Underwater Wireless Communication”,

JIEMS, AKKALKUWA Department of Computer
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APPROVED BY AICTE, NEW DELHI & AFFILIATED TO NORTH
MAHARASHTRA UNIVERSITY, JALGAON CERTIFIED BY ISO 9001:2008
Jamia Institute of Engineering & Management
Studies, Akkalkuwa
.
Department of Computer Engineering
Seminar report on
“Underwater Wireless Communication”
Presented by
Mr. Saba Karim
[BE COMPUTER]
For the academic year 2018-19
Under the guidance of
Mr. Sk. Sharique Ahmad

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Jamia Institute of Engineering & Management
Studies, Akkalkuwa
CERTIFICATE
This is to certify that the seminar report of seminar entitled,
“Underwater Wireless Communication”, being submitted by Mr. Saba Karim
to Computer Engineering Department is a record of bonafied work carried out
by him under my supervision and guidance during year 2018-2019.
Date:
Place:
Seminar Guide Head of Department
[Mr. Sharique Ah] [Prof. Patel Suhel Ishaq]
I/c Principal
[Prof. Saiyed Irfan]

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ACKNOWLEDGEMENT
I take this opportunity to express my heartfelt gratitude towards the Department of
Computer Engineering, JIEMS, Akkalkuwa that gave me an opportunity for
presentation of my seminar.
It is a privilege for me to have been associated with Mr. Sharique Ahmad, my
guide during this seminars work. I have been greatly benefited by his valuable
suggestions and ideas. It is with great pleasure that I express my deep sense of gratitude
to him for his valuable guidance, constant encouragement and patience throughout this
work.
I express my gratitude to Prof. Patel Suhel I [HOD of CO] for his constant
encouragement, co-operation, and support and also thankful to all friends and my
family who have contributed in their own way in making this seminar success.
I take this opportunity to thank all our classmates for their company during the
course work and for useful discussion I had with them.
Under these responsible and talented personalities, I am efficiently able to
complete seminar in time with success..
Mr. Saba Karim
(B.E. CO)

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Table of Content
SR
NO.
CONTENT
PAGE
NO
1. Abstract 3
2. Introduction 4
3. History 5
4. Necessity of UWC 6
5. Methodology 7
6. Communication channel 7
7. Wave Propogation 7-9
8. Acoustic modem 10
9. Under water networks 11-14
10. Application 15
11. Hardware Platform 15
12. Advantages 16
13. Disadvantages 16
14. Conclusion 17
15. References 18

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Chapter 1: - Abstract
While wireless communication technology today has become part of our daily life,
the idea of wireless undersea communications may still seem far-fetched. However, research
has been active for over a decade on designing the methods for wireless information
transmission underwater. Human knowledge and understanding of the world’s oceans, which
constitute the major part of our planet, rests on our ability to collect information from remote
undersea locations.
The major discoveries of the past decades, such as the remains of Titanic, or the
hydro-thermal vents at bottom of Deep Ocean, were made using cabled submersibles.
Although such systems remain indispensable if high-speed communication link is to exists
between the remote end and the surface, it is natural to wonder what one could accomplish
without the burden (and cost) of heavy cables.
Hence the motivation and interest in wireless underwater communications. Together
with sensor technology and vehicular technology, wireless communications will enable new
applications ranging from environmental monitoring to gathering of oceanographic data,
marine archaeology, and search and rescue missions.

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Chapter 2: Introduction
While wireless communication technology today has become part of our daily life, the
idea of wireless undersea communications may still seem far-fetched. However, research has
been active for over a decade on designing the methods for wireless information transmission
underwater. Human knowledge and understanding of the world’s oceans, which constitute
the major part of our planet, rests on our ability to collect information from remote undersea
locations.
The major discoveries of the past decades, such as the remains of Titanic, or the hydro-
thermal vents at bottom of deep ocean, were made using cabled submersibles. Although such
systems remain indispensable if high-speed communication link is to exists between the
remote end and the surface, it is natural to wonder what one could accomplish without the
burden (and cost) of heavy cables.
Hence the motivation, and interest in wireless underwater communications. Together with
sensor technology and vehicular technology, wireless communications will enable new
applications ranging from environmental monitoring to gathering of oceanographic data,
marine archaeology, and search and rescue missions.

