Optical Wireless Communication (OWC) has attracted the researchers as an alternative broadband technology for wireless communication. In OWC optical beams are used to transport data through atmosphere or even vacuum. We have proposed an OWC model and analyze the transmission performance of OW channel for indoor/ outdoor application. The performance has been judged on the basis of key parameters like BER and OSNR. A theoretical model has also been presented and validated by the simulation results. The proposed OWC channel was simulated in Optisystem which is a powerful tool of Optical communication System

1. (IJCSIS) International Journal of Computer Science and Information Security,
Vol. 16, No. 3, March 2018
Analysis of Key Transmission Issues in Optical Wireless
Communication for Indoor and Outdoor Applications
Muhammad Waqas Khan1
, Mehr-e-Munir2
,Umar Farooq3
, Amjad Amer4
Departmentof Electrical Engineering , Iqra National University ,Peshawar Pakistan
1,2,3,4
Email: m.waqas@inu.edu.pk1
, mehre.munir@cusit.edu.pk2
, umer.farooq@inu.edu.pk3
, amjadaamer008@gmail.com4
Abstract- Optical Wireless Communication (OWC) has
attracted the researchers as an alternative broadband
technology for wireless communication. In OWC optical
beams are used to transport data through atmosphere or
even vacuum. We have proposed an OWC model and
analyze the transmission performance of OW channel for
indoor/ outdoor application. The performance has been
judged on the basis of key parameters like BER and
OSNR. A theoretical model has also been presented and
validated by the simulation results. The proposed OWC
channel was simulated in Optisystem which is a powerful
tool of Optical communication System
Keywords- OOW Model, Laser, OWC Model
I. INTRODUCTION
The OWC provides optical bandwidth connections using
lasers. 2is an optical wireless communication technique in
which light spread in the space, free space, i.e. space, air,
transmission of data wirelessly for computer and
telecommunication networking. At present optical wireless
communication has a capacity of transmitting around 2.5
Gega byte /s, voice, video and other forms of data
transmission through space permits optical connectivity
without the need for optic fibre cable or getting spectrum
licenses. Optical wireless communication operates b/w the
780 to 1600 nm bands by using converters i.e. electrical to
optical and Optical to electrical. OWC needs light, which can
be focused by using lasers or LEDs. Using the lasers is very
similar to using fibre optic cables for transmission difference
is the medium .
OWC connectivity doesn’t require any optic fibre cable, or
security license for the RF (radio frequency) solution. Digging
is not popular in metropolitan cities and also prohibited by
local administration. Also cost may be increase for digging
specially for river and railway tracks.. So OWC can provide
cost effective connectivity. OWC provides low BER, high
SNR, low cost, power efficient, easy installation and
maintenance
Personal communication system (PCS) is a major area of
application of OW. The progress in optic technology has
enabled the mass with optical components that are fast and
available at low costs are suitable for short ranged OW. In the
1990 Optical Wireless becomes an emerged technology for
data communication transfer for Personal Computers as the
IDA (Infrared data association)[2] has developed the required
protocols which enabled the standardization and
commercialization the OW ports which are very popular and
are now found on mobile phones and PCs.
Almost 30 years ago OWC (Optical wireless
communications) a new broadband technology for wireless
transmission to use as was suggested. [1]. OW has a very
simple basic concept: utilization of Laser to carry data
through vacuum and free spacev. This means that the
architecture of OW link is very similar to that of point to point
fiber optic links, except for the fact that optical fibres are not
used as a transmission medium. It is also like to Radio
Frequency links but light waves are used instead of radio
waves and an antenna with an optical trans-receiver for free
space media. In spite of the apparent resemblance b/w the
two(RF links and OW). OW has many better characteristics
compared to RF. Optical components are very power and cost
efficient in comparison to RF components. Also they don’t
undergo interference or multipath fading and operate under
strict safety protocols. This does not at all mean that OW can
replace RF completely. RF technology is of no match when it
comes to area coverage and user mobility compared to OW
which is quite limited. But because their photo-electric
conversion mechanism impacts light noise sources, incoherent
OW receivers present lower sensitivity compared to RF
receivers.
