Li-Fi
Li-Fi (Light Fidelity) is a
bidirectional, high speed and fully networked wireless communication
technology similar to Wi-Fi.
Coined by Prof. Harald Haas,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 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.
A complete solution includes an
industry led standardization process.
Technology
details
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.
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.
Both Wi-Fi and Li-Fi transmit data over
the electromagnetic 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 frequency spectrum.
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 pureLiFi.
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. By August 2013, data rates of over 1.6 Gbit/s were
demonstrated over a single color LED.
In September 2013, a press release said
that Li-Fi, or VLC systems in general, do not require line-of-sight
conditions. In October 2013, it was reported Chinese manufacturers
were working on Li-Fi development kits.
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 foresee boosting speeds up to 5
GB/second in the near future.
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.
Standards
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.
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/IP protocol.[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.