Abstract: Internet data communication is a crucial activity for modern society. Since internet communication needs secure, efficient and high data rate communication, researchers propose different form of internet data communication. The current wireless data communication Wireless-Fidelity is based on radio frequency and uses router for signal transmitter and Wi-Fi card or chip as receiver which are built in modern computers and smart phones. This radio frequency based technology is limited in bandwidth, interfered with signals of different electronic equipment and easily accessed or hacked by unwanted hidden peoples. Light Fidelity (Li-Fi) is a new technology that, proposed in late 2011 by prof. Harald Haas, uses illumination for internet data communication and will be implemented in a near future. Li-Fi uses semiconductor diodes for both data source and data receiver. It uses different color light emitting diodes (LEDs) as a transmitter and photodiodes as a receiver which are connected with computers or smart phones. Li-Fi technology uses the very simple technique of transmitting data using LED bulbs ie, if the LED is ON, then the digital signal 1 is transmitted else, if the LED is OFF, the digital signal 0 is transmitted which are detected by the photodiode at the receiver side. Li-Fi has many advantages over wireless fidelity (Wi-Fi). The advantage of Li-Fi over Wi-Fi is due to data communication spectrum differences. The electromagnetic spectrum bandwidth used for visible light communication (VLC) of Li-Fi is 10,000 times greater than for electromagnetic spectrum bandwidth of radio frequencies for Wi-Fi. Li-Fi technology has many advantages over Wi-Fi as a result of its unlimited bandwidth, its poor object penetration capacity, its low electromagnetic interference property and its possibility to integrate with the existing light infrastructure. But Li-Fi technology has some draw backs than Wi-Fi due to its radiation range, radiation direction and penetration capacity through objects and opaque materials. Since Li-Fi is clean cheaper and efficient and secure, most computer related companies will join and the draw backs will be reduced.
Keywords: Wireless-Fidelity (Wi-Fi), Light Fidelity (Li-Fi), Light Emitting Diode (LED), LDR (Light Dependent Register).