The rapid improvement in the efficiency of solid-state lighting has led to predictions that it will be the dominant source used for most indoor lighting applications in the future. At present an attractive candidate for generating white-light are blue LEDs that excite a yellow phosphor, with a resultant colour emission. Such solid state sources can be used for both illumination and communications simultaneously, offering the possibility of creating wireless broadcasting within a room or office space. In this paper we outline a typical basic configuration, and the performance available using simple modulation schemes. Unmodified LEDs typically have modulation bandwidths of several MHz, but typical lighting levels provide a communications channel with a Signal to Noise Ratios in excess of 40dB. Techniques such as equalisation can be used to improve available data rate significantly, and in this paper we outline several approaches that have the potential to offer data rates of 100Mb/s and above.
Nowadays, a lot of researchers are working on the development of light-emitting diode (LED) lighting system. The LED lighting system can achieve lower power consumption and has a longer life-time compared to the fluorescent lamp system.In this 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.Our prototype achieves a transmission data rate of 100 kHz in a direction of 160 o field of view with a radius of 1.7 meters. In this 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.
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