ISO/IEC 30140-1:2018

ISO/IEC 30140-1
Edition 1.0 2018-02
INTERNATIONAL
STANDARD
Information technology – Underwater acoustic sensor network (UWASN) –
Part 1: Overview and requirements

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ISO/IEC 30140-1
Edition 1.0 2018-02
INTERNATIONAL
STANDARD
Information technology – Underwater acoustic sensor network (UWASN) –

Part 1: Overview and requirements

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 35.110 ISBN 978-2-8322-5372-4

– 2 – ISO/IEC 30140-1:2018 © ISO/IEC 2018
CONTENTS
FOREWORD . 5
INTRODUCTION . 6
1 Scope . 7
2 Normative references . 7
3 Terms and definitions . 7
4 Abbreviated terms . 9
5 UWASN overview and applications . 9
5.1 Overview. 9
5.2 Application domain of UWASN . 11
6 Characteristics of UWASN in terms of the effects of propagation variability . 12
6.1 Underwater acoustic communication . 12
6.2 Acoustic signal strength attenuation . 12
6.3 High propagation delay . 12
6.4 Multipath . 13
6.5 Propagation loss . 13
6.6 Noise . 14
7 Differences between UWASN and terrestrial sensor network . 14
7.1 Types of underwater communication technologies . 14
7.2 Housing case . 16
7.3 Costs associated with sensor nodes . 16
7.4 Omni-directional and directional transducers for data transmission and
reception . 16
7.5 Underwater object and event localization and 3D relay node . 17
7.6 Energy harvesting technology for UWASN . 18
8 Specificities of UWASN and related requirements . 18
8.1 Three structural scales of UWASN network . 18
8.2 Deployments of 2D and 3D topology . 21
8.2.1 General . 21
8.2.2 Two-dimensional UWASN architecture . 21
8.2.3 Three-dimensional UWASN architecture . 22
8.3 Cross layering . 24
8.4 Underwater acoustic modem . 25
8.5 Doppler spread . 25
8.6 Deployment considering water depths . 26
8.7 Underwater wired and wireless communication . 26
8.8 Time synchronization . 27
8.9 Data transmission period for energy saving . 28
8.10 Routing . 29
8.11 Network coding . 31
8.12 Data compression . 31
8.13 Delay and disruption tolerant network (DTN) . 31
9 UWASN further general requirements . 32
9.1 General . 32
9.2 General requirements for UWASN – Cross layering . 32
9.3 General requirements for the UWASN – Communication technology . 32
9.4 General requirements for the UWASN – Other system requirements . 33

Annex A (informative) Selected applications of UWASN . 34
A.1 Environmental monitoring – Chemical and biological changes . 34
A.1.1 Description . 34
A.1.2 Physical entities . 35
A.1.3 Normal flow . 35
A.1.4 Conditions . 35
A.2 Detection of pipeline leakages . 35
A.2.1 Description . 35
A.2.2 Physical entities . 36
A.2.3 Normal flow . 36
A.2.4 Conditions . 37
A.3 Exploration of natural resources . 37
A.3.1 Description . 37
A.3.2 Physical entities . 38
A.3.3 Normal flow . 38
A.3.4 Conditions . 39
A.4 Fish farming . 39
A.4.1 Description . 39
A.4.2 Physical entities . 40
A.4.3 Normal flow . 40
A.4.4 Conditions . 40
A.5 Harbour security . 40
A.5.1 Description . 40
A.5.2 Physical entities . 41
A.5.3 Normal flow . 41
A.5.4 Conditions . 42
Bibliography . 43

Figure 1 – Overview of a UWASN . 10
Figure 2 – Omni-directional and directional transducers for data transmission and
reception . 17
Figure 3 – Underwater cluster network . 18
Figure 4 – Underwater ad-hoc network. 19
Figure 5 – UWA-UN communication network . 19
Figure 6 – UWA-UN communication network using fixed gateway . 20
Figure 7 – UWA-EUN communication network . 21
Figure 8 – Two-dimensional UWASN architecture . 22
Figure 9 – Three-dimensional UWASN architecture . 23
Figure 10 – UWA-cross layer protocol stack . 25
Figure 11 – Underwater wired and wireless communication . 27
Figure 12 – Time synchronization for data transmission . 28
Figure 13 – Using active and sleep modes for energy saving . 29
Figure 14 – UWASN routing . 30
Figure A.1 – Illustration of the environmental monitoring use case . 34
Figure A.2 – Oil and gas pipeline leakage monitoring use case . 36
Figure A.3 – Flow – Oil and gas pipeline leakage monitoring . 37

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Figure A.4 – Underwater resource exploration use case . 38
Figure A.5 – Fish farming and monitoring use case . 39
Figure A.6 – Harbour security monitoring use case . 41

Table 1 – UWASN market segments and their current and future applications list . 11
Table 2 – Summary of the features of acoustic, radio, and optical waves in seawater
environments . 15
Table 3 – Differences between underwater communication technologies [10][12] . 15
Table 4 – Comparison between 2D and 3D UWASNs. . 24

INFORMATION TECHNOLOGY –
UNDERWATER ACOUSTIC SENSOR NETWORK (UWASN) –

Part 1: Overview and requirements

FOREWORD
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International Standard ISO/IEC 30140-1 was prepared by subcommittee 41: Internet of Things
and related technologies, of ISO/IEC joint technical committee 1: Information technology.
The list of all currently available parts of the ISO/IEC 30140 series, under the general title
Information technology – Underwater acoustic sensor network (UWASN), can be found on the
IEC and ISO websites.
This International Standard has been approved by vote of the member bodies, and the voting
results may be obtained from the address given on the second title page.
This document has been drafted in accordance with the ISO/IEC Directives, Part 2.

