LI-FI(Light Fidelity)

Presented By:Nishil Patel(140410754012)ME – Embedded System

Contents

• Introduction• History• Present scenario• Issues regarding Radio Spectrum• Working process• Modulation Techniques• Difference between Li-Fi and Wi-Fi• Advantages • Limitations • Application

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Introduction

LI-FI (Light Fidelity)

LI-FI is transmission of data through illumination, sending data through a LED light bulb that varies intensity faster than human eye can follow.

Light based WI-FI Light is used instead of radio-waves to transmit

information

05/01/2023 Fig.1 data trough light

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History of Li-Fi

The technology truly began during the 1990's in countries like Germany, Korea, and Japan where they discovered LED's could be retrofitted to send information. 

Prof. Harald Haas (University of Edinburgh) has introduced the idea of “wireless data from every light” in the year 2012.

In April, 2014 Russian company stins comon has announced the development of Li-FI wireless local network.

Prof. Harald Hass05/01/2023

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Present scenario

Radio spectrum is congested, but the demand for wireless data doubles each year. Mobile phone transmits more than 600TB of data. Every thing, it seems want to use wireless data but the capacity is drying up

1.4 Million 5 Billion

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Issues Regarding Radio Spectrum

capacity

Efficiency Security

Availability

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Conti…

Capacity• Expensive• Less bandwidth compared to other spectrum• Insufficient spectrum for increasing data

Efficiency • Millions of base stations consume huge amount of energy for 1.Transmitting the radio waves 2.To cool the base station cabins• 5% Efficiency

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Conti…

Availability • Available within the range of Base stations• Limited availability• Unavailable in aircrafts , Petrochemical plants

Security • Less secure than LIFI

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Electromagnetic spectrum

VLC, which uses visible light between 400 THz (780 nm) and 800 THz (375 nm) as optical carrier for data transmission and illumination.

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Fig 2 Electromagnetic Spectrum[2]

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Why only VLC?

In electromagnetic spectrum, gamma, UV rays are dangerous for human body. X-rays have similar health issues. IR rays are not used due to eye safety regulations.

05/01/2023Fig 3. Electromagnetic spectrum[2]

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Conti…

Four major concerns i.e., capacity, efficiency, availability, security related with Radio waves.

Wireless communication has become a utility like electricity & water.

But on the other hand we have 40 billions of light box already installed and light is part of electromagnetic spectrum.

Bandwidth is 10,000 times bigger than the radio frequency spectrum

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WHO CAN REPLACE RADIO WAVES FOR WIRELESS COMMUNICATION ?

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How LI-FI works:[3]

Operational procedure is very simple. If LED is ON, digital data ‘1’ is transmitted & if LED is OFF, digital data ‘0’ is transmitted. LEDs varies in intensity so fast that a human eye cannot detect it A controller connected at the back side of these LEDs is used to code data.Flicker depending upon the data we want to encode . Every light source can works as a hub for data transmission

05/01/2023Fig 4 LI-FI model

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Working process [4]

05/01/2023Fig 5 block diagram of LI-FI

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Conti…

On one end all the data on the internet will be streamed to a lamp driver when the led is turned on the microchip converts the digital data in form of light .

A light sensitive device (photo detector) receives the signal and converts it back into original data. This method of using rapid pulses of light to transmit information wirelessly is technically referred as Visible Light Communication .

Instead of Wi-Fi modems, Li-Fi would use transceiver-fitted LED lamps that can light a room as well as transmit and receive information.

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Conti…

Array of LEDs for parallel data transmission, or using mixtures of red, green and blue LEDs to alter the light‘s frequency with each frequency encoding a different data channel.[6]

Such advancements promise a theoretical speed of 10 Gbps – meaning one can download a full high-definition movie in just 30 sec.

