 802.11 bb for 5G+bidirectional VLC application scenarios.

Bidirectional visible light communication

Visible light communication (VLC) is a data transmission technology that uses the LED lighting infrastructure to simultaneously illuminate and communicate. The ubiquitous existence of LED lamps opened a new opportunity for addressing VLC in many indoor communication scenarios. The motivation for the presented application is the efficient management of warehouses supported by autonomous navigation robots that grab goods and deliver them at the packaging station. This functionality demands bidirectional communication between infrastructures and vehicles. We propose links for infrastructure-to-vehicle (I2V), vehicle-to-infrastructure (V2I), and vehicle-to-vehicle (V2V) to perform indoors, bidirectional communication. A bidirectional communication system between a static infrastructure and a mobile robot (I2V) is proposed. The LED lamps of the warehouse illumination system are used to lighten the space and to transmit information on position and racks’ contents. The mobile robots communicate with the infrastructure (V2I) to transmit information on the items that are being removed and carried to the packaging station. The communication among robots (V2V) provides information on the number of items intended to be collected when the vehicles are in the same lane. The proposed coding schemes are used as modulation for the ON-OFF keying method. Trichromatic white LEDs and a photodetector based on a-SiC:H/a-Si:H with selective spectral sensitivity are used at the emitter and receiver. Position information is provided by each LED lamp to the vehicle by adequate modulation of the RGB emitters. The decoding strategy is based on accurate calibration of the output signal. Different scenarios were designed and tested. Requirements related to synchronous transmission and flickering were addressed to enhance the system performance. The decoding task is discussed using a bit parity error control methodology to ensure simultaneous detection and correction of bit errors. The consequent increase of bit error rate in the VLC transmission is discussed in the I2V link.

Indoor Fine Particulate Matter Monitoring in a Large Area Using Bidirectional Multihop VLC

These particulate matter (PM) causes lethal diseases to humans, and both short term and long term exposure are known to have hazardous effects. PM10 and PM2.5 have diameters less 10 and $2.5~\mu \text{m}$ , respectively, which makes them more dangerous to the human body. Thus, information regarding PM concentrations in indoor environments of dust-sensitive places is essential for proper precaution. In this study, we measured PM values in a large area and transferred this information using visible light communication (VLC) to the monitoring node. VLC is considered as an efficient technique due to its unique advantages and is currently unregulated. We applied bidirectional VLC to transfer information to ensure two-way communication. We also applied a multihop strategy to make the system function as a query answering system at extended distances. At one end, we generated a request to relay the request to the proper node and received the response in the form of PM data. In our experiment, we implemented four nodes and conducted multihop communication utilizing only a VLC link. We achieved a distance of 13.5 m with a zero-error rate between the two nodes using nonreturn to zero on-off keying (NRZ-OOK) modulation. In case of multihop, we achieved a distance greater than 40 m using four nodes to send dust information with a minimal error rate. This can be applied to large indoor areas where radio frequency is restricted.

EMI-Free Bidirectional Real-Time Indoor Environment Monitoring System

Indoor air quality, temperature, and relative humidity affect the thermal comfort and health of the inhabitants. Therefore, monitoring these parameters is essential to prevent indoor air pollution and to improve labor productivity. Most recently, the research conducted has used radio frequency wireless communications to monitor the indoor environment. However, long-term exposure to electromagnetic interference (EMI) causes a detrimental impact on the human body, especially on the elderly, patients, and infants, while it concurrently affects the operation of electronic devices. Thus, we propose a unique indoor environment monitoring system using an EMI-free bidirectional visible light communication technology. The sensing data from the smart sensor tag and the command data used to request the environmental sensing data are transferred bidirectionally between the base station and the smart sensor tag by being modulated into the light-emitting diode (LED) light beam. The proposed smart sensor tags are designed to measure five important parameters of indoor environments, such as CO2 concentration, volatile organic compound level, O2 concentration, temperature, and relative humidity, at multiple positions in real time. In addition, a proposed average-voltage tracking algorithm is adopted to allow the LED illumination to be used as a lighting system and as a long-range wireless communication system. As a result, the proposed system is demonstrated to be error-free when the distance between the base station and the smart sensor tags is 6 m. The measured live data are aggregated and visualized in a cloud platform by a graphical user interface. A web-based application and a mobile application are also developed to display the real-time data.

Transfer-printed micro-LED and polymer-based transceiver for visible light communications.

Visible light communications (VLC) is an emerging technology that uses LEDs, such as found in lighting fixtures and displays, to transmit data wirelessly. Research has so far focused on LED transmitters and on photoreceivers as separate, discrete components. Combining both types of devices into a single transceiver format will enable bi-directional VLC and offer flexibility for the development of future advanced VLC systems. Here, a proof of concept for an integrated optical transceiver is demonstrated by transfer printing a microsize LED, the transmitter, directly onto a fluorescent optical concentrator edge-coupled to a photodiode, the receiver. This integrated device can simultaneously receive (downlink) and transmit (uplink) data at rates of 416 Mbps and 165 Mbps, respectively. Its capability to operate in optical relay mode at 337 Mbps is experimentally demonstrated.

