[LINK] Light instead of wireless, Li-Fi

[stephen at melbpc.org.au]

"Harald Haas: Wireless Data From Every Lightbulb"   Posted: 16th Dec 2011

<http://www.huffingtonpost.com/2011/12/16/harald-haas-wireless-
data_n_1153538.html?1324050673> (snip)


. Traditionally, (much of) the information we move around is transmitted 
using radio frequency spectrum.

It is forecast that by the year 2015, we will transmit six exabytes every 
month through wireless networks. This is a ten-fold increase on the 
amount of data we send now.

In order to meet this increased demand, we need either 10 times more 
radio frequency spectrum for commercial wireless networks, or, we have to 
make the existing radio frequency spectrum 10 times more efficient.

We are heading to a saturation point in terms of how efficiently we can 
use the radio frequency spectrum. The only way out of this is to find new 
ways to transmit data wirelessly. 

Fortunately, the electromagnetic spectrum not only incorporates the radio 
frequency spectrum, but also includes the visible light spectrum.

In the past decade, there have been massive developments in the use of 
light emitting diodes (LEDs). Since LEDs are far more energy efficient 
than incandescent bulbs, they are at the heart of the latest generation 
of lights. In fact, research by my team at the University of Edinburgh 
has shown that, if all the world's incandescent light bulbs were replaced 
by LED, the energy saved would be equivalent to that produced by more 
than 100 nuclear power stations.

However, this is not the only advantage of LEDs. 

We have harnessed this feature to develop novel techniques that enable 
ordinary LED light bulbs to wirelessly transmit data at speeds many times 
faster than WiFi routers. 

We have named the new technology Li-Fi (light fidelity) which we now 
commercialize via the university spin-out company VLC Ltd.

In our lab, under ambient light conditions, we are able to achieve data 
speeds of 130 megabits per second. 

If all light bulbs were able to do this, it would create a simple, energy-
efficient solution to the lack of available radio frequency spectrum for 
future wireless broadband communication. 

The new Li-Fi technology utilizes existing infrastructures and as a 
result the installation costs are minimal, let alone the reduced cost of 
the technology as it does not require an antenna.

On top of this, there are other advantages to this technology. 

Light does not penetrate walls, and so internet signals cannot be 
intercepted outside the room in which they are transmitted, which 
enhances security. Light is inherently safe and can be used in places 
where radio frequency communication is often deemed problematic, such as 
in aircraft cabins or hospitals. 

In the not-too-distant future, a day in the life of an average person, 
whom we'll call Sally, could look like this:

* When Sally switches on the light in the morning, she gets the latest 
news flashed on her smartphone. From the breakfast table she sends a few 
emails through the table light.

* Sally gets into her car and drives to work. On the way, a cat crosses 
the street and she has to brake hard. Her LED backlights tell the car 
behind to slow down even before the driver has a chance to brake -- an 
accident is avoided.

* Sally stops in front of a traffic light that operates using LEDs. While 
showing red, the traffic light is able to send a signal to switch off the 
engine in Sally's car, reducing CO2 emissions. The traffic light also 
communicates with the navigator inside the car, and helps Sally avoid a 
traffic jam ahead.

* In the office, Sally's fast internet access is provided through the LED 
ceiling lights. She has internet access in all meeting rooms, but no-one 
on the street outside can intercept the signals.

* After work she decides to go to an art gallery to pass the time until 
she meets Tom, her new boyfriend, for a date at a restaurant downtown. 
The LED spotlights in the gallery illuminate the pictures and provide 
information about them.

* Sally leaves the art gallery and, on the way downtown, she passes some 
shops. LED lights in the shop windows broadcast offers. She buys a pair 
of shoes on sale.

* The restaurant is in a large shopping mall. Sally's navigation system 
guides her there. Inside the mall, LED ceiling lights take over the task 
of guiding her to the restaurant.

* Once inside the restaurant, LED table lights beam the menu card onto 
Sally's smart-phone. She enjoys her meal and leaves a recommendation on 
the restaurant's home page, using the connection from the same table 
light.

* By the time Sally leaves the restaurant it is dark. She is in a good 
mood after her date. On the way back to her car, she leaves a little 
message at a street light, which acts as a local message board, 
saying "Sally loves Tom" -- just as in the past she might have carved the 
same into a tree

-----------

Also, at a VLC Ltd site <http://visiblelightcomm.com> ...

Light at the end of the Ethernet
Posted on October 27, 2011 by GordonPovey 

Where does PoE fit with VLC?

I have previously talked about Ethernet over power, also known as power 
line communications (PLC) and the fact that this is a complementary 
technology to VLC since it allows the communications backhaul to be 
carried over the existing lighting power circuits.  

Now I want to consider Power over Ethernet (PoE), a technology that has 
been around for a while but is growing in popularity.  Ethernet cables, 
such as CAT5, are clearly designed to carry data, but there are PoE 
standards designed to allow them also to carry power.  The idea being 
that low power Ethernet connected devices, such as VoIP phones, networked 
cameras etc. can have just a single connector and no additional power 
adapter is required.

PoE comes in a number of flavours.  There are two IEEE standards; 802.3af 
and 802.3at which both use a spare pair of conductors to carry the 
power.  The more common af standard can provide up to 15W of d.c. power 
rated at 44V, 350mA.  The more recent at standard known as PoE+ provides 
up to 30W.  There are a number of non-standard variants and Cisco’s 
recently announced universal PoE variant (UPOE) can carry up to 60W of 
power using two pairs of cables from a CAT5e or CAT6 cable.

So why not use PoE to power high efficiency LED lighting installations 
since now the power, voltage and current parameters are well matched to 
this application.  

It seems to me, not just feasible that PoE infrastructure could be 
utilised for lighting, control and communications within a building, but 
it also seems very sensible.  We have ourselves demonstrated high speed 
data communications transmitted from an IP connected light bulb.


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