Under Water Communication through Visible Light

Visible Light Communication (VLC) is a wireless method that uses LEDs to transfer information similar to Wi-Fi. VLC is a free-space optical wireless communication technology that uses visible light to transmit data across distances . VLC and Wi-Fi use electromagnetic waves for data trans

Project Title

Under Water Communication through Visible Light

Project Area of Specialization

Electrical/Electronic Engineering

Project Summary

Visible Light Communication (VLC) is a wireless method that uses LEDs to transfer
information similar to Wi-Fi. VLC is a free-space optical wireless communication technology
that uses visible light to transmit data across distances . VLC and Wi-Fi use
electromagnetic waves for data transmission . Wi-Fi uses radio waves. The radio waves
do not work underwater because of the conducting nature of the medium. It can penetrate
underwater to a few tens of meters. VLC uses visible light in the range of 100Mb/s.
Generally, VLC provides a fast data rate in the range of 500Mb/s .
Li-Fi was invented by Harald Haas, a German Professor at the University of Edinburgh. It is
a fast data transmitter because of the light velocity. Li-Fi (Light Fidelity) works on the
principle of Visible Light Communication. Li-Fi consists of LED light that forms a wireless
communication network. When an electrical current is passed to a LED light a stream of the
photon is ejected from the light. The Signal can be received by a photo-detector.
VLC transmission is the best alternate source of Wi-Fi. Radio waves are harmful to aquatic
species. Light sources are better for underwater data transmission. In underwater
communication, the role of Li-Fi is used for navigation, alert sea divers, prevent accidents,
audio and text transmission, image and video transmission. For deep-sea analysis, Li-Fi
is the most suitable choice. The data transmission in Li-Fi provides accurate results in the
dark place. The live data can be capture and transmitted to the receiver side.

In the Electromagnetic Spectrum, the frequency of the visible light ranges from 450THz to
750THz, and the radio frequency band of VLC is between 1Hz to 3THz. Li-Fi produces
data rates that should be higher than 1 GB/s which is faster than Wi-Fi. The properties of
visible light communication are the speed of light for best communication and greater
bandwidth. The system provides high-quality video transmission.
The modulated data can be transfer through white LEDs at the transmitter end. The
photodetector is placed at the receiver end it can demodulate the output. The data transfer
at the transmitter end can be accurately received at the receiver end. All the collected
information is stored in a folder to retrieve anytime and anywhere.

Project Objectives

In broad area of Wi-Fi Internet devices, most of the people are using 2.4-5GHz RF to deliver
wireless Internet access surrounded our offices, schools, home, and some public places
also. We become quite dependent upon these nearly ubiquitous services . While Wi-Fi
cover an entire house, school, the bandwidth is limited to 50-100 megabits per seconds
(Mbps). It is a mostly current Internet services, but insufficient for moving large data files
such as HDTV movies, music libraries and video games. The most of the dependent upon
the cloud or our own media services to store all of our files, including audio and video
devices, movies, photos, games, the more and most bandwidth and speed should be
needed to access this data. Hence RF-based technologies Wi-Fi are not the optimal way. In
addition, Wi- Fi may not be the most efficient way to provide new desired capabilities such
as gesture recognition and precision indoor positioning. The optical wireless technologies,
sometimes called visible light communication (VLC), and more recently referred to as Li-Fi.
On the other hand, offer an entirely new paradigm in wireless technologies in communication
speed, usability and flexibility, reliability. VLC is the possible solution to the global wireless
spectrum storage.LI-FI technology is a fast and cheap optic al version of Wi-Fi. It is a based
on Visible Light communication medium using Light between 4000 THZ to 375 THZ as
optical carrier for the data illumination. The data is encoded into light to generate data
stream by varying the flickering rate, to be clearer, by modulating the LED light with the data
signals, it illustrates the communication source. This is a whole new spectrum of
possibilities as compared to the radio waves spectrum and is 1000 times more in size radio
waves

Project Implementation Method

General working principle:

Light emitting diodes (LEDs) can be switched on and off faster than the human eye can detect since the operating speed of

LEDs is less than 1 ?s, thereby causing the light source to appear to be continuously on. This invisible on-off activity enables

data transmission using binary codes. Switching on an LED is binary ‘1’, switching it off is binary ‘0’. It is possible to encode

data in light by varying the rate at which LEDs flicker on and off to give different strings of 1s and 0s. Modulation is so rapid

that humans cannot notice it. A light sensitive device (photo detector) then receives the signal and converts it back into original

data.

This method of using rapid pulses of light to transmit information wirelessly is technically referred to as Visible Light

Communication (VLC).The term Li-Fi has been inspired due to its potential to compete with conventional Wi-Fi. The VLC uses

visible light between 400 THz (780 nm) and 800 THz (375 nm) as the optical carrier for data transmission and for illumination.

Data rates of greater than 100 Mbps can be achieved by using high speed LEDs with adequate multiplexing. Parallel data

transmission using arrays of LEDs where each LED transmits a separate stream of data can be used to increase the VLC data

rate. Though the lights have to be kept on in order to transmit data, they can be dimmed to the point that they are not visible to

humans but still be capable of transmitting data.