Artificial magnetic conductor is used for miniaturization of
an antenna and it reduces an antenna size but results in lower
gain [1]. Complementary split ring resonators are used for
miniaturization but size reduction is only 10% [2]. Size
reduction of 21% is presented by using Koch fractal shape but
after few iterations gain starts to decrease [3]. In short
circuited technique, patch is shorted to the ground plane and
this technique reduces size up to great extent but gain also
decreases [4]. .Another main problem of the smaller size
antenna is its narrow impedance bandwidth and lower gain
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2. (IJCSIS) International Journal of Computer Science and Information Security,
Vol. 16, No. 3, March 2018
[5]. In multiband response of the microstrip patch antenna is
reported but gain is very smaller for most of bands [6].
Miniaturization of microstrip patch antenna with multiband
performance is presented but impedance bandwidth is very
narrow for all the desired bands [7]. Meta materials are used
as ground plane to reduce antenna size [8].
With the high permittivity substrates size of antenna can be
reduced upto great extent but this technique reduces radiation
efficiency of antenna and impedance bandwidth of antenna
also reduces [9]. Magnetic substrates can be used for this
purpose but pure magnetic substrates are unlikely to obtain
[10].
Therefore in the present study we used technique for
miniaturization of double patch antenna with a good gain and
satisfactory impedance bandwidth for each band. We used
combination of U-Shape and L-Shape slots on the ground
plane and H-Shape slot on the fractal patch. We also employed
shorting pin between fractal patch and ground plane. By the
combination of all these proposed techniques size of antenna
reduced upto 69.29% and it produced multiband response in
the frequency range of 1-8GHz and impedance bandwidth and
gain are satisfactory for each band. We can adjust different
bands by changing position of shorting pin.
II. Network architecture of the proposed OWC
model
Fig1. Shows Network Architecture of Proposed OWC
Model
In figure 3 for user are using OWC. they are mux together at
MUX showing above. Then there combined data is modulated
by using a modulator. The modulating data is then transmitted
through a light beam / laser transmitter. The light beam
coming out from transmitter coming through the straight beam
through some distance. Some of data however scattered by the
way .
At receiver end photo detector receive the OWC signal and
collect the information. This signal then pass through the
demodulator which demodulate the data of four users. The
signal then passed through the Demux where data of four users
is separated and four user the data and required information.
The laser emit the light which is ristricted to a narrow cone.
But when Laser propagates the beam out ward it fans out
slowly or it diverge. For an electromagnetic beam, beam
divergence is the angular measure of the increase in the radius
with distance from the optical aperture as the beam emerges.
The laser beam divergence can be calculate if the beam
diameter d1 and d2 at two separate distances are known. Let
z1and z2 are the distances along the laser axis, from the end of
the laser to points “1” and “2”.
Fig 2 . laser beam divergence
The divergence angle is taken as the full angle of
opening of the beam. Then,
 =
Half of the divergence angle can be calculated as
 =
Where w1 and w2 are the radii of the beam at z1 and z2.
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3. (IJCSIS) International Journal of Computer Science and Information Security,
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Like all other electromagnetic beams, the lasers beam are
subject to divergence, which is measured in mill radians (mrad)
or degrees. Lower divergence beam is preferable for many
applications.
Atmospheric attenuation effects OWC, limiting the
reliability and performance. Scintillation, rain, fog and haze
cause atmospheric attenuation which has a harmful effect on
OWC. Mie scattering contributes the most in the scattering on
the laser beam. The aerosol that existed in the atmosphere due
to fog and haze causes this scattering and visibility can be
used to calculate it whose value can go up to 100s of decibels
in thick fog which reduces visibility lower than 50 meters and
can effect the performance of OWC. Rain (non-selective)
scattering does not affect considerable attenuation in wireless
IR links as it does not depend on wavelength, it affects mainly
on radio system and microwave that transmit energy at longer
wavelengths. Scintillation and laser beam spreading and
wander are the three main effects on turbulence. Change in
refractive index of air causes scintillation which causes the
light intensity to be non-uniform. The OWC components such
as divergence of the beam, diameter of the aperture of both the
transmitter and receiver are the responsible values for
geometric attenuation. The sum of geometric and atmospheric
attenuation is the total attenuation.
To design OWC system the effect of geometric loss and
atmospheric attenuation is small, to reduce the total
attenuation.
III. RESULTS AND DISCUSSION
Visibility depend on the climatic condition, as a quantity
measured by a human observer which is defined as (Kruse
model) the distance where an optical signal is reduced from
550nm to 0.02 of its original. But there are many objective and
physical factors effect this estimation. The essential
meteorological quantity, namely the transparency of the
atmosphere, can be measured objectively and it is called the
Runway Visual Range (RVR) or the meteorological optical
range. Some values of atmospheric attenuation due to
scattering based on visibility are presented in Table 1.
