VLC has special importance in the present scenario of communication, as it does not use our valuable radio frequency spectrum. Spectrum crisis is becoming a threatening factor when a number of devices are transmitting tremendous amount of data for connecting to the Internet either through the mobile network or through Wi-Fi/ WiMAX. But use of Light for communication will make it possible to face this situation in a big way. In the near future, LEDs will replace almost all conventional illumination light sources world wide, since they can act as low cost and reliable lighting devices and communication transmitters simultaneously. Every LED light source can be used like a Wi-Fi hotspot to transmit wireless data. It can be used for private, business or public purposes everywhere. Wi-Fi users are not much happy due to its limitations in speed and security. Also wireless networks are more vulnerable to hackers and easily accessible to external parties as it is available next to the walls. In response to the demand for fast and secure wireless connectivity, a group of technology innovators have formed the Li-Fi Consortium. It is an international non-profit industry association, which brings up the awareness of optical wireless communication technologies. It provides resources for developers to introduce new products. Dr. Gordon Povey of UK who is doing research in this area has already achieved a data rate of 130 Mbps over a distance of 2 metres. Li-Fi Consortium estimates a data rate of more than 10Gbps by using specially constructed LEDs.
Figure-1: Li-Fi System
Figure-1 shows a Li-Fi system. Similar to a Wi-Fi Modem/Router, here also there is a Li-Fi Modem/Router, which is exactly a VLC Transceiver with Router function incorporated. VLC Transceiver consists of a VLC Transmitter and VLC Receiver. The main element of a VLC Transmitter is a visible LED or an array of visible LEDs. Compared to the conventional communication transmitter, the VLC transmitter belongs to a different entity. It simultaneously acts as a Communication transmitter and an illumination device. Here LED is the modulating device in which the visible light it produces, is the optical carrier for communication. This optical carrier is to be modulated with respect April 2012ď ŽExecutive Knowledge Linesď Ž9