Li-Fi: IEEE Standard 802.15.7

Number of internet devices using wireless communication is increasing day-by-day and situation might come in near future where Wi-Fi alone would not be sufficient to service all wireless communication needs while delivering the same speed and performance. Then we will have to look for alternatives!

One such alternative solution is provided by German physicist Dr. Harald Hass, who in 2011 demonstrated that by flickering light from an LED one could transmit large amount of data. This technology is called Li-Fi or light fidelity and it refers to visible light communication.

As we know in Wi-Fi, data is transmitted using radio frequency waves while in the case of Li-Fi visible light from LED source and optical wireless networking technology is used for data transmission. Just like Wi-Fi specifications are defined by IEEE 802.11, IEEE 802.15.7 is a standard for short range wireless communication using visible light. Data rate in this standard is sufficient for audio and video applications while taking in account the mobility of link. It is claimed that Li-Fi is more secure, cost effective, offers higher bandwidth and is faster. In the laboratory environment speed of over 2000Gb/sec has been achieved using Li-Fi and during the trial runs in offices and other indoor environment, speed upto 1Gb/sec has been achieved which is 100 times faster than Wi-Fi. Block diagram of Li-Fi system is shown in figure below.

Fig. 1: Block Diagram of Li-Fi (Source: Ref [4])

Working principle of Li-Fi is quite simple. By modulating the intensity of light data can be transmitted and is received by a photo-detector at the receiver end. The intensity of light is varied at such high speed that it is impossible for human eye to notice the flickering of the LED light. White LED light is preferred as data transmitting source, silicon photo-diode is used as a receiver and modulation technique used is amplitude modulation. In order to transmit digital 1, LED needs to be ON and for digital 0 it needs to be OFF. In order to transmit string of 0s and 1s (the digital data), LED needs to go OFF and ON very-very fast. This switching time is less than a micro second and is barely noticeable to human eye.

Though there are several advantages of Li-Fi over Wi-Fi as mentioned above but it is ideal only for short distance indoor communication and offers high density coverage. It suffers from limitation like line of sight requirements and requirements of no obstacles in the pathway. Scientists believe that Li-Fi would not entirely replace Wi-Fi however both technologies can work in sync to offer high speed and most importantly highly secured wireless network.

By: Ms. Nirmaljeet Kaur, Assistant Professor (CSE), Chitkara University, H.P.

References

1. http://trak.in/tags/business/2018/01/30/ministry-wants-lifi-india-tests-10-gbps-light-based-wireless-internet-iit-madras/
2. Harald Haas, Cheng Chen, Dominic O'Brien, "A guide to wireless networking by light", Progress in Quantum Electronics, Elsevier,vol.5, pages 88-111, Sept 2017.
3. Harald Haas, "LiFi is a paradigm shifting 5G technology", Reviews in Physics, Elsevier,vol.3, pages 26-31, Oct 2017.
4. Usama, Muhammad & Saeed, Kamran & Yousaf, Adnan. (2015). A Review on Nomadic Access of Li-Fi Technology.