Building a Prototype of Visible Light Communication System in an Indoor Stadium

This dissertation discusses the need for Visible Light Communication (VLC) due to the limitations of Radio Frequency (RF) communication. It covers the hardware construction of a VLC system, modulation techniques, and considerations for indoor stadiums. The report also includes a study of the uses, structures, and methods that modulate and standardize VLC. The suggested technique uses Orthogonal Frequency Division Multiplexing (OFDM) and is practically proven in the range of a large-velocity beam of laser light communication set up with cheap LASER beam of wavelength 450 nm of the blue color.

How to build a prototype of working Visible Light
Communication System in an indoor stadium
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Abstract
Radio Signal interaction is suffering from disturbance and large dormancy problems.
Additionally, Radio signal interaction takes an individual set up for transmitting and
acceptance of those signals. Conquering the prescribed restrictions, Communication through
Visible Light (Visual Light Communication) is a favored approach due to a large bandwidth
and low response to the disturbances coming from electrically magnetic resources. This trend
of the steady state light brings an alternative to florescent lights by Light Emitting Diodes
(Light Emitting Diodes) that furthermore motivates in the utilization of communication
through the light that is visible. The report brings a study of the uses, structures, methods that
modulates, standardizing and find out the difficulties in communication through Visual Light.
There is a technique that is recommended with another type of modulation known as
Orthogonal Frequency Division Multiplexing (OFDM). This is practically proven in the
range of a large-velocity beam of laser light communication set up with cheap LASER beam
of wavelength 450 nm of the blue color. This procedure is utilized in order to decrease a large
peak-to-average power percentage of the Orthogonal Frequency Division Multiplexing wave.
The practical outcomes display an effectively accomplished speed of 2.5 Gb/s below the
communication in the free space of the size 5m and a Peak to Average Power decrease,
approximately of 3.3 dB in a constant function of cumulative distribution in the order of
about 10-3 in comparison with the standard system with no scheme.
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Table of contents
Abstract.......................................................................................................................................i
Table of contents........................................................................................................................ii
Acknowledgement....................................................................................................................iv
Attestation..................................................................................................................................v
1 Introduction........................................................................................................................1
2 Visible Light Communication (VLC)................................................................................2
2.1 History.........................................................................................................................3
3 What is the need?...............................................................................................................5
4 Hardware construction of a VLC system...........................................................................6
4.1 MAC Layer..................................................................................................................6
4.2 Physical Layer.............................................................................................................7
4.3 Channel configuration.................................................................................................8
4.3.1 Comparison with IR...........................................................................................10
4.4 Transmitter................................................................................................................11
4.4.1 Light Emitting Diodes characteristics................................................................13
4.4.2 Brightness control..............................................................................................13
4.5 Receiver.....................................................................................................................16
5 Modelling of for Indoor stadium lighting........................................................................21
5.1 Configuration of VLC link........................................................................................21
5.2 Model of directed LOS channel................................................................................22
5.3 Model of non-directed LOS optical channel.............................................................24
5.4 Signal to Noise ratio..................................................................................................25
6 Visual Light Communication considerations for indoor stadium....................................27
6.1 Multiple wavelengths................................................................................................27
6.2 Optical interference noise..........................................................................................28
6.3 Recent research..........................................................................................................29
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7 Modulation Techniques for Visual Light Communication..............................................30
7.1 Factors that affects the modulation............................................................................30
7.1.1 Dimming............................................................................................................30
7.1.2 Flickering...........................................................................................................30
7.2 Modulation techniques used in the constructed VLC system...................................31
7.2.1 ON-OFF Keying (OOK)....................................................................................31
7.2.2 Pulse Modulation Techniques............................................................................31
7.2.3 Color Shift Keying (CSK)..................................................................................32
8 Advantages.......................................................................................................................34
8.1 Capability..................................................................................................................34
8.2 Effectiveness..............................................................................................................34
8.3 Availability................................................................................................................34
8.4 Protection...................................................................................................................34
9 Disadvantages..................................................................................................................35
10 Conclusion........................................................................................................................36
10.1 Future work............................................................................................................36
References...................................................................................................................................i
iii

Acknowledgement
I want to acknowledge my teachers, staff and fellow students without whom my work
wouldn’t have finished. Their support was precious. The constant support encouraged me to
see the actual scenario of this area in today’s world.
Apart from them I would like to thank my parents who were always behind me throughout
this project and helped me to research from the sources and last but not the least a special
thanks to the god almighty because he helped me a lot and inspired me to make my way
through the challenges that came before me while designing this project.
iv

Attestation
The nature of Plagiarism is very well understood by me and also I understand the policy of
my University in this regard. Violation of any copyright is a cyber- crime and I am very much
aware of this.
I certify that this report is my genuine work by me in the University session except that I
gathered some knowledge with the help of certain books which I clearly referenced.
v

