I look as I watching the LED light Li-Fi (Light Fidelity) is a bidirectional, high speed and fully networked wireless communication technology similar to Wi-Fi. Coined by Prof. Harald Haas,[1] Li-Fi is a subset of optical wireless communications (OWC) and can be a complement to RF communication (Wi-Fi or Cellular network), or a replacement in contexts of data broadcasting. It is so far measured to be about 100 times faster than Wi-Fi, reaching speeds of 224 gigabits per second.[2]
It is wireless and uses visible light
communication or infra-red and near
ultraviolet (instead of radio frequency waves) spectrum, part of optical
wireless communications technology, which carries much more information, and
has been proposed as a solution to the RF-bandwidth limitations.[3] A complete solution
includes an industry led standardization process.
This OWC technology uses light from light-emitting diodes (LEDs) as a medium to deliver networked,
mobile, high-speed communication in a similar manner to Wi-Fi.[4] The Li-Fi market is
projected to have a compound annual growth
rate of 82% from 2013 to
2018 and to be worth over $6 billion per year by 2018.
Visible light communications (VLC) works by switching the
current to the LEDs off and on at a very high rate, too quick to be
noticed by the human eye. Although Li-Fi LEDs would have to be kept on to
transmit data, they could be dimmed to below human visibility while still
emitting enough light to carry data.The light waves cannot
penetrate walls which makes a much shorter range, though more secure from
hacking, relative to Wi-Fi.] Direct line of sight
isn't necessary for Li-Fi to transmit a signal; light reflected off the walls
can achieve 70 Mbit/s.
Li-Fi has the advantage of being useful in electromagnetic
sensitive areas such as in aircraft cabins, hospitals and nuclear power plants[citation needed] without causing electromagnetic
interference.[8][9] Both Wi-Fi and Li-Fi
transmit data over theelectromagnetic
spectrum, but whereas Wi-Fi utilizes radio waves, Li-Fi uses visible
light. While the US Federal Communications Commission has warned of a potential
spectrum crisis because Wi-Fi is close to full capacity, Li-Fi has almost no
limitations on capacity. The visible light
spectrum is 10,000 times larger than the entire radio frequencyspectrum.Researchers have reached data rates of over 10 Gbit/s, which is much faster than typical
fast broadband in 2013.Li-Fi is expected to be ten times cheaper than
Wi-Fi. Short range, low
reliability and high installation costs are the potential downsides.
PureLiFi demonstrated the first commercially available Li-Fi system, the
Li-1st, at the 2014 Mobile World Congress in Barcelona.
Bg-Fi is a Li-Fi system consisting of an application for a
mobile device, and a simple consumer product, like an IoT (Internet of Things)
device, with color sensor, microcontroller, and embedded software. Light from
the mobile device display communicates to the color sensor on the consumer
product, which converts the light into digital information. Light emitting
diodes enable the consumer product to communicate synchronously with the mobile
device.
History
Professor Harald Haas,
from the University of Edinburgh in the UK, is widely recognised as the
original founder of Li-Fi. He coined the term Li-Fi and is Chair of Mobile
Communications at the University of Edinburgh and co-founder of pure LiFi.
The general term visible light
communication (VLC), includes any
use of the visible light portion of the electromagnetic spectrum to transmit
information. The D-Light project at Edinburgh's Institute for Digital
Communications was funded from January 2010 to January 2012. Haas promoted this technology in his 2011 TED Global talk and helped start
a company to market it. PureLiFi, formerly pureVLC, is an original equipment
manufacturer (OEM) firm set up to
commercialize Li-Fi products for integration with existing LED-lighting systems.
In October 2011, 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.
A number of companies offer
uni-directional VLC products 
, which is not the same as Li-Fi.[citation needed]
VLC technology was exhibited in 2012 using Li-Fi.[24] By August 2013, data rates of over 1.6 Gbit/s were demonstrated
over a single color LED.[25] In September 2013, a press release said that Li-Fi, or VLC
systems in general, do not require line-of-sight conditions.[26] In October 2013, it was reported Chinese manufacturers were
working on Li-Fi development kits.[27]
In April 2014, the Russian company Stins Coman announced the
development of a Li-Fi wireless local network called BeamCaster. Their current
module transfers data at 1.25 gigabytes per second but they foresee boosting
speeds up to 5 GB/second in the near future.[28] In 2014 a new record was established by Sisoft
(a Mexican company) that was able to transfer data at speeds of up to 10Gbps
across a light spectrum emitted by LED lamps[
Like Wi-Fi, Li-Fi is wireless and uses similar 802.11 protocols;
but it uses visible light communication (instead of radio frequency waves), which has
much wider bandwidth.
One part of VLC is modeled after communication protocols
established by the IEEE 802 workgroup. However, the IEEE 802.15.7 standard is
out-of-date, it fails to consider the latest technological developments in the
field of optical wireless communications, specifically with the introduction of
optical orthogonal frequency-division multiplexing (O-OFDM) modulation methods which have been
optimized for data rates, multiple-access and energy efficiency.[30] The introduction of O-OFDM means that a new drive for
standardization of optical wireless communications is required.
Nonetheless, the IEEE 802.15.7 standard defines the physical layer (PHY) and media
access control (MAC) layer. The
standard is able to deliver enough data rates to transmit audio, video and
multimedia services. It takes into account optical transmission mobility, its
compatibility with artificial lighting present in infrastructures, and the
interference which may be generated by ambient lighting. The MAC layer permits
using the link with the other layers as with the TCP/IPprotocol.[citation needed]
The standard defines three PHY layers with different rates:
·
The PHY I was
established for outdoor application and works from 11.67 kbit/s to 267.6
kbit/s.
·
The PHY II layer permits
reaching data rates from 1.25 Mbit/s to 96 Mbit/s.
·
The PHY III is used
for many emissions sources with a particular modulation method called color
shift keying (CSK). PHY III can deliver rates from 12 Mbit/s to 96 Mbit/s.
The modulation formats recognized for PHY I and PHY II are on-off keying (OOK) and variable pulse position modulation(VPPM). The Manchester coding used for the PHY I and PHY II layers includes
the clock inside the transmitted data by representing a logic 0 with an OOK
symbol "01" and a logic 1 with an OOK symbol "10", all with
a DC component. The DC component avoids light extinction in case of an extended
run of logic 0's.[citation needed]
The first VLC smartphone prototype was presented at the Consumer Electronics Show in Las Vegas from January 7–10 in 2014. The
phone uses SunPartner's Wysips CONNECT, a technique that converts light waves
into usable energy, making the phone capable of receiving and decoding signals
without drawing on its battery. A clear thin layer of crystal glass can be added to small
screens like watches and smartphones that make them solar powered. Smartphones
could gain 15% more battery life during a typical day. This first smartphones
using this technology should arrive in 2015. This screen can also receive VLC
signals as well as the smartphone camera. The cost of these screens per smartphone is
between $2 and $3, much cheaper than most new technology.
Philips lighting company has developed a VLC system for shoppers
at stores. They have to download an app on their smartphone and then their
smartphone works with the LEDs in the store. The LEDs can pinpoint where they
are located in the store and give them corresponding coupons and information
based on which aisle they are on and what they are looking at.
