The attached narrated power point presentation discusses the merits, demerits, challenges faced and the standards as applicable to visible light communication systems. The material will be useful for KTU final year B Tech students who prepare for the subject EC 405, Optical Communications.

1. Visible Light Communication
Systems - II
MEC

2. Contents
• Advantages of VLC Systems.
• Disadvantages of VLC Systems.
• VLC Challenges.
• Need for Standardisation.

3. VLC Advantages
Huge Bandwidth:
- unlimited and unlicensed bandwidth.
- 380 nm to 780 nm.
- VLC 350 THz support multi-gigabit-per-
second data rates with LED arrays in a
multiple-input multiple-output (MIMO)
configuration.
- alternative to indoor IR that operates at
780–950 nm.

4. VLC Advantages
Low Power Consumption:
- provides both communication and
lighting, at Gbps data rates.
- consume low power compared to
costly RF alternatives.
Low Bandwidth:
- inexpensive components, compact, light
weight, amenable to dense integration,
very long lifespan.

5. VLC Advantages
- large unlicensed optical spectrum.
- lower power-per-bit cost compared to
RF communications.
- cheaper.
 No health concerns:
- no generate radiation that leads to
public health concern.

6. VLC Advantages
- lowers carbon dioxide emission.
- little extra power consumption for
communication.
 Ubiquitous Computing:
- wide range of network connectivity.
- may incorporate luminous devices like
traffic signs, commercial displays,
indoor/outdoor lamps, TVs, car head
lights/tail lights.

7. VLC Advantages
 Inherent security:
- high security.
- highly intricate for a network intruder
outside to pick up the signal.
- alternative technology in sensitive or
hazardous environments.
 Indoor localization:
- existing RF-based global positioning
system (GPS) gives inadequate/no
network coverage.

8. VLC Advantages
- high attenuation, multipath, and safety
regulation, accuracy of only up to
a few meters for the RF-based GPS.
- VLC-based indoor positioning to attend to
issues in enclosed environments.
- high accuracy to within a few cm.
- indoor localization system using the white
LEDs.

9. VLC Advantages
- LEDs give better light source more than
400 lux.
- LEDs have longer lifespan, ecological
and financial benefits.
- high-speed data transmission.
- simultaneous employment of light
sources for data communication as well
as illumination.

10. Challenges
 Flicker mitigation:
- Flicker:
variation in the brightness of light perceived
by human naked eye.
result of continuous switching on and
off of the light source during data
transmission.
can instigate negative/harmful physiological
changes in humans.

11. Challenges
• Flicker prevented by making changes in
brightness to be within the maximum
flickering time period (MFTP).
• MFTP - maximum time period within which
the light intensity can be changed without
any perception by the human eye.
• Modulation formats for flicker mitigation.
• IEEE 802.15.7 standard proposes variable
pulse position modulation (VPPM) for VLC
system.

12. Challenges
 Dimming support:
• Variable pulse position modulation (VPPM)
for VLC system for ability to control
dimming.
• VPPM integrates PPM and PWM to
support communication with dimming
control.

13. Challenges
• High path losses.
• Multipath induced intersymbol interference
(ISI).
• Artificial light-induced interference.
• Blocking.
• LED electro-optic response nonlinearity.
• Interference between VLC devices.
• Integration with existing technologies.

14. VLC Standardisation
• Standardisation to tackle challenges.
• Performed by Visible Light Communication
Consortium (VLCC), Japan and IEEE.
• Japan Electronics & Information
Technology Industries Association (JEITA)
CP-1221, JEITA CP-1222 and JEITA CP-
1223 published by VLCC.
• IEEE 802.15.7 standard for physical and
MAC layers - minimum benchmark for
development of new products.

15. Why Standardisation
• Providing access to several hundred THz
bands.
• Providing immunity against EMI.
• Communication that complements extra
services to the existing visible light
infrastructure.
• Specifying FEC schemes, modulation
techniques and data rates for VLC
communication.

16. Why Standardisation
• Channel access mechanisms such as
Contention Access Period (CAP),
Contention-Free Period (CFP) and
visibility support when channel access
described.
• PHY layer specifications, such as optical
mapping, Tx-Rx turn around time, Rx-Tx
turn around time and flicker and dimming
mitigation explained.

17. Will Continue…..