1 Introduction
The not so abundant band of Radio Frequency puts restrictions over the rising needs for
uninterrupted connection with large capability. As per CISCO, you will see an eleven time
upsurge of the cellular data visitors in 2018 in comparison with the year 2013. This upsurge
of products in getting hold of the cellular systems plays the principal role behind the sudden
upsurge in the cellular traffic. Additionally, with the advent of social services (like Facebook,
linked in and Twitter) boosted the additional data visitors. In addition to the spectrum
insufficiency problems in Radio Frequency wireless communication, disturbances cause
further issues because most of the wireless systems are electrically magnetic in nature. The
Radio Frequency interaction is suffering from issues like (a) Crossing over, relating to
Federal Aviation Administration (FAA) the usage of mobiles upon airplanes triggers
disturbance with the devices that helps in navigation. Additionally, mobiles on plane will also
stimulate the interruption with floor program towers since discussed by Federal Conversation
Commission (FCC). (b) Whatever is the disturbance, it is clear that in a communication that
requires no wire which requires surprisingly low requirements of latency (such as with motor
communication, security networks), usage of radio rate of recurrence cannot be really
appropriate because of its restrictions on the bandwidth. (c) Radio Frequency signals easily
permeate through wall space, they have problems with security problems. (d) Upsurge in
Radio Frequency signals, transmitting power past a threshold level leads in the endangerment
of human’s health (e) Communicating with Radio Frequency signals suffers from electric
power shortage since everyone need an individual set up for Radio Frequency
communication. To combat the disadvantages as mentioned, it truly is vital in the
implementation of a new style in the communication area.
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2 Visible Light Communication (VLC)
Communication using visible spectrum of Light devices uses the band of light visible to
human eyes in order to communicate, occupying the band from 380 nm to 750 nm as
depicted in figure 1. The reduced bandwidth problem in RF communication is usually solved
in Visual Light Communication as a result of option of the large bandwidth. The Visual Light
Communication receiver just gets indicators if indeed they have a home in a similar space to
the transmitting device, which means receiving devices beyond your area from Visible Light
Communication resource that never will be capable in having signals and therefore gets the
security protection conditions that happens in the Radio Frequency systems. Like a normal
source of light could be utilized for lighting as well as communication, consequently, saving
the excess energy needed in Radio Frequency systems. Remembering the mentioned positive
aspects, Visible Light Communication becomes an encouraging competitor due to top
features, large width of band and less energy usage (Khan, 2017), (Dilouie, 2014), (Saadi &
Wuttisittikulkij, 2017).
Figure 1 (Khan, 2017)
Important uses of Visual Light Communication are Light Fidelity, motor to motor interaction,
Robotic machines used in hospitals, for communication under water and data portrayed on
signal planks. The Light Fidelity employs noticeable beam of light intended for interaction to
supply broadband net up to 10G pieces /s. Visual Light Communication can easily be utilized
found in motor connection in street alteration notification, sensing the crash before actual
happening and traffic rules violation in order to caution to prevent incidents. The uses
discussed above need interaction with less dormancy, given by Visual Light Communication
due to its large band width, simpler set up because of the existing existence of automobile
lamps and indicators used in traffics. Visual Light Communication offers usage in places
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delicate to electrically magnetic signals, for example in hospitals and airplanes. Here in fact
the indicators of the radio signals hinder other waves. Light is utilized to provide both
illumination and communication using Visual Light Communication schemes. As an
instance, everyone uses light in a place to supply the quantity recognition to a room also other
building information. Problems which are included in the execution of Visual Light
Communication are (a) Crossing over with all the available sources of light, (b) crossing over
among Visual Light Communication products, and (c) interaction of the Visual Light
Communication with the previous systems like Wireless Fidelity. To manage these
difficulties, a Visual Light Communication’s standardization is essential. MAC layer and
PHY layer are expressed for brief communication spectrum using noticeable light-beam.
Around the transmitting part, light-beam is produced depending upon converters of the
wavelength and Light Emitting Diodes (Chen, et al., 2017), (Chen, et al., 2016), (Khalifeh, et
al., 2018), (Lin, et al., 2015). White-colored light-beam predicated on Light Emitting Diodes
are usually produced in di, tri and tetra chromatic settings. The information around the
transmitting part is light modulated; nevertheless, this modulation has to be achieved in so as
to prevent fluctuation. Likewise, the level of dimming that may be chosen to get the desired
degree of modulation so that lighting backup by Light Emitting Diodes is achieved. The
normal Visual Light Communication recipient includes a great amplification signal, optical
filtration system and optic concentrator (Wang, et al., 2012), (King Abdullah University of
Science and Technology, 2018), (McCormick, 2017), (Ould & Mouhamedou, 2017), (Bazzi,
et al., 2016).
2.1 History
In historic occasions, light-beam was employed so as to communicate with the help of
procedures like smoke and fire indications. Romans utilized shining metal discs intended for
sunshine representation for handling lengthy communication over distance. Lines of
Semaphore centered OC (optical communication). The 1st visible telegraphy system
originated by Claude Chappe in France. Some towers outfitted with semaphores were being
used in order to exchange the information between towns. A wireless photo voltaic telegraph-
system known as Heliograph was produced by United States Armed Service was predicated
on flashes of Morse code with reflection. These whizzes were founded through possible
cross-over from light having a shutter or perhaps momentary reflection attachments. Later
around 1880, a photo phone that was launched by Graham Bell, predicated in sending tone of
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sound transmission over the light. This tone of sound, usually extending towards a reflection
that in turn caused vibration over the reflection. Reflections were reflected by the light,
capturing the vibrations as well. In receiving part this light-beam was gathered and
transformed again to tone of sound transmission. A greatest disadvantage of this system is the
fact it generally doesn’t works very nicely in gloomy conditions. Optic interaction didn't
earned a lot of recognition until the introduction of Mild Amplification simply by Stimulated
Release of Rays (Laser beam). In the 1970s, Corning Integrated effectively constructed
optical fibers in order to use in commercial needs with less damping. The Gallium Arsenide
semiconductor laser beam was the first one to be designed in those days use with optical
dietary fiber cables to get long range communication. In-fiber Bragg grating and optical
fibers amplifier introduction was the foundation in trending in optical communication in
twentieth century (GBI Research, 2011). Visual Light Communication is a kind of
communication in optics, using a number of signals falling under 430-790 THz. 2003
witnessed data transmission using only the Light Emitting Diodes at the Nakagawa
Laboratory in Keio University, Japan (Yuan, et al., 2017), (John, 2018).
4