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LI-FI Networks

Li-Fi connector and router are the main components for a network[7]

1. Room connector Optical signals cannot penetrate through walls, in order to provide

an optical WLAN, rooms need to be connected with each other Li-Fi room connector is a replicator, which sends the data stream

from one side of the wall to the other side via an optical fiber. For smaller rooms, connector act as the only Li-Fi hotspot in the

room

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Fig 7 Room Connector

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Conti…

2. LI-FI RouterServes as a connector to external link like DSL.

Covers a radius of about 20 meters

The transmission speed is minimum 100 Mbps.

Suitable for small office or home use

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Fig 8. LI-FI Router

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Modulation techniques

In order to actually send out data by means of LEDs, it is required to modulate these into a carrier signal. The carrier signal consists of light pulses sent out at short intervals. The manner in which this is done depends on the modulation scheme employed.

1. On/off keying(OOK):2. Variable Pulse Position Modulation (VPPM):3. Color Shift Keying (CSK):4. Frequency Shift Keying (FSK): 5. SIM-OFDM (Sub-Carrier Index Modulation OFDM):

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1.On/off keying:[1]

OOK uses "on" to represent symbol "1" and "off" for symbol "0”.the long stream of "1" and "0" produces flicker, which is not acceptable for lighting purposes. Instead of sending raw data by OOK, Light encodes OOK with Manchester Encoding to achieve DC-balanced (50%). 

The period of positive pulses is same as the period of negative ones, however this doubles the bandwidth required for transmission

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Fig 9. OOK Modulation

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2.Variable Pulse Position Modulation (VPPM)[2]

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22PPM encodes the data using the position of the pulse within a set time period. The duration of the period containing the pulse must be long enough to allow different positions to be identified. VPPM is similar to PPM but it allows the pulse width to be controlled to support light dimming.

Fig 10. VPPM Modulation

3. Color shift keying (CSK)[2]

This is used if the illumination system uses RGB-type LEDs. By combining different colors of light, the output data can be carried by the color itself and hence the intensity of the output can be near constant.

Mixing of RGB primary sources produces different colors which are coded as information bits.

The disadvantage is that it increases the complexity of the transceivers.

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4. Frequency shift keying (FSK)[2]

In this method, data is represented by varying the frequencies of the carrier signal. Before transmitting two distinct values (0 and 1), there needs to be two distinct frequencies.

5. SIM-OFDM (Sub-Carrier Index Modulation OFDM):This is a new approach to transmission in which an additional

dimension is added to conventional 2D amplitude/phase modulation (APM) techniques such as quadrature amplitude modulation (QAM) and amplitude shift keying (ASK).

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Conventional OFDM[1]

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25 OFDM system with the following parameters: 16 subcarriers,

modulation type: QAM (each subcarrier is loaded by 2 bits), and symbol transmit power: 1 W.

Fig 11 Conventional OFDM

SIM-OFDM[1]

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Fig. 12 SIM-OFDM

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length of:N(log2 (M)/2 + 1)

where, - N is the number of subcarriers, - M is the constellation size of the respective M-QAM modulation scheme. Each of these blocks is divided into two parts. - The first N bits of the block form a sub block, which referred to as Book. - The remaining N(log2 (M)/2) bits form a second sub block, which will be referred to as BQAM.

Overcoming Wi-Fi issues[5]

CAPACITY Spectrum is 10,000 times greater than that of radio frequency

EFFICIENCY Highly efficient since LED consumes less energy

AVAILABILITY Light waves available everywhere.

SECURITY Cannot penetrate through walls. Hence data cannot be intercepted.

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Difference between WI-FI and LI-FI[3]

Characteristics WI-FI LI-FI

Standard 802.11 802.15Range 100 m Based on LED lightData transfer rate 800 kbps – 11 Mbps >1 GbpsPower consumption Medium LowCost Medium High Security Less secure High secure Latency In order of microseconds In order of milliseconds

Spectrum Narrow spectrum 10,000 times broader than Wi-Fi

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Advantages[3]

Data rate is about 10 Gbps, HD film to be downloaded in 30 seconds Use anywhere, even in RF restricted areas; Since light waves will not interfere with

radio waves.[6]

Mostly LED light bulbs are used, which consumes less energy. Hence cost efficient. As light waves cannot penetrate through walls, the data cannot be intercepted; Thus

provides secured communication. Quick and reliable.

