4. WHAT IS LI-FI?
The term Li-Fi was coined by Prof. Harald Haas during
his TED Global talk .
It is a bidirectional, high speed and fully networked
wireless communications similar to Wi-Fi.
Li-Fi is a subset of optical wireless communication.
Optical version of Wi-Fi.
Li-Fi is based on Visual Light Communication(VLC).
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5. Working Of Li-Fi
Its working is much simply explained as follows :
If the LED is on ,the digital 1 is transmitted
And if it is off ,the digital 0 is transmitted.
It is possible to encode the data in the light by varying the
rate at which the LEDs flicker on and off to give different
strings of 1s and 0s
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6. Cont’d…
Due to the increasing demand for wireless data
communication the available radio spectrum below
10GHz has become insufficient.
The wireless communication industry has responded to
this challenge by considering the radio spectrum above 10
GHz
According to Friis free space equation as frequency (f),
increases the path loss (L) also increases.
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7. Cont’d…
LiFi is a natural continuation of the trend to move to
higher frequencies in the electromagnetic spectrum.
LiFi could be classified as nm-wave communication.
LiFi uses LEDs for high speed communication
Able to provide speed of over 3 Gbps from a single
micro LED
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8. Concept of attocells
The optical Access Point(AP) in Li-Fi is referred to as an
attocell.
The Li-Flame ceiling unit connects to an LED light to
form an atto-cell, which provides communication in the
LED Light illuminated area.
If we equip a room with multiple light and that each light
function as a very small radio base station, the result is a
network of very small cells that is known as ‘optical atto
cells’.
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9. Cont’d…
As attocells operates in the visible light spectrum, the
optical attocell does not interfere with the macro cellular
network.
Li-Fi attocells allow for extremely dense bandwidth reuse
due to the inherent properties of light waves.
The coverage of each single attocell is very limited, and
walls prevent the system from suffering from cochannel
interference.
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10. Cont’d…
Each atto cellular AP results in co-channel interference
reduction.
This technique allows the cellular coverage area to be
broken down further into areas of low interference and
areas of high interference.
A similar concept realized at the receiver side where
multiple receiver elements provide a means for enhanced
interference mitigation capabilities.
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11. Cont’d…
Due to the requirement for illumination indoors, the
infrastructure already exists, and this type of cell
deployment results in the very high, practically
interference-free bandwidth reuse.
The user data rate in attocell networks can be improved by
up to three orders of magnitude.
Moreover, Li-Fi attocells can be deployed as part of a
heterogeneous VLC-RF network.
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12. Modelling LiFi Networks
In a LiFi attocell network, the placement of the APs affects the
system performance.
The light signal from a neighbouring AP causes interference
which limits the signal-to-interference-plus –noise ratio
(SINR).
The bandwidth can be shared among different optical APs
according to the well-known frequency reuse concept.
The placement of the optical APs is mainly determined by the
lighting design.
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13. Cont’d…
Optical attocell networks exploit the ability of LiFi to
achieve a massive spatial reuse.
To demonstrate the high data density achieved by an
optical attocell system, the area data rate, sarea, is used, and
this is defined as:
sarea =s/Acell.
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22. Future of Li-Fi
In November 2014, Li-Fi pioneers pure LiFi joined
forces with French lighting company Lucibel aiming to
bring out Li-Fi enables products, by the end of 2016.
Li-Fi is reportedly being tested in Dubai, by UAE-based
telecommunications provider and claims to have
successfully provided internet, audio and video streaming
over a Li-Fi connection
Reports suggest that Apple may build future iPhones with
Li-Fi capabilities.
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