IRJET- Audio Transmission and Waveform Shaping using Visible Light Communication

International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
p-ISSN: 2395-0072Volume: 06 Issue: 04 | Apr 2019 www.irjet.net
© 2019, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 4172
AUDIO TRANSMISSION AND WAVEFORM SHAPING USING VISIBLE
LIGHT COMMUNICATION
K. Booma1, N. Aravindan2, A. Sivanantha Raja3
1PG Student, Dept. of Electronics and Communication Engineering, Alagappa Chettiar government college of
Engineering and Technology, Tamil Nadu, India
2TRA, Dept. of Electronics and Communication Engineering, Alagappa Chettiar government college of Engineering
and Technology, Tamil Nadu, India
3Associative Professor, Dept. of Electronics and Communication Engineering, Alagappa Chettiar government
college of Engineering and Technology, Tamil Nadu, India
---------------------------------------------------------------------***----------------------------------------------------------------------
Abstract - Wireless communication today has a huge
demand due to its limited bandwidth. With the increase in the
bandwidth's huge demand, it became the nightmare for every
individual. To overcome these problems, the Visible Light
Communication (VLC) is latest technology that acts as a
compliment to the radio frequencies and its communication.
The use of visible light in wireless communication is an
exciting prospect that is still in the development stage.
However, this communication branch has several advantages
as it can provide extra security, faster transmission, higher
bandwidth that is lacking in traditional wireless
communication. When data transmitted over a channel, data
transmitted as a digital signal due to some channel effect
there will be loss in the signal. In order to overcome this issue
waveform shaping circuit is used. In this project, we
investigated real-time audio transmission and waveform
shaping using visible light communication. In the waveform
shaping, the square pulse is tested with and without the usage
of the waveform shaping circuit and analyzed the bandwidth
of the system with its rise time.
Key Words: Audio transmission, Bandwidth, Rise time,
Visible light communication, Waveform shaping,
Wireless communication.
1. INTRODUCTION
Recent years transfer of data is the most important daily
activities. The wireless communication technologies used for
short-range communication nowadays is Bluetooth and WiFi.
The frequency spectrum used by these methods is very
scanty. The current short-range wireless networks are not
fast when numerous devices are connected to it, while the
connected devices are getting increased, that might cause the
network overloaded which results in the poor data transfer
rate. Due to increasing the requirement for wireless data, the
available RF spectrum below 10GHz has become scarce[2].
The existing technologies have drawbacks like high cost,
insecurity of data, high power consumption and also it is
harmful to the living beings. So, there is an immense
requirement of a technology that could conquer all the
drawbacks of existing technologies. Using fast light
waveforms to transmit data without any physical connection
between the transmitter and receiver is termed as Visible
light communication (VLC)[1].
VLC is arising as an alternative for upcoming generations
data transmission technology for short range application. It
acts as a contender to the current wireless communication by
attaining larger bandwidth and higher data rate[1].The
spectrum range of VLC is 10,000 times greater than RF
spectrum and it is unlicensed[2].It comes under the branch of
optical wireless communication. This communication uses
Light Emitting Diode as a transmitter and photodiode or solar
panel or a digital camera as a detector in the receiver.
Implementation of VLC can be carried out in the two ways,
firstly by connecting the signal source into the transmitter
optic and then emitted data can be received directly by the
optical receiver[3].
Fluorescent lights are used in indoor environment can
also be used as they flicker at a speed that is fast enough that
the human eye cannot see. There is an issues with fluorescent
light. While they could be used for communications, they can
only do so at relatively low frequencies, due to the fact that
fluorescent bulbs cannot be switched at high speed. The
resulting transmission rate would be approximately 10 kbps.
This rate is not high enough to support the transmission of
data such as video or audio, while LEDs, have a much faster
switching speed, as they are capable of providing up to 500
Mbps and possibly even more. Transmitting a data over light
is by flickering of the LED for carrying logic low and high
signal. By turning ON and OFF signal, the Led will transmit 0's
and 1's correspondingly [1]. This is the one of the simplest
method that visible light can be used for digital
communication. Switching the light could allow for the
transmission of more than one bit of information. LED-based
visible light communication provides concurrent illumination
and communication [6].The data transmitted by the light of
LEDs whose intensity varies quickly[7].The fast switching of
the LED cannot be visualized by the human eye. When the
visible light signal passed over from the transmitter to the
receiver, the receiver converts these optical signal into an
electrical signal and the original signal is recovered [1].With
VLC technology is becoming more prominent in this world,
Li-Fi(Light Fidelity), a subset of VLC. Li-Fi is built upon VLC

