I am working on a visible light communication research. My aim is to send characters wirelessly from keyboard to microcontroller & then to LED & reception by photodiode/phototransistor & displaying the character on LCD via a microcontroller.
I am stuck at the reception part.
How can we code or use any synchronization technique such that the photodiode/phototransistor recognizes & differentiates the information we send, from the continuous on-signal it is receiving from LED which remains on for the lighting purpose otherwise.1111...: This is the signal which photodiode receives when LED is on for lighting purpose. 10010011(or any other 8 bit data I send from keypad) is the information which the photodiode should differentiate for displaying on LCD.
I request you to suggest at the earliest since I have deadlines.
Visible light communication (VLC) is a data communications medium which uses visible light between 400 and 800 THz (780–375 nm). VLC is a subset of optical wireless communications technologies.
The technology uses fluorescent lamps (ordinary lamps, not special communications devices) to transmit signals at 10 kbit/s, or LEDs for up to 500 Mbit/s. Low rate[vague] data transmissions at 1 and 2 kilometres (0.6 and 1.2 mi) were demonstrated. RONJA achieves full Ethernet speed (10 Mbit/s) over the same distance thanks to larger optics and more powerful LEDs.
Specially designed electronic devices generally containing a photodiode receive signals from light sources, although in some cases a cell phone camera or a digital camera will be sufficient. The image sensor used in these devices is in fact an array of photodiodes (pixels) and in some applications its use may be preferred over a single photodiode. Such a sensor may provide either multi-channel communication (down to 1 pixel = 1 channel) or a spatial awareness of multiple light sources.
VLC can be used as a communications medium for ubiquitous computing, because light-producing devices (such as indoor/outdoor lamps, TVs, traffic signs, commercial displays and car headlights/taillights) are used everywhere. Using visible light is also less dangerous for high-power applications because humans can perceive it and act to protect their eyes from damage.