65 research outputs found
Using an LED as a sensor and visible light communication device in a smart illumination system
The need for more efficient illumination systems has led to the proliferation of
Solid-State Lighting (SSL) systems, which offer optimized power consumption.
SSL systems are comprised of LED devices which are intrinsically fast devices
and permit very fast light modulation. This, along with the congestion of the
radio frequency spectrum has paved the path for the emergence of Visible Light
Communication (VLC) systems. VLC uses free space to convey information by
using light modulation. Notwithstanding, as VLC systems proliferate and cost
competitiveness ensues, there are two important aspects to be considered.
State-of-the-art VLC implementations use power demanding PAs, and thus it is
important to investigate if regular, existent Switched-Mode Power Supply (SMPS)
circuits can be adapted for VLC use. A 28 W buck regulator was implemented
using a off-the-shelf LED Driver integrated circuit, using both series and parallel
dimming techniques. Results show that optical clock frequencies up to 500 kHz are
achievable without any major modification besides adequate component sizing.
The use of an LED as a sensor was investigated, in a short-range, low-data-rate
perspective. Results show successful communication in an LED-to-LED configuration,
with enhanced range when using LED strings as sensors. Besides, LEDs
present spectral selective sensitivity, which makes them good contenders for a
multi-colour LED-to-LED system, such as in the use of RGB displays and lamps.
Ultimately, the present work shows evidence that LEDs can be used as a
dual-purpose device, enabling not only illumination, but also bi-directional data
communication
Advanced Trends in Wireless Communications
Physical limitations on wireless communication channels impose huge challenges to reliable communication. Bandwidth limitations, propagation loss, noise and interference make the wireless channel a narrow pipe that does not readily accommodate rapid flow of data. Thus, researches aim to design systems that are suitable to operate in such channels, in order to have high performance quality of service. Also, the mobility of the communication systems requires further investigations to reduce the complexity and the power consumption of the receiver. This book aims to provide highlights of the current research in the field of wireless communications. The subjects discussed are very valuable to communication researchers rather than researchers in the wireless related areas. The book chapters cover a wide range of wireless communication topics
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