LI-FI TECHNOLOGY

WHAT IS LI-FI….???

•        LIFI –”LIGHT FIDEALITY” is transmission of data through illumination, i.e. sending data through a LED light bulb that varies in intensity faster than human eye can follow.

•        Li-Fi is a light-based Wi-Fi it uses light instead of radio waves to transmit information.

•    Transceiver fitted LED lamps acts like Wi-Fi modems.

•        LED lamps can light a room as well as transmit-receive information.
•    Provides illumination as well as data communication

HISTORY OF LI-FI

The technology truly began during the year 1990’s in countries like Germany , Korea and Japan where they discovered LED’s could be retrofitted to send information.

Introduced by Professor Herald hass, at the university of Edinburgh.

Established in 2011 TED global talk.

The promotion of idea through TED helped to start a company, Pure LiFi

Pure LiFi, formerly pure VLC, is an original equipment manufacture firm setup to commercialize Li-Fi products for integration with existing LED lighting systems

In October 2011, few companies and industries group formed Li-Fi consortium to promote the high speed optical wireless systems

WHY LI-FI WHEN WE HAVE WI-FI ?

• Radio spectrum is congested, but the demand for wireless data doubles each year.
• Issues regarding radio spectrum, such as capacity, availability, efficiency, security are solved using LIFI.
• Speed of data transmission can be increased.

OVERCOMING WIFI ISSUES

•      CAPACITY: 
    Spectrum is 10,000 times greater than that of radio frequency

•       EFFICIENCY:

     Highly efficient since LED consumes less energy

•      AVAILABILITY:

    Light waves available everywhere.

         ·       SECURITY: 

              Cannot penetrate through walls. Hence data cannot be intercepted

VISIBLE LIGHT COMMUNICATION

Ø In electromagnetic spectrum, gamma, UV rays, X-rays are dangerous for human body
.

Ø IR rays, due to eye safety regulations, are not used.

Ø Radio waves have limited bandwidth and are not very much secure

Ø Visible light is not used but is safe for larger bandwidth

HOW LI-FI WORKS?

•         Operational procedure is very simple

•         If LED is ON, digital data ‘1’ is transmitted & if LED is OFF, digital data ‘0’ is transmitted.

•         LEDs varies in intensity so fast that a human eye cannot detect it, that is flickering rate is very high

•         A controller connected at the back side of these LEDs is used to code data.

•         Also called as 5G optical communication

•         Every light source will work as a hub for data transmission

IMPLEMENTATION OF LI-FI

•      The LI-FI product consists of three primary sub assemblies

•      A. Emitter

•      B. RF Driver

•      C. Power Supply

FUNCTION OF BULB ASSEMBLY

•      At the heart of LI-FI is the bulb sub assembly where a sealed bulb is embedded in a dielectric material.

•      The dielectric material serves two purposes:

A. Wave guide

B. Electric field

RF DRIVER

•      Power amplifier (PA) assembly that uses an LDMOS device.

•      Converts electrical energy into RF .

•      The PA is designed to ruggedness and efficiency.

•      The RF driver also contains controls circuit for digital and analog lighting controls.

ABOUT LDMOS

•         LDMOS (laterally-diffused metal-oxide semiconductor) is a planar double-diffused MOSFET (metal–oxide–semiconductor field-effect transistor) used in amplifiers, including microwave power amplifiers, RF power amplifiers and audio power amplifiers. These transistors are often fabricated on p/p+ silicon epitaxial layers

•         The fabrication of LDMOS devices mostly involves various ion-implantation and subsequent annealing cycles.As an example, The drift region of this power MOSFET is fabricated using up to three ion implantation sequences in order to achieve the appropriate doping profile needed to withstand high electric fields.

SUMMARY OF IMPELMENTATION

•      All the data from Internet is streamed into lamp driver.

•      Data from internet is used to modulate the intensity of LED light source.