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Chapter 3: History
The science of underwater acoustics began in 1490, when Leonardo Da Vinci, stated.
In 1687 Isaac Newton wrote his Mathematical Principles of Natural Philosophy which
included the first mathematical treatment of sound in water.
In 1877 Lord Rayleigh wrote the Theory of Sound & established modern acoustic
theory.
In 1919, the first scientific paper on underwater acoustics was published.
Many advances in underwater acoustics were made which were summarized later in
the series Physics of Sound in the Sea, published in 1946.
After world war two, the development of sonar systems was driven largely by the
cold war, resulting in advances in the theoretical & practical understanding of underwater
acoustics, aided by computer based techniques.

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Chapter 4: Necessity of UWC
• Wired underwater is not feasible in all situations as shown below-:
• Temporary experiments
• Breaking of wires
• Significant cost of deployment
• Experiment over long distances.
• To cope up with above situations, we require underwater wireless communication.
• With advances in acoustic modem technology, sensor technology and vehicular
technology, ocean engineering today is moving towards integration of these
components into autonomous underwater networks
• The signals that are used to carry digital information through an underwater
channel are not radio signals, as electro-magnetic waves propagate only over
extremely short distances.
• This dependence severely limits the available bandwidth: for example, at
distances on the order of 100 km, the available bandwidth is only on the order of 1
kHz.

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Chapter 5: Methodology
1. Communication channel:
The signals that are used to carry digital information through an underwater channel
are not radio signals, as electro-magnetic waves propagate only over extremely short
distances. Instead, acoustic waves are used, which can propagate over long distances.
However, an underwater acoustic channel presents a communication system designer with
many difficulties.
The three distinguishing characteristics of this channel are frequency-dependent
propagation loss, severe multipath, and low speed of sound propagation. None of these
characteristics are nearly as pronounced in land-based radio channels, the fact that makes
underwater wireless communication extremely difficult, and necessitates dedicated system
design.
2. Wave propogation:
Fig. 1: Shallow water multipath propagation: in addition to the direct path, the signal propagates via
reflections from the surface and bottom.

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Path loss that occurs in an acoustic channel over a distance d is given as A=dka(f)d, where k
is the path loss exponent whose value is usually between 1 and 2, and a(f) is the absorption
factor that depends on the frequency.
This dependence severely limits the available bandwidth: for example, at distances on
the order of 100 km, the available bandwidth is only on the order of 1 kHz. At shorter
distances, a larger bandwidth is available, but in practice it is limited by the transducer. Also
in contrast to the radio systems, an acoustic signal is rarely narrowband, i.e., its bandwidth is
not negligible with respect to the center frequency.
Fig. 2: Ensemble of channel impulse responses (magnitudes).
Within this limited bandwidth, the signal is subject to multipath propagation, which is
particularly pronounced on horizontal channels. In shallow water, multipath occurs due to
signal reflection from the surface and bottom, as illustrated in Figure 1.
In deep water, it occurs due to ray bending, i.e. the tendency of acoustic waves to
travel along the axis of lowest sound speed. Figure 2 shows an ensemble of channel
responses obtained in deep water. The multipath spread, measured along the delay axis, is on
the order of 10 ms in this example. The channel response varies in time, and also changes if
the receiver moves. Regardless of its origin, multipath propagation creates signal echoes,
resulting in inter symbol interference in a digital communication system.
While in a cellular radio system multipath spans a few symbol intervals, in an
underwater acoustic channel it can spans few tens, or even hundreds of symbol intervals! To
avoid the inter symbol interference, a guard time, of length at least equal to the multipath
spread, must be inserted between successively transmitted symbols.