– 6 – ISO/IEC 30140-1:2018 © ISO/IEC 2018
INTRODUCTION
Water covers approximately 71 % of the surface of the Earth. Modern technologies introduce
new methods to monitor the body of water, for example pollution monitoring and detection.
Underwater data gathering techniques require exploring the water environment, which can be
most effectively performed by underwater acoustic sensor networks (UWASNs). Applications
developed for the UWASNs can record underwater climate, detect and control water pollution,
monitor marine biology, discover natural resources, detect pipeline leakages, monitor and
locate underwater intruders, perform strategic surveillance, and so on.
The ISO/IEC 30140 series provides general requirements, reference architecture (RA)
including the entity models and high-level interface guidelines supporting interoperability
among UWASNs in order to provide the essential UWASN construction information to help
and guide architects, developers and implementers of UWASNs.
Additionally, the ISO/IEC 30140 series provides high-level functional models related to
underwater sensor nodes and relationships among the nodes to construct architectural
perspective of UWASNs. However, the ISO/IEC 30140 series is an application agnostic
standard. Thus, ISO/IEC 30140 series specifies neither any type of communication waveforms
for use in UWASNs nor any underwater acoustic communication frequencies. Specifying
communication waveforms and/or frequencies are the responsibility of architects, developers
and implementers.
Acoustical data communication in sensor networks necessitates the introduction of acoustical
signals that overlap biologically important frequency bands into the subject environment.
These signals may conflict with regional, national, or international noise exposure regulations.
Implementers of acoustical communication networks should consult the relevant regulatory
agencies prior to designing and deployment of these systems to ensure compliance with
regulations and avoid conflicts with the agencies.
The purpose of the ISO/IEC 30140 series is to provide general requirements, guidance and
facilitation in order for the users of the ISO/IEC 30140 series to design and develop the target
UWASNs for their applications and services.
The ISO/IEC 30140 series comprises four parts as shown below.
Part 1 provides a general overview and requirements of the UWASN reference architecture.
Part 2 provides reference architecture models for UWASN.
Part 3 provides descriptions for the entities and interfaces of the UWASN reference
architecture.
Part 4 provides information on interoperability requirements among the entities within a
UWASN and among various UWASNs.
___________
Architects, developers and implementers need to be aware of the submarine emergency frequency band, near
and below 12 kHz, and it is recommended to provide a provision for such submarine emergency band in their
UWASN design and applications.

INFORMATION TECHNOLOGY –
UNDERWATER ACOUSTIC SENSOR NETWORK (UWASN) –

Part 1: Overview and requirements

1 Scope
This part of ISO/IEC 30140 provides a general overview of underwater acoustic sensor
networks (UWASN). It describes their main characteristics in terms of the effects of
propagation variability and analyses the main differences with respect to terrestrial networks.
It further identifies the specificities of UWASN and derives some specific and general
requirements for these networks.
2 Normative references
The following documents are referred to in the text in such a way that some or all of their
content constitutes requirements of this document. For dated references, only the edition
cited applies. For undated references, the latest edition of the referenced document (including
any amendments) applies.
ISO/IEC 29182-2, Information technology – Sensor networks: Sensor Network Reference
Architecture (SNRA) – Part 2: Vocabulary and terminology
3 Terms and definitions
For the purposes of this document, the terms and definitions given in ISO/IEC 29182-2 and
the following apply.
ISO and IEC maintain terminological databases for use in standardization at the following
addresses:
• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
ad-hoc node
device in a wireless ad-hoc network
Note 1 to entry: A wireless ad-hoc network is defined in ISO/IEC 27033-6:2016[1], 3.12, as a “decentralized
wireless network which does not rely on a pre-existing infrastructure”.
3.2
cross-layer
technology that permits communication between different layers by allowing one layer to
access data of another layer to exchange information and enable interaction
3.3
management cross-layer
technology that provides a system-level management service to all or selected OSI layers in a
wireless network system
___________
Numbers in square brackets refer to the Bibliography.

