An Introduction to Li-Fi

Advancements in Li-Fi Technology By Monenco Iran, July 2016

Advancements in Li-Fi
Technology
Presented by Telecommunications Department,
Monenco Iran

Presentation Organization
o Why a replacement for Radio?
o What is VLC?
o What about Li-Fi?
o History of Li-Fi
o How does it work?
o Li-Fi Hardware
o Lighting + Data
o Energy Harvesting + Data
o Li-Fi Networks
o Cellular Li-Fi
o Wireless HetNet and Li-Fi

Presentation Organization
o Applications of Li-Fi
o Li-Fi Technology key players
o Li-Fi Energy Efficiency
o Advantages and Limitations
o Comparison of Wi-Fi and Li-Fi
o Conclusion

Why a replacement for Radio?
• Radio Spectrum is really congested
• Some conducted researches found radio waves harmful to human health
• Radio spectrum offers less bandwidth compared to other portions of spectrum
• Using Radio is prohibited in certain areas
• Passing through walls makes it unsecure

What is VLC?

What is VLC?
Visible Light Communication
Any form of data communication via Visible Light

What is VLC?
Visible Light Communication

What is VLC?
The idea behind Visible Light Communication
• Radio Spectrum is BW limited and expensive
• IR is harmful to human eye
• UV, X-Ray and Gamma are harmful to human
body
• Visible spectrum (430 to 770 THz) is a good
choice and has the potential for high rate
data communication

What about Li-Fi?
Light Fidelity
• Li-Fi is the same as VLC but also defines networking features
• Like Wi-Fi, Li-Fi uses similar 802.11 protocols, but takes benefit of visible light as
the communication medium
• Li-Fi uses IEEE 802.15.7 standard for PHY and MAC layers

What about Li-Fi?
Key Features of Li-Fi
Mobile High Speed
Bidirectional Networked

History of Li-Fi
Alexander Graham Bell demonstrated the first VLC called Photophone in 1880
Bell's assistant transmitted a wireless voice telephone message over a 213m distance

History of Li-Fi
Modern Concept of Li-Fi was introduced by Professor Harald Haas at the
University of Edinburg in 2010
Haas demonstrated their concept of Li-Fi in a TED talk in 2011

History of Li-Fi
o A group of companies formed Li-Fi Consortium to promote high-speed optical
wireless systems in Oct. 2011
o Haas started PureLiFi in 2012, the first OEM company to commercialize Li-Fi
o In 2013 data rates of over 1.6 Gbit/s were demonstrated over a single color LED
o Uni-directional VLC was standardized under IEEE 802.15.7r1 specification in 2014
o In 2014 Sisoft tested data at speeds of up to 10 Gbit/s across a light spectrum
emitted by LED lamps

How does it work?
Main Components of a VLC System
Network
Interface
Processing
Board
Light Source
Optical
Medium
Photodetector

How does it work?
A simple demo
White LED Photodetector

How does it work?
A simple demo

How does it work?

How does it work?
Data Modulation Light Source
PhotodetectorDemodulationData
Optical Path

How does it work?
o Data is used to modulate the intensity of LED light source
o Fast variations of current makes the optical output to vary at
extremely high speed
o The photodetector picks up the signal
o The receiver dongle then converts the tiny changes in amplitude
into a data stream

How does it work?
o Real-valued modulation schemes must be used to drive LEDs
Modulation Techniques
OOK PAM
PPM
o These techniques suffer from inter-symbol interference (ISI) at high speeds

How does it work?
o At high data rate transfers, a more resilient technique, such as OFDM is desirable
o Conventional OFDM generates complex-valued bipolar signals
o Some modifications must be applied to convectional OFDM to be suitable for VLC
Modulation Techniques
OOFDM

How does it work?
Bidirectional and Multiple Access
• Users may see multiple Access Points
• Access Points may see multiple users

How does it work?
Mobility and Hand-over Support
• Users can move from one light source to
another
• Users may connect to the strongest light
source

Li-Fi Hardware
LED Technology Data Rates

Li-Fi Hardware
Receiver LiFi MIMO ASIC Transmitter LiFi MIMO ASIC

Lighting + Data
LEDs
+

Energy Harvesting + Data
+
Solar Cells

Li-Fi Networks
Fiber optics can be used to transfer
optical data streams between rooms

Cellular Li-Fi
Macrocell
• Conventional cell towers covering 10s of km
Microcell
• Covering about a km, used for temporary additional coverage
Picocell
• Supporting 100 users and 100s of meters area, used to improve coverage in
offices and buildings
Femtocell
• Supporting a few users and providing “5 bar” signal in a small area

Cellular Li-Fi
An optical Attocell network is an indoor
small-cell cellular network based on VLC

