This document summarizes a group project on measurement and sensor technology focusing on Li-Fi (Light Fidelity) communication. It outlines the motivation for using Li-Fi due to increasing wireless devices and limited radio spectrum. It then describes how Li-Fi works using intensity modulated visible light and the available modulation methods. The document details simulations using LTSpice and an experimental setup using Arduino boards and LEDs to transmit and receive data at distances up to 20cm and 500 bits/s. Test cases are presented and references cited.

1. MEASUREMENT AND SENSOR
TECHNOLOGY
Group 10 : Hrishkesh Pattepu
Mu Zhang
Ugur Bolat
Vivek Maru
28/06/2017

2. 2
Outline
Chair for Measurement and Sensor Technology
Group 10
• Motivation – What and Why ?
• How it works ?
• VLC Realization using LTSpice Simlation
• Experimental Setup
• Test cases and Results
• Refrences

3. 3
What is Li-Fi? Why Li-Fi?
Chair for Measurement and Sensor Technology
Group 10
• Li-Fi : Light-Fidelity , Data transmission through illumination by LED that
varies intensity faster than a human eye can follow.
Prof. Harald Hass, www.ted.com
• Also known as VLC – Visible Light
Communication
• Data communication using LEDs / Visible light
• Standerd availabe – IEEE 802.15.7 [8]
Li-Fi Technology, www.techworld.com
• Coined the term „Li-Fi“ in 2011 in TED Global.
• One of the most influencing person in Li-Fi
technology
• Why do we need it?
• By 2020 – 50 Billion Devices connected to Internet wirelessly.
• Radio spectrum will run out of capacity.
• Huge available license free bandwidth. 430 THz to 790 THz.
• Very less extra device setup needed – Normal Illumination LED can be
used.
• About 100 time faster than Wi-Fi
• Data security

4. 4
How Visual light communication works?
Chair for Measurement and Sensor Technology
Group 10
• Light ON : Bit – 1
• Light OFF : Bit – 0
• Data rate depends on the type of data.
• Modulation methods available [2]
• Can flickering be Harmful?
• Flickering can be controlled – Not noticable by human eyes above 25 Hz.
• Frequency above 200 Hz is recommended.
The VLC radio transmitter and receiver based on intensity modulation/direct detection[1]

5. 5
Realization of VLC using LTSpice
Chair for Measurement and Sensor Technology
Group 10
The Simulation setup for VLC communication
• Input signal from a 3.5 mm
audio jack.
• DC offset through Vdc – Input
value above 0.
• If not given, -ve of input can
damage LED.
• Received signal
• Two amplification stage
• Both applies Gain of 50.
• Final signal compared to
the original input.

6. 6
Realization of VLC using LTSpice (Cont.)
Chair for Measurement and Sensor Technology
Group 10
Input Audio
Output Audio
Simulation results using LTSpice






 dB
signalnoisepower
signalinputpower
SNR 39
)_(
)_(
log20

7. 7
Experimental setup using Arduino
Chair for Measurement and Sensor Technology
Group 10
VLC setup using two Arduino modules
(Transmitter located on Left side and
Receiver on right)
• Ardiono UNO modules
• 1 watt Blue LED
• Solar panel as receiver
VLC setup using two Arduino modules

8. 8
C code Flow
Chair for Measurement and Sensor Technology
Group 10
Receiver Code flowTransmitter Code flow
Data frame for Manchester Encoding

9. 9
Test Cases
Chair for Measurement and Sensor Technology
Group 10
Distance : 17 cm, Angle : 0 Degree

10. 10
Test Cases (Cont.)
Chair for Measurement and Sensor Technology
Group 10

11. 11
Test Cases (Cont.)
Chair for Measurement and Sensor Technology
Group 10

12. 12
Test Cases (Cont.)
Chair for Measurement and Sensor Technology
Group 10
• Best results came at the line of sight with 0 degree and 20 cm distance.
• Data rate of 500 bit/s.
• Using better configuration of devices, data rate can be increased

13. 13
References
Chair for Measurement and Sensor Technology
Group 10
[1] A. Jovicic, J. Li, and T. Richardson, “Visible light communication: Opportunities, challenges and the path to
market,” IEEE Communications Magazine, vol. 51, no. 12, pp. 26–32, 2013.
[2] S. Rajagopal, R. D. Roberts, and S. K. Lim, “IEEE 802.15.7 visible light communication: Modulation
Schemes
[3] H. Haas, L. Yin, Y. Wang, and C. Chen, “What is LiFi ?” Journal of Light ware Technology, vol. 34, no. 6, pp. 1533–1544,
2015
[4] S. Rajbhandari, H. Chun, G. Faulkner, K. Cameron, A. V. N. Jalajakumari, R. Henderson, D. Tsonev, M. Ijaz, Z. Chen, H.
Haas, E. Xie, J. J. D. McKendry, J. Herrnsdorf, E. Gu, M. D. Dawson, and D. O’Brien, “High-Speed Integrated Visible Light
Communication System: Device Constraints and Design Considerations,” IEEE Journal on Selected Areas in Communications,
vol. 33, no. 9, pp. 1750–1757, 2015.
[5] P. Pathak, X. Feng, P. Hu, and P. Mohapatra, “Visible Light Communication, Networking and Sensing: Potential and
Challenges,” IEEE Communications Surveys & Tutorials, vol. 17, no. c, pp. 1–1, 2015.
[6] A. Jovicic, J. Li, and T. Richardson, “Visible light communication: Opportunities, challenges and the path to market,” IEEE
Communications Magazine, vol. 51, no. 12, pp. 26–32, 2013.
[7] J. M. Kahn and J. R. Barry, “Wireless Infrared Communications,” Proc. IEEE, vol. 85, no. 2, Feb. 1997, pp. 265–98.
[8] IEEE Standard for Local and Metropolitan Area Networks-Part 15.7: Short-Range Wireless Optical Communication Using
Visible Light, IEEE Std. 802.15.7, Sep. 2011.
[9] www.arduino.cc

14. 14Chair for Measurement and Sensor Technology
Group 10
Thank you !!