Experimental demonstration of IDMA‐OFDM for visible light communications

We experimentally demonstrate a multicarrier interleave division multiple access (IDMA) scheme for bidirectional visible light communications using orthogonal frequency division multiplexing (OFDM), which has the advantages of good tolerance against multi-path, high spectral efficiency and excellent transmission performance. The generated IDMA signals are modulated on OFDM subcarriers and the different users are separated by the interleavers. When compared with orthogonal frequency domain multiple access, IDMA-OFDM offers increased transmission spans of 30 and 50 cm at a bit error rate (BER) of 10 -3 in the cases of two and four users, respectively.

Color Filter Identification for Bidirectional Visible Light Communication

ABSTRAKSaat ini, cahaya tampak dimanfaatkan oleh manusia hanya sebagai penerangan saja. Akan tetapi, beberapa penelitian telah membuktikan bahwa cahaya tampak dapat dimanfaatkan pula pada sistem komunikasi, yang dinamakan Visible Light Communication (VLC). Pada penelitian ini, sebuah metoda menggunakan color filter diidentifikasi dalam mengimplementasikan sistem bidirectional pada teknologi VLC. Dengan adanya penelitian ini, sebuah sistem bidirectional Visible Light Communication (Bi-VLC) dapat diimplementasikan dengan menggunakan color filter tertentu yang dipasangkan pada posisi uplink dan downlink. Sinyal informasi berupa sinyal audio ditansmisikan melalui VLC transmitter (Tx) yang dipasang color filter dan diterima oleh color filter pada VLC receiver (Rx) setelah melalui media cahaya. Pengujian menunjukan bahwa sistem telah dapat melewatkan sinyal pada frekuensi audio dengan jarak maksimum dari sistem adalah 2,3 m. Sedangkan pasangan color filter yang memiliki kinerja paling baik untuk BI-VLC adalah Azure (Tx) dengan Charteuse Green (Rx), Charteuse Green (Tx) dengan Charteuse Green (Rx), dan Rose (Tx) dengan Charteuse Green (Rx).Kata kunci: Bidirectional, Visible Light Communication (VLC), Color Filter, AudioABSTRACTCurrently, visible light are utilized by humans as illumination only. However, several research have proven that visible light can also be used in communication systems, called Visible Light Communication (VLC). In this research, a method of using color filters was identified for bidirectional systems on VLC technology. With this research, a bidirectional Visible Light Communication (Bi-VLC) system can be implemented using a specific color filter paired in uplink and downlink mode. The audio signal as information is transmitted through a VLC transmitter (Tx) installed by a color filter and received by the color filter on the VLC receiver (Rx) after going through the light media. The result shows that the system has been able to pass the signal at the audio frequency with the maximum distance of the system is 2.3 m. While the best performance of color filter pair for BI-VLC is Azure (Tx) with Charteuse Green (Rx), Charteuse Green (Tx) with Charteuse Green (Rx), and Rose (Tx) with Charteuse Green (Rx).Keywords: Bidirectional, Visible Light Communication (VLC), Color Filter, Audio

Bidirectional Visible Light Communication System Using a Single VCSEL With Predistortion to Enhance the Upstream Remodulation

The demand of higher data rates has made it attractive to consider a low-cost laser diode (LD), such as vertical-cavity-surface-emitting laser (VCSEL) for use in visible light communication (VLC) transmitters (Tx) due to their higher electrical-to-optical modulation bandwidth, beam convergence, and energy efficiency. Many reported LD-based VLC systems only had a solitary downstream transmission. We demonstrate a 3-m bidirectional signal remodulated VCSEL-based VLC system using visible-light modulator to produce the upstream signal. The visible-light external modulator usually has limited modulation bandwidth. By using the predistortion, the upstream remodulated data rate is enhanced by ∼2.8 times. Hence, the VCSEL-based VLC system with 10.64-Gb/s downstream signal and 5-Mb/s upstream remodulated signal can be achieved. We also analyze via numerical simulations how the predistorted signal can enhance the transmission data rate by mitigating the intersymbol interference introduced by the bandwidth limitation of the upstream modulator.

Power analysis based side-channel attack on visible light communication

Visible light communication (VLC) technology has emerged as a significant and necessary improvement to the wireless communication technologies; VLC systems are considered to be more secure than wireless fidelity (Wi-Fi) systems by design, since light cannot penetrate most walls and obstacles. This paper presents a design for a bidirectional VLC system, and it also introduces a method to jeopardize the security aspect of this system. The methodology in this paper is side-channel attack which is defined as exploiting data based on the information gained from physical implementation. It is not a cyber attack on the theoretical weaknesses in the algorithms, but rather is a sideway approach to a fully-functioning physical system. Thus, the authors became the attackers and implemented a current sensor on the power lines from the power supply to the VLC system; the instantaneous power consumed by the communication system has become their main source to obtain the binary data transmitted by visible light. The work has resulted in effective attacks which could successfully extract the information and it has demonstrated side channel attacks on VLC systems through their instantaneous power consumption analysis.

