This paper proposes using MIMO techniques in visible light communication (VLC) systems to achieve high data transmission rates. It simulates various VLC system configurations (SISO, MISO, MIMO) using overlapping pulse position modulation. The results show that a MIMO system using an array of LEDs at the transmitter and receiver achieves much lower bit error rates than SISO or MISO systems as SNR increases. Specifically, at high SNR the MIMO system can provide bit error rates several orders of magnitude smaller. This confirms that MIMO is well-suited for VLC and can enable data rates of several hundred megabits per second or even gigabits per second depending on the configuration. The paper concludes OPPM
The aim of this paper is to determine the viability of Indoor Optical Wireless Communication System. This paper introduces Visible Light Communication along with its merits, demerits and applications. Then the main characteristics of VLC system are described, around which the project is designed. Multiple Input-Multiple Output (MIMO) technique is used in the project in order to enhance the data rate of transmission. Instead of using a system of only one LED and one APD, which transmits only one bit at a time, a system of 4 LEDs and 4 APDs is introduced, which increases the data rates by 300% from the previous case. We observe the signal, noise, SNR, BER etc. across the room dimension. Finally, in the last chapter we summarize our results on the basis of MATLAB simulations and propose some modifications to this model that can be implemented in future.
Development of an Audio Transmission System Through an Indoor Visible Light ...Mohammad Liton Hossain
This study presents an approach to develop an indoor visible light communication system capable of transmitting audio signal over light beam within a short distance. Visible Light Communication (VLC) is a pretty new technology which used light sources to transmit data for communication. In any communication system, both analog and digital signal transmission are possible, though, due to having the capability of providing a faithful quality of signal regeneration after the transmission process, digital communication system is much more popular than the analog one. In the current project, digital communication process was adopted also. To convert the analog audio signal into the digital transmission signal and vice versa, Pulse Width Modulation (PWM) was used as the signal encoding strategy. As the light emitter, white Light Emitting Diodes (LEDs) were used and as photo sensor, a solar cell was used instead of a photodiode to obtain greater signal power and sensitivity. In the system, the carrier signal for transmission was chosen to have a frequency of 50 KHz. At the receiving end, a 4th order Butterworth lowpass filter having a cutoff frequency of 8 KHz was used to demodulate the audio signal. Using only 2 white LEDs, the indoor transmission range of this visible light communication system was found to be 5 meters while reproducing a satisfactory quality audio.
The aim of this paper is to determine the viability of Indoor Optical Wireless Communication System. This paper introduces Visible Light Communication along with its merits, demerits and applications. Then the main characteristics of VLC system are described, around which the project is designed. Multiple Input-Multiple Output (MIMO) technique is used in the project in order to enhance the data rate of transmission. Instead of using a system of only one LED and one APD, which transmits only one bit at a time, a system of 4 LEDs and 4 APDs is introduced, which increases the data rates by 300% from the previous case. We observe the signal, noise, SNR, BER etc. across the room dimension. Finally, in the last chapter we summarize our results on the basis of MATLAB simulations and propose some modifications to this model that can be implemented in future.
Development of an Audio Transmission System Through an Indoor Visible Light ...Mohammad Liton Hossain
This study presents an approach to develop an indoor visible light communication system capable of transmitting audio signal over light beam within a short distance. Visible Light Communication (VLC) is a pretty new technology which used light sources to transmit data for communication. In any communication system, both analog and digital signal transmission are possible, though, due to having the capability of providing a faithful quality of signal regeneration after the transmission process, digital communication system is much more popular than the analog one. In the current project, digital communication process was adopted also. To convert the analog audio signal into the digital transmission signal and vice versa, Pulse Width Modulation (PWM) was used as the signal encoding strategy. As the light emitter, white Light Emitting Diodes (LEDs) were used and as photo sensor, a solar cell was used instead of a photodiode to obtain greater signal power and sensitivity. In the system, the carrier signal for transmission was chosen to have a frequency of 50 KHz. At the receiving end, a 4th order Butterworth lowpass filter having a cutoff frequency of 8 KHz was used to demodulate the audio signal. Using only 2 white LEDs, the indoor transmission range of this visible light communication system was found to be 5 meters while reproducing a satisfactory quality audio.