•      Thus by fast and subtle variations of current, optical output can be made to vary at extremely high speed.

•      The photodetector picks up the signal.

•      The receiver dongle then converts the tiny changes in amplitude into a data stream.

LI-FI NETWOKS IN REAL LIFE

•         Li-Fi connector and router are the main components for a network

•         Room connector:

Ø Optical signals cannot penetrate through walls, in order to provide an optical WLAN, rooms need to be connected with each other.

Ø Li-Fi room connector is a replicator, which sends the data stream from one side of the wall to the other side via an optical fiber.

Ø For smaller rooms, connector act as the only Li-Fi hotspot in the room

APPLICATIONS OF LI-FI

•      LIFI can be used in sensitive areas such as aircrafts for data transmission without causing interference

•      Places where it is difficult to lay optical fibers like operation theaters

•      Traffic scenarios, thereby reducing accidents

•      Underwater applications where radio waves cannot propagate.

•      Industries like petrochemical plants, nuclear power plants ,petrol pumps etc

•      Location based services:-GPS

•      Used for modern medical instruments

A PROVEN TECHNOLOGY

•         Harald has demonstrated Li-Fi using an ordinary table lamp and a computer located below the lamp

•         He successfully transmitted data at speed exceeding 10Mbps using light waves from LED light bulbs

•         Also he periodically blocked the beam of light, causing the connection to drop

ADVANTAGES

1.    Larger bandwidth

2.    High efficiency

3.    More availability

4.    High security

5.    Thousands and millions of street-lamps can be converted to Li-Fi spots

6.    No license needed

7.    Green information technology

8.    Lighting points used as Hotspots

9.    The issues of the shortage of radio frequency bandwidth may be sorted out by Li-Fi.

10.  This technology worldwide can be used for every street

11.  lamp would be a free data access points.

12.   Data rate greater than 10 Gbps.

13.   Theoretically allowing HD film to be downloaded in 30 seconds

14.  Can be used anywhere, even in RF restricted areas. 
       Since light waves will not interfere with radio waves.

15.   Mostly LED light bulbs are used, which consumes less energy. Hence cost efficient.

16.   As light waves cannot penetrate through walls, the data cannot be intercepted; Thus provides secured communication.

17.  Efficient alternative to radio based wireless, since it is quick and reliable

LIMITATIONS

1.    Li-Fi doesn’t work in the dark

2.    Line of sight (LOS) is needed

3.    Li-Fi has a big drawback compared to Wi-Fi, unlike Wi-Fi we cannot move to other rooms unless there are wired bulbs too.

4.    Light can’t pass through the objects

5.    Interference from external sources like sun light, normal bulbs, and opaque materials in the path of transmission will course interruption in the communication.

6.    A major challenge facing Li-Fi is how the receiving device will transmit back to transmitter i.e bi-directional capability.

7.    High installation cost of the VLC systems

CHALLENGING PROBLEMS

•      Connectivity:

Ø This problem is like the connectivity problem in cellular network when you move from one area of the city to another area while speaking with cell-phone.

Ø The solution is called “handover”, using which the user is transferred from one light source to another.

•      Multiuser support:

Ø This problem is caused when a lot of users are there on a single light source which leads to confusion and sometimes data losses also.

Ø Solution is time division multiplexing (TDM).

Ø Each frame is divided into equal time slots.

Ø Each user transmit data in one time slot in a predefined order

CONCLUSION

•      Overcomes the limitations of radio spectrum.

•      High speed of 10Gbps can be achieved.

•      The possibilities are numerous and can be explored further.

•      If this technology can be put into practical use, every bulb can be used something like a Wi-Fi hotspot.

•      We will proceed toward the cleaner, greener, safer and brighter future.

•      This may solve issues such as the shortage of radio-frequency bandwidth.

•       Allows internet where traditional radio-based wireless isn’t allowed such as aircraft or hospitals .

•       LI-FI is enabled by advance digital transmission technologies.