Abstract
Although visible light communication (VLC) systems provide high density links for use in Internet-of-Things (IoT) devices, the design of high rate VLC transmitters that maintain luminaire efficacy is an open problem. In this article, a novel approach to the integration of VLC within light-emitting diode (LED) drivers is proposed through the replacement of freewheeling/blocking diodes with light-emitting devices termed a light-emitting commutating diodes (LECDs). In this manner, communications and illumination can be provided using a simple, cost effective design while employing no additional components. The subtle change of LED driver control signals facilitates the transmission of data from LECDs while simultaneously supporting illumination functions. Lighting controls such as dimming are maintained and combined with modulation through the use of overlapping pulse position modulation (OPPM) and performance is quantified. Prototype buck and boost converters with LECDs are implemented and their efficacy is measured. Though current commercial LEDs are not intended for such signalling applications, we experimentally demonstrate their feasibility in this application and suggest methods to make such converters reliable. It is demonstrated that the addition of an LECD improves the efficacy of the luminaire as compared to conventional LED drivers while simultaneously enabling a VLC downlink.
Highlights
The use of high density, short range, wireless communication links is increasing with the rise of the Internet-of-Things (IoT)
Among the simplest solution to this radio frequencies (RF) spectral crunch is the adoption of wireless physical layers that do not interact with RF directly such as optical wireless communications (OWC)
The light-emitting diode (LED) used were white Philips Lumiled 3535 L or CREE XLamp XP-E2. These devices are not intended to be operated in reverse bias, our testing of 20 LEDs each illustrated a reverse breakdown of approximately 40 V to 45 V
Summary
The use of high density, short range, wireless communication links is increasing with the rise of the Internet-of-Things (IoT). The number of wireless connected devices is forecast to continue to increase to a staggering 15.7 billion devices by 2023 [1]. Radio frequencies (RF) are used to establish these links, as the number of devices increases, so too does interference. Among the simplest solution to this RF spectral crunch is the adoption of wireless physical layers that do not interact with RF directly such as optical wireless communications (OWC). LED luminaires have become ubiquitous in modern lighting solutions due to their advantages in efficacy and lifetime. Solid-state lighting has allowed for visible light communications
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