Free-Space Optical Networking Using the Spectrum of Visible LightIJTET Journal
Radio frequency technology suffers from limited bandwidth and electromagnetic interference. The recent
developments in solid-state Light Emitting Diode (LED) materials and devices are driving resurgence into the use of Free-Space Optical (FSO) wireless communication. LED-based network transceivers have a variety of competitive advantages over RF
including high bandwidth density, security, energy consumption, and aesthetics. They also use a highly reusable unregulated part of the spectrum (visible light). Many opportunities exist to exploit low-cost nature of LEDs and lighting units for widespread deployment of optical communication. The prime focus is to reducing cost, and for that, we have to make appropriate selection
of system’s components, e.g. modulation, coding, filtering. The objective is to describe the viability of an optical free-space visible light transceiver as a basis for indoor wireless networking and to achieve acceptable bit error rate (BER) performance for indoor use, with a low cost system.
What is VLC
Visible light & Spectrum
VLC process
-Transmitter
-Receiver
-Modulation
VLC characteristics
Comparison with RF & IR
Demerits of VLC
Applications
The study LiFi (Light Fidelity) demonstrates about how can we use this technology as a medium of communication similar to Wifi . This is the latest technology proposed by Harold Haas in 2011. It explains about the process of transmitting data with the help of illumination of an Led bulb and about its speed intensity to transmit data. Basically in this paper, author will discuss about the technology and also explain that how we can replace from WiFi to LiFi . WiFi generally used for wireless coverage within the buildings while LiFi is capable for high intensity wireless data coverage in limited areas with no obstacles .This research paper represents introduction of the Lifi technology,performance,modulation and challenges. This research paper can be used as a reference and knowledge to develop some of LiFitechnology.
LOW POWER CLASS AB SI POWER AMPLIFIER FOR WIRELESS MEDICAL SENSOR NETWORK bioejjournal
The objective of this research was to design a 2.4 GHz class AB Power Amplifier (PA), with 0.18um
Semiconductor Manufacturing International Corporation (SMIC) CMOS technology by using Cadence
software, for health care applications. The ultimate goal for such application is to minimize the trade-offs
between performance and cost, and between performance and low power consumption design. This paper
introduces the design of a 2.4GHz class AB power amplifier which consists of two stage amplifiers. This
power amplifier can transmit 10dBm output power to a 50Ω load. The power added efficiency is 7.5% at
1dB compression point and the power gain is 10dB, the total power consumption is 0.135W. The
performance of the power amplifier meets the specification requirements of the desired.
PC to PC Transfer of Text, Images Using Visible Light Communication (VLC)IJAEMSJORNAL
Light Emitting Diodes are assuming a noteworthy part in numerous regions of our everyday life. Aside from transmitting light, these LED's can be used for data transmission utilizing Visible Light Communication (VLC). In this paper, We propose a complete model to transfer text, images from one device to another using Visible light communication, in which transmitter transmits the encrypted data through visible light and the receiver at the receiving end identifies the transmitted data and decrypts it to retrieve the data sent.
Free-Space Optical Networking Using the Spectrum of Visible LightIJTET Journal
Radio frequency technology suffers from limited bandwidth and electromagnetic interference. The recent
developments in solid-state Light Emitting Diode (LED) materials and devices are driving resurgence into the use of Free-Space Optical (FSO) wireless communication. LED-based network transceivers have a variety of competitive advantages over RF
including high bandwidth density, security, energy consumption, and aesthetics. They also use a highly reusable unregulated part of the spectrum (visible light). Many opportunities exist to exploit low-cost nature of LEDs and lighting units for widespread deployment of optical communication. The prime focus is to reducing cost, and for that, we have to make appropriate selection
of system’s components, e.g. modulation, coding, filtering. The objective is to describe the viability of an optical free-space visible light transceiver as a basis for indoor wireless networking and to achieve acceptable bit error rate (BER) performance for indoor use, with a low cost system.