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However, this will reduce the overall symbol rate, which is already limited by the
system bandwidth. To maximize the symbol rate, a receiver must be designed to counteract
very long inter symbol interference.
The speed of sound underwater varies with depth and also depends on the
environment. Its nominal value is only 1500 m/s, and this fact has a twofold implication on
the communication system design. First, it implies long signal delay, which severely reduces
the efficiency of any communication protocol that is based on receiver feedback, or hand-
shaking between the transmitter and receiver. To avoid this distortion, a non-coherent
modulation/detection must be employed. Coherent modulation/detection offers a far better
utilization of bandwidth, but the receiver must be designed to deal with extreme Doppler
distortion.
Summarizing the channel characteristics, one comes to the conclusion that an
underwater acoustic link combines in itself the worst aspects of radio channels: poor quality
of a land-mobile link, and high latency of a space link. In addition, current technology offers
limited transducer bandwidth (typically a few kHz, or few tens of kHz in a wideband
system), half-duplex operation, and limited power supply of battery-operated instruments.
.
Fig. 3: Multichannel adaptive decision-feedback equalizer (DFE) is used for high-speed underwater
acoustic communications.
It supports any linear modulation format, such as M-ary PSK or M-ary QAM

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3. Acoustic modem:
Acoustic modem technology today offers two types of modulation/detection:
frequency shift keying (FSK) with noncoherent detection and phase-shift keying (PSK) with
coherent detection. FSK has traditionally been used for robust acoustic communications at
low bit rates (typically on the order of 100 bps).
To achieve bandwidth efficiency, i.e. to transmit at a bit rate greater than the available
bandwidth, the information must be encoded into the phase or the amplitude of the signal, as
it is done in PSK or quadrature amplitude modulation (QAM). For example, in a 4-PSK
system, the information bits (0 and 1) are mapped into one of four possible symbols, ±1±j.
The symbol stream modulates the carrier, and the so-obtained signal is transmitted
over the channel. To detect this type of signal on a multipath-distorted acoustic channel, a
receiver must employ an equalizer whose task is to unravel the inter symbol interference.
Since the channel response is not a-priori known (moreover, it is time-varying) the equalizer
must ―learn‖ the channel in order to invert its effect. A block diagram of an adaptive
decision-feedback equalizer (DFE) is shown in Figure 3.
In this configuration, multiple input signals, obtained from spatially diverse receiving
hydrophones, can be used to enhance the system performance. The receiver parameters are
optimized to minimize the mean squared error in the detected data stream. After the initial
training period, during which a known symbol sequence is transmitted, the equalizer is
adjusted adaptively, using the output symbol decisions. An integrated Doppler tracking
algorithm enables the equalizer to operate in a mobile scenario.
This receiver structure has been used on various types of acoustic channels. Current
achievements include transmission at bit rates on the order of one kbps over long ranges (10-
100 nautical miles) and several tens of kbps over short ranges (few km) as the highest rates
reported to date. On a more unusual note, successful operation was also demonstrated over a

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basin scale (3000 km) at 10 bps, as well as over a short vertical channel at a bit rate in excess
of 100 kbps.
The multichannel DFE forms the basis of a high-speed acoustic modem implemented
at the Woods Hole Oceanographic Institution.
The modem, shown in Figure 4, is implemented in a fixed-point DSP, with a floating-
point co-processor for high-rate mode of operation. When active, it consumes about 3 W in
receiving mode, and 10-50 W to transmit.
The board measures 1.75 _ 5 in, and accommodates four input channels. The modem
has successfully been deployed in a number of trials, including autonomous underwater
vehicle (AUV) communications at 5 kbps.
Fig. 4: The WHOI micromodem has dual mode of operation: low

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4. Under water networks:
With advances in acoustic modem technology, sensor technology and vehicular
technology, ocean engineering today is moving towards integration of these components into
autonomous underwater networks. While current applications include supervisory control of
individual AUVs, and telemetry of oceanographic data from bottom-mounted instruments,
the vision of future is that of a ―digital ocean‖ in which integrated networks of instruments,
sensors, robots and vehicles will operate together in a variety of underwater environments.
Examples of emerging applications include fleets of AUVs deployed on collaborative
search missions, and ad hoc deployable sensor networks for environmental monitoring.
Fig. 5: Centralized network topology
Fig. 6: Decentralized network topology.

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Depending on the application, future underwater networks are likely to evolve in two
directions: centralized and decentralized networks. The two types of topologies are illustrated
in Figure 5 and Figure 6. In a centralized network, nodes communicate through a base station
that covers one cell. Larger area is covered by more cells whose base stations are connected
over a separate communications infrastructure.
The base stations can be on the surface and communicate using radio links, as shown
in the figure, or they can be on the bottom, connected by a cable. Alternatively, the base
station can be movable as well. In a decentralized network, nodes communicate via peer-to-
peer, multi-hop transmission of data packets. The packets must be relayed to reach the
destination, and there may be a designated end node to a surface gateway. Nodes may also
form clusters for a more efficient utilization of communication channel.
To accommodate multiple users within a selected network topology, the
communication channel must be shared, i.e. access to the channel must be regulated.
Methods for channel sharing are based on scheduling or on contention. Scheduling, or
deterministic multiple-access, includes frequency, time and code-division multiple-access
(FDMA, TDMA, CDMA) as well as a more elaborate technique of space-division multiple
access (SDMA).
Contention-based channel sharing does not rely on an a-priori division of channel
resources; instead, all the nodes contend for the use of channel, i.e., they are allowed to
transmit randomly at will, in the same frequency band and at the same time, but in doing so
they must follow a protocol for medium-access control (MAC) to ensure that their
information packets do not collide. All types of multiple-access are being considered for the
underwater acoustic systems.
Experimental systems today favor either polling, TDMA, or multiple-access collision
avoidance (MACA) based on a hand-shaking contention procedure that requires an exchange
of requests and clearances to send (RTS/CTS). Intelligent collision avoidance appears to be
necessary in an underwater channel, where the simple principle of carrier sensing multiple
accesses (CSMA) is severely compromised due to the long propagation delay—the fact that
the channel is sensed as idle at some location does not guarantee that a data packet is not
already in transmission at a remote location.

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One of the major aspects of the evolving underwater networks is the requirement for
scalability. A method for channel sharing is scalable if it is equally applicable to any number
of nodes in a network of given density. For example, a pure TDMA scheme is not scalable, as
it rapidly loses efficiency on an underwater channel due to the increase in maximal
propagation delay with the area of coverage.
In order to make this otherwise appealing scheme scalable, it can be used locally, and
combined with another technique for spatial reuse of channel resources. The resulting scheme
is both scalable and efficient; however, it may require a sophisticated dynamic network
management.
In contrast, contention-based channel allocation offers simplicity of implementation,
but its efficiency is limited by the channel latency. Hence, there is no single best approach to
the deployment of an underwater network. Instead, selection of communication algorithms
and network protocols is driven by the particular system requirements and
performance/complexity trade-offs.
Fig. 7: A deep-sea observatory.
Research today is active on all topics in underwater communication networks: from
fundamental capacity analyses to the design of practical network protocols on all layers of the
network architecture (including medium access and data link control, routing, transport
control and application layers) as well as cross-layer network optimization.
In addition to serving as stand-alone systems, underwater acoustic networks will find
application in more complex, heterogeneous systems for ocean observation. Figure 7 shows
the concept of a deep sea observatory.

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At the core of this system is an underwater cable that hosts a multitude of sensors and
instruments, and provides high-speed connection to the surface. A wireless network,
integrated into the overall structure, will provide a mobile extension, thus extending the reach
of observation. While we have focused on acoustic wireless communications, it has to be
noted that this will not be the only way of establishing wireless communication in the future
underwater networks.
Optical waves, and in particular those in the blue-green region, offer much higher
throughput (Mbps) albeit over short distances (up to about 100 m). As such, they offer a
wireless transmission capability that complements acoustic communication.