– 8 – ISO/IEC 30140-1:2018 © ISO/IEC 2018
Note 1 to entry: Examples of management cross-layer are device management cross-layer, network management
cross-layer, QoS management cross-layer, security management cross-layer, localization management cross-layer,
power management cross-layer, etc.
3.4
underwater acoustic fundamental network
UWA-FN
wireless communication network that is built either exclusively using one or more cluster
networks or exclusively using one or more ad-hoc networks for underwater environment using
acoustic modems
Note 1 to entry: Fundamental network consists of only one network type, either cluster network or ad-hoc network.
Note 2 to entry: Wireless acoustic communication and data links are realized using an acoustic modem.
Note 3 to entry: A modem is defined in ISO/IEC 2382:2015[2], 2124386, as a “functional unit that modulates and
demodulates signals”.
3.5
underwater acoustic united network
UWA-UN
wireless communication network that is made of two or more underwater acoustic
fundamental networks (3.4) and relay nodes
Note 1 to entry: A relay node is, for example, an unmanned underwater vehicle, communication node, beacon, etc.
3.6
underwater acoustic extended united network
UWA-EUN
wireless communication network that is made of two or more underwater acoustic united
networks (3.5)
3.7
underwater acoustic sensor node
UWA-SNode
sensor network element that includes at least one sensor and, optionally actuators with
communication capabilities and data processing capabilities, which is built for underwater
applications using acoustic modem as a communication unit internal to this element
Note 1 to entry: Wireless acoustic communication and data links are realized using an acoustic modem.
Note 2 to entry: A modem is defined in ISO/IEC 2382:2015, 2124386, as a “functional unit that modulates and
demodulates signals”.
[SOURCE: ISO/IEC 29182-2:2013, 2.1.8 – modified: the original definition of sensor node is
adapted to an underwater acoustics context.]
3.8
underwater acoustic cluster head
UWA-CH
unit that receives data from underwater acoustic sensor nodes (3.7) and transmits the data to
one or more relay nodes or a nearby underwater acoustic gateway (3.9)
3.9
underwater acoustic gateway
UWA-GW
unit connecting different underwater networks or parts of one underwater network and
performing any necessary protocol translation in underwater environment using acoustic
modem
[SOURCE: ISO/IEC TR 29108:2013, 3.1.88.3 – modified: the original definition is adapted to
an underwater acoustics context.]

4 Abbreviated terms
2D two dimensional
3D three dimensional
BER bit error rate
DG distance group
DTN delay and disruption tolerant network
EM electromagnetic wave
EMI electromagnetic interference
GPS global positioning system
kbps kilobits per second
LED light emitting diode
µPa Micropascal
Mbps megabits per second
MCCP minimum cost clustering protocol
QoS quality of service
RF radio frequency
RSS received signal strength
UUV unmanned underwater vehicle
UWASN underwater acoustic sensor network
UWA-CH underwater acoustic cluster head
UWA-DTN underwater delay tolerant network
UWA-DTN-GW underwater DTN gateway
UWA-EUN underwater acoustic extend united network
UWA-FN underwater acoustic fundamental network
UWA-GW underwater acoustic gateway
UWA-SNode underwater acoustic sensor node
UWA-UN underwater acoustic united network
5 UWASN overview and applications
5.1 Overview
Figure 1 shows the basic topology of UWASN. In a cluster-based network, the data sensed by
underwater acoustic sensor nodes (UWA-SNodes) are transmitted via acoustic
communication to an underwater acoustic gateway (UWA-GW) using an underwater acoustic
cluster head (UWA-CH), unmanned underwater vehicle (UUV), or relay nodes. Users receive
the transmitted data through various externally connected networks (e.g. radio frequency (RF)
or satellite communication). During these processes, underwater communication is
implemented by acoustic communication. In general, UWA-GWs are either moving nodes or
fixed nodes. Topologies and communication configuration models could be adaptively
modified according to the application domain’s needs at any given time.

– 10 – ISO/IEC 30140-1:2018 © ISO/IEC 2018

IEC
Key
1 Internet 6 Surface 11 UWA-DTN-GW 16 UWA-SNode
2 Satellite 7 RF 12 Acoustic link 17 Ad-hoc network
3 Base station 8 UWA-GW 13 Relay node 18 UUV
4 RF link 9 Buoy 14 Cluster 19 UWA-CH
5 Moving gateway 10 Fixed gateways 15 Underwater 20 User

Figure 1 – Overview of a UWASN
RF communication systems are used in terrestrial sensor networks. The reasons for this are
their high efficiency and low cost. Underwater RF communication is very difficult due to limited
wave propagation characteristics that arise from the high attenuation due to the conductivity
of water. Underwater communications can also be achieved by optical links employing lasers
or LED light sources. Optical waves are still affected by attenuation, but can typically operate
over longer ranges than RF.
Diode laser beams and low cost light sources such as LEDs can also be utilized. A light
source for an underwater communications system is practicable using LEDs with an optical
wavelength between 400 nm and 550 nm.[3]
Presently, underwater acoustic communication is the primary method for establishing wireless
communication among UWA-SNodes, UUVs and UWA-GWs. This is because sound travels
much further in water than RF radio signals. A UWASN consists of different types of

UWA-SNodes and UUVs positioned so as to perform collective underwater monitoring.
UWA-SNodes and UUVs are organized autonomously into a network that should adapt to
changing ocean environments over time.[4]
UWA-SNodes are applicable to pollution monitoring, oceanographic information gathering,
strategic observation, assisted navigation, offshore examination, and disaster prevention.
Several UUVs with equipped sensors explore underwater resources and gather precise
location information. To make this possