In Visible Light Communication project, the characteristic of short transient time in turning the light on/off processes was further investigated. A high-speed wireless communication system, which is embedded in our LED lighting system, was built. The duplex communication system consists of both downlink and uplink media through different frequencies of lights.Several experiments were conducted in the visible light communication system. In this communication system, off-the-self components were taken part in building the driver circuit and the performance of the system was evaluated, such as, data transmission rate, data transmission distance and the field of view of the transmitter.
In Visible Light Communication paper, transmission of MP3 music was demonstrated by using warm-white LED transmitter. Not limit to this, multiple source signals simultaneously in different frequency bands were transmitted through the RGB LED circuitry, and the signals were recovered successfully. This demonstrates the feasibility studies of our design in signals broadcasting
The Visible Light Communications Consortium (VLCC) which is mainly comprised of Japanese technology companies was founded in November 2003. It promotes usage of visible light for data transmission through public relations and tries to establish consistent standards. A list of member companies can be found in the appendix. The work done by the VLCC is split up among 4 different committees:
1. Research Advancement and Planning Committee
This committee is concerned with all organizational and administrative tasks such as budget management and supervising di_erent working groups. It also researches questions such as intellectual rights in relation to VLC.
2. Technical Committee
The Techincal Committee is concerned with technological matters such as
data transmission via LEDs and uorescent lights.
3. Standardization Committee
The standardization committee is concerned with standardization efforts and
proposing new suggestions and additions to existing standards.
4. Popularization Committee
The Popularization Committee aims to raise public awareness for VLC as a promising technology with widespread applications. It also conducts market
research for that purpose
Every kind of light source can theoretically be used as transmitting device for VLC. However, some are better suited than others. For instance, incandescent lights quickly break down when switched on and off frequently. These are thus not recommended as VLC transmitters. More promising alternatives are fluourescent lights and LEDs. VLC transmitters are usually also used for providing illumination of the rooms in which they are used. This makes uorescent lights a particularly popular choice, because they can icker quickly enough to transmit a meaningful amount of data and are already widely used for illumination purposes.
However, with an ever-rising market share of LEDs and further technological improvements such as higher brightness and spectral clarity [Won et al. 2008], LEDs are expected to replace uorescent lights as illumination sources and VLC transmitters. The simplest form of LEDs are those which consist of a bluish to ultraviolet LED surrounded by phosphorus which is then stimulated by the actual LED and emits white light. This leads to data rates up to 40 Mbit/s.
GB LEDs do not rely on phosphorus any more to generate white light. They come with three distinct LEDs (a red, a blue and a green one) which, when lighting up at the same time, emit light that humans perceive as white. Because there is no delay by stimulating phosphorus _rst, Data rates of up to 100 MBit/s can be achieved using RGB LEDs
It should be noted that VLC will probably not be used for massive data transmission. High data rates as the ones referred to above, were reached under meticulous setups which cannot be expected to be reproduced in real-life scenarios. One can expect to see data rates of about 5 kbit/s in average applications, such as location estimation. The distance in which VLC can be expected to be reasonably used ranges up to about 6 meters