3 What is the need?
Necessity of band for information exchange is raising with a speed of 109% per annum yet
the current developments achieved just 13% development annually. The present systems of
communication will be extremely ineffective like in Radio Frequency systems just a few
energy is usually used for interaction, rest all is definitely wasted. Credited to extremely large
traffic in channel, issue continues in current systems. Radio Frequency can be clinically
demonstrated to become unfit for human beings plus it provides surge many neurological
illnesses and additional complications as well. Right now the query comes Why just Visual
Light Communication? The solution is usually around you that people possess several
quantities of Light Emitting Diodes about us after that why to maintain their particular make
use of restricted to lighting goal. Light Emitting Diodes can provide trend in these systems.
The Light Emitting Diodes offers recently developing within an exponential method. As the
1960s Light Emitting Diodes possessed bending of the resultant light and energy
effectiveness. Light Emitting Diodes will certainly function like a communication goal and
lighting applications and therefore decreases price, raising the performance. New Light
Emitting Diodes arriving inside the marketplace referred to as Resonant Cavity (RC) Light
Emitting Diodes are extremely effective. They will possess extremely shiny mild and low
power usage. In spite of the ideals being positive conjecture of white light-beam Light
Emitting Diodes, real Luxeon Rebel Light Emitting Diodes accomplish ideal 75 luminous/
Watts, with a good life time of 50,000 hours with 70% repair, after powering up with a
current of 699mA. And the advanced Luxeon K2 Light Emitting Diodes is capable of
attaining around two hundred lm/w, and a life time of 50,000 hours with the same repair rate,
once powered with 1A current (Biton & Arnon, 2018), (J, 2018).
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4 Hardware construction of a VLC system
Both the elements of the Visual Light Communication system: the transmitting and receiving
parts generally contain 3 common levels. They will be the physical coating, MAC level and
software layer as shown in figure 2. In IEEE 802.15.7. 1215.7, just two levels (namely
physical and MAC layers) are defined in order to achieve simplicity. Here we will be using
BBB, Beaglebone Black as the platform for developing. It has many advantages. It is cheap
and powerful computer and small as well.
Figure 2 (Khan, 2017)
4.1 MAC Layer
Tasks accomplished simply by MAC (Medium Gain access to Control) consist of the
following supports:
(1) Flexibility (2) Dimming (3) Presence (4) Security (5) Techniques in the minimization of
fluctuations (6) Color function (7) Network beacons era (8) VPAN association and
disassociation (9) Offering trusted hyperlink among peer MAC organizations. The following
are supported by the MAC layer- peer-to-peer, star and broadcast, illustrated in figure 2.
Communication inside the star methodology is conducted using a separate central controller.
All the nodes talk to one another throughout the centralized control. The role from the
coordinator inside the peer-to-peer methodology is conducted simply by one of both involved
nodes with interaction with one another as shown in figure 3.
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Figure 3 (Chen, et al., 2017)
4.2 Physical Layer
The physical standards of the components that are used in a VLC system are defined by the
physical layer employed. Figure 4 shows the block diagram of the physical level execution in
a VLC system basically the VLC program. At the first place, a bit stream executed and
passed using an encoder channel. There are certain things which can be used to improve the
overall performance. They are linear block codes, convolution codes and the Turbo courts.
After this the bit stream is passed through an encoder called the line encoder to produce the
output encoded bit stream. Modulation techniques such as on off keying, PPM, PWM etc. are
then applied on the output encoded bit stream. At last this bit stream is conducted and the
data is given towards the Light Emitting Diodes for transmitting throughout the channel.
Subcarrier Multiplexing (SCM) & Wavelength division multiplexing (WDM) are accustomed
so as to achieve the transmission in both the directions. Apart from this, Quadrature
Amplitude Modulation (QAM) and orthogonal frequency division multiplexing (OFDM)
helps in boosting the rate of data. The velocity of the Visual Light Communication system is
risen to three or more. 75 Gigabytes/s when compared with previous that was 575Mb/s
downlink and 225Mb/s uplink. In the recipient part, the recipient receives the waves. The
stream of bits is then handed throughout the channel decoders in producing the bits of the
result after demodulation and decoding, (Delgado, et al., 2018).
7

Figure 4 (Khan, 2017)
4.3 Channel configuration
The optical wireless communication (Optical Wireless Communication) explains wireless
communication using technologies used in optics. Generally, Optical Wireless
Communication contains Free Space Optics for long and IR for short range. The visible light
communication implies the technology using a light-beam through optical fibers for data
transmission and lightening. Today, Light Emitting Diodes in the wavelengths of 380 nm ~
780 nm are positively created and could be utilized like a source for communication.
Normally, the silicon photodiode that displays great responsivity for visible wavelength area
is utilized as getting component. The transmitting medium is usually the air, whether it is
interior or exterior. This report discusses the interior uses of Visual Light Communication.
Since the hyperlink configurations of Visual Light Communication are actually comparable
to IR communication, The Visual Light Communication stations will be categorized using the
standard IR communication. The additional concepts associated with optical area can easily
become used likewise, including the light transmitting and glare. The hyperlink
configurations happen to be categorized in to four fundamental types, based on the presence
of hurdles because route as well as the directionality from the transmitter towards the
recipient. The simple hyperlink types consist of the aimed non-directed LOS, line-of-sight
(LOS), the non-directed non-LOS, the described non-LOS. The thought that the hyperlink
being either LOS or non-LOS depends if presently a good hurdle is found to stop the
transmission of light between a transmitting and a receiving part. The non-directed MIS
hyperlink in Visual Light Communication system can be essential because the general
lighting is employed for LOS environment and usually isn’t really concentrated & aimed
perhaps aimed. Figure 5 displays the simple design for a non-directed indoor LOS hyperlink,
with the transmitting device above the roof and the recipient on the low level surface area.
Pursuing the evaluation for the described MIS hyperlink, the gathered optical power G at a
recipient is usually indicated as shown in figure 6 (Le & Jang, 2015),
8

Figure 5 (Chen, et al., 2016)
Figure 6 (Chen, et al., 2016)
where ‘Pt’ is the sent power coming from an Light Emitting Diodes, φ denotes the angle of
irradiance with regards to the axis perpendicular to the transmitter surface area, ψ is the angle
of incidence with respect to the axis perpendicular for the receiver surface area,‘d’ denotes
the distance among an Light Emitting Diodes and a good detector’s surface area. ‘Ts (ψ)’
denotes the filter transmission. ‘g (ψ)’ denotes the concentrator gain. ‘Ψc’ denotes the
concentrator field of view (FOV), at the semi-angle at fifty percent charged power, ‘m’ is the
order of Lambertian emission, and is usually provided with the transmitter semi angle (at fifty
percent power) 1/2Φ as shown in figure 7,
Figure 7 (Chen, et al., 2016)
Here, ‘m’ = 1 particular in the case of 1/2Φ = 60° (Lambertian transmitter). Considering the
symmetry about the axis in figure 5, It can be represented by φ=ψ. An optical filter and
concentrator can be utilized in front side of the photo-detector. During experiment, it had
been not really enhanced for a Light Emitting Diodes beam, with Ψc≈ 90 and g (ψ) ≈ n2
9