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Limitations

Visible light cannot penetrate through solid objects. A major challenge of LiFi is how the receiving device will transmit back

to transmitter.[5]

Interferences from external light sources like sunlight, in the path of transmission will cause interruption in the communication.

Data transmission can be easily blocked by any object placed in front of LED source.

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Application

In sensitive areas such as aircrafts for data transmission without causing interference

Places where it is difficult to lay optical fibers like operation theaters

Traffic scenarios, thereby reducing accidents

Underwater applications where radio waves cannot propagate.

Industries like petrochemical plants, nuclear power plants , petrol pumps Lecture/seminar halls, home and office

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Literature survey Title 1

“ LI-FI Technology: Data transmission Through Visible Light”

Author Anurag Sarkar, Prof. Shalabh Agarwal Journal International Journal of Advance Research in Computer Science and

Management Studies Summary • Li-Fi is a wireless optical networking technology that uses light

emitting diodes (LEDs) for transmission of data.• LI-FI uses VLC which has more frequency range than Radio wave.• LIFI uses different modulation techniques like : OOK(On-Off Keying) VPPM(variable pulse positioning Modulation), CSK(color shift Keying), SIM-OFDM (sub carrier index modulation OFDM)

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Title 2

“LiFi Technology in Wireless Communication”

Author Revathi Ganesan

Journal INTERNATIONAL JOURNAL & MAGAZINE OF ENGINEERING,TECHNOLOGY, MANAGEMENT AND RESEARCH

Summary • This paper proposed that use of Visible Light for data transmission which prevents the RF interferences and harmful RF radiation.

• Bandwidth is high due to broad spectrum of VLC• High security due to non-penetration of light through walls • A micro-LED light bulb can transmit 3.5 Gbps and data rates of more

than 10 Gbps are possible.

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Conclusion

• If this technology can be put into practical use , every bulb can be used something like a Wi-Fi hotspots to transmit wireless data.

• In the future we will not only have 14 billion light bulbs, we may have 14 billion LIFI deployed worldwide for a cleaner, greener and even brighter future.

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References

1. Dobroslav Tsonev, Sinan Sinanovic and Harald Haas “Enhanced Subcarrier Index Modulation (SIM) OFDM, Enabling Green Wireless Multimedia Communications IEEE 2011

2. Revathi Ganesan, “LiFi Technology in Wireless Communication” INTERNATIONAL JOURNAL & MAGAZINE OF ENGINEERING,TECHNOLOGY, MANAGEMENT AND RESEARCH, 2016

3. Anurag Sarkar, Prof. Shalabh Agarwal, “LI-FI Technology: Data transmission Through Visible Light” International Journal of Advance Research in Computer Science and Management Studies.

4. Sharma, R.R., Sanganal, A., Pati, S. (2014). Implementation of a Simple Li-Fi Based System, International Journal of Computing and Technology (IJCAT), Vol. 1 Issue 9, October 2014

5. Khandal, D., Jain, S. (2014). Li-Fi (Light Fidelity): The Future Technology in Wireless Communication, International Journal of Information & Computing Technology, Vol. 4 No. 16, 2014

6. Singh, A.J., Veeraiahgari (2014). Light Fidelity Technology IOSR Journal of Electronics and Communication Engineering (IOSR-JECE), Vol. 9 Issue 2, Mar – Apr 2014

7. Singh, J., Vikash (2014). A New Era in Wireless Technology using Light-Fidelity, International Journal of Recent Development in Engineering and Technology (IJRDET), Vol. 2 Issue 6, June 2014

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THANK YOU