Search query: The transmitter of the visible light communication system

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abstract: In recent years, semiconductor lighting technology, also known as green lighting, has been developed rapidly. The light emitting diode (LED) is one of the most promising solid green light sources of the twenty first century.
author_names: Nan Chi
title: The Transmitter of the Visible Light Communication System
year: 2018

abstract: The method of implementations visible light communication system and the transmitting and receiving devices, including post transmitting side data to be sent constellation modulation, maps the modulated signal to the light source corresponding to and data to be sent optical signal transmitted through; receiving end will receive the the optical signal into an electrical signal, and determines the signal constellation of modulated light source according to the received signal corresponding to the received data obtained after demodulation. In the present invention, the transmission end in accordance with the visible light source is placed constellation modulation constellation, and the data to be transmitted is a signal obtained after the modulation constellation, mapped onto constellation points corresponding to the position of light source and driving the light source, so that by an optical signal transmitted data to be sent to the receiver; the receiver terminal determines the corresponding constellation point constellation according to a modulation signal source emitting a position, to acquire data from the sender. By the process of the present invention, to achieve a visible light communication, a visible light to meet the future demand scenarios.
title: Implemented method of visible light communication system and transmitter and receiver means
year: 2013

abstract: Due to limited interference range, the advantage of visible light communication (VLC) over wireless fidelity (WiFi) lies more in the unit area transmission rate rather than the single link transmission rate. To characterize the achievable transmission rate per unit area, we consider an indoor downlink VLC network with dense attocell configuration for the transmitters with single color light emitting diode (LED) and multi color LEDs, assuming binomial distributed users. We divide each attocell into central region and boundary region, and propose the transmission protocols based on such attocell division. We optimize the LED half power angle to maximize the mean achievable transmission rate per unit area. More specifically, we investigate the rates of cell center and cell boundary users under fairness consideration for the single LED transmitter system. We characterize the mean achievable transmission rate per unit area under the white light constraints in the multiple LEDs transmitter system. The performance of the proposed transmission protocols is evaluated by numerical results.
author_names: Jiaojiao Xu

Chen Gong

Jianghua Luo

Zhengyuan Xu
title: LED Half Power Angle Optimization for Ultra Dense Indoor Visible Light Communication Network Deployment
venue: IEEE Open Journal of the Communications Society
year: 2020

abstract: A high efficiency linear assisted Visible Light Communication (VLC) LED driver working as a transmitter is presented in this work. A linear assisted transmitter is based on the idea of using a high efficiency but bandwidth limited circuitry which delivers most of the power and a low efficiency but fast linear amplifier (linear assistance) which corrects the distortion of the signal. The presented solution takes advantage of the light in a VLC system by summing the contribution of the linear amplifier in light instead of electrically, which leads to a electrical isolation between both stages and a reduction of the complexity comparing to the traditional approach used in Envelope Tracking (ET) and Envelope Elimination and Restoration (EER) techniques. As experimental results, the design of a linear assisted Class E amplifier delivering a 16 PSK phase digital modulation with a 1 MHz carrier is presented. On one hand, the Class E amplifier delivers most of the power (92% of the signal power) at high efficiency (81 and, on the other hand, the linear amplifier only delivers the error signal at lower efficiency. The efficiency of the signal circuitry is up to 75% and the efficiency of the whole system considering the signal and the LED biasing circuitry is up to 85%
author_names: Daniel Garcia Aller

Diego G Lamar

Pablo Fernandez Miaja

Juan Rodriguez

Javier Sebastian
title: Design of a Linear Assisted VLC LED Transmitter Based on Summing the Light
venue: IECON 2019 45th Annual Conference of the IEEE Industrial Electronics Society
year: 2019

abstract: The emergence of visible light communication (VLC) as a subset of optical wireless communication (OWC) in the early 2000s has turned any light emitting diode (LED) source into a potential data transmitter. The design process for any VLC or OWC system typically involves a link budget analysis performed by studying the signal to noise ratio (SNR) at the receiver. Since this SNR strongly depends on the radiant flux collected by the receiver, an accurate model for this parameter is required. The point source model has been widely used since 1979 and generally provides a good approximation of the received radiant flux. However, it might be less accurate for typical extended lighting sources like LED panels or large area organic LEDs. In this paper, the radiant flux distribution of flat Lambertian rectangular or circular sources is derived from a vector analysis of their irradiance. It is then validated through actual measurements in the case of a circular source. The resulting extended source models thus better capture the light beam pattern of such transmitters to enable a more accurate link budget. It provides at the same time almost identical results to the point source model for small sources and can, therefore, be seen as a natural extension of this already widely used model.
author_names: Juan Camilo Valencia-Estrada

Bastien Bechadergue

Jorge Garcia-Marquez
title: Full Field Radiant Flux Distribution of Multiple Tilted Flat Lambertian Light Sources
venue: IEEE Open Journal of the Communications Society
year: 2020

abstract: Visible light communications (VLC) is a short range optical wireless communication technology that uses light emitting diodes (LEDs) as lighting devices and data transmitters. This paper describes a multiuser VLC system using Hadamard coded modulation (HCM) for indoor data transmission. Considering the peak transmitted power limit of the LEDs, a DC reduced HCM (DCR HCM) is used to reduce the nonlinear clipping distortion. Since the Hadamard codewords have different bandwidth requirements for a given symbol rate, they can be assigned to users with varying hardware capabilities. Optimally assigning codewords to users is found to significantly improve the average throughput, up to twice higher than a random assignment for a typical scenario. When the number of active users is less than the size of the Hadamard matrix used, more than one codeword can be assigned per user, which further improves the throughput. This paper also examines a scenario where multiple lamps in an indoor space transmit the same data. Since the time of arrival for the received signals emitted from different lamps is different, the Hadamard codes received are no longer orthogonal, resulting in multiple access interference and inter chip interference. The number of acceptable codewords is computed based on the specific interference experienced in different parts of the indoor space. The spatial distribution of the maximum throughput is also simulated, showing that the ratio of the maximum to the minimum data rate can be as high as 10 when considering the entire area of a typical indoor room. This article is part of the theme issue 'Optical wireless communication'
author_names: Jie Lian