(refractive index).
4.3.1 Comparison with IR
In order to possess a very vivid idea about Visual Light Communication, it’s required to
review this with the IR. The variations between Visual Light Communication and IR is
outlined in table 1.
Table 1 (Delgado, et al., 2018)
The standardization of IR is done by the Infrared Info Association as well as the Infrared Info
Association continues to designing higher levels of uses of IR. The rate of data for IR
interface contains 3.9 Megabytes/s, 15.9 Megabytes/s etc. The Visual Light Communication
rate of data is usually dependent on the Light Emitting Diodes bandwidth after modulation
and physical layer standardization. In some cases it reached about 19.9 Megabytes/s.
transmitting range for Visual Light Communication can be feasible till many meters credited
by the lighting necessity. Since IR is utilized for a long range control, optimum range usually
varies around few meters. The Visual Light Communication transmitting part releases many
waves of different wavelengths ranging from red to violet and the precise evaluation becomes
even more complicated than IR. Credited towards the length of wave from light source, sound
resources certainly becomes diverse. For IR, disturbance comes from light made up of IR
10

component. In the case of Visual Light Communication, light-beam and various others may
end up being sound resources. Likewise, the light-beam has become a part of our daily lives
and can identify it with a man’s vision. Consequently, Visual Light Communication is
normally attention secure. IR provides a lengthy background with several uses possess
developed. Additionally, Visual Light Communication offers short background as well as the
little quantity of applications offers recently been suggested. However, the lighting is present
almost everywhere and the Visual Light Communication using the lighting facilities could be
utilized smoothly and simply using the features of Visual Light Communication hyperlink,
usually anticipated in order to become applicant facilities for interior /outdoor general public
ubiquitous communication technology in the close to potential.
4.4 Transmitter
The block diagram is shown in figure 8. The LEDs are used and their intensities are changed
rapidly by varying the current. Beagle bone black cannot do so and therefore transistors are
used. The switching transistors are used for this purpose.
Figure 8
Light emitting diodes are becoming more and more popular day by day. They have emerged
as a new trend of communication medium. Light emitting diodes have already outmatched
the incandescent light sources because light emitting doubts are more dependable, energy-
efficient and more illuminant than any previous existing source of light. The efficiency of the
light-emitting diodes is much higher than the incandescent sources. Due to these are the
features, light-emitting diodes and Lasers are employed as transmission elements in VLC.
LEDs are can be used wherever the communication as well as the elimination is required
from a single device. The vital produced through the LEDs can be split it into its constituent
components through the converters serve as an excellent option needed as a transmitter.
There are many modes that are used to prepare a white light from Delhi. They are bi, tri and
Tetra chromatic mediums. The most popular mode used to produce a white light from the
light emitting diodes is undoubtedly tri chromatic which involves the involvement of three
primary colors, red, green and blue popularly known as RGB. This procedure of generation
11

of the white light helps to provide a large bandwidth and hence increases the rate of data. The
intensity variation changes the rise time. More the intensity higher will be the rise time and
vice versa. Moreover the high intensity requires higher power, Beagle bone black offers a
maximum current of 1 A and a maximum voltage of 1V. It can send maximum frequency of
50 kHz. Note that if the intensity of high the heat dissipated will also be very high. To meet
the challenges CREE MCE4WT-A2-0000-000HE7. It is a white light made up of 4 LEDs
having forward voltage of 3.1 to 3.9V. The maximum wavelength is 450 nm and 610 nm.
This LED can work well at 50kHz as offered by the Beagle bone black. Figure 9 shows the
circuit diagram of the transmitter. Here three MOSFETS are used and each one is controlled
independently using the GPIO pins of the Beagle bone black. The MOSFET used is
IRLR3715ZPBF. The current through the diodes can be switched to 8 levels and thus we can
control the intensity of the light through the LEDs. These eight levels are enough to make use
of many encoding techniques such as pulse amplitude modulation or OOK. The issue of
flickering can be prevented when we open any one transistor and toggle between the other
two. Normal resistors are used that have a tolerant value of 0.25 W, two capacitors are used
in which one is of 100 microfarads and the other is of low value of 100 nanofarads. These
capacitors helps to remove the ripples from the power source (Lin, et al., 2015), (Lee, et al.,
2012), (Sung, et al., 2015), (Guan, et al., 2018).
Figure 9
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4.4.1 Light Emitting Diodes characteristics
The prime characteristic that is viewed in LEDs is its brightness for good transmission in
VLC systems. The reader should be very high in terms of brightness so that it is visible
clearly. There are two types of entities that provide visible wavelength signals. One type is a
separate single color LED, white in color made by phosphorus. The other type involves the
usual RGB LEDs. Arjun abilities as many benefits and that is why it is much popular today.
It gives a good combination of colors and hence the spectrum. They produce a wide range of
wavelength depending upon the applicability. The output that is taken from LED is much
higher than the input requirements of it and therefore it consumes very less energy and hence
are a prime choice for elimination and communication. The output energy is dependent upon
the input current linearly. The degree of linearity and the data modulation are greatly
interconnected and both of these factors are responsible for the overall performance of the
system. The output depends upon the heat or the energy. This temperature dependence of the
systems vary from system to system and hence the performance also varies accordingly.
Practically speaking whenever the temperature of the system increases, output decreases and
vice versa. LEDs is a very efficient and are many features. There are environment friendly,
produced no pollution, they have a very high lifetime, requires very less maintenance, they
are cheap and they can generate a wide variety of wavelength depending upon the
application. Talking about its application in VLC systems, the LEDs should have a very low
response time because in the communication the response time plays an important role. In
this regard the phosphorus vitality is provide a little more response time than the RGB LEDs
because of the absorption and emission of the energy in the phosphorus bands. However, both
the categories find the application. But this also true that the lesser the response time, the
greater is the data rates and hence a better communication is provided in the real systems.
.
4.4.2 Brightness control
In LED lighting, dimming plays an important role and is highly required because it controls
the brightness of dairy, there are many dimming strategies that are employed and their
greatly, one such dimming method is called as AM dimming. The DC forward current is
changed and hence the luminous flux that is emitted by the lady can be easily controlled. The
methodology is extremely easy and it can be applied also very easy but it can trigger certain
chromatic points of light. Another popular method is pulse width modulation commonly
called as PWM as shown in figure 10. This method the weight of the pulse is buried
13

accordingly. Out of the hundred percent duty cycle, some part of the cycle is intended be
carried out and hence the intensity varies. The PWM signal possess and amplitude which is
constant therefore, the spec drop is also constant which is emitted from the ladies. Another
very popular method is the pulse frequency modulation commonly called as PFM. In this
technique the frequency component of the signal whose width is constant is varied as shown
in figure 11. This way the current that is entered into the LED is also controlled. The bit angle
modulation or BAM, sometimes it is called as binary code modulation also, method is
represented in figure 12. This method uses a sequence of binary bits that helps in the
encoding of the dimming level of the LED. Every single bit in BM pulse corresponds to
binary number for example if we take an example of an 8-bit BM system, for the pulse of size
27 =128, the most significant bit b7 corresponds. Similarly the next bit b6 corresponds to the
pulse of the size26 = 64. Similarly the next bit b5 response to the pulse of the size 25, b4 t0 24
and so on. The least significant bit b0 corresponds to the pulse of the size 1. Just like AM
dimming, BAM is also a basic method and can be applied easily. The multiphase PWM
technique is different is suggested to decrease the transient current generated at the output
and an also the electrical and magnetic disturbances that are generated by the energy signals
including some noise as well. All these issues can be removed by moving specific PWM
waves. That is, wearing the width of the signal accordingly
(Chen, et al., 2018), (Vitasek, et al., 2018).
14