Wireless HetNet and Li-Fi
Heterogeneous Network is used to maintain service when moving between cells

Applications of Li-Fi
Vehicles & Transportation

Indoor Positioning

Industrial RF Restricted Environments

Home/Office high speed optical downlink

In-Airplane Internet Access

Lecture/Seminar Halls

In Hospitals

Street lights as access points

Myths about Li-Fi
The lights flicker
Modulation is done at very high speed and is not sensible by human

Myths about Li-Fi
You cannot dim the lights
LEDs used for VLC are dimmable, however data rate decreases by dimming

Myths about Li-Fi
VLC is uni-directional
VLC can be used for transmission in either direction, however
downlink-only implementations are simpler

Myths about Li-Fi
Downlink/Uplink Isolation
Wavelength Time Code Optical

Myths about Li-Fi
There will be interference from sunlight
Interferences from other sources can be simply eliminated using optical filters

Myths about Li-Fi
Lights need to be on so this is inefficient
In industrial, commercial and retail environments the lights are on when occupied
Watt/bit energy consumption for Li-Fi is comparable to radio

Myths about Li-Fi
You must have line-of-sight
It is preferable to have LOS, but Li-Fi can work in NLOS at lower speeds

Myths about Li-Fi
This is a disruptive technology
VLC is complementary to radio, like Wi-Fi and LTE

Myths about Li-Fi
You need special LEDs
Excellent results can be achieved with COTS LED devices, however high data rates
are achievable using custom designed LEDs

Li-Fi Technology key players

Li-1st

Li-Flame
Ceiling Unit Desktop Unit

Li-Flame
-Multiple Users per AP
-Halfduplex at 10Mbps

LiFi-X
Access Point Station

LiFi-X
Access Point Features:
 Support for Power over Ethernet (PoE) or Power Line Communications (PLC)
 Simple installation
 Connect to a wide range of LED light fixture to form an atto-cell
 Multiple access
 Handover control enables seamless switching between APs

LiFi-X
Station Features:
 USB 2.0 powered
 Supports handover, allowing user to move maintain their wireless session

Solar charging and connectivity at the same time

A high efficiency dimmable LED driver combined to an Indoor Positioning System

A high efficiency dimmable LED driver with a bi-directional Li-Fi communication
Not Available For Sale Right Now

Point to Point Network Features:
 Uses Laser
 Up to 10Gbps bidirectional connectivity
 Up to 40m indoor range
 Requires LOS

Point to Multi-Point Network Features:
 Up to 1Gbps per user
 Bidirectional connectivity
 Requires LOS

Advantages and Limitations
Advantages
Provides High Bandwidth
Cost efficient
Safe for health
Very Secure
Does not suffer from fading
Can be used in RF restricted areas

Advantages and Limitations
Limitations Lights must be always ON
LOS is usually needed
Bidirectional connectivity is
complex
Limited to a small area
External sources can interfere

Comparison of Wi-Fi and Li-Fi
Parameter Wi-Fi Li-Fi
Speed High Very High
Range Medium Low
Data Density Low High
Security Low High
Reliability Medium Medium
Transmit/Receive Power Medium High
Ecological Impact Medium Low
Obstacle Interference Low High
Market Maturity High Low

Li-Fi Energy Efficiency
Li-Fi is more energy efficient than Wi-Fi when the number of users is increased

Conclusion
 Li-Fi takes benefit of visual spectrum to provide high-throughput data connectivity
 High data rate and security are the main advantages
 There are no health concerns about Li-Fi as it is with Wi-Fi
 Li-Fi does not replace Wi-Fi, it is complementary to other wireless technologies
 It is still under development and there are very few commercial products available

Any questions?

Thanks for your attention

Monenco Iran is a consulting engineering company formed in 1973 as
a joint venture between the private sector of Iran and Montreal
Engineering Company of Canada. In 1999, Mapna, AMEC, and Mir
Company became the main share holders of Monenco.
Currently, Monenco plays the main role in Iran power industry and
provides engineering, consultancy and supervision services in a broad
range of target markets worldwide including; Combined Cycle and
Thermal Power Plants, Renewable and Cogeneration, Distributed
Generation, Electrical Power Transmission Lines, High Voltage
Substations, Telecommunication, SCADA and Dispatching Centers,
Electrical Railways, Electrical Network Studies, System and Energy
Studies, Oil & Gas and Mining, Architecture, Civil, Urban Design and
Roads.
Telecommunications department at Monenco Iran is active in different
areas including RF solutions, IP networks and Fiber Optic
infrastructures. We believe that spreading knowledge about emerging
technologies is the first step towards their utilization.
Who we are?

An Introduction to Li-Fi

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