and is a high-speed bidirectional wireless network similar to
the wireless fidelity. This is achieved by having a transmitter
and receiver built in each device where it transmits light and
receives incoming light from another device. It transmit the
audio signal much better and faster than that of other
technologies. Light is pervasive so communication is more
flexible.
Dr. Harald Haas, a professor at the University of
Edinburgh School of Engineering, who shown publically the
proof of Light Fidelity(Li-Fi).Here we formulated a VLC
paradigm of an Real-time audio transmission system and
tested square waveform with this system. In the audio
transmission system, White LED used for illumination and
transmitting audio that is placed at certain distance. The
system is analyzed with the square waveform to measure its
bandwidth. This analysis is done (i) With the use of a
waveform shaping circuit (ii) without the use of a waveform
shaping circuit. This paper is systemized as: In section2;
System model of Audio transmission system is presented. In
section3; illustrates the system working, In section4; Results
are analyzed and In section5; Concludes the article.
2. SYSTEM MODEL
In this section system model of the audio transmission
system and the square waveform analysis is presented.
Fig -1: Block diagram of Audio transmission system
Fig- 2: Block diagram of system to analyze square pulse
Fig- 3: Block diagram to analyze the square waveform
with waveform shaping circuit
2.1 White LED
LED stands for Light Emitting Diode. White LED is the
semiconductor devices that produce white light when an
electric current pass to it. It works on the principle of
electroluminescence effect. There are two approaches to
create white light a) Mixed color white light b) Using blue
LED with a phosphor coating. Here we used white LED, the
properties of the White LED is listed in the tablebelow:
Table -1: White LED Details
Properties Description
Led Light Colour Cool White Colour
Temperature 6000-6500K
Luminous Intensity 1200
Frequency Range 50-60Hz
Total Power 20W
Aluminium Alloy 5mm High Strength Glass
(Cover)
Life Span 50,000 Hours
Power 90-240V
Glass 5mm Tempered
2.2 Solar panel
The solar panel is an aggregation of solar or photovoltaic
cells. It is used to generate electricity through the
photovoltaic effect. Photovoltaic means they used for the
conversion of sunlight into electrical energy. Here we used a
solar panel for the energy conversion only.
2.3 Audio jack
It is a Mobile connector used to connect the mobile
phones with the audio device. Here it is used to connect the
mobile device or any other device like musical devices with
Li-Fi as input audio signal.