Visibility S
(Line of Sight)(km)
𝞴=800 nm (db/km) 𝞴=2500 nm (db/km)
0.5 32.5 30.8
0.7 23 21
0.9 18 16
1.1 14.5 12.5
1.3 12 10
1.5 10 8.33
Source
The visibility depends on the degree of coherence of the
source, on the distance between the paths as well as on the
location of the detector with regard to the source. The
coherence between different beams reaching the detector
depends on the crossed media. For an example, the diffusing
medium can decrease the coherence. For links referred to as
“in direct sight” links, coherent sources can be used, given that
parasitic reflections do not interfere with the principal beam,
inducing modulations of the detected signal.
Fig 3.Simulation Setup for Optical Wireless Channel
The Network Architecture of the OWC link show in figure
3.1 is simulated in Optisys Software as shown in Fig.3.4 .The
transmitter consist of a DPSK transmitter. A CW Laser
modulates the basic information at DPSK Transmitter. The
Launch power is measured by Power meter, Then it is passed
through a optical wireless channel working as same as a beam
light. The Parameters of OWC channel is shown in Fig. 3.5.In
the receiving end a DPSK Receiver is used to receive the
signal. Which regenerate the signal. We have analyzed the
transmission performance of the proposed OWC channel using
parameters of BER, SNR, Range, Beam Divergence and
Receiver Aperture. Next section will cover the simulation
results of various parameters.
Different results taken from simulation as shown in
graphical interpretation we compare different parameters to
check the link performance. As given below.
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Fig 4. Received Power
In figure 4 we can see that as the bit error rate is low
received power is high. As u can see in graph bit error rate at -
9 is acceptable in OWC communication. In this graph we use
some constant parameters i-e launched power=5mW,
Attenuation=25 dB/km, Beam divergence=2mrad,range=500
m and we vary receiver aperture.
Fig 5. Received Apperture
In fig 5 we can see relation of bit error rate and receiver
aperture if we increases receiver aperture bit error rate is low.
In this graph we vary receiver aperture and beam divergence,
launch power, attenuation and range is constant.
Fig 6. Beam Divergence
In figure 6 we see the effect of noise figure on receiver
power there is not much effect on it as u can see in figure. As
received power is increases noise figure decreases as not too
much effect on it.
Fig 7. Noise Figure
In figure 7 we can see the effect of noise figure on receiver
aperture it is not much effect on it. As we increase receiver
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aperture the noise figure is low. In this case we vary receiver
aperture.
Fig 8. Bit Error Range
In this figure 8 we see the effect of bit error rate on received
power u can see in figure if we increased received power bit
error rate is low and performance is good in this case we vary
beam divergence and received aperture, launched power and
attenuation is constant.
Fig 9. Beam Divergence on Bit Error Rate
In figure 9 we can see the effect of beam divergence on BER
as we can see as beam divergence is increase bit error rate also
increased. We vary beam divergence to see the effect of BER.
Fig 10. Effect on Noise Figure in Received Power
In figure 10 we can see the effect on noise figure on received
power. As received power increased noise figure decrease in
this case beam divergence is variable and receiver aperture,
transmitted power, attenuation is constant.
Fig 11. Comprise between Noise Figure and Beam divergence
In this figure 11 we comprise between noise figure and beam
divergence. As we increase beam divergence noise figure also
increased in this case we vary beam divergence to see effect on
noise figure under some constant parameters i-e receiver
aperture, attenuation, launch power.
IV. CONCLUSION
We have done analysis on Optical wireless
communication parameters and we conclude that Optical
wireless communication is considered a promising technology
for the long range distance communication we proposed and
analytically demonstrate a transmission link based on Optical
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wireless communication. An analytical model has been
presented and validated by simulation. .
In our experiments we have selected the DPSK as
transmission modulators. DPSK is investigated on the basis of
the key issues related to range, attenuation and data rate has
been addressed.
Bit error rate (BER) and optical signal to noise ratio
shows the good transmission performance with the 500m
range, 1Gbps data rate and up to 150 dB/km of attenuation in
analyzed optical wireless communication.
We have simulate OWC link in optisystem and we
have done some analysis on some parameter like Beam
divergence, receiver aperture, transmitter aperture, BER, noise
figure by keeping some parameters constant and some variable
and also we show our analyses on graphical interpretation and
finally we implement practically a transmitter which transmit
a audio data signal through free space optics and receiver to
receive that signal.
.
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