SYSTEM DESIGN

The overall block diagram of proposed system design is

shown in Figure 3. The communication system is designed

to support point-to-point in one direction. Tx-PC is used to

transmit data stream in the form of text in ASCII format.

The data stream is then sent to Tx microcontroller (Tx-?C).

The communication between Tx-PC and Tx-?C is performed

using a USB to UART converter. Tx-?C will modulate the

data received from the Tx-PC and perform data framing. The

modulated data will be fed to the analog front end transmitter

Benefits of the Project

(i) Underwater Explorations and Communications

Remotely operated underwater vehicles or ROVs work well except in situations when the tether is not long enough to fully

explore an underwater area or when they get stuck. If instead of the wires, light were used then the ROVs would be freer to

explore. With Li-Fi, the headlamps could also then be used to communicate with each other, data processing and reporting

findings back to the surface at regular intervals, while also receiving the next batch of instructions. Radio waves cannot be used

in water due to strong signal absorption. Acoustic waves have low bandwidth and disrupt marine life. Li-Fi offers a solution for

conducting short-range underwater communications.

(ii) Medical and Healthcare

Due to concerns over radiation, operating rooms do not allow Wi-Fi and even though Wi-Fi is in place in several hospitals,

interferences from computers and cell phones can block signals from medical and monitoring equipment. Li-Fi solves these

problems. Lights are an essential part of operating rooms and Li-Fi can thus be used for modern medical instruments. Moreover,

no electromagnetic interference is emitted by Li-Fi and thus it does not interfere with any medical instruments such as MRI

scanners.

(iii) Airlines and Aviation

Wi-Fi is often prohibited in aircrafts. However, since aircrafts already contain multiple lights, thus Li-Fi can be used for data

transmission.

(iv) Power Plants and Hazardous Environments

Wi-Fi is not suitable for sensitive areas like power plants. However, power plants still require fast and interconnected data

systems for monitoring grid intensity, demand, temperature etc. In place of Wi-Fi, Li-Fi can provide safe connectivity

throughout the power plant. Li-Fi offers a safe alternative to electromagnetic interference due to radio waves in environments

such as petrochemical plants and mines.

(v) Traffic

Li-Fi can be used for communications between the LED lights of cars to reduce and prevent traffic accidents. LED headlights

and tail-lights are being implemented for different cars. Traffic signals, signs and street lamps are all also transitioning to LED.

With these LED lights in place, Li-Fi can be used for effective vehicle-to-vehicle as well as vehicle-to-signal communications.

This would of course lead to increased traffic management and safety.

Technical Details of Final Deliverable

Hardware Design

The hardware part in the proposed system design is the

analog front end (AFE) at both transmitter and receiver. At

the transmitter, Tx-AFE comprises LED driver, while at the

reciver Rx-AFE consists of trans impedance ampli?er (TIA)

and comparator serving as signal conditioner. The technical

speci?cations of the white LED and photodiode used in our

experiment are shown in Table I.

TABLE I. TECHNICAL SPECIFICATIONS OF LED AND PHOTODIODE

Component Speci?cation

LED Voltage rating: 8-12 V

Power: 5 W

View angle: 120 ?

Luminuous intensity: 180-300 lx

Wavelength: 380-760 nm

Photodiode Spectral response: 400-1000 nm

Rise/fall time: 50 ?s

Cutoff frequency: 100 kHz

At the transmitter side, the LED driver is used to control

the LEDs for on off switching by a microcontroller. The LED

driver circuit used in this experiment is shown in Figure 4a.

Transistor Q2 is used to amplify the voltage as the output of

the microcontroller only 3.3 V while the LED voltage rating

of at least 8 V, whereas transistor Q1 is used to amplify the

current.

The analog circuit at the receiver side is used to condition

the output signal from the photodiode since the output signal

of the photodiode will experience attenuation and distortion.

For the output of the photodiode is electrical current, TIA

is necessary to convert the current into a voltage. Current

to voltage converter is made by the op-amp U1:B as shown

in Figure 4b. Once converted into a voltage, this signal

is fed to the comparator to overcome the distortion in the

signal. Potentiometer RV1 can be tuned manually to set the

comparator threshold. The output of the comparator is then

connected to the Rx-?C.

Software Design

The software part is designed for PC (as GUI) and mi-

crocontroller. The software designed for Tx-PC serves as an

interface with the user so that the user can enter the data in

form of text paragraph up to 1000 characters. In addition, it

also serves as a data ?ow controller so that the data stream to be transmitted does not accumulate on the microcontroller.

The software designed on Tx-?C consists of data buffer

(from Tx-PC), data covertion from ASCII into the bit stream,

data framing for synchronization, and data modulation. The

modulated data is then connected to the LED driver.

Final Deliverable of the Project

HW/SW integrated system

Core Industry

IT

Other Industries

Core Technology

Others

Other Technologies

Sustainable Development Goals

Life Below Water

Required Resources

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