The Future Technology LiFi
The LiFi technology invented by the by the German physicist Prof. Harald Haas in the year 2011. He proposed the LiFi technology, provides data transmission through the beam of light by sending data through a Light Emitting Diode (LED) that varies in intensity faster than the human eye can catch. Because of increasing demand in the wireless data communication. The available radio spectrum below or up to 10GHz nowadays become insufficient. The wireless communication industries have responded to this challenge by taking into consideration the radio spectrum above 10GHz. However, higher frequencies (f), means that the path loss (L), increases according to the Friis free space equation (L ∝ f2) . As transmission of data from the one place to another is one of the major activities day-to-day, in present days the current wireless networks that connect us to the internet are slow if in that networks multiple devices connected. And the solution to this problem is by the use of LiFi. LiFi technology provides data transmission through the light beam by sending data through LED (shown in Fig. 1).
A. Why Need LIFI?
LiFi Technology is based on all various kinds of light.
In the worlds light is present everywhere, and there are many bulbs, the only thing is to replace by LED’s for the data transmission.
Light has 10000 times wider bandwidth than radio waves  that proves better capacity.
Light cannot penetrate the walls, which provides the security.
LiFi is very cheaper for data transmission purpose.
WiFi cannot be use under water. But, LiFi can be, light can be used under the water.
By using LiFi technology, every street light anywhere would be free data hotspot.
LIFI SYSTEM CONSTRUCTION
LiFi is fast and cheap optical version of WiFi. The LiFi technology is based on Visible Light Communication (VLC). VLC technology is a medium for data communication, uses light (visible light) between 400THz to 900THz, as it is predefined (see Table.1), as the optical carrier for the transmission of data. LiFi uses pulses of light to transmit data over wireless networks. The main components of LiFi systems are:
High brightness white LED, which acts as the transmission source.
A good silicon photodiode, as a receiving element.
By using LiFi, it is possible to get the high speed of 100Mbps and more with the help of various multiplexing techniques. The LiFi emitter system consists of 4 primary subassemblies:
2) RF power amplifier circuit (PA)
3) Printed Circuit Board (PCB)
HOW LIFI DOES WORKS ?
The LiFi technology is based on the Visible Light Communication (VLC) system, uses light for the transmission of data. As the Intensity and Speed of the light is very high, and the transmission of the data is also high. How LiFi is works is very simple. The LED is fitted on the one end and on another end there is photo detector or photo sensor is fitted. When LED is turned ON the photo sensor detected the binary 1 and if LED turns OFF the photo sensor detected binary 0. To make any message, the LED flashes number of times, or use an Array of LED of perhaps a few different colours to obtain data rules in the range of hundreds of megabits per seconds . The data is being received and has been encoded into the light by vary in the flickering rate at which the LED turn ON and OFF to generate the different strings of 1s and 0s.
The source of light constantly appears because the LED can be turned ON and OFF quickly and the intensity is rapidly modulated that human eye cannot catch even though it is flickering. The bulb activity of ON-OFF which seems invisible and enables the transmission of data using the binary codes i.e. 0s and 1s, for switch ON LED it is a logical ‘1’, and for switch OFF LED it is a logical ‘0’. This method of using rapid pulses of light to transmit information wirelessly is technically referred to as visible light communication (VLC) .
In the WiFi technology, the radio waves are be penetrate the walls, through the walls, which has become the disadvantage related to the security purpose. Because of this, anyone can misuse it. But, in the LiFi technology, the optical signals are not able to penetrate the walls, which is the security issue advantage of LiFi. This technology contains two main components: LiFi Router and LiFi room connector. As optical signals are not able to penetrate through the walls. So, the rooms need to be connected to each other in the accounts to provide an optical wireless LAN (Local Area Network), and that is done by the using LiFi room connector. The LiFi room connector sends the data from one side of the wall to another side using the optical cable, LiFi room connector work as a replicator. For external link connection, LiFi router is used. It connects offices and it covers 20m radius with the transmission speed of 100Mbps. LiFi sends data using light with ‘LiFi-Flame’ prototype.
Teams at the University of Oxford and the University of Edinburgh are focusing on parallel data transmission using array of LED’s, where each LED transmits a different data stream. Other groups are using mixtures of red, green and blue LED’s to alter the light frequency encoding a different data channel. [2, 4]
DISADVANTAGE OF LIFI
The LiFi one of the major disadvantages is that the light cannot penetrate through the walls, and other opaque materials. LiFi is not able to work in direct line of sight.
APPLICATIONS OF LIFI
1) LiFi never harm living thing whereas radio waves affect the human body, birds and plants.
2) LiFi technology is useful in nuclear sector, airlines, power plants, and etc.
3) LiFi technology provides smart way to manage traffics.
4) It is applicable to GPS usage .
Had been surveyed that the LiFi technology is very advanced to WiFi as for wider bandwidth, quick response time and faster than WiFi. In the world every light can be replaced by the LED’s and would acts as data hotspot. As it is very cheap everyone can be facilitated, and as it fast everyone can access easily. The problem of radio frequency bandwidth shortage can be solve by using this technique.
 “What is LiFi” by Harald Haas, Liang Yin, Yunlu Wang and Cheng Chen published in Journal of Lightwave Technology.
 “Li-Fi: The Future Bright Technology” by Akanksha R. Shrivas published in Special Issue of International Journal of Electronics, Communication & Soft Computing Science and Engineering
 Wireless data from every light bulb Harald Haas, TED Global, Edinburgh, July 2011
 ISP Review-
 “An Architecture for Wireless Communication Systems using Li-Fi technology” by D. Satyanarayana, Alex Roney Mathew and Sathyashree.
 Z. Chen, D. Tsonev and H. Haas, “A novel double-source cell configuration for indoor optical attocell networks”, Global Telecommunication Conf.Austin, TX, USA, Dec.8-12, 2014
 S. Rajagopal, R. Roberts and S.K. Lim, “IEEE 802.15.7 visible light communication: Modulation schemes and dimming support”, IEEE Commun. Mag., Vol. 50, no.3, pp. 72-82, 2012
 S. Rajbhandari, H. Chun, G. Faulkner, K. Cameron, A. V. N. Jalajakumari, R. Henderson, D. Tsonev, M. Ijaz, Z. Chen, H. Haas, E. Xie, J. J. D. McKendry, J. Herrnsdorf, E. Gu, M. D. Dawson and D. O’Brien, “High-speed integrated visible light communication system: Device constraints and design considerations”, IEEE J. Sel. Areas Commun., vol. 33, no. 9, pp. 1750-1757, 2015.
 Khalid, A. M., Cossu, G., Corsini, R., Choudhury, P., and Ciaramella, E., “1-Gb/s Transmission Over a Phosphorescent White LED by Using Rate-Adaptive Discrete Multitone Modulation,” IEEE Photonics Journal 4, 1465–1473 (Oct. 2012).
 Cossu, G., Khalid, A. M., Choudhury, P., Corsini, R., and Ciaramella, E., “3.4 Gbit/s Visible Optical Wireless Transmission Based on RGB LED,” Optics Express 20, B501–B506 (2012).
 “Li-Fi Technology Transmission of data through light” by Rahul R. Sharma, Raunak and Akshay Sanganal published in International Journal of Computer Technology & Applications, Vol. 5 (1), 150-154
 http://www.extremetech.com/computing/152740-researchers-create-3gbps-lifinetwork-with-led-bulbs View publication stats
 IJSRD – International Journal for Scientific Research & Development| Vol. 4, Issue 08, 2016 | ISSN (online): 2321-0613