Mohammad Noshad

Maite Brandt-Pearce
title: Indoor multiuser visible light communication systems using Hadamard coded modulation
venue: Philosophical Transactions of the Royal Society A
year: 2020

abstract: Visible light communication (VLC) is an emerging paradigm that enables multiple functionalities to be accomplished concurrently, including illumination, high speed data communications, and localization. Based on the VLC technology, visible light positioning (VLP) systems aim to estimate locations of VLC receivers by utilizing light emitting diode (LED) transmitters at known locations. VLP presents a viable alternative to radio frequency (RF) based positioning systems by providing inexpensive and accurate localization services. In this paper, we consider the problem of localization in visible light systems and provide an extensive survey of various location estimation techniques, accompanied by discussions of their relative merits and demerits within the context of accuracy and computational complexity. In addition, we investigate a cooperative VLP system architecture in which VLC receiver units are able to communicate with each other for the purpose of cooperation, and present a low complexity, iterative localization algorithm to demonstrate the benefits of cooperation in VLP systems. Finally, we investigate optimal strategies for power allocation among LED transmitters to maximize the localization accuracy subject to power and illumination constraints.
author_names: Musa Furkan Keskin

Ahmet Dundar Sezer

Sinan Gezici
title: Localization via Visible Light Systems
venue: Proceedings of the IEEE
year: 2018

abstract: Mobile wireless communication heavily relies on the radio frequency to convey message and data. However, its limited spectrum can hardly meet the demands for the future high data rate applications. Optical wireless communication, in particular visible light communication, opens up vast optical spectrum for communication, and meanwhile can retrofit the light sources as the communication transmitters in the existing working or living environments. In conjunction with the ubiquitous cameras in hand held consumer electronics such as smartphones and pads, optical camera communication (OCC) further takes advantages of image sensors as the communication receivers and realizes low cost communication systems. This article first provides an overview of OCC systems. It then addresses some practical constraints, ranging from sensor low frame rate and instability, rolling shutter readout, to visual qualities of displayed images and videos, and link blockage between the transmitter and receiver. Accordingly, it introduces existing and new solutions to deal with those constraints by data modulation, newly developed camera structures, post processing of sensed signals and non line of sight OCC as a new form. In particular, indirect paths by either the indoor surface reflection or the outdoor atmospheric scattering are explored for link connectivity under blockage. Finally, some future research directions are suggested. This article is part of the theme issue 'Optical wireless communication'
author_names: Weijie Liu

Zhengyuan Xu
title: Some practical constraints and solutions for optical camera communication
venue: Philosophical Transactions of the Royal Society A
year: 2020

abstract: Visible light communication (VLC) systems are inherently signal to noise ratio (SNR) limited due to link budget constraints. One favourable method to overcome this limitation is to focus on the pre log factors of the channel capacity. Multiple input multiple output (MIMO) techniques are therefore a promising avenue of research. However, inter channel interference in MIMO limits the achievable capacity. Spatial modulation (SM) avoids this limitation. Furthermore, the performance of MIMO systems in VLC is limited by the similarities among spatial channels. This limitation becomes particularly severe in intensity modulation/direct detection (IM/DD) systems because of the lack of phase information. The motivation of this paper is to propose a system that results in a multi channel transmission system that enables reliable multi user optical MIMO SM transmission without the need for a precoder, power allocation algorithm or additional optics at the receiver. A general bit error performance model for the SM system is developed for an arbitrary number of light emitting diodes (LEDs) in conjunction with pulse amplitude modulation. Based on this model, an LED array structure is designed to result in spatially separated multiple channels by manipulating the transmitter geometry. This article is part of the theme issue 'Optical wireless communication'
author_names: Tezcan Cogalan

Harald Haas

Erdal Panayirci
title: Optical spatial modulation design
venue: Philosophical Transactions of the Royal Society A
year: 2020

abstract: To support multiple users in an indoor multiple input multiple output visible light communication (MIMO VLC) system adopting spatial multiplexing, orthogonal frequency division multiple access (OFDMA) is usually adopted, where the overall modulation bandwidth is shared by all the users. In this paper, by fully exploiting the spatial distributions of light emitting diode (LED) transmitters in the ceiling and end users around the receiving plane, we propose a space division multiple access (SDMA) technique for indoor spatial multiplexing based MIMO VLC systems. When applying SDMA, users within the MIMO VLC system are divided into different user groups (UGs) based on their spatial locations with respect to different LED transmitters. Specifically, each UG can use the overall modulation bandwidth of the system. For efficient implementation of SDMA, two distributed user grouping (DUG) approaches are proposed, including basic DUG and transmit diversity enhanced DUG (TD DUG) and a two step resource allocation algorithm is further designed. The achievable rates of the MIMO VLC system employing SDMA with both basic DUG and TD DUG are derived accordingly. To verify the superiority of SDMA over conventional OFDMA, detailed analytical and simulation results are presented. Moreover, a proof of concept experiment is conducted to demonstrate the advantage of SDMA in a practical spatial multiplexing based MIMO VLC system.
author_names: Chen Chen

Yanbing Yang

Xiong Deng

Pengfei Du

Helin Yang
title: Space Division Multiple Access With Distributed User Grouping for Multi User MIMO VLC Systems
venue: IEEE Open Journal of the Communications Society
year: 2020