Introduction to visible light communication

1. Outline
2
 Optical Wireless Communication (OWC)
 Visible Light Communication:
 Introduction
 History
 Motivation
 VLC Applications
 Advantages and Challenges
 System
 Topics of interest

2. Optical Wireless Communication (OWC)
A form of optical communication
Visible Light (VL)
Infrared (IR)
Ultraviolet (UV)
Divide into 5 categories based on the transmission range
Ultra-short range: chip-to-chip communication
Short range: Underwater communication
Medium range: Indoor IR and VLC
Long range: Free-Space Optical Communication (FSOC)
Ultra-long range: inter-satellite links
1
2
3

3. Satellite Communication
Inter-Chip
Free Space Optical Communication (FSOC)
Visible Light Communication
Optical Wireless Communication (OWC)

4. 6G Network Architecture
VLC: Visible Light Communication
FSO: Free Space Optical
BBU: Base Band Unit
Cloud RAN
UAV: Unmanned Aerial Vehicles
Cell Free mMIMO

5. Frequency spectrum used in different generations of mobile networks

6. VLC New communication technology using “
⇒ Visible
Light”.
 Main purpose: General Lighting
 Added Value: Communication
Wavelength between ~400nm (750THz) and ~700nm
(428THz)
General Characteristic:
 Security: What You See Is What You Send.
 Health: Harmless for human body and electronic devices
 Using in the restricted area: office, house, hospital, university
7
VLC: Introduction

7. VLC: History
7

8. VLC: History - Photophone
 Bell’s Photophone (1880)
• Optical source : sunlight
• Externally modulation by vibrating mirror
• Receiver : parabolic mirror with crystalline selenium cells
• 700 ft (213m) sound transmission
Excerpted from: The New Idea Self-Instructor edited by Ferdinand
Ellsworth Cary, A. M. (Monarch Book Company, Chicago &
Philadelphia, 1904)
http://www.freespaceoptic.com/
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9. Visible Light Communication
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o Advancements in illumination industry
o Invention of LED
o Features:
 High power efficiency
 High keying rate
 High tunability

10. 10
Source: Cisco
 VLC is a good candidate to meet the data rate requirement of 6G.

11. Low Frequency
(Long wavelength)
Coverage
Mobility
visible
IR UV
700nm 400nm
100μm
RF
3cm
1m 1nm
428THz 750THz
3THz
10GHz
300MHz 300PHz
High Frequency
(Short wavelength)
Bandwidth
Security
1mm
300GHz
IrDA
802.15.3c
IG-THz
IG-VLC
802.11
802.16
Frequency band for VLC
12

12. 12
Data
rate
(bps)
115K
4M
100M
480M
16M
50M
UFIR
FIR
IR
VIR
VLC
HDR UWB
1 11
3
Distance (m)
2 6 20 50
UWB
802.11a
802.11b
Bluetooth
ZigBee
VLC Characteristic

13. 13
VLC vs. Infrared (IR) and Radio-frequency(RF)

14. VLC: Applications
Hazardous Environments.
Underwater Communication
Defence and Military Applications
Hospital and Healthcare
Location-Based Services
5
2
1
3
4
15
Indoor Outdoor Underwater Underground
0
500
1000
1500
2000
2500
3000
3500
4000
4500
4163
940
171
24
Number of publications on different VLC environments from several
journals (IEEE, MDPI, Elsevier and OSA) from 2003 to 2021.
Number
of
Publications

15. VLC: Applications
16
Source: Oxford
University
(OMEGA project)

16. 17
 Greater availability of spectrum (400–800 THz)
 Unlicensed spectrum
 High data rate
 Easy to implement
 Low cost: Use of LED
 Energy efficiency
 Physical layer security
 “ Top security levels are reached for VLC just by shutting doors and windows ”
 No interference on RF signals
VLC: Advantages

17. VLC: Challenges
 Line-of-sight requirement between Tx and Rx
o Limits its range
o Easily block
o Using RIS, Hybrid with WiFi
 High path loss and limited coverage area
 Interference
o Sensitivity to ambient light
o Interference between neighbor cells
 Connectivity while moving (Limited mobility)
o Frequent Handovers
o Hybrid with WiFi
 Extra constraints
o Eye safety constraints
o Illumination constraints
 Uplink
o RF, IR
 Dimming and No light
o Light modulation
 Flickering
o Fluctuation of the light brightness
 Transmission techniques
o Nonnegativity
o IM/DD
o Difficulty in implementation of more
complex modulations, like OFDM
 Shadowing
 LED Non-Linearity and Modulation BW

18. VLC: System
Transmitter
o Baseband processing in electrical domain
o Data is transmitted by modulating the intensity of
light
o E/O Conversion
 LED (large FoV and LOS/NLOS)
Channel
o Line Of Sight (LOS)
o Non-Line Of Sight (NLOS)
Receiver
o O/E Conversion by Photodetector (PD)
o Baseband processing in electrical domain
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19. VLC: System Structure

20. VLC: Transmitter
RCLED
R+G+B LED
B + Phosphor LED
~40 Mb/s ~100 Mb/s ~500 Mb/s
• Higher cost
• Potentially higher
bandwidth
• Potential for WDM
• Low cost
• Phosphor limits
bandwidth
BW < 5 MHz BW < 20 MHz
Note: LED modulation bandwidth is limited. So, the full spectrum available bandwidth cannot be

21. 21
Performance and Price comparison
Source: Credit Suisse,
2006.11.2

22. VLC: Topics of interest
 Statistical Channel modeling and channel estimation
 New multiple access technologies in VLC networks (e.g., Non-
Orthogonal Multiple Access (NOMA))
 Resource allocation
 Reconfigurable Intelligent Surface (RIS)-aided VLC
 Hybrid VLC-RF communication
 Indoor localization/positioning
 VLC network planning
 Higher data-rate, SINR, energy efficiency, … for VLC