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.

How Li-Fi Works?

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.

Applications

Vehicle Communication

Real Time Usage of Li-Fi

Application in Airlines

Underwater Communication

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

Thank You!...Any Questions ?

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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

Challenges and Solutions

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

Challenges and Solutions 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

Challenges and Solutions

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)

Challenges and Solutions 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

Challenges and Solutions 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)