4,245 research outputs found

    Dimming Consideration for OFDM-Based Visible Light Communications

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    In the field of indoor wireless networks, visible light communications would be contributing a vital role in the future. This paper investigates the performances of data transmissions using visible light based on unipolar orthogonal frequency division multiplexing (OFDM) and discusses possible approach for light dimming. Asymmetrically clipped optical OFDM (ACO-OFDM) is considered as a unipolar modulation scheme for intensity modulation with direct detection (IM/DD) on which visible light communications is based. This modulation can incorporate light dimming while not corrupting the communication link since, compared to the traditional DC biased optical OFDM (DCO-OFDM), ACOOFDM noise clipping component does not fall on data carrying subcarrier. To create more dimming levels pulse width modulation (PWM) is proposed to be used in conjunction with ACO-OFDM.Keywords: Orthogonal frequency division multiplexing (OFDM), light emitting diode (LED), signal clipping, visible light communication.Cite as:Sunil Deka, Poompat Saengudomlert, Sunandan Baruah "Dimming Consideration for OFDMBased Visible Light Communications", ADBU J.Engg.Tech., 2(1)(2015) 0021101(5pp

    A Real-Time Visible Light Communication System on Chip Design for High Speed Wireless Communication

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    The increasing demand of wireless communication bandwidth due to advancement of IoT and smartphone technology, requires the new wireless communication technology that can provide high speed wireless communication. The Visible Light Communication (VLC) has been proven can provide multi gigabit wireless communication throughput using unlicensed visible light spectrum. Therefore, VLC is a promising technology to solve bandwidth limitation problem. In order to achieve high speed throughput, VLC signal processing has to be implemented using Application Specific Integrated Circuits (ASICs) technology. In this research, we develop a baseband processor architecture for VLC application. We use System on Chip (SoC) design approach to reduce design time and easy system integration to various applications. In order to increase spectrum efficiency, we utilize OFDM modulation scheme. Several OFDM processing blocks, such as synchronizer, FFT/IFFT, modulator, demodulator, are designed in the system. The real-time system performance is verified in FPGA based system prototyping. The design includes optical wireless front end module, baseband processing and network layer. The developed prototype shows a real-time performance for high speed internet access

    OFDM based visible light broadcasting systems

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    Visible light communication (VLC) involves the use of light emitting diode (LED)- based illumination infrastructure for communication purposes [1]. Recent experimental studies on VLC have demonstrated data speeds more than 3 Gigabits per second [2]. Although indoor spaces usually have more than one light source, most of the existing works on VLC in the current literature consider point-topoint communication and few efforts have been made on the scenarios with multiple transmitters. In this work, we consider a broadcasting scenario in which multiple transmitters (light sources) simultaneously emit the same information using orthogonal frequency division multiplexing (OFDM)

    VLC: Implementation of OFDM Modulation Format

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    Import 03/11/2016Diplomová práce se zabývá problematikou komunikace ve viditelném světle VLC (Visible Light Communication), konkrétně modulační technikou ortogonálního frekvenčně děleného multiplexu OFDM, která je trendem v dnešních informačních systémech, jako je DVB-T nebo Wi-Fi. V prvních kapitolách práce je popsán koncept komunikace ve viditelném světle. V následujících kapitolách je popsána základní teorie k modulačním formátům, které využívá modulační technika OFDM a v závěrečné kapitole teorie je popsán ortogonální frekvenčně dělený multiplex (OFDM). V praktické části je rozebrán postup návrhu modulátoru a demodulátoru OFDM včetně komunikačního kanálu. Pro ověření funkčnosti navrženého OFDM systému bylo provedeno simulační měření, byly proměřeny základní parametry jako je BER, EVM nebo PAPR. Implementovaný OFDM systém pak byl realizován pro přenos dat pomocí signálového generátoru, bodového LED světla a signálového analyzátoru. V této části byla určena vzdálenost, kterou je možné dosáhnout pomocí našeho konceptu.Diploma thesis deals with the problematic with Visible Light Communication VLC, specifically modulation technique OFDM, which is trend in today information systems like as DVB-T or Wi-Fi. In the first chapters of thesis is described concept of visible light communication. In following chapters is described basic theory to modulation formats, which are used for OFDM modulation technique and in last chapter of theory is described orthogonal frequency division multiplexing. In the practical part of diploma thesis is analyze design of modulator and demodulator OFDM including communication channel. To verify the functionality of the proposed OFDM system simulation measurements was performed and basic parameters such as BER, EVM or PAPR were measured. Implemented OFDM system was then realized to transfer data using the signal generator, LED spot light and signal analyzer. In this section was determined distance, which can be achieved by using our concept.440 - Katedra telekomunikační technikyvýborn

    OFDM based visible light broadcasting systems

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    Visible light communication (VLC) involves the use of light emitting diode (LED)- based illumination infrastructure for communication purposes [1]. Recent experimental studies on VLC have demonstrated data speeds more than 3 Gigabits per second [2]. Although indoor spaces usually have more than one light source, most of the existing works on VLC in the current literature consider point-topoint communication and few efforts have been made on the scenarios with multiple transmitters. In this work, we consider a broadcasting scenario in which multiple transmitters (light sources) simultaneously emit the same information using orthogonal frequency division multiplexing (OFDM)

    Dimming control in visible light communication using RPO-OFDM and concatenated RS-CC

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    Increasing wireless data traffic is creating pressure on the conventional dwindling radio frequency spectrum. A new and reliable communication medium becomes a necessity. Visible Light Communication (VLC), a subset of optical wireless communication uses the visible light spectrum between 400 and 800 THz as a medium for communication. VLC utilizes the illumination of LED to establish a communication medium. The research focused on achieving a successful VLC communication link at low intensities of light without affecting the speed, accuracy and efficiency of VLC. The achievement of the paper was to devise a method to reduce the LED brightness, reducing energy consumption and most importantly maintain a reliable, efficient and successful VLC communication link at low intensities of LED. The research comprises of a Reverse Polarity Optical-Orthogonal Frequency Division Multiplexing (RPO-OFDM) modulator, a Forward Error Correction (FEC) encoder block that uses concatenated Reed Solomon - Convolutional Coding, a digital PWM dimming control circuit, an RPO-OFDM demodulator and a FEC decoder. The decoding is performed using the Berlekamp-Massey algorithm and the Viterbi algorithm. Extensive research on various modulation schemes, coding and error correction techniques along with various driver circuit design for dimming control in VLC were thoroughly investigated to conclude the best reliable solution for dimming control in VLC

    SDR-Based Real Time Video and Audio Transmission using OFDM Modulation for Visible Light Communication (VLC)

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    Tato diplomová práce se zabývá přenosem obrazu přes komunikaci viditelným světlem pomocí modulace OFDM na bázi softwarově definovaného rádia. V první části je popsána komunikace viditelným světlem a následně modulace OFDM. V další části jsou navrženy dvě metody pro hodnocení kvality obrazu. V praktické části je prováděno měření hodnot přijatého obrazu a jeho porovnání s vyslaným.This thesis deals with video transmission of images by Visible Light Communication using OFDM modulation based on Software Defined Radio. The first section describes Visible Light Communication and then OFDM modulation. In the second section are introduced two ways of rating quality of image. In the practical part are performed measurements of the values related to received images and its comparison with sent images.440 - Katedra telekomunikační technikyvelmi dobř
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