RESUMEN
Visible light communications emerges as a promising wireless communication technology that has been found suitable for numerous indoor and outdoor applications. In this article, a new in-vehicle VLC system is designed, implemented, and experimentally evaluated. The purpose of this new system is to provide car passengers with optical wireless communications. The proposed system consists of a VLC emitter integrated into the vehicle's ambient lighting system and a mobile VLC receiver. Unlike any previous works, this article proposes a VLC emitter in which the light from a 3 W LED is distributed on a 2 square meter surface using 500 optical fibers whose main purpose is a decorative one. The proposed prototype has been implemented on a car and evaluated in relevant working conditions. The experimental evaluation of the proposed system has demonstrated the viability of the proposed concept and showed a data rate of 250 kb/s while providing a BER lower than 10-7. As far as we know, the proposed concept is totally new in the VLC literature, opening a new area of utilization for VLC technology: using VLC with optical fiber distributed light.
RESUMEN
Freeform optical surfaces are of great importance because of two main properties. The first is their ability to enhance the image quality of image-forming optical systems; the second is their inherent reduction in the number of surfaces in image and nonimage-forming optical systems. However, the main characteristic of freeform surfaces is that they lack symmetry about any spatial axis. This attribute allows describing freeform surfaces with a mathematical parametric representation. Unfortunately, parametric representation can be extremely extended. On the other hand, when describing freeform surfaces, the explicit representation is commonly preferred because of its compactness and CAD-format exportable easiness. Parametrically represented freeform surfaces can nonetheless be exported to a CAD format, with no significant departure of surface shape, as shown here. The vector method presented here guarantees that the surface's sampling density be proportional to the irradiance on the surface.
RESUMEN
Visible light communication (VLC) is an attractive complementary communication technology for vehicular applications such as platooning. Although data rates around 100 kbps are enough for crucial data transmission, it may be useful to reach a few megabits per second for other applications like networking. Such data rates can be reached by using appropriate modulations and clock rates. In this paper, three forms of pulse amplitude modulations (PAM) are compared in a vehicular context: on-off keying (OOK), PAM-4 and generalized space-shift keying (GSSK). A prototype based on off-the-shelf light-emitting diodes (LED) headlamps is used for static tests in straight line configuration, with an inter-vehicle distance up to 30 m, and curves of minimum radius 100 m and inter-vehicle distance of 10 m. These tests show that OOK and GSSK are the most interesting modulations for highway platooning applications. OOK provides indeed a good mobility while remaining simple to implement. A 1 Mbps link of BER below 10-6 is thus demonstrated. In GSSK, the data rate reaches 2 Mbps for an equivalent BER. These performances are obtained by using, in particular, two spatially distinct receivers, which limits strongly the complexity of GSSK decoding.