i3 - July/August 2016 - 25

Another drawback is that Li-Fi requires the LED
lightbulb to be on at all times to provide connectivity,
so the lights will need to be on during the day, reducing the energy efficiency advantage LEDs enjoy over
traditional lighting sources.
Also not helping the Li-Fi cause are published
reports that Li-Fi is "100 times faster than Wi-Fi."
Simply put that's not so. The latest Wi-Fi standard
(IEEE 802.11ad - otherwise known as Wi-Gig)
operating in the 60 GHz frequency band supports
data rates of 7 Gbps. For Li-Fi to be 100 times faster
it would have to achieve 700 Gbps and nothing close
to that has been achieved, not even in a laboratory.
The speed of Li-Fi is directly affected by the type and
size of the LED. Many commercial LEDs use a phosphor coating to convert blue light to white light; this
coating limits how fast the devices can be modulated,
slowing down data rates and, as a result, phosphorcoated white LEDs can only go as fast as 100Mbps
(fast enough for an HD movie to be downloaded in
seconds). The more expensive red, green, blue (RGB)
LEDs can deliver anywhere from 3 to 5 Gbps via Li-Fi,
according to lab tests, and laser-based white LEDs, a
technology which itself is still in the research lab stage,
can transfer data at a rate of 100Gbps.
Some Li-Fi critics have pointed out that while there
is a lot of information floating around regarding the
concept of LEDs as transmitters a lot less has been
offered about Li-Fi receivers beyond the fact that lab
researchers have fabricated sensitive detector arrays
using high-gain avalanche photodiodes to detect the
encoded light streams from LEDs. In an avalanche
photodiode a photon striking the receiver produces a
plethora of electrons, amplifying the signal.
A related issue is how do you send data back to the
LED bulb and then on to a server, the Cloud
or wherever else it needs to be sent? Getting digital
data from the light fixture to the internet will require
either physical wiring or an RF link. For Li-Fi to be

DATA STREAM

An overhead lamp fitted
with an LED with signalprocessing technology
(below) streams data
embedded in its beam
at ultra-high speeds to
the photo-detector. A
receiver dongle then
converts the tiny changes
in amplitude into an electrical signal, which
is then converted back
into a data stream and
transmitted to a computer or mobile device.
C TA . t e c h / i 3

55
OF THE
TOTAL MOBILE
DATA TRAFFIC
WILL BE
OFFLOADED
FROM
CELLULAR
TO WI-FI
OR SMALL CELL
NETWORKS.

practical in the home it also will need to handle omnidirectional radiation, which consumes a good amount
of power, not available in mobile devices.
Offsetting some of these Li-Fi disadvantages is
the fact that Wi-Fi is subject to interference issues
from nearby access points (routers). With Li-Fi there
can be tens or more LEDs bulbs in a room without
interference. Wi-Fi also can create electromagnetic
interference (EMI), known to interfere with airplane
instruments and equipment in hospitals. Li-Fi uses
light instead of radio waves and does not create EMI.
Interference with Wi-Fi transmissions can be
problematic in a manufacturing setting. Currently,
most manufacturers use Wi-Fi connectivity in their
production lines. Interference increases the risk of
partial or complete production downtime.
What is more, just as in consumer use the allotted
radio frequencies are already in industrial settings
by diverse applications requiring the transmission
of large data volumes. Demonstrating that Li-Fi can
provide a viable alternative to Wi-Fi in factories,
the Fraunhofer Institute for Telecommunications,
Heinrich Hertz Institute (HHI ) showed a Li-Fi optical wireless communication solution for secure data
exchange in industrial cases.

Consumer Product Development

(Source:Pur eLifi)

In 2012, Professor Haas and his colleagues set up a
company called pureLiFi to commercialize the technology. The latest generation of drivers and receivers
introduced in 2016 from pureLiFi is called LiFi-X. It
consists of an access point that connects to any LED
light, as well as a small dongle that can be operated
from any USB 2.0 enabled mobile device. LiFi-X
brings the receiver down to a convenient, business
card size. It offers full duplex communication with a
40Mbps downlink and 40Mbps uplink.
Also pureLiFi has joined forces with the French
LED lighting company Lucibel to develop a Li-Fi
luminaire ready for market later this year.
New Delhi startup Velmenni is also developing a
smart LED bulb called Jugnu, capable of sending
data to smartphones at 10Mbit/sec. The company has
created a prototype to demonstrate visible light communication and has successfully transferred serial data
synchronously from a PC/Laptop screen to a microcontroller board using visible light. The company is
working on a smart LED bulb which can transfer data
to other bulbs, mobile phones and the internet. It is
also working on an Android app. Velmenni is targeting
2018-2019 for launching commercial Li-Fi LED bulbs.
Fortunately, Li-Fi LEDs may help to support and
provide an alternative to wireless communications so
that the IoT can continue to grow and thrive.
■
JULY/AUGUST 2016

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i3 - July/August 2016

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