In future you may get your broadband through your light bulb

Source: By The Conversation, 04/10/2015

Smart lighting products are emerging that can offer various additional
features, including linking your laptop or smartphone to the
internet.


The tungsten lightbulb has served well over the century or so since it
was introduced, but its days are numbered now with the arrival of LED
lighting, which consume a tenth of the power of incandescent bulbs and
have a lifespan 30 times longer.


Potential uses of LEDs are not limited to illumination: smart lighting
products are emerging that can offer various additional features,
including linking your laptop or smartphone to the internet. Move over
Wi-Fi, Li-Fi is here.


Wireless communication with visible light is, in fact, not a new idea.
Everyone knows about using smoke signals on a desert island to try to
capture attention.


Perhaps less well known is that in the time of Napoleon much of Europe
was covered with optical telegraphs, otherwise known as the
semaphore.


Alexander Graham Bell, inventor of the telephone, actually regarded
the photophone as his most important invention, a device that used a
mirror to relay the vibrations caused by speech over a beam of
light.


In the same way that interrupting (modulating) a plume of smoke can
break it into parts that form an SOS message in Morse code, so visible
light communications – Li-Fi – rapidly modulates the intensity of a
light to encode data as binary zeros and ones.


But this doesn`t mean that Li-Fi transceivers will flicker; the
modulation will be too fast for the eye to see.


Wi-Fi vs Li-Fi
The enormous and growing user demand for wireless data is placing huge
pressure on existing Wi-Fi technology, which uses the radio and
microwave frequency spectrum.
With exponential growth of mobile devices, by 2019 more than ten
billion devices are expected to exchange around 35 quintillion (1018)
bytes of information each month.


This won`t be possible using existing wireless technology due to
frequency congestion and electromagnetic interference.


The problem is most acutely felt in public spaces in urban areas,
where many users try to share the limited capacity available from
Wi-Fi transmitters or mobile phone network cell towers.
A fundamental communications principle is that the maximum data
transfer possible scales with the electromagnetic frequency bandwidth
available.


The radio frequency spectrum is heavily used and regulated, and there
just isn`t enough additional space to satisfy the growth in
demand.

So Li-Fi has the potential to replace radio and
microwave frequency Wi-Fi.



Visible light spectrum
Visible light spectrum has huge, unused and unregulated capacity for
communications.


The light from LEDs can be modulated very quickly: data rates as high
as 3.5Gb/s using a single blue LED or 1.7Gb/s with white light have
been demonstrated by researchers in our EPSRC-funded Ultra-Parallel
Visible Light Communications programme.


Unlike Wi-Fi transmitters, optical communications are well-confined
inside the walls of a room. This confinement might seem to be a
limitation for Li-Fi, but it offers the key advantage that it is very
secure: if the curtains are drawn then nobody outside the room can
eavesdrop.


An array of light sources in the ceiling could send different signals
to different users. The transmitter power can be localised, more
efficiently used and won`t interfere with adjacent Li-Fi
sources.

Indeed the lack of radio frequency interference is
another advantage over Wi-Fi.


Visible light communications is intrinsically safe, and could end the
need for travellers to switch devices to flight mode.


A further advantage of Li-Fi is that it can use existing power lines
as LED lighting so no new infrastructure is needed.



How a Li-Fi network will work
Lightening the burden of the internet of things
The internet of things is an ambitious vision of a hyper-connected
world of objects autonomously communicating with each other.


For example, your fridge might inform your smartphone that you have
run out of milk, and even order it for you. Sensors in your car will
directly alert you though your smartphone that your tyres are too worn
or have low pressure.


Given the number of "things" that can be fitted with sensors and
controllers then network-enabled and connected, the bandwidth needed
for all these devices to communicate is vast.


Industry monitor Gartner predicts that 25 billion such devices will be
connected by 2020, but given that most of this information needs only
to be transferred a short distance, Li-Fi is an attractive – and
perhaps the only – solution to making this a reality.


Several companies are already offering products for visible light
communications.


The Li-1st from PureLiFi, based in Edinburgh, offers a simple
plug-and-play solution for secure wireless point-to-point internet
access with a capacity of 11.5 Mbps – comparable to first generation
Wi-Fi.


Another is Oledcomm from France, which exploits the safe, non-radio
frequency nature of Li-Fi with installations in hospitals.


There are still many technological challenges to tackle but already
the first steps have been taken to make Li-Fi a reality. In the future
your light switch will turn on much more than just
illumination.


• Pavlos Manousiadis, Research Fellow, University of St Andrews;
Graham Turnbull, Professor, Head of the School of Physics and
Astronomy, University of St Andrews, and Ifor Samuel, Professor of
Polymer Optoelectronics, University of St Andrews
• This article was originally published on The Conversation. Read the
original article.


More on broadband technologies
Using LED lights to move data at 300Mbps
This is what 2.4GHz Wi-Fi looks like