Figure 11 (Chen, et al., 2018)
Figure 11 (Khan, 2017)
Figure 12 (John, 2018)
15

4.5 Receiver
The light signal received from the transmitter has to be converted into the corresponding
current. This is done by the photodiode. This current has to be converted into its
corresponding voltage and supplied to the Beagle bone black. But the Beagle bone black
supports a maximum of 3.3 V. So circuit has to be constructed between the photo diode and
the Beagle bone black. First of all the signal is received by the photodiode and converted into
its corresponding current which is then converted into its corresponding voltage. The signal is
amplified using the trans-impedance amplifier. This is filtered by high pass filter. To make
sure that the distance between the transmitter and receiver is changed doesn’t change the
overall performance of the system, we use automatic gain controller (AGC). To make sure
that Beagle bone black receives digital signals, analog to digital converter or ADC is used as
shown in figure 13 (Narmanlioglu, et al., 2017).
Figure 13
The normal VLC received includes a great application network, optical filtering and optical
concentrator switches shown in figure 14. The beam divergence occurring in LED is credited
to eliminating good-sized areas, leads to a donation therefore the optical concentrator is are
employed to pay for the damping occurring. Inside the visual lighting negation receiving part,
light beam is recognized using photodiode, which is then converted into photo current. The
standard of the parameters changes as a result of higher interaction due to many waves of
different wavelengths. The photodiode and PIN avalanche both are used in visual lighting
communication. The magnitude of gain is high in photodiode as compared to PIN diode but
they are expensive. The visual lighting communication is prone to the disturbances from
many agents, such as natural sunlight and other sources of light. Therefore optical filters
should be used to protect systems from outer agents that affects it’s of operation and also to
remove the DC part that is actually the noise component in the signal which is received by
VLC. The photodiode accepts the incoming signal and serves as the main component of the
VLC receiver. Sometimes an imaging sensor is used instead of a photodiode because of a
16

greater field of view, commonly called as a fully, but there is a disadvantage of using imaging
sensors. They are costly and sluggish, and therefore the cost of the system calculated
becomes more than expected, it is better used for retired instead of imaging Centre. It
depends upon the type of application and the accuracy to be achieved in a system that decides
the costing of the overall system otherwise for retired point and it works pretty well no doubt.
The photodiode used is ‘Vishay BPW21R’. The requirement was low response time and
higher radiant are. In the market most of the photodiodes are made for fiber optics which has
less radiant area .A transimpedance is also used to convert current to voltage instead of
resistor because of high gain and low response time. It is nothing but an operational amplifier
and that to closed loop. The oscillations are not desired in this process and they can occur if
the phase difference is not maintained. This is avoided by using a feedback capacitor ‘C f’ in
parallel to the feedback resistor ‘R f’ as shown in figure 15. There is another issue that is
solved. The photodiodes have an internal resistance ‘R’ and capacitance ‘C’ making time
constant of RC. If the value of resistance is high, the gain is also large but the thing is that the
circuit becomes slow because of the increment in the value of the time constant, To avoid this
issue the transimpedance amplifier is connected to the photodiode. This way the gain is
determined by this amplifier and the time constant no longer depends on ‘R’ and ‘C’. The
operational amplifier used is UA741CD from Texas Instruments. It a common type of
amplifier and has a bandwidth of 1 MHz. The feedback resistor chosen is of 470 ohms and
capacitance of 5.6 picofarads as the feedback capacitor (Ye, et al., 2019), (The Engineer,
2011).
Figure 14 (Khan, 2017)
17

Figure 15
To remove the unwanted noise from the circuit high-pass filters are used. For simplicity, we
use RC filters as shown in figure 16.
Figure 16
The transmitter uses a frequency which is greater than the surrounding frequency, but in the
course of transmission some low frequencies components may also add up to this and
therefore the need of high-pass filters is very necessary at the receiver end. The values of
resistance 10 kilo-ohms and the capacitance chosen is 100 nanofarads. AGC used is TL026
with a bandwidth of 50 MHz. It has a peak gain of 38 decibels as shown in figure 17 (Liu, et
al., 2017), (Hyok, et al., 2018).
18

Figure 17
The output from AGC is not compatible with the Beagle bone black and it has to be brought
down. This is done by voltage division the voltage is brought down from 5 V to 2.5 V. This is
a good voltage for Beagle bone black. The potential at Beagle bone black is 2.5 V when the
output of AGC is high after closing the transistor. When the output of AGC is low, the
transistor is opened and the voltage at Beagle bone back becomes zero. The diode is used to
remove the negative voltage from the output of AGC. The transistor used is NPN BC 547A
and resistors as 10 kilo-ohms as shown in figure 18.
Figure 18
The complete circuit of the receiver is shown in figure 19.
19

