In this paper, we propose the wireless optical communication system with white colored LEDs for wireless home link (WHL). The white colored LEDs have a high power output and are regarded as lamps for the next generation. In the proposed system, this device is used for wireless home link. The proposed system is suitable for private networks such as consumer communication networks. From numerical and simulation results, it is confifmed that the proposed system is available and the problems to be solved are made clear.
White LEDs were invented the 1990's. Since then they have been extensively researched and applied in various ways. Compared with conventional lighting devices, the white LED has lower power consumption, lower voltage requirements, longer lifetime, smaller size, faster response, and cooler operation. The white LED will eventually replace incandescent or fluorescent lights in offices and homes.We have proposed an indoor visible light wireless communication system that utilizes multiple white LED lighting equipment. In this system, the equipment is used not only for illuminating rooms but also for an optical wireless communication system. The system has significantly higher power levels than infrared wireless communication systems, since it also functions as the main lighting equipment. One problem is we tend to install many lighting sources on a ceiling in order to illuminate the room as evenly as possible. While the number of sources permits site diversity transmission over LOS links, the optical path difference between the multiple sources triggers intersymbol interference (ISI), which significantly degrades system performance.This paper overcomes the ISI problem by proposing an adaptive equalization system. We elucidate the most effective training sequence interval for channel estimation in a mobile environment. And we show that the adaptive equalization system with the effectual interval alleviates the influence of shadowing.
In this study, we propose an indoor navigation system that utilizes visible light communication technology, which employs LED lights and a geomagnetic correction method, aimed at supporting visually impaired people who travel indoors. To verify the effectiveness of this system, we conducted an experiment targeting visually impaired people. Although acquiring accurate positional information and detecting directions indoors is difficult, we confirmed that using this system, accurate positional information and travel direction can be obtained utilizing visible light communication technology, which employs LED lights, and correcting the values of the geomagnetic sensor integrated in a smartphone.
SUMMARYThis study introduces an image sensor based visible light communication (VLC) and its application to pose, position, and range estimations. There are two types of visible-light receiver: a photodiode and an image sensor. A photodiode is usually used as a reception device of VLC, and an image sensor consisting of a large number of pixels can also be used as a VLC reception device. A photodiode detects the signal intensity of incoming light, while an image sensor not only detects the incoming signal intensity but also an accurate angle of arrival of light emitted from a visible light transmitter such as a white LED light. After angles of arrival of light are detected by an image sensor, positioning and data reception can be performed. The ability of an image sensor to detect an accurate angle of arrival will provide attractive applications of VLC such as pose, position calculation, and range estimation. Furthermore, because the image sensor has the ability to spatially separate sources, outdoor positioning even with strong sunlight is possible by discarding the associated pixels of noise sources.
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