Manuel A. Vieira; Manuela Vieira; Paula Louro; Pedro Vieira
Abstract
In this paper the use of Visible Light Communication (VLC) in Vehicle Communication Systems is analyzed. The system aims to ensure communication between LED based emitters and SiC based receivers located at the vehicles. The proposed smart lighting system combines the functions of lighting, positioning, ...
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In this paper the use of Visible Light Communication (VLC) in Vehicle Communication Systems is analyzed. The system aims to ensure communication between LED based emitters and SiC based receivers located at the vehicles. The proposed smart lighting system combines the functions of lighting, positioning, and communications. The SiC receivers is used as a encoder/decoder device. This photosensitive element features active filter properties, it multiplexes the modulated polychromatic signal coming from the LEDs in an electrical signal, performs multiplexing/demultiplexing techniques and decode the received information. A traffic scenario is established and two connected vehicular communications simulated. Infrastructure-to-Vehicle (I2V) follow by Vehicle-to-Vehicle (V2V) communications are analyzed. In the V2V communication, the emitter is based on the front headlights of the vehicle, while for the study of the I2V communication system, the emitter was built on the streetlights. The VLC receiver acts as a Wavelength Division Multiplexer (WDM) and increases the signal conditioning capability to decode the transmitted information. Each receiver is a two terminal p-i'(a-SiC:H)-n/p-i(a-Si:H)-n heterostructure located on both the tails and on the top roof of vehicles. The spectral sensitivity of the receiver and its optical gain are analyzed. For message transmission, the individual chips of the white trichromatic RGB LEDs are modulated acting, for data transfer, as individual VLC channels. A violet LED is used for error control and to identify the ID position of the transmitter. Free space is the medium of transmission. An on-off modulation scheme (OOK) is used to transmit data. An algorithm for decoding information is established. The connected I2V2V system was tested. The experimental results show that using white modulated LEDs for lighting and data transmission and a SiC WDM device to decode the information is possible to build a VLC vehicular system that ensures de communication between the outside infrastructures and the cars. Copyright © 2018 VBRI Press.
Paula Louro; Manuela Vieira; Manuel A. Vieira; J. Costa
Abstract
We propose the use of Visible Light Communication (VLC) for localization services and navigations. The proposed lighting system supplies the dual function of lighting and data transmission. It uses commercial RGB white LEDs for the generation of the light and of the modulated optical signals that are ...
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We propose the use of Visible Light Communication (VLC) for localization services and navigations. The proposed lighting system supplies the dual function of lighting and data transmission. It uses commercial RGB white LEDs for the generation of the light and of the modulated optical signals that are transmitted in free space using an on-off coding scheme. The red, green and blue emitters of white LEDs are independently modulated, transmitting each different information. The photodetector is a multilayered device based on a-SiC:H, designed for the detection of visible optical light. The generated electrical signal by the photodetector is strictly related to the input optical excitation and its demodulation and decode enables the identification of the input light signals that carry the information necessary to perform the positioning and navigation tasks. The photodetector works as an active optical filter presenting self-amplification at selectable wavelengths. It is a multilayered device composed by two stacked pin photodiodes fabricated between conductive transparent electrical contacts. The positioning system includes multiple, identical navigation cells. The decoded signal by the photodetector identifies the input emitter cell and supplies enhanced accuracy within the spatial region covered by the cell. The methodology used for the photocurrent signal processing involves Fourier transform analysis for frequency identification and the use of a photodetector with spectral selective properties of wavelength identification. An algorithm to decode the information is established and the positioning accuracy is discussed. The experimental results, confirmed that the proposed VLC architecture is suitable for the intended application. Copyright © 2018 VBRI Press.