Figure 19
20

5 Modelling of for Indoor stadium lighting
In both Visual Light Communication based interior localization devices and Visual Light
Communication systems, the optical signals released from your Light Emitting Diodes
traverse the complex communication channel. Credited for some negative features of the
Visual Light Communication stations including reflection, diffusion, disturbance and
disturbance, the channel causes the reduction, diminishing and disfigurement from the sent
signal. In addition, the bandwidth and SNR of the channel straight impact the channel
capability, the pattern of modulation plan, the sent power, and the data transmitting rate. The
channel of Visual Light Communication offers particular features that are quite different
through the stations of wireless communication. Consequently, this is usually extremely
essential to well appreciate of the attributes of different stations of Visual Light
Communication, and set up appropriate designs for all those stations. Nevertheless, some
earlier content and review papers with this subject did not address the concern of channel
versions obviously, and experienced a few complicated meanings, deductions and equations.
We strategy the channel versions in a fairly organized way. We 1st check out 3 feasible
arrangement techniques of Visual Light Communication links, and check out the aimed LOS
optical channel unit and the non-directed LOS optical channel. After that we analyze the
electrical SNR, analyze the impact of detecting region on the electrical SNR and getting
bandwidth, and obtain some beneficial outcomes. Finally, we explain some
misunderstandings in the related paper through evaluation and deductions (Barman & Halder,
2017), (Li, et al., 2015).
5.1 Configuration of VLC link
Within a standard room environment, visible light signal will be reflected by surfaces, the
roof, and the floors of a few additional items such as home furniture and gadgets in the room.
Presently, you will find many methods to set up visible light communication links in a
common room. It briefly investigates three generally used adjustments in Visual Light
Communication and localization centered Visual Light Communication: directed LOS, non-
directed LOS and dissipate construction. Inside the directed LOS settings, a point-to-point
communication link should become constructed straight between the transmitter and the
optical recipient. This kind of construction does not suffer from multipath signal deformity
triggered simply by glare, and may mainly decrease the disturbance caused by simply normal
light from various other light resources. Also, this needs low optical power for the
21

transmitter, yet can provide the greatest data rate provided a similar sent power and the same
range between transmitter and recipient. Nevertheless, the disadvantage of LOS configuration
is obvious also. The protection region of the optical signal is usually extremely little, and this
is usually not really simple to accurately line up the recipient and transmitter. non-directed
LOS settings includes large beam audio receivers, wide field-of-view (FOV optical receivers,
and will not really need immediate positioning from the transmitter as well as the recipient,
because proven in Fig. non-directed LOS construction will offer a wide signal insurance
coverage region. They can overcome signal blocking problem by getting reflected signals
from surfaces of objects in the room. This is usually, consequently, regarded as since the
many versatile settings. Nevertheless, the non-directed LOS link induce a high optical route
reduction and multipath disturbance, and as a result needs higher sent power. Also it provides
about inter symbol disturbance (ISI) for the LOS signal, therefore restricting the data rate.
Inside the diffuse construction, a transmitter points straight towards the roof and provides off
a wide light beam. Comparable to non-directed LOS settings, this kind of construction will
not really need immediate position of the transmitter and the recipient, and the optical signal
may cover a wide region. Nevertheless, the received signal suffers large route reduction and
serious multipath disturbance during the transmission in the diffuse link.
5.2 Model of directed LOS channel
Intended for indoor LOS which is directed and LOS which is not directed techniques, we
have an undirected LOS optical link between the Light Emitting Diodes and the optical
receiver. With this LOS optical link, the Light Emitting Diodes is usually the light resource,
and the photodetector is utilized to gather optical signal and changes the optical signal to
photocurrent. For the sunshine supply, presuming that the Light Emitting Diodes light offers
a Lambertian radiation structure, the circulation of radiation strength ‘R(ϕ)’ is definitely
provided simply by the equation as shown in figure 20, where ‘m’ is the Lambertian order
which can be given simply as m= -ln 2/cos(ɸ12) where ‘ɸ12’ is the transmitter’s half power
angle, ‘ɸ’ is the irradiance angle in relation to the transmitter axis, and ‘r’ is defined as the
range between a Light Emitting Diodes and a receiver (Delwar, et al., 2018).
22

Figure 20 (Ivankov, 2018)
For the recipient, supposing the photodetector provides a great energetic region A, as well as
the optical signal impinges around the detector in the position ‘Ψ’, the effective collecting
area of the detector can be provided by the equation as shown in figure 21.
Figure 21 (Lin, et al., 2015)
In order to improve overall effective collecting area, the non-imaging concentrator is used in
the recipient. The concentrator’s gain, ‘g (Ψ)’ is certainly provided by equation as shown in
figure 22.
Figure 22 (Narmanlioglu, et al., 2017)
Where, ’nc‘is the index of refraction, and ‘Ψc’ is definitely the field-of-view (FOV) of
concentrator.
After that the DC gain of the channel from the LOS optical link from the Light Emitting
Diodes towards the photodetector can easily become model Light Emitting Diodes as shown
in figure 23.
Figure 23 (Chen, et al., 2016)
Where, ‘Ψ’ is the incident angle, ‘Ts (Ψ)’ is the optical filter gain.
23

The mean transmitted optical power of light released through the Light Emitting Diodes is
normally Pt, which usually is usually provided by the figure 24.
Figure 24 (Jiang, et al., 2015)
Where, ‘x (t)’ represents the instantaneous transferred optical power. After that, the average
received optical power ‘Pt‘that photodetector collects is denoted by the figure 25.
Figure 25 (Chen, et al., 2016)
5.3 Model of non-directed LOS optical channel
Intended for indoor non-directed LOS and diffuse techniques, there exists non-directed LOS
optical channel between Light Emitting Diodes as well as the optical recipient. This channel
is usually impacted by many conditions, such as the room sizing, the setup of wall space and
items in the room, the reflectivity of the wall space, roof, and the areas of the items in the
room. Consequently, it is actually difficult to accurately characterize this type of channel, and
also to forecast the related route reduction between the Light Emitting Diodes and the
recipient. Previously, experts do a great deal of study dealing with this issue, and attempted to
effectively characterize non-directed LOS optical channel. Right here, we consider glare from
your wall space, which is definitely a fairly basic case. For the recipient, the average received
optical power can be provided simply by the figure 26, where ‘Hd (0)’ is the DC gain of the
channel of the path which is directed, and ‘Href (0)’ signifies pathways after reflections.
Figure 26 (Chen, et al., 2016)
24