What is VLC
Visible light & Spectrum
VLC process
-Transmitter
-Receiver
-Modulation
VLC characteristics
Comparison with RF & IR
Demerits of VLC
Applications
The study LiFi (Light Fidelity) demonstrates about how can we use this technology as a medium of communication similar to Wifi . This is the latest technology proposed by Harold Haas in 2011. It explains about the process of transmitting data with the help of illumination of an Led bulb and about its speed intensity to transmit data. Basically in this paper, author will discuss about the technology and also explain that how we can replace from WiFi to LiFi . WiFi generally used for wireless coverage within the buildings while LiFi is capable for high intensity wireless data coverage in limited areas with no obstacles .This research paper represents introduction of the Lifi technology,performance,modulation and challenges. This research paper can be used as a reference and knowledge to develop some of LiFitechnology.
LOW POWER CLASS AB SI POWER AMPLIFIER FOR WIRELESS MEDICAL SENSOR NETWORK bioejjournal
The objective of this research was to design a 2.4 GHz class AB Power Amplifier (PA), with 0.18um
Semiconductor Manufacturing International Corporation (SMIC) CMOS technology by using Cadence
software, for health care applications. The ultimate goal for such application is to minimize the trade-offs
between performance and cost, and between performance and low power consumption design. This paper
introduces the design of a 2.4GHz class AB power amplifier which consists of two stage amplifiers. This
power amplifier can transmit 10dBm output power to a 50Ω load. The power added efficiency is 7.5% at
1dB compression point and the power gain is 10dB, the total power consumption is 0.135W. The
performance of the power amplifier meets the specification requirements of the desired.
PC to PC Transfer of Text, Images Using Visible Light Communication (VLC)IJAEMSJORNAL
Light Emitting Diodes are assuming a noteworthy part in numerous regions of our everyday life. Aside from transmitting light, these LED's can be used for data transmission utilizing Visible Light Communication (VLC). In this paper, We propose a complete model to transfer text, images from one device to another using Visible light communication, in which transmitter transmits the encrypted data through visible light and the receiver at the receiving end identifies the transmitted data and decrypts it to retrieve the data sent.
Wireless Networks using Visible Light Communication: A Reviewijwmn
Provisioning of quality of service (QoS) is a critical issue in visible light communication (VLC) systems and other wireless communication systems. LED lights are becoming widely used for homes and offices for their luminous efficacy improvement. VLC is a new way of wireless communication. Typical transmitters used for visible-light communication are visible-light LEDs, and receivers are photodiodes and image sensors. We present new applications that will be made possible by visible light communication technology. Especially location-based services are considered suitable for visible light communication applications.
Visible Light Communication for Visually Impaired People using Sustainable LEDsijtsrd
We developed navigation system prototype for the visually impaired using LED lights. Where LED lights emit visible light with location data and a smartphone or blind persons stick with a visible light receiver receives the data. The controller with receiver calculates the optimal path to a designation and speaks to the visually impaired through a headphone or turns stick left or right with the help of motor. The prototype is able to navigate the visually impaired users fairly well with speech guidance. We believe that the application of visible light communication belongs to location-based services and new graphical user interfaces that combine visual imagery with visible light communication. For this application, users are able to know the information associated with a transmitter. If a transmitter is attached to a building or a fixed place, location information will be obtained. Indoor navigation is convenient for everyone, and it is especially useful for visually impaired. If a transmitter is attached to a building or a fixed place, location information will be obtained and conveyed to receiver using LED light. Indoor navigation is convenient for everyone, and it is especially useful for visually impaired. Pradnya Kulkarni | Prof. M. B. Tadwalkar"Visible Light Communication for Visually Impaired People using Sustainable LEDs" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-1 | Issue-5 , August 2017, URL: http://www.ijtsrd.com/papers/ijtsrd2236.pdf http://www.ijtsrd.com/engineering/electronics-and-communication-engineering/2236/visible-light-communication-for-visually-impaired-people-using-sustainable-leds/pradnya-kulkarni
Performance evaluation of VLC system using new modulation approachjournalBEEI
We propose a modified OFDM modulation based on multiband scheme for visible light communications (VLC) system. The method called catenated-OFDM VLC system can efficiently boost the propagation distance and combat multipath induced the inter symbol interference and inter carrier interference. Design parameters such as number of optical bands, input power, distance and data rate are varied to see their effect on the system performances. Simulation analysis is done using Optisys software Ver. 11.0. The results show that the proposed system offers a good performance at longer transmission distance of 12 m for input power of 2 dBm in case of Band=3 with 10 Gbps data rate. BER curves also indicates that the proposed system can be operated at very high data rate of 15 Gbps. This exhibits the ability of the proposed system to be one of the candidate for future optical wireless communication system.
About
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface.
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Technical Specifications
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
Key Features
Indigenized remote control interface card suitable for MAFI system CCR equipment. Compatible for IDM8000 CCR. Backplane mounted serial and TCP/Ethernet communication module for CCR remote access. IDM 8000 CCR remote control on serial and TCP protocol.
• Remote control: Parallel or serial interface
• Compatible with MAFI CCR system
• Copatiable with IDM8000 CCR
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
Application
• Remote control: Parallel or serial interface.
• Compatible with MAFI CCR system.
• Compatible with IDM8000 CCR.
• Compatible with Backplane mount serial communication.
• Compatible with commercial and Defence aviation CCR system.
• Remote control system for accessing CCR and allied system over serial or TCP.
• Indigenized local Support/presence in India.
• Easy in configuration using DIP switches.
Industrial Training at Shahjalal Fertilizer Company Limited (SFCL)MdTanvirMahtab2
This presentation is about the working procedure of Shahjalal Fertilizer Company Limited (SFCL). A Govt. owned Company of Bangladesh Chemical Industries Corporation under Ministry of Industries.
NO1 Uk best vashikaran specialist in delhi vashikaran baba near me online vas...Amil Baba Dawood bangali
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Event Management System Vb Net Project Report.pdfKamal Acharya
In present era, the scopes of information technology growing with a very fast .We do not see any are untouched from this industry. The scope of information technology has become wider includes: Business and industry. Household Business, Communication, Education, Entertainment, Science, Medicine, Engineering, Distance Learning, Weather Forecasting. Carrier Searching and so on.
My project named “Event Management System” is software that store and maintained all events coordinated in college. It also helpful to print related reports. My project will help to record the events coordinated by faculties with their Name, Event subject, date & details in an efficient & effective ways.
In my system we have to make a system by which a user can record all events coordinated by a particular faculty. In our proposed system some more featured are added which differs it from the existing system such as security.
Sachpazis:Terzaghi Bearing Capacity Estimation in simple terms with Calculati...Dr.Costas Sachpazis
Terzaghi's soil bearing capacity theory, developed by Karl Terzaghi, is a fundamental principle in geotechnical engineering used to determine the bearing capacity of shallow foundations. This theory provides a method to calculate the ultimate bearing capacity of soil, which is the maximum load per unit area that the soil can support without undergoing shear failure. The Calculation HTML Code included.
Courier management system project report.pdfKamal Acharya
It is now-a-days very important for the people to send or receive articles like imported furniture, electronic items, gifts, business goods and the like. People depend vastly on different transport systems which mostly use the manual way of receiving and delivering the articles. There is no way to track the articles till they are received and there is no way to let the customer know what happened in transit, once he booked some articles. In such a situation, we need a system which completely computerizes the cargo activities including time to time tracking of the articles sent. This need is fulfilled by Courier Management System software which is online software for the cargo management people that enables them to receive the goods from a source and send them to a required destination and track their status from time to time.
Automobile Management System Project Report.pdfKamal Acharya
The proposed project is developed to manage the automobile in the automobile dealer company. The main module in this project is login, automobile management, customer management, sales, complaints and reports. The first module is the login. The automobile showroom owner should login to the project for usage. The username and password are verified and if it is correct, next form opens. If the username and password are not correct, it shows the error message.
When a customer search for a automobile, if the automobile is available, they will be taken to a page that shows the details of the automobile including automobile name, automobile ID, quantity, price etc. “Automobile Management System” is useful for maintaining automobiles, customers effectively and hence helps for establishing good relation between customer and automobile organization. It contains various customized modules for effectively maintaining automobiles and stock information accurately and safely.
When the automobile is sold to the customer, stock will be reduced automatically. When a new purchase is made, stock will be increased automatically. While selecting automobiles for sale, the proposed software will automatically check for total number of available stock of that particular item, if the total stock of that particular item is less than 5, software will notify the user to purchase the particular item.
Also when the user tries to sale items which are not in stock, the system will prompt the user that the stock is not enough. Customers of this system can search for a automobile; can purchase a automobile easily by selecting fast. On the other hand the stock of automobiles can be maintained perfectly by the automobile shop manager overcoming the drawbacks of existing system.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two type of water scarcity. One is physical. The other is economic water scarcity.
Welcome to WIPAC Monthly the magazine brought to you by the LinkedIn Group Water Industry Process Automation & Control.
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A case study of the used of Advanced Process Control at the Wastewater Treatment works at Lleida in Spain
A look back on an article on smart wastewater networks in order to see how the industry has measured up in the interim around the adoption of Digital Transformation in the Water Industry.
Explore the innovative world of trenchless pipe repair with our comprehensive guide, "The Benefits and Techniques of Trenchless Pipe Repair." This document delves into the modern methods of repairing underground pipes without the need for extensive excavation, highlighting the numerous advantages and the latest techniques used in the industry.
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Gen AI Study Jams _ For the GDSC Leads in India.pdf
Iisrt 2-mitigating effect of flickering and dimming in visible light communication using mimo
1. International Journal of Electrical and Computing Engineering
Vol. 1, Issue. 1, July – 2014 ISSN (Online): 2349-8218
Mitigating Effect of Flickering & Dimming in Visible
Light Communication Using MIMO
A. Suban
[1]
, P. Prabu
[2]
, R. Manikandan
[3]
, M. Pradeep
[4]
Assistant professor, Dept of ECE, Velammal College of Engineering and Technology, Madurai
[2]
PG student, Dept of CSE, Indian Institute of Information Technology, Trichy
[3]
Project Engineer, WIPRO Lmited, Chennai,
[4]
Lecturer, Nagasiva Polytechnique College
Abstract— Visible Light Communication (VLC) refers
to short-range optical wireless communication using
visible light spectrum from 380 to 780nm and it has
many advantages such as it can provide a maximum
speed of 10GB/S. The other advancement is that the
bandwidth available for visible light communication is
300THz whereas it is below 6GHz on RF
communication. The transmission of data in VLC is
done with the intensity modulating optical source,
such as light emitting diodes (LEDs) because of its
energy efficiency and recent advancement in LED
technology with fast nanoseconds switching time. This
paper applies OPPM (Overlapping Pulse Position
Modulation) to provide higher data rate during its
transmission of digital data when we compared to
other modulation techniques. The result shows that
the best performance can be obtained using OPPM,
making it an ideal modulation technique for future
visible light communication. MATLAB and Lab View
are the two methodologies we used for simulation
purpose. Moreover Multiple Input Multiple Output
(MIMO) techniques is potentially adopted for
achieving high data rates. MATLAB Simulations are
carried out and depicted.
Index Terms— Visible light, White LED, On Off
Keying, Variable Pulse Modulation, Overlapping
Pulse Position Modulation.
I. INTRODUCTION
In the development of wireless communication
system when the third generation mobile communication
system is employed, manufacturers and the scientific
group are increasingly turning their research interest
towards future wireless communication system because
traditional radio frequency (RF) communication below 6
GHz is rapidly running out of spectrum bandwidth for
high data-rate communication. Visible Light
Communication has recently been developed by scientists
seeking to create an ultra-high speed, high security,
biologically friendly communication networks
Suban. A, Electronics & Communication Engineering, Velammal
College of Engineering and Technology, Madurai
Prabu.P, Computer Sceince & Engineering, Indian Institute of
Information Technology
Manikandan.R, Project Enineer, WIPRO Limited, Chennai.
Pradeep.M, Electrical & Electronics Engineering, Nagasiva
Polytechnique College, Madurai
that allow the creation and expansion of continuous
computing applications using very large bandwidth high-
frequency pulsed light instead of radio waves and
microwaves. Visible Light Communication (VLC) is the
short-range optical wireless communication using the
visible light spectrum from 380 to 780nm. With ~300 THz
of bandwidth available for VLC, multi-gigabit-per second
data rates could be provided over short distances.
This wide spread of bandwidth removes one of
the major difficulties faced by new communication
schemes. Some of the noted advantages of visible light
communication over RF (Radio Frequency) and IR (Infra-
Red) based systems are:
Higher security than RF communication system.
No restriction on transmission power unlike in
IR communication system.
No regulations in the use of the visible
electromagnetic spectrum.
The key advantage of VLC is the duality in the
use of the visible light. The same light that is
used for the communication can also be used for
illumination applications such as domestic light
bulbs, LED TVs, and traffic lights.
In an optical communication system, there is a
possibility of modulating the transmitted optical signal in
a variety of ways. The phase, frequency and the intensity
of the optical signal can be modulated. VLC transmits
data by the intensity modulating optical sources, such as
light emitting diodes (LEDs) and laser diodes, because it
is easy to implement and the optical output power is
simply changed in accordance with the modulating signal.
There has been renewed interest in visible light optical
communication due to widespread deployment of LEDs
for energy efficiency and recent advancements in LED
technology with fast nanosecond switching times.
Figure 1. An Alternate Technology-VLC
8
2. International Journal of Electrical and Computing Engineering
Vol. 1, Issue. 1, July – 2014 ISSN (Online): XXXX-XXXX
LED VISIBLE LIGHT COMMUNICATION
In this 21st century, LEDs are extensively used
in various electronic devices, consumer products and due
to their small size they are preferred for illuminating
technologies. Recently experiments have shown that
advance in semiconductor material and manufacturing
techniques of LED is to be suitable for general indoor and
outdoor applications. In addition to that LED produces
less heat than other fluorescent and incandescent light
bulbs. In the industry side, LEDs are referred as “cool
lights” and most sustainable in light technology. Low cost
LED instead of lasers can be used as communication
transmitters connected to the electric grid, receiving high-
bit rate signals. So LED (Light Emitting Diode) Visible
Light Communication systems are recognized as creating
a possible valuable addition to future generation of
technology, which have the potential of using light for the
purpose of advanced technological communication at
ultra-high speed surpassing that of current wireless
systems. If it is developed correctly, the possibility exists
than many of the problems associated with present day
infrared, Bluetooth and radio wave could be at least
partially resolved, and industries and the general public
can gain a more biologically friendly system. The main
reasons for using LED are followed:
• High usage of bandwidth.
• Existing local power line infrastructure can
potentially be utilized.
• Very simple transmitter and receiver circuit
and it is not expensive.
• Eco-friendly.
• Long life expectancy.
A further advantage is that VLC systems can
transmit data more securely over short distances than
other communication devices whose signals can be easily
detected outside the rooms and buildings they originate in.
In the following section, the paper describes the system
design for the visible light communication, modulation
method and their benefits for flickering.
III. SYSTEM DESIGN
A typical Visible Light Communication system
contains two parts namely transmitter module and
receiver module. VLC system appears in the form of point
to multi-points which permits data transmission in one
direction only. The following figure shows the overall
VLC system block diagram. The receiver occupant may
realize information uplink with extra optical devices, and
more sophisticated the duplex system is the duplex
system.
A. TRANSMITTER MODULE
In the transmitter module, the Light Emitting Diode is
used to transmit the data and it has to be designed in such
way that power and the colour temperature both safe and
comfortable for human eyes.
when the same LED is used for illumination because it
won't make people feel uncomfortable and dizzy. It’s
important to note that the receiver occupant may block the
light beam and put the receiver in shadows, so more than
two LED lamps should be modulated simultaneously from
various directions to cover a larger recipient area. In some
case where the receiver loses connection with the
transmitter, it will be able to receive data from another
transmitter instantaneously.
Figure 2. Visible Light Communication Transmitter and Receiver Block
Diagram
B. RECEIVER MODULE
A receiver module is mostly composed of PIN
detectors and signal conditioning devices. The output
signal from the detector is weak with a lot of background
light noise and a long free space communication distance
only makes the situation worse. Therefore, the critical part
of our VLC system is the signal conditioning circuit .
The receiver’s PIN photo detector is connected to a trans-
impedance amplifier to convert the current signal into a
voltage signal. A high pass filter is applied next to bypass
the light noises and power line noises. Finally, the signal
is amplified by a main amplifier and it is reshaped by
comparator.
IV. MODULATION TECHNIQUE IN VLC
In the modulation process, the baseband signals
constitute the modulating signal and the high-frequency
carrier signal is a sinusoidal waveform or cosine
waveform. The sine wave carrier can be normally
modulated by three basic ways. For the modulation of
binary digital data, the three modulation techniques used
are binary amplitude-shift keying (BASK), binary
frequency-shift keying (BFSK) and binary phase shift
keying (BPSK).
A. AMPLITUDE SHIFT KEYING
Amplitude-shift keying (ASK) is a form of modulation
technique that represents digital data as variations in the
amplitude of a carrier wave. To transmit digital data over
optical fibre ASK technique is normally used. For
transmission using LED, binary 1 is represented by a short
pulse of light whereas absence of light represents binary 0.
This process is said to On Off Keying (OOK).
9
3. International Journal of Electrical and Computing Engineering
Vol. 1, Issue. 1, July – 2014 ISSN (Online): XXXX-XXXX
Figure 3. MATLAB simulation of Bit Error Rate for various
modulation methods
C. OVERLAPPING PULSE POSITION
MODULATION
Although VPM can provide data rates in terms of
few hundred megabits/s but even higher data rate than the
existing one is not possible due to its inherent throughput
limitations. Reducing the pulse width is the one and only
way to increase the throughput of the VPM. So there is a
need for some other modulation methods to provide
higher data rate but that should not have the limitations as
with that of VPM. OPPM is one of the promising
modulation scheme that allows more than one pulse per
pulse width and it has some of the useful properties such
as equal energy signals and low duty cycle.
Figure 4. Lab View simulation of Bit Error Rate for various
modulation methods
From the simulated results, the following conclusions
are made. The error rate for all the modulation techniques
decreases monotonically with increasing value of SNR.
For any given value of SNR, coherent PSK & OOK
produces same and smaller error rate than any of the other
modulation technique. So, coherent PSK and OOK are the
optimum system for transmitting binary data because it
achieves the minimum probability of symbol error for the
given value of SNR. But considering OOK and coherent
PSK, OOK is the best and most efficient modulation
technique in terms of bandwidth and power consumption.
DPSK require an SNR that is 3 dB less than that of
coherent FSK and noncoherent FSK to achieve same error
rate. For higher values of SNR, DPSK and noncoherent
FSK performs almost as well as coherent PSK and
coherent FSK. For higher values of SNR, coherent PSK
and QPSK have same error rate performance. Also it has
been inferred that MSK has exactly the same error
performance as that of QPSK.
B. Variable Pulse Position Modulation
Pulse position modulation (PPM) encodes the
data using the position of the pulse within a set time
period. The duration of the period containing the pulse
must be long enough to allow different positions to be
identified.
Figure 5. MATLAB simulation of Data rate Vs Duty cycle for OOK &
OPPM
Figure 6. Lab View simulation of Data rate Vs Duty cycle for
OOK & OPPM
From the simulated results, the following conclusions are
made. We can see that the OPPM signal has the best
flicker performance, followed by VPM and OOK.
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4. International Journal of Electrical and Computing Engineering
Vol. 1, Issue. 1, July – 2014 ISSN (Online): XXXX-XXXX
The flicker severity value is 0.525 for any dimming
levels, which is far less than the limited value. We can
also notice that the 90% duty cycle VPM signal has
the same flicker performance as OPPM. But the flicker
severity of OPPM signal is invariant with changing
different dimming levels.
D. MULTI-ANTENNA CONFIGURATION
Solid-state lighting is a rapidly growing area of
research and applications, due to the reliability and
predicted high efficiency of these devices. The white LED
sources that are typically used for general illumination
can also be used for data transmission, and Visible Light
Communications (VLC) is a rapidly growing area of
research. One of the key challenges is the limited
modulation bandwidth of sources, typically several MHz
However, as a room or coverage space would typically be
illuminated by an array of LEDs there is the potential for
parallel data transmission, and using optical MIMO
techniques is potentially attractive for achieving high data
rates. In this paper we investigate non-imaging and
imaging MIMO approaches: a non-imaging optical
MIMO system does not perform properly at all receiver
positions due to symmetry, but an imaging based system
can operate under all foreseeable circumstances.
Simulations show such systems can operate at several
hundred Mbit/s and up to Gbit/s in many circumstances.
Figure 6. MATLAB simulation of Bit Error Rate (BER) Vs
Signal to Noise Ratio (SNR) for various systems such as SISO,
MISO and MIMO using OPPM Technique
From the simulated results,it can be inferred that
using SISO system model i.e. using single LED in the
transmitter side and a single photodiode or LED in the
receiver side we have very large bit error rate for increase
in SNR for given input. In the next case of MISO,i.e.
using two LED transmitter side at the transmitter side and
a single LED or photodiode at the receiver side we
achieve the bit error rate smaller than SISO system but
not smaller than MIMO system. In the next case of
MIMO system,i.e.using arrays of LED at the transmitter
side and arrays of LED or photodiode at the receiver side
we get a very smaller BER when we compared to SISO
and MISO system and it proved that VLC is adaptable for
MIMO configuration and it give best results when we
compared to all other system configurations.
Following assumptions are made for the
simulated results
Channel: AWGN
Modulation technique used: OPPM
ANTENNA SIZE: 2*2 for MIMO
1*1 for SISO
2*1 for MISO
V. DISCUSSIONS
We analysed the Performances of OOK and OPPM
signals by investigating the cutoff data rate and Bit Error
Rate analysis of various modulation techniques. We
proved that OPPM signal has the smallest and constant
flicker severity under all dimming levels spanning a
reasonably large brightness dimming range. This
modulation scheme also provided the largest and steady
cutoff data rate. OPPM appears as the desirable
modulation solution to emerging LED-based high
capacity visible light communication.
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