B.tech Major Project: In this project I have simulated the illuminance distribution, optical power distribution on received optical plane for Line of Sight(LOS) condition as well as Diffuse link, SNR distribution and graph showing the variation of RMS Delay Spread for different sample receiver positions using MATLAB.

1. Presented by:
Nikhil Singh
(IIITU15210)
Aditya Kumar
(IIITU15211)
Guided by:
Ms. Gurpreet Kaur

2. 1.1 Light Fidelity(Li-Fi)
1.2 Need for Li-Fi
1.3 Literature Review
1.4 How it works?
1.5 Block diagram of VLC System
1.6 Simulation Setup
1.7 Indoor VLC Configurations for Line of Sight
1.8 Indoor VLC Configuration for Diffuse Link
1.9 Calculation of Transmitted power
2.0 Calculation of Received power
2.1 System parameters
2.2 Calculation of reflected power
OUTLINE

3. 2.3 Calculation of Channel delay spread
2.4 Calculation of SNR
2.5 Illuminance Distribution
2.6 Optical power distribution in received optical plane
2.7 Optical power distribution of received reflected power
2.8 RMS delay spread for 4 transmitters
2.9 SNR distribution of 1 transmitter and 4 transmitters
3.0 RMS delay spread at several receiver positions
3.1 Conclusion
3.2 Future scope in Li-Fi
3.3 References
OUTLINE(contd.)

4. • Light is used instead of Radio Waves to transmit information
• Wireless Communication System Based on use of Visible
Light between 390-700nm wavelength or 400-800THz
frequency
• Transceiver fitted LED lamps act like Wi-Fi modems
• Provides illumination as well as data communication
Fig 1. Visible Light Spectrum[1]
1.1 Light Fidelity(Li-Fi)

5. 1.2 Need for Li-Fi
• Radio Spectrum is Congested but the demand for Wireless
data doubles each year
• Issues regarding:
• CAPACITY:
Spectrum is 10,000 times greater than radio frequency
• EFFICIENCY:
Highly efficient since LED consumes less energy ; unimpeded
radio interference
• AVAILABILITY:
Light waves are available everywhere
• SECURITY:
Cannot penetrate through walls hence data cannot be
intercepted ; prevents piggybacking

6.  Alexander Graham Bell demonstrated the first VLC system in 1880
 In 2011, at TED Global, demonstration of VLC project by Professor Harald
Haas. He showed a HD video being transmitted from a standard LED lamp
at a speed of 10Mbps
 VLC technology was exhibited in 2012 using Li-Fi
 By 2013, VLC System did not require line of sight conditions
 In 2014, transfer rates of 1.25Gbps were recorded
 In 2015,IEEE used single photon avalanche diode to increase the efficiency
of energy usage
 By February,2018 Geist expands VLC technology to android
 By August,2018 China develops a chipset for VLC
1.3 Literature Review

7.  If LED is “ON” ,digital data ‘1’ is transmitted while if LED is
“OFF” then digital data ‘0’ is transmitted
 A controller is connected to the back side of LED lamp that
will process the data and code it in the form of binary signals
which would result in flickering of LED
 LED’s vary in intensity so fast that human eye cannot detect it
 LED source will act as the transmitter while photodetector
will act as a receiver.
 Visible light will be the medium of transmission
1.4 How it works?

8. Fig 2. Block diagram for indoor VLC[5]
1.5 Block diagram of VLC system

9. Fig 3. Indoor Visible Light Communication Environment[3]
1.6 Simulation Setup

10. Fig 4. Proposed model for Line of Sight VLC using Single LED and LED array[1]
1.7 Indoor VLC Configuration for Line of Sight

11. Fig 5. Proposed model for Diffuse link VLC using Single LED and 4 LED’s[5]
1.8 Indoor VLC configuration for Diffuse link

12. • Luminous intensity is used for expressing the brightness of anLED
• Luminous intensity is the luminous flux per solid angle and is givenas[2]
I=
dФ
dΩ
--(1)
– where Φ is the luminous flux and Ω is the spatial angle
• Φ can be calculated from the energy flux Φe as[2]
Ф=km 380
780
V λ Фe λ dλ --(2)
– where V(λ) is the standard luminosity curve, and Km is the maximum visibility,
which is ~683 lm/W at 555 nm wavelength
• The transmitted optical power 𝐏𝐭 is given as [4]
Pt=km Λmin,0
Λmax,2π
Φe dƟ dλ --(3)
-- where Λmin and Λmax are determined from the photodiode sensitivity curve
1.9 Calculation of Transmitter Power

13. • Assuming that an LED lighting has a Lambertian radiation pattern, the radiation
intensity at a desk surface is given by[1]
I(∅)=I(0)cosml(∅) --(4)
-where ∅ is the angle of irradiance with respect to the axis normal to the transmitter surface,
I(0) is the center luminous intensity and ml is the order of Lambertian emission defined as[1]
ml=
ln(2)
ln(cos Φ1/2)
--(5)
-where Φ 1/2 is the semi-angle at half illuminance of an LED.
2.0 Calculation of Received Power

14. • The horizontal illuminance/intensity at a point (x, y) and the received power at the
receiver are given as[3]
Ihor=I(0)cosml(∅) / d2.cos(ψ) --(6)
Pr=Pt
(ml+1)
2πd2 cosml(∅) Ts(ψ)g(ψ)cos(ψ) , 0≤ψ≤ ψcon --(7)
-where ψ is the angle of incidence with respect to the axis normal to the receiver surface,
𝐓𝐬(ψ) is the filter transmission, g(ψ) and 𝛙 𝐜𝐨𝐧 are the concentrator gain and FOV,
respectively and d is the distance between the LED and a detector surface
• The gain of the optical concentrator at the receiver is defined by[3]
g(ψ)=
n2
sin2ψcon
, 0 ≤ ψ ≤ ψcon
0, 0 ≥ ψcon
--
(8)
-where n is the refractive index
Calculation of Received Power(contd.)

15. Table 1: Parameters and their default values[4]
2.1 System Parameters
Parameters Values
Room Size
Reflection coefficient 0.8
Source Location(1 LED) (2.5,2.5,3)
Location(4 LED) (1.25,1.25,3), (1.25,3.75,3),
(3.75,1.25,3), (3.75,3.75,3)
Semi-angle at half power(FWHM)
Transmitted power 20mW
No. of LED’s per array 60*60(3600)
Centre luminous intensity 300-910lx
Receive Receive plane above the floor 0.85m
Active area
Half-angle FOV
Elevation angle
Azimuth angle
Δt 0.5 ns

16. • The average received optical power[5]
Pr=Hd 0 Pt --(9)
--where 𝐇 𝐝(𝟎) is the channel DC gain
• The reflectivity of the walls depends on the wavelength and materials used in the wall.
The plaster wall has the highest reflectivity followed by floor and ceiling, respectively
• Considering reflection from the wall, the received power is given by the
channel DC gain on directed path 𝐇 𝐝(𝟎) and reflected path 𝐇 𝒓𝒆𝒇(𝟎) [5]
Pr= 0
NLED′s
{PtHd 0 + 0
Reflections
PtdHref(0)} --(10)
• The DC channel gain of the first reflection is given by[5]
--(11)
2.2 Calculation of Reflected Power

17. • For multipath scenario, the total received power is given by[2]
PrT= i=1
M
Pd,i + j=1
N
Pref,j --(12)
--where M and N represent the number of direct paths from transmitters to a specific
receiver and reflection paths to the same receiver, 𝐏 𝐝,𝐢 is received optical power from
the ith direct path and 𝐏𝐫𝐞𝐟,𝐣 is the received optical power from the jth reflected path
• The RMS delay spread is the critical performance criterion for the upper bound
of the data transmission rate. The mean excess delay is defined by[4]
ū=
i=1
M
Pd,itd,i+ j=1
N
Pref,jtref,j
PrT
--(13)
• And the RMS delay spread is given by[3]
Drms= μ2 − (ū)2 --(14)
-where
μ2=
i=1
M
Pd,itd,i
2
+ j=1
N
Pref,jtref,j
2
PrT
--(15)
2.3 Calculation of Channel Delay Spread