Since the 1st reflection through the wall structure offers largest impact on the LOS optical
signal, right here we consider the channel DC gain of the initial reflection, which usually is
usually provided by the figure 27, where ‘D1‘ may be the distance involving the Light
Emitting Diodes and one point which is reflecting about the surface, ‘D2‘ is definitely the
distance between the device and the reflective surface, ‘A’ is nothing but the area of the
detector, ‘ρ’ is the reflectance factor, ‘DAwall‘ is a little refractive area inside the wall, ‘φ’ is
the position of irradiance in relation to the Light Emitting Diodes axis, ‘α’ is the incidence
angle to a reflecting point, ‘β’ is the viewpoint of irradiance to the recipient, and ‘ψ’ is the
incidence angle as demonstrated very clearly in the figure 28. Every part of the equation is
well expressed in that.
Figure 27 (Chen, et al., 2016)
Figure 28 (Chen, et al., 2018)
5.4 Signal to Noise ratio
With this section, all of us will evaluate the electrical signal-to-noise ratio (SNR), that is, the
SNR from the photocurrent produced by the detector. In optical stations, the quality of
transmitting is usually typically centered by shot sound. The shot disturbance primarily
comprise of shot disturbance triggered simply by signals and shot disturbance activated by
simply extreme ambient light. Likewise we want to consider the impact of heat disturbance.
All of us presume the sounds because self-sufficient additive white Gaussian disturbance.
25

The received electrical power H as well as the electrical SNR are provided by the figure 29,
where R may be the detector responsivity, N is the variances of all noises and interferences
activated simply by the optical channel (Wang, et al., 2017).
Figure 29 (Chen, et al., 2016)
26

6 Visual Light Communication considerations for indoor stadium
6.1 Multiple wavelengths
In Infrared communication system, monochromatic light is used. The same assumption has
been taken into consideration for many studies on visual light, irrigation systems. There is a
relation between the optical powers expressed in watts, the wavelength of the monochromatic
light to the illuminance I (0) as shown in figure 30.
Figure 30
The eye sensitivity function or V (λ), ‘φ’ as the irradiance angle respect to an axis that is
perpendicular to the surface of the transmitter and’ ψ’ as the incident angle in relation to say
that is perpendicular to the receiving area of surface, ‘Dd’ is the range between the light
emitting diode and the surgery of the detector. The constant 683 is derived and is used in the
denominator of the transformation formula as shown in figure 31 which expresses the relation
between the photometric and the radiometric device,
Figure 31 (Chen, et al., 2016)
Relating to the photometry, in the wavelength of 545 nm (green), all of us possess the same
situation as one and in the wavelength of 70 nm (red) the sensitivity is quite less and it is
equal to 0.01. No doubt light emitting doubt it is used in VLC provides rates of multiple
wavelengths that falls under the visible spectra of light that is between 380 nm to 70 nm
approximately. In order to calculate the relation between the illuminance and the receipt
optical power, it is required to incorporate the other wavelengths taken by the light beam
inside the function of eye sensitivity. The optical power that is received can be represented as
shown in figure 32.
27

Figure 32 (Chen, et al., 2016)
Here, P (λ) is the power spectral density.
6.2 Optical interference noise
The agents which contributes to noise in a visual lighting communication system greatly
affects the operation of the various components. Among these sunlight plays an important
role. Other sources of light such as incandescent and fluorescent also do the same. These
interferences and disturbances have to be analyzed. The discharge current or the glossy
current was calculated to be in the area of 0.85 centimeters square. This place the calculated
loss or the underlying current that produced by an incandescent light source consuming a
power of 60 W such that it is situated at a distance of 1 m also 8 fluorescent light sources,
each of 36 W placed at a distance of 2.2 m in dimensional area of 5 x 6 m square. Comparing
the generated by the three resources, the contribution of sunlight is the greatest next comes
the contrition of the incandescent bulb while the contribution of fluorescent lights with the
least. The background current can be reduced with the help of optical filters that filters out
the loss current efficiently. Practical it is seen that the optical filters work efficiently in the
case of fluorescent light sources.
Table 3 (Kocharoen, 2016)
28

6.3 Recent research
Many researchers have been done in the areas of optical wireless commutation commonly
called as OWC particularly in the areas of infrared concussion. There are many modulation
techniques that are used for OWC systems such as on-off keying or OOK, dual header 12
modulation, modulation involving many subcarriers, PSK and many more. Since the
wavelengths of the infrared and visible light a different, the modulation technique used in
Infrared Systems can be employed in VLC systems as well after considering the flexibility,
many user connections, environment and many more. Lately, researches in VLC started in
Japan, providing many documents that have analyzed the real systems. Among them one such
as the evaluation of the VLC system and the interconnection of the various components and
competition with the power line. It was released that the dimension outcomes of a light
emitting diode having high brightness for modulation bandwidth in order to reveal the
feasibility. Oxford industry also revealed many resonant techniques that helps in the
equalization and improving the bandwidth of the light emitting diode for real systems.
Kinnartz released a technique called as the code time division multiple gain access to pulse
width modulation in order to mark every light emitting diode light after sending PPM and
PWM coded signal in a light emitting diode system of high power. This method is usually
suggested for lighting purpose.
29

7 Modulation Techniques for Visual Light Communication
The modulation in case of Visual Light Communication is different as a result of Radio
Frequency communication due to the features that does not support encoding. Obviously, the
amplitude and phase modulation cannot be used in Visual Light Communication. Visual
Light Communication Modulation is definitely accomplished applying variants inside the
strength in the light related to the details in the concept signal (Azim, et al., 2018), (Chizari,
et al., 2017).
7.1 Factors that affects the modulation
There are two factors that are kept in mind before building the techniques for modulation.
7.1.1 Dimming
Different activities require different illuminances, for example 30-100 lux is usually needed
for regular visible actions in general places. A nonlinear association demonstrated in figure
33 between tested light and identified light and the connection is usually provided simply as
shown in figure 34 (Zuo, et al., 2018), (Zhuang, et al., 2016).
Figure 33 (Khan, 2017)
Figure 34 (Khan, 2017)
30

7.1.2 Flickering
The changes that happen during the elimination of the light up to modulation must be carried
out in such a way so that it doesn’t leads to human variances. According to IEEE
802.12.17.7, the turning has to be performed at a speed faster than 200 Hz in order to stay
away from undesirable results.
7.2 Modulation techniques used in the constructed VLC system
7.2.1 ON-OFF Keying (OOK)
In this modulation technique, depending upon the brakes present in the sequence, the light
emitting diode either turns on or turns of. For example if there is a binary bit one in a
sequence then it denotes the high-level that is the current will be supplied to the LED and
hence it will flop similarly the bandwidth zero in the binary sequence represents an of state.
In OOK, the light emitting diode is not really turned off in the case of off state, however that
the claimant in the range of voltage or we can say the voltage drop is noticeable and wide.
The greatest advantage of using OOK can be the easy execution of this technique. Previously
this on and off feature was applied using a vitality, however it imposed a restriction on the
usage of the band did a slow time response because of the phosphorus. Because the response
time is very less in OOK, it is used in place of the vitality which was previously used. As
high as a speed of 10 MB per second has been observed working with non-return to zero
OOK modulation technique using the vitality. (Rouse, 2015).
7.2.2 Pulse Modulation Techniques
There are certain limitations of OOK technique which was later realized by the researchers.
One of which is the low data rate. This led to the utilization of a new technique called pulse
modulation technique which supports higher data rates. The output signal after pulse width
modulation has changed with. Since the frequency in PWM is high, many amounts of
dimming easily becomes accomplished between the ranges of 0 to hundred. The restriction of
this technique is the lower rate of data but higher than OOK. When the output. Signal is
mixed with discrete multitoned signal with dimming control, we can have a much higher data
rate compared to that offer pulse position modulation signal output, which is centered on the
position of the pulse in other side. The division of the total time period into many small
equivalent time periods say ‘t’ slots, is carried out in PPM as well as the transmission with
the pulse is usually completed in a slot machine. Increase the data rates of the PPM signal
31

further can be easily shown through figure 35. In order to produce PPM more effectively and
in an effective manner with the usage of multiple pulses that is found in each time simple
slot, multiphase PPM was launched. Another technique called expurgated PPM is an
alternation to the pulse position modulation technique in order to increase the overall
performance of the committee system. Multilevel EPPM is another technique serving the
same purpose as expurgated PPM but in an improved manner. Table 4 shows the comparison
of different techniques.
Figure 35 (Khan, 2017)
Table 4 (Khan, 2017)
7.2.3 Color Shift Keying (CSK)
CSK came into existence suggested so that the data rate is improved, which was less as
compared to previous modulation techniques. The transition capability decreases the straight
down after the generation of white light making use of yellowish phosphor and blue Light
Emitting Diodes. Consequently, a great alternative method to create the white colored light is
usually the usage of 3 individual Light Emitting Diode such Golf course, Red and blue
(Singh, et al., 2018). Color Shift Keying is definitely carried out using the strength of all the
32

three primary colors within an RGB Light Emitting Diodes source. The color space affects
the chromaticity of CSK (Zhuang, et al., 2016), (Zuo, et al., 2018). Table 5, demonstrates
visible wavelength into eight groups using their centers that can be perceived by man as
shown in figure 36 (Le & Jang, 2015), (Vitasek, et al., 2016)eff.
Table 5 (Khan, 2017)
Figure 36 (Khan, 2017)
33

8 Advantages
Visual Light Communication technology is usually based about Light Emitting Diodes or
perhaps additional florescent light source based on an electromagnetic spectrum for data
transfer. That is usually, the sunshine can become the unseen, UV or the noticeable
component of the spectra. The Visual Light Communication’ communication velocity is
definitely even more than adequate for installing data in extremely much less period. Also,
Visual Light Communication overcomes the restrictions which have been place on the
consumer by the Wi-Fi. Wi-Fi gets caused problems with whenever we make use of even
more routers exact same place yet Visual Light Communication will not really obtain get in
the way, this kind of can be the best benefit of Visual Light Communication over Wi-Fi
(Povey, 2011), (Kocharoen, 2016), (ReportBuyer, 2017).
8.1 Capability
Light Emitting Diodes or additional florescent light offers ten thousand occasions larger
bandwidth than RF waves. Also, light resources are currently set up at offices, house and
general public locations etc. Therefore, Visual Light Communication tools are very easily
obtainable with better data transmitting capability (Ivankov, 2018).
8.2 Effectiveness
Light Emitting Diodes utilized for data transmitting are of low price with much longer life
time, large effectiveness and much less strength usage therefore Data transmitting using
Visual Light Communication is usually extremely effective (Atkinson, 2015).
8.3 Availability
Vast amounts of light resources are present in globe therefore simply by changing all the
resources with Light Emitting Diodes data can easily become transfer quickly working with
Visual Light Communication (Johnson, 2017).
8.4 Protection
Light waves perform not really penetrate through wall space and various other opaque
components. Therefore, the data obtain avoided from wrong use. With the introduction of
Visual Light Communication, right now this is usually not really required to end up being
within an area allowed by Wi-Fi in order to gain internet access. (Chow, et al., 2015).
34

9 Disadvantages
The artificial light cannot permeate into wall space and additional opaque components.
Therefore a Visual Light Communication allowed end gadget will by no means become
mainly because fast and useful just like Wi-Fi allowed gadget inside the open up air flow. It
just functions on immediate line of view. Still, it is beneficial as it uses up radio waves
bandwidth. No doubt it is the 1st decision for being able to access internet within a limited
space at less expensive price. Additional interference may occur. Sunlight will produce
disruptions. Entire fresh facilities for Li-Fi would have to be built (Blinowski, 2015), (Lewis,
2017).
35

10 Conclusion
From this report it can be easily concluded that with the growing the demand for a better,
reliable and fast communication system it is important to develop a better communication
system than the previous existing one. Previously we had the radio frequency
communication, but as we have seen it has many disadvantages and issues associated with it.
The main one is the power loss. Infrared communication when compared with a new
technology called as visible light communication or VLC, many points have been laid down
that makes VLC above every communication technology. VLC has the prime component of
LCD as we all know. The substantial matters possess have been referred to incorporating
many aspects of light emitting diode such as dimming and the impact of the waves of
different wavelengths. Latest research states standardization of the system. There are many
standards that have been designed in order to improve this technology. The system is an
excellent source of bandwidth and it doesn’t interfere is with the vehicle radio frequencies
and electrically magnetic waves. And therefore they are harmless to human beings. It is a
long range system and fast also. Light fidelity is one of the most popular committee systems
being developed today it is faster than Wi-Fi, which usually uses it to frequency signals.
There are many applications of VLC systems. One is Li-Fi, other being visible light
identification systems, robots, underwater navigation systems and many more. This
department is under research and analysis.
10.1 Future work
Visible light communication system is a very simple method that can replace the
conventional communication system. But it has a problem of line of sight and has a big
problem. This is not the case with radio frequency communication. VLC can conquer the
whole world only if it solves this issue. This will allow us to completely use the capabilities
offered to gain access consumer products.
36

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