2.4 Amplifier
An Amplifier is mostly a power amplifier. Its main
function is to upgrade low power audio signal to a high power
audios sufficient for the loudspeaker or any stereo speaker. It
boosts up the signal level.
2.5 Speaker
A Speaker which converts Electrical or Analog signals to
the audible form to reach the Receptor. It converts an
electrical signal into the sound signal with the help of
Electromagnets present in the speaker.
2.6 Waveform shaping circuits
Waveform shaping means altering the waveform of the
transmitting pulses. The main aim of this process is to set the
signal better suitable for the communication. By filtering the
signal the signal noise and interference are kept in control. An
ideal waveform shaping circuit would convert a distorted
signal into an exact output with a rounded maximum, whose
maximum height is directly related to the peak height of the
input function. With the usage of Waveform shaping circuits,
the bandwidth of the system is analyzed by the rise time of
the pulse. Rise time is the time taken for the signal to vary
from specified lower threshold value to the upper threshold
value that specified.
Where tr is the risetime and BW is the bandwidth.
Fig.4: Schematic diagram of the pulse shaping circuit
3. WORKING
In Real-time Audio transmission system fig.1, it
comprises of two sections the transmitter section and the
receiver section. In the transmitter section, it consists of
Microphone/Mobile or any of the audio source, White LED, an
audio jack and the DC Voltage source. The Receiver section,
composed of Solar panel, an amplifier, battery and finally a
speaker. The white LED is placed at certain distance from
receiver, then the input audio signal from the source device
along with the supply voltage is given to the LED with the
LED Driver. The LED receives and converts it into a light
signal. In the receiver section, the solar panel receives the
light signal and transforms it, the electrical signal is given to
the amplifier. An amplifier along with a speaker will boost up
the signal and then finally received through the speaker. The
transmission is tested at a distance of 3 meters and analyzed
the quality of the sound.
In the case of testing the square pulse, the transmitter
side it consists of Audio Frequency Oscilloscope (AFO) along
with LED and in the Receiver side, it consists of a solar panel
and Digital Storage Oscilloscope and the waveform shaping
circuit. The square waveform testing with this system by (i)
without waveform shaping circuit (ii) With the waveform
shaping circuit. In the case of without the waveform shaping
circuit fig.2, The square waveform from the AFO is given to
the LED, where the electrical signal is transformed into a light
signal. Then the light signal is received by the panel and it can
be seen through the DSO where the bandwidth is analyzed by
the rise time of the signal. In the case of with the waveform
shaping circuit fig.3, the square waveform from AFO is given
to the light emitting diode, where the electrical signal is
converted into a light signal and then it acquired by the panel
and is given to the shaping circuit. This circuit will shape the
waveform and finally, it can be seen through the DSO. From
the two testing, the bandwidth is analyzed from the
waveform rise time.
4. RESULT AND DISCUSSION
An Audio transmission using visible light communication
is the live transmission of Audio signals without any signal
loss and noise. The sound clarity of audio is clear and sounds
loudness is analyzed at the distance of 3 meters. The square
waveform tested with the system and the bandwidth analysis
is done with the rise time equation. The bandwidth analyses
of the rise time for the different frequencies is graphically
explained here. While comparing two, the bandwidth of the
without waveform shaping circuit is lesser than that of the
waveform shaping circuit, the bandwidth of without
waveform shaping circuit is having the bandwidth of
3.910KHz to 397.7KHz and the bandwidth of with waveform
shaping circuit is in the range of 22.42KHz to 507.24KHz
under the range of frequency of 100Hz to 150KHz both are
presented in the chart-1,chart-2.

100
700
15K
45K
75K
150K
Chart-1: Response Graph of without waveform shaping
circuit testing
In the chart-1,chart-2 the bandwidth is analyzed for
different frequencies. The two chart represents the
response graph without and with the waveform shaping
circuit and the bandwidth is analyzed by the rise time of
the signal. The bandwidth is inversely proportional to the
rise time.
9.00E-04
8.00E-04
7.00E-04
6.00E-04
4.1Output of without waveform shaping circuits
Fig. 7: Output waveform at the frequency of 100Hz
Fig. 8: Output waveform at the frequency of 150KHz
From the above output fig.7,8, represents without any
waveform shaping circuit, the output waveform is get altered
due to the communication channel.
4.2 Output of with waveform shaping circuits
5.00E-04
4.00E-04
3.00E-04
2.00E-04
1.00E-04
BANDWIDTH
RISETIME
FREQUENCY
Fig. 9: Output waveform at the frequency of 100Hz
Chart-2: Response Graph of with waveform shaping
circuit testing
Fig. 10: Output waveform at the frequency of 150KHz

From the above output fig.9,10, it is clearly seen that by
using the waveform shaping circuit the original shape of the
waveform is recovered.
5. CONCLUSION
VLC replaces the RF. VLC was utilized in various fields.
Using VLC in audio transmission can progress the speed of
communication. By using this VLC we created an audio
transmission system and also tested the square waveform
in order to transmit the data via this technology this testing
is experimentally analyzed. The audio transmission is
secured due to use of this technology. By this technology we
can use LED for both the illumination and audio
transmission. It can even use in varies areas where
frequencies can be restricted. This technology is faster,
cheaper and provides secure communication. VLC can be
utilized to resolve the problems such as scarcity of radio
frequency bandwidth. Thus, this technology provides huge
benefits and it will take our life to the nearfuture.
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