LiFi-
the latest technology in Wireless Communication.
Abstract
Li-Fi
is the term some have used to label the fast and cheap wireless-communication
system, which is the optical version of
Wi-Fi. The term was first used in this
context by Harald Haas in his TED Global talk on Visible Light Communication(VLC). The technology was demonstrated at
the 2012 Consumer Electronics Show in Las Vegas using a pair of Casio
smartphones to exchange data using light of varying intensity given off from
their screens, detectable at a distance of up to ten metres.
In
October 2011 a number of companies and industry groups formed the Li-Fi
Consortium, to promote high-speed optical wireless systems and to overcome the
limited amount of radio-based wireless spectrum available by exploiting a
completely different part of the electromagnetic spectrum. The
consortium believes it is possible to achieve more than 10 Gbps, theoretically
allowing a high-definition film to be downloaded in 30 seconds. Li-Fi has the advantage of being able to be
used in sensitive areas such as in aircraft without causing interference.
However, the light waves used cannot penetrate walls. Later in 2012, VLC, a
firm set up to commercialize Li-Fi, will bring out Li-Fi products for firms
installing LED-lighting systems. In future data for laptops, Smartphone's, and
tablets can be transmitted through the light in a room by using LiFi.
1. Introduction
LiFi is transmission of data
through illumination by taking the fiber out of fiber optics by sending data through a LED light bulb that varies in intensity faster than the human eye can follow. The LED bulb will hold a micro-chip that will
do the job of processing the data. The light intensity can be manipulated to send
data by tiny changes in amplitude. This technology uses visible spectrum of
light ,a part of the electromagnetic spectrum that is still not greatly
utilized. In fact the technology
transfers thousands of streams of data simultaneously, in parallel, in higher
speeds with the help of special modulation, using a unique signal processing
technology.
2. How it works
Color rendering index, or CRI, is a measure of the quality of color light, devised by the International Commission on Illumination (CIE). It generally ranges from zero for a source like a low-pressure sodium vapor lamp, which is monochromatic, to one hundred, for a source like an incandescent light bulb, which emits essentially blackbody radiation. It is related to color temperature, in that the CRI measures for a pair of light sources can only be compared if they have the same color temperature. A standard "cool white" fluorescent lamp will have a CRI near 62.
The lumen output will be reduced
once the lamp is inside the lighting fixture; typically the final lumen output
is at 10,000 lumens. Since heat is directly related to the wattage,
the LiFi plasma lamp produces about the same heat per watt as standard
discharge lamps, however since it is using less wattage per lumen it does run
cooler to achieve the same lumen output. There are fins on the emitter housing
to help shed the heat away from the electronics.”
2.1. Li Fi
Construction
|
Bulb
|
1. Bulb
2. RF
power amplifier circuit (PA) PA
3. Printed circuit board
(PCB)
4. Enclosure
|
PCB
|
The PCB controls the electrical inputs and outputs of the lamp and
houses the microcontroller used to manage different lamp
functions.
|
LIFI Block Diagram
|
An RF (radio-frequency) signal is generated by the solid-state PA
and is guided into an electric field about the bulb. The high
concentration of energy in the electric field vaporizes the
contents
of the bulb to a plasma state at the bulb’s center; this
controlled
plasma generates an intense source of light. All of these
subassemblies are contained in an aluminum enclosure.
Li Fi Function of a Bulb
Sub-assembly
At the heart of LIFI is the bulb sub-assembly
where a sealed bulb is embedded in a dielectric material. This design is more reliable than
conventional light sources that insert degradable electrodes into the bulb. The dielectric material serves two purposes;
first as a waveguide for the RF energy transmitted by the PA and second as an
electric field concentrator that focuses energy in the bulb. The energy from the electric field rapidly
heats the material in the bulb to a plasma state that emits light of high
intensity and full spectrum.|
Dielectric material
|
|
Bulb
|
|
Li-Fi Bulb Sub-Assembly
|
This technology has higher potential. It is very much possible to transmit the data via light by changing the flicker rate that gives different strings of 1 and 0, and it's intensity is modulated so quickly that the human eyes cannot notice.
2.2. Why we need to get a Li-Fi
Radio spectrum is congested but the demand for wireless data doubles each year. Everything, it seems, wants to use wireless data but the capacity is drying up. Wireless radio frequencies are getting higher, complexities are growing and RF interference continues to grow. So what can carry this excess demand in the future?
The solution is Li-Fi. Direct modulation of LED devices is a low cost, secure, and safe way to transmit data, and there is an abundance of free visible light spectrum. High intensity LEDs used in light bulbs, flash lights and cameras can transmit very high data rates, faster than Wi-Fi!
2.3 Visible light communication(VLC)
A flickering light can be incredibly annoying, but has turned out to have its upside, being precisely what makes it possible to use light for wireless data transmission. Light-emitting diodes (commonly referred to as LEDs and found in traffic and street lights, car brake lights, remote control units and countless other applications) can be switched on and off faster than the human eye can detect, causing the light source to appear to be on continuously, even though it is in fact 'flickering'. This invisible on-off activity enables a kind of data transmission using binary codes: switching on an LED is a logical '1', switching it off is a logical '0'. Information can therefore be encoded in the light by varying the rate at which the LEDs flicker on and off to give different strings of 1s and 0s. This method of using rapid pulses of light to transmit information wirelessly is technically referred to as Visible Light Communication (VLC), though its potential to compete with conventional WiFi has inspired the popular characterisation Li-Fi.
