An explanation about Visible light communication. Which sort of Problems and challenges are there to perform communication through Visible Light.

1. MuhammadShaoor (11-ENC-52)
ShaheryarAhsan (11-ENC-97)
NabeelAhmad (11-ENC-98)
HafizUmairMunir (11-ENC-106)

2. Topic of Presentation
Visible Light Communication
(Problems and Challanges)

3. Basic Concept
• Visible light communication (VLC) is a data
communication using visible light.
VLC = Illumination + Communication

4. Solid State Lightning
• Solid-state lighting (SSL) is a special type
of lighting that uses semiconductor light-emitting
diodes (LEDs).
• They are the source of illumination which are used
instead of fluorescent lamps and arc lamps etc.
• Now-a-days Solid state lights are becoming more
popular because they are not used only for
illumination but also for communication.

5. Band of Interest
 Visible range of spectrum lies between 400nm to
700nm.

6. Advantages of VLC
 Using visible light is less dangerous for high-
power applications because humans can
perceive it and is also protect their eyes from
damage.

7. Advantages of VLC
 LED’s which are used in visible light communication
will not only be used for illuminating rooms but also
for optical wireless communication.
 The LEDs Used in VLC has the ability to switch on
and off thousands of times per second.
 These LED’s will turn ON and OFF at such high
speed that human won’t be able to detect any
change.
 It will appear ON to them but actually it will keep
turning ON and OFF.

8. Optical Wireless communication
 Optical Wireless communication (OWC) is a
general term which refers to all types of
optical communications where cables (optical
fibres) are not used.
 VLC, FSO, Li-Fi and infra-red remote controls
are all examples of OWC.
 The term VLC is different from from all these
other terms.

9. Transmitter
Receiver
VLC LINKS
Channel

10. TRANSMITTER
 White LEDS
 Blue LEDS
 RGB LEDS
varying the color to the LEDs, and also allows
different data to be sent on each device
maintaining color balance can be challenging and the
devices are complex. The single LED approach is
simpler

11. Block Diagram

12. Channel

13. Channel
 Diffuse
o Multipath from
Transmitter to Receiver
o Robust to blocking
o Large coverage
o Path loss More
o Subject to multipath
dispersion
• LoS
- o Single path from Transmitter
to Receiver
o No dispersion
o Path loss Less
o Very high bandwidth
available
o Difficult to provide
coverage

14. Receiver
 Photo detector
 Pre and post amplifier
 Filter
 Eye Bit diagram
if the LED modulation bandwidth is less than
approximately 90MHz then the LED bandwidth
constrains the system data rate.

15. Block Diagram

16. CHALLENGES OF VLC
1- Increasing Data Rate .
 Using Blue Filter.
 Transmitter Equalisation .
 Receiver Equalisation .
 Complex Modulation .
 Parallel Communication (Optical MIMO) .
2- Provision of Uplink / Two Way Communication.
3- Regulation .

17. 1- Using Blue Filter :
Most convenient way to improve data rate is
through optical filtering in which yellow
phosphor component of visible light is
blocked.
For blue comp.
Bandwidth ≈ 10 MHz
For overall white light
Bandwidth ≈ 2 MHz

18. 2-Transmitter Equalisation :
An array of LEDs can be used with different peak
frequencies and amplitudes, and this can create a
channel with improved bandwidth . This can be done
by using an LC circuit for each LED .
Increased data rate
upto 40 mb/s .
Increased B/W
upto 25 MHz .

19. 3- Receiver Equalisation :
Transmitter equalisation is very complex .
Equalisation at the receiver allows complexity to
be at the receiver only. A simple first-order analogue
equalizer can be modeled which can increase data
rate .
 Incraesed data rate upto 32 Mb/s .
 If used with equlaised transmitter ,
data rate can be upto 73 Mb/s .