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Chapter 6: Application
 Future applications could enhance myriad industries, ranging from the
offshore oil industry to aquaculture to fishing industries, she noted. Additionally,
pollution control, climate recording, ocean monitoring (for prediction of natural
disturbances) and detection of objects on the ocean floor are other areas that
could benefit from enhanced underwater communications.
 Environmental monitoring to gathering of oceanographic data.
 Marine archaeology
 Search and rescue missions
 Defences

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Chapter 7: HARDWARE PLATFORM
 Sensor Interface:
 Must develop common interface with different sensors (chemical, optical,
etc.) and communication elements (transducer).
 Wide (constantly changing) variety of sensors, sampling strategies.
 Communication Interface: -
 Amplifiers, Transducers.
 Signal modulation
 Hardware:
 Software Defined Acoustic Modem (SDAM)
 Reconfigurable hardware known to provide, flexible, high
performance Implementations for DSP applications.

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Chapter 8: Advantages
 It can be used to provide the pre-warnings
 Of tsunamis by undersea earthquakes.
 Avoids data spoofing and privacy leakage.
 Can be used for monitoring underwater pollution and changes in habituates.
 Can be used to discover old and lost antiques undersea.

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Chapter 9:-Disadvantages
 Battery power is limited and usually batteries cannot be recharged also
because solar energy cannot be exploited.
 The available bandwidth is severly limited.
 Channel characteristics including long and variable propagation delays.
 Multipath and fading problems.
 High bit error rate.

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Conclusion
 In this topic we overviewed the main challenges for efficient communication in under
water acoustic sensor networks. We outlined the peculiarities of the under water
channel with particular reference to networking solutions the ultimate objective of
this topic is to encourage research efforts to lay down fundamental basics for the
development of new advanced communication techniques for efficient under water
communication and networking for enhanced ocean monitoring and exploration
applications
 The aim of this is to build a acoustic communication.
 This is not only the way for underwater communication.
 By using optical waves which offers higher throughput (Mbps) over short distances
(up to about 100 m).

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References
 [1] Underwater Wireless Optical Communication- Hemani Kaushal & Georges
Kaddoum
 Published in: IEEE Access ( Volume: 4 ) : Page(s): 1518 – 1547: Date of
Publication: 11
 April 2016 : Electronic ISSN: 2169-3536 Chitre, S. Shahabudeen, and M.
Stojanovic, "Underwater.
 [2] AcousticCommunications Networking: Recent Advances and
FutureChallenges,"Marine Technology Society Journal vol.Spring 2008,
page(s):103-116, 2008.
 [3] John heidemann, Milica Stojanovic and MicheleZorzi.‖Underwater Sensor
Networks:
 Applications, advances, andChallenges.‖Philosophical Transactions of the Royal
Society
 A.370, 1958), 158-175, Jan 2012.
 [4] Underwater AcousticWireless Sensor Networks: Advances and Future Trends
in Physical, MAC and Routing LayersSalvador Climent 1;*, Antonio Sanchez 1,
Juan Vicente Capella 1, Nirvana Meratnia 2and Juan Jose Serrano 1Received: 1
November 2013; in revised form: 24 November 2013 / Accepted: 27 November
2013 /Published: 6 January 2014.
 [5] www.ieee.org/organizations/pubs/newslette
rs/oes/html/spring06/underwater.html.
 [6] M. Stojanovic, J. Proakis, and J. Catipovic, ―Analysis of the impact of channel
estimation errors on the performance of a decision-feedback equalizer in fading
multipath channels,‖ IEEE Trans. Commun., vol. 43, pp. 877-886, Feb.Nar.lApr.
1995.
 [7] http://www.researchcorridor.com/underwater-wirelesscommunication-
market7.

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