VLC's advantages in hazardous conditions or tough environments. They say it will transform air travel by allowing overhead cabin lights to connect mobiles and laptops in-flight; and that it will improve conditions for those working underwater -- on oil rigs, for example -- where radio waves cannot penetrate. Traffic lights could better regulate traffic flow using data; and LED car lights might alert drivers when other vehicles are too close. More pervasively, anyone seeking an internet connection could connect using light from streetlamps and electric shop signs.
2.4 The full-featured local Li-Fi cloud
Private home wireless data network with local cloud & server function .
The concept of the Li-Fi cloud creates an environmental friendly, healthy and smart network environment.
This picture shows local optical communication network with local data cloud structure and in house server/router. Including "on the move" data transfer at 100 Mbit/s , GigaSpeed datatransfer and reception up to10 Gbit/s , security features , energy saving/environmental features and controlling for example, by optical smart phone
1. It connects all office and entertainment equipment .
2.It controls all data and entertainment equipment via smartphone
3. It displays all files on any screen (TV,PC, etc.)
4. It supports file access from any point + and via any device
5. It stores all data in one central server/computer
6 .It supports data transfer and reception at 10 Gbit/s
7. It supports "on the move" data transfer at 100 Mbit/s
8. It monitors the entire optical network area
9. It detects motion in the entire optical network area if wanted
10. It controls all security features via smart phone
11 .It controls lighting via smart phone
12. It supports control of heating
13. It supports control of any connected electrical equipment
14. It supports energy saving/environmental features via smart phone
15. It bridges disparate data formats
16. It connects your local cloud to external line (fiberoptic, GigE, ADSL, etc.)
3 .Features of Li Fi.
Up to ~4000 lumen output (can be used in both collimated mode for LCD/LCoS, and focused mode for DLP)
20,000+ lifetime (about 5x longer than conventional UHP lamps)
Up to 10x faster turn-on rate
Dynamic brightness control (can be electronically dimmed between 20-100%)
Nominal power use: 270W (includes microwave transmitter)
Dimensions: 5.3" x 3.6" x 6.8" (135 x 91 x 173mm)
3.1 Applications of Li Fi
A. It can be used in the places where it is difficult to lay the optical fiber like hospitals. In operation theatre LiFi can be used for modern medical instruments.
B. In traffic signals LiFi can be used which will communicate with the LED lights of the cars and accident numbers can be decreased.
C. Thousand and millions of street lamps can be transferred to LiFi lamps to transfer data.
D. In aircraft LiFi can be used for data transmission.
E. It can be used in petroleum or chemical plants where other transmission or frequencies could be hazardous.
Some other applications of LiFi are.
3.1.1 For security
applications.
It is an optical receiver chips monitor Li-Fi cloud area and each optical receiver chip has integrated motion detector function.
1-It monitors the Li-Fi cloud area via smart phone
2-It detects movement within the Li-fi cloud area
3-It gives notice of movements via smart phone wherever you might be
4-It helps to know who is ringing on your door bell
5-It helps you answer the door bell from wherever you are and monitor each room individually from wherever you are.
6-It is also using for home or office security , Intercom system for home and office and baby monitoring systems.
3.1.2 Optical
Lighting control
2.The communication point controls lighting fixture
3.It programs each lighting fixture according to day-night rhythm and Dims each lighting fixture individually
4.It control the use of energy.
3.1.3 Smart home applications
1. It control the energy use through smart phone and controls the electrical equipment through smart phone and also control heating and airconditioning through smart phone
2. It can be connected to any electrical equipment and
controls energy supply to the connected equipment remotely.
3. Energy saving
4. Increase user control over equipment .
4 . Conclusion
LiFi lamps offer similar capability and life expectancies as LED-based lamp technologies, but at a reduced cost of entry. While the actual lamp part of the system is about 1/8th the size of a typical Tungsten lamp, the entire assembly is a bit larger, which shouldn't be a problem for rear projection sets. At 20,000 hours you're nearing the end-of-life for a television set, unless you're the type who runs soaps, QVC and The Price Is Right all day long. The only real negative with the technology so far is that it takes more energy to run, but not so much as to be considered a power hog. Currently a typical HID lamp-based television from Panasonic requires around 240W to run (with volume at maximum). At the same screen size, a new LIFI-based set requires 360W. That's a 50% increase in power needs over prior models (calculations based on a 50-inch set).
LED seems to be the main competition (and a better choice in terms of power consumption and color range) however for some reason the prices have not yet sufficiently dropped on that type of light generation technology. In the meantime, this is a good stopgap, provided that the low-level microwave system doesn't present any issues for users of this technology. As more and more price drops are encountered with flat panels TVs it will be a miracle if rear projection sets under 50-inches are even in the marketplace a few years from now.