20. 4- Complex Modulation :
Such Modulation Schemes which can be used in
“Bandwidth Constrained channels” and take
advantage of “High SNR of the channel” to improve
data rate should be used .

21. 5- Parallel Communication (MIMO)
 Significant number of LEDs can be used in parallel
to transmit data to an array of receivers,
each transmitting different data .
 Radio-frequency MIMO techniques can be applied
to such optical transmission systems to relax the
necessary alignment between the array of detectors
and array of sources.
 A special algorithm ‘ H Matrix ’is used to achieve this .
 This can increase data rate significantly .

22. TWO WAY COMMUNICATION :
 Optical Transceiver are used for this purpose ,
which can transmit and receive data simultaneously .
 To isolate the two data paths from each other ,
following methods are used :
• Optical isolation .
• Wavelength Division Multiplexing .
• Time Division Multiplexing .

23. REGULATION (for compatability)
 VLC is making use of solid state lighting
sources used for illumination purposes .
 Therefore , a VLC standard must encompass both
communications and associated lighting standards
and a collaboration between them is needed .
 At present there is an IEEE 802.15c study group
working on standardization for VLC , to bring it in
practical use .

24. Visible Light
Communication
Applications

25. Indoor Based VLC
System
 A basic indoor-based VLC
system consists of a light
source, preferably a LED bulb,
free space as the propagation
medium, and a
light detector.
 Information, in the form of digital
or analog signals, is input to
electronic circuitry that
modulates the light intensity at
high speeds.
o Visible light communication is a new way of wireless communication using visible
light.
o Typical transmitters used for visible light communication are visible light LEDs and
receivers are photodiodes and image sensors.
o Location-based services are considered to be especially suitable for visible light
communication applications.

26.  SMART LIGHTING
Smart buildings require smart lighting.
Smart lighting with VLC provides the
infrastructure for illumination, control
and communications and will greatly
reduce wiring and energy consumption
within a building.
 VEHICLE &
TRANSPORTATION
Many cars already LED lamps. Traffic
signage, traffic lights, and street lamps
are adopting the LED technology so
there are massive applications
opportunities here.

27.  HOSPITALS &
HEALTHCARE
There are advantages for using VLC in
hospitals and in healthcare. Mobile
phones and WiFi’s are undesirable in
certain parts of hospitals, especially
around MRI scanners and in operating
theatres.
 MOBILE
CONNECTIVITY
By pointing a visible light at another
device you can create a very high
speed data link with inherent
security. This overcomes the problems
of having to pair or connect and
provides a much higher data rate
than Bluetooth or WiFi.
 UNDERWATER
COMMUNICATIONS
RF does not work underwater but visible
light can support high speed data
transmission over short distances in this
environment. This could enable divers
and underwater vehicles to talk to each
other.

28.  LOCATION BASED
SERVICES
Each visible light information source
can be uniquely identified, so the
location of any VLC device can be
identified quickly and accurated.
 WiFi SPECTRUM
RELIEF
WiFi’s have got faster over but cannot
keep up with demand for wireless
data. VLC can provide data rates greatly
in excess of current WiFi and this can be
done at low cost since the RF components
and antenna system have been
eliminated.
 DEFENCE &
SECURITY
The ability to send data quickly and
in a secure way is the key to many
applications. The fact that the
visible light cannot be detected on
the other side of a wall had great
security advantages.
 AVIATION
Radio is undesirable in passenger
compartments of aircraft. LEDs are
already used for illumination and can
also be used instead of wires to
provide media services to
passengers. This reduces the aircraft
construction costs and its weight..

29. Conclusion and Outlook
 Increased Data Rate.
 More Advanced Modulation.
 Parallelize Communication by using groups of Emitters and
Recievers.
 No expensive patent-license necessary.
 Visible light does not cause any health problems.
 No EM-interference occurs.
 No interception because the transmission range is narrowly
confined.
 Ever-increasing market share of LEDs makes VLC easily
available.