18. • The electrical SNR can be expressed in terms of the photodetector responsivity
R, received optical power and noise variance as[1]
SNR=
(RPr)2
σshot
2
+σthermal
2 --(16)
• The shot and thermal noise variances are given by[1]
σshot
2
=2qRPrB + 2qIBI2B --(17)
σthermal
2
=
8πKTk
Gol
CpdAI2B2 +
16π2KTkГ
gm
Cpd
2
A2I3B3 --(18)
--where the bandwidth of the electrical filter that follows the photodetector is represented
by B Hz, κ is the Boltzmann’s constant, 𝐈 𝐁 is the photocurrent due to background
radiation, 𝐓𝐤 is absolute temperature, 𝐆 𝐨𝐥 is the open-loop voltage gain,𝐂 𝐩𝐝 is the fixed
capacitance of photodetector per unit area, Γ is the FET channel noise factor, 𝐠 𝐦 is the
FET trans-conductance and noise-bandwidth factors 𝐈 𝟐 = 0.562 and 𝐈 𝟑 = 0.0868
2.4 Calculation of SNR

19. Fig 6(a). Single Transmitter LED
Fig. 6(b) 4 transmitter LED’s
2.5 Illuminance Distribution

20. Fig 7(a). Using Single transmitter LED’s
2.6 Optical Power Distribution in received optical plane

21. Fig 7(b). Using 4 transmitter LED’s
Optical Power Distribution in received optical plane(contd.)

22. Fig 8 Distribution of reflected power
2.7 Optical Power Distribution of received reflected power

23. Fig 9. RMS delay spread for 4 transmitter LED’s
2.8 RMS Delay Spread for 4 transmitters

24. Fig 10(a). SNR distribution for single LED
Fig 10(b). SNR distribution for 4 LED’s
2.9 SNR distribution of 1 and 4 transmitters

25. Fig 11. Graph showing the variation of RMS delay spread for several
receiver positions
Table 2: Points vs co-ordinates
3.0 RMS delay spread at several sample receiver positions

26. o The signal suddenly drops to zero in the corners as seen in the graph
of received optical power.
o The RMS delay spread is more uniform in case of single LED
transmitter.
o The SNR is much more in the case of 4 transmitter LED’s as
compared to single transmitter LED
3.1 Conclusion

27. Connectivity while moving: users need to be connected when they
move inside the indoor environment
Multiuser support: in large areas is vital, many users need to have
access to the network at the same time
Dimming: is an important feature in VLC when communications is
integrated with lighting
Shadowing: happens when the direct paths from user to all sources
are blocked
3.2 Future Scope in Li-Fi

28. [1] Huy Quang Nguyen1, Joon-Ho Choi1, Tae-Gyu Kang2, Sang-Kyu Lim2, Dae Ho Kim2, Moonsoo Kang3
and Chung Ghiu Lee ,”Effect of LED emission cross section in indoor visible light communication”,
EURASIP Journal on Wireless Communications and Networking 2012
[2] Xiaohui Yu,Jianping Wang,Huimin Lu , Single LED-Based Indoor Positioning System Using Multiple
Photodetectors , Volume 10, Number 6, December 2018
[3] Ram Sharma, A. Charan Kumari , Mona Aggarwal, Swaran Ahuja, Performance Analysis of LED Based
Indoor VLC System Under Receiver Mobility, International Conference on Computing, Communication and
Automation (ICCCA2017)
[4 ]H.Q.Nguyen, J.H. Choi, M.Kang, Z. Ghassemlooy, D.H. Kim, S.K. Lim, T.G. Kang, C.G. Lee, A
MATLAB Based Simulation Program for indoor visible light communication CSNDSP 2010 IEEE
[5] Z. Ghassemlooy, W.Popoola, S. Rajbhandari, Optical Wireless Communication, CRC Press, Taylor and
Francis Group
3.3 References