Study on non - audible acoustic communication uplink for bidirectional visible light communication

Background/Objectives: In this paper, we present a problem of conventional unidirectional visible light communication and limited bidirectional visible light communication, and propose a suitable uplink feedback communication structure.Methods/Statistical analysis: In the visible light communication environment using only the conventional LED, bidirectional communication for feedback of user data information between the transmitter and receiver is limited. When all the receiving devices transmit the feedback information through the LED light source, it is inconvenient for the users due to the unnecessary light source generation in the indoor lighting environment due to the characteristics of the visible light communication system performing both the communication and the illumination. In addition, interference due to a plurality of light sources occurs, and the performance of the system is deteriorated.To solve this problem, we propose the uplink system configuration using the non - audible band acoustic wave communication in the visible light communication system.Findings: The uplink transmission is a necessary function for transmitting the feedback information of the terminal, and a transmission scheme capable of ensuring sufficient transmission distance, interference elimination of LED illumination, and power efficiency should be used. In this paper, we have solved the problem of optical interference between downlink transmission and uplink transmission by securing transmission distance using non - audible band acoustic communication.In addition, the problem of the conventional unidirectional visible light communication can be solved by actively transmitting a signal to a channel state change due to communication distance or communication environment change through state information and position information feedback of devices using non-audible sound wave communication.Improvements/Applications: The non-audible sound wave communication uplink system can be applied as fusion technology to various environments such as an IoT network environment requiring a bidirectional network or an indoor small-scale network configuration and a home network configuration.

LED作为收发元件的双向可见光通信系统方案及实现

LED作为收发元件的双向可见光通信系统方案及实现

Using a Single VCSEL Source Employing OFDM Downstream Signal and Remodulated OOK Upstream Signal for Bi-directional Visible Light Communications

In this work, we propose and demonstrate for the first time up to our knowledge, using a 682 nm visible vertical-cavity surface-emitting laser (VCSEL) applied in a bi-directional wavelength remodulated VLC system with a free space transmission distance of 3 m. To achieve a high VLC downstream traffic, spectral efficient orthogonal-frequency-division-multiplexing quadrature-amplitude-modulation (OFDM-QAM) with bit and power loading algorithms are applied on the VCSEL in the central office (CO). The OFDM downstream wavelength is remodulated by an acousto-optic modulator (AOM) with OOK modulation to produce the upstream traffic in the client side. Hence, only a single VCSEL laser is needed for the proposed bi-directional VLC system, achieving 10.6 Gbit/s OFDM downstream and 2 Mbit/s remodulated OOK upstream simultaneously. For the proposed system, as a single laser source with wavelength remodulation is used, the laser wavelength and temperature managements at the client side are not needed; and the whole system could be cost effective and energy efficient.

Physical layer design with analog front end for bidirectional DCO-OFDM visible light communications

Visible light communication (VLC) is a promising wireless communication technology that utilizes existing lighting system infrastructure. This paper presents the bidirectional VLC physical layer design that supports both pulse width modulation (PWM) and direct current-biased optical orthogonal frequency division multiplexing (DCO-OFDM) for downlink, and an infrared pulse position modulation (PPM) for uplink. The physical layer consists of an analog front end (AFE) and digital signal processing (DSP) circuits on both the transmitter and the receiver. The AFE circuit on the receiver is specifically designed to compensate for impairments in optical channels, such as ambient light and uneven distribution of light intensity. The evaluation results show that the designed AFE circuit minimizes the interference in the receiver without increasing the TX power. In addition, the PWM is found to be more robust in the optical channel than the DCO-OFDM. In respect of data transmission rate, however, it is observed that the DCO-OFDM is superior to the PWM; namely, the DCO-OFDM modulation using quadrature phase shift keying (QPSK) attains a data rate of 26.8kbps, while the 2-PWM modulation achieves a data rate of 6.2kbps.

Experimental demonstration of block interleaved frequency division multiple access for bidirectional visible light communications

We propose a power efficient multiple access scheme for visible light communications (VLC) based on the block interleaved frequency division multiple access (B-IFDMA) which provides large frequency-diversity, flexible bandwidth allocation, low complexity of channel equalization, and user separation. Bidirectional B-IFDMA VLC transmission is experimentally demonstrated to verify its feasibility. The impact of the number of subcarriers per block on the transmission performance under wireless optical channel is investigated.

Network Architecture of Bidirectional Visible Light Communication and Passive Optical Network

Network architectures to combine the fiber network outside the building and the visible light communication (VLC) access network inside the building are important for effectively distributing the high-capacity data to different users. In this paper, we propose a bidirectional network combining the VLC access network and the time–wavelength-division-multiplexed passive optical network (TWDM-PON). Orthogonal frequency division multiplexed modulation is used since it offers high spectral efficiency for both the TWDM-PON and the VLC access network. Low-cost phosphor-based white-light light-emitting diodes are (LEDs) used; hence, the VLC access network can combine with the lighting systems.

Smart home multi-device bidirectional visible light communication

Driven by increase in automation, smart homes play an important role in today's human life. This paper presents a new model for smart home technologies based on multi-device bidirectional visible l...