Kuldeep ppt11

Presentation By:
Kuldeep Narayan Shukla
Seminar
On
Visible Light Communication
Li-Fi Technology

Content
 Introduction
 What is Visible Light Communication (Li-Fi)
 History
 How Li-Fi Works?
 How it is different?
 Wi-Fi vs Li-Fi
 Applications
 Advantages
 Disadvantages
 Conclusion

Introduction
 Li-Fi is a wireless optical networking technology that
uses light-emitting diodes (LEDs) for data
transmission.
 However, Li-Fi bulbs are outfitted with a chip that
modulates the light for optical data transmission.
 Li-Fi data is transmitted by the LED bulbs and
received by photoreceptors.
 Li-Fi Based on Visible light communication (VLC)

What is Visible Light Communication (Li-Fi)
 Visible Light Communication (Li-Fi) is bidirectional, high speed
and fully networked wireless communications similar to Wi-Fi.
 Li- Fi is a subset of optical wireless communication (OWC) and
can be a complement to RF communication (Wi-Fi or Cellular
network), or a replacement in contexts of data broadcasting.

What is Visible Light Communication
 Visible Light Communication is a Data Communication Medium, which
uses the Visible Light between 400 THz(780nm) and 800THz(375nm) as
optical carrier for Data Transmission

History
 Professor Harald Haas, from the University of Edinburgh in the
UK, is the original founder of Li-Fi.
 Haas promoted this technology in his 2011 TED Global talk and
helped start a company to market it.
 In October 2011, companies and industry groups formed to
promote high-speed optical wireless systems .
 The first Li-Fi Smartphone prototype was presented at the
Consumer Electronics Show in Las Vegas from January 7–10 in
2014.

Existing wireless technology - Why do
we need an alternate technology?
 CAPACITY - 1000 times more then the Radio wave.
 EFFICIENCY - Highly efficient because LED consumes less energy.
 AVAILABILITY - Light is present every where and Data is present where
light is present.
 SECURITY - Light is blocked by the walls and hence will provide more
secure data.

Advantages of LI-FI
 Li-Fi can solve problems related to the insufficiency of radio
frequency bandwidth because this technology uses Visible light
spectrum that has still not been greatly utilized.
 High data transmission rates of up to 10Gbps can be achieved.
 Since light cannot penetrate walls, it provides privacy and
security that Wi-Fi cannot.
 Li-Fi has low implementation and maintenance costs.

Disadvantages
 Light can't pass through objects.
 A major challenge facing Li-Fi is how the receiving device will
transmit back to transmitter.
 High installation cost of the VLC systems.
 Interferences from external light sources like sun, light, normal
bulbs, opaque materials.

Conclusion
 The possibilities are numerous and can be explored further.
 If his technology can be put into practical use, every bulb can be
used something like a Wi-Fi hotspot to transmit wireless data and
we will proceed toward the cleaner, greener, safer and brighter
future.

References
 IEEE Papers
 Optical wireless communication system and
channel modeling CRC Press Taylor & Francis
Group
 www.wikipedia.com
 www.google.com
 YouTube

Next slides are for my own use
kuldeep …….

Challenges and Solutions
 Main challenges for indoor VLC systems are
 Connectivity while moving: users need to be connected
when they move inside the indoor environment
 Multiuser support: in large areas is vital, many users need to
have access to the network at the same time
 Dimming: is an important feature in VLC when
communications is integrated with lighting
 Shadowing: happens when the direct paths from user to all
sources are blocked
 Some solution has been proposed for each one

 Solution for connectivity
 This problem is similar to the connectivity problem in cellular network when you
move from one area of the city to another area while speaking with cell-phone
 The solution is called “handover”, using which the user is transferred from one
BS to another
 Handover is done in the area that two BS’s have common coverage
 Similar solution can be used in signal processing domain for VLC
 The user can be transferred from one light source to another in the area that is
under the coverage of both

 Solution for multiuser support
 One solution is time division
multiplexing (TDM)
 Each frame is divided into equal
time slots
 Each user transmit data in one time
slot in a predefined order
 The other solution is code division multiple access (CDMA)
 Codes are assigned to users
 Each user transmit its data using the assigned signature pattern
 It is used in 3G and 4G cellular networks
 CDMA has been adopted and developed for optical systems
 Optical orthogonal codes (OOC) are used as signature pattern for
users

 Solution for multiuser support
 Last solution is spatial multiplexing
 Can use to increase data rate or to add users
 Rely on LED arrays and multiple receivers
 Or can use an imaging receiver (camera)

 Solution for dimming
 Two main solutions are proposed for solving dimming
problem in VLC systems
 Pulse width modulation (PWM) is combined with other
modulation schemes in order to control the duty cycle of the
transmitter signal
 By controlling the width of the PWM signaling, the
dimming level can be controlled
 The other solution is using modified forms of PPM
 In these schemes multiple pulses are transmitted instead of
one pulse
 By controlling and changing the ratio between the number of
pulses and the length, the dimming level can be altered

 Solution for shadowing
 As shown before, the
impulse response in VLC
systems has two parts
 When the line-of-sight
(LOS) part (which is
received via direct path) is
blocked, the impulse
response is only the second
part
 Then the data can be
recovered using the second
part which is indeed the
received data from the
indirect paths (multipath
signal)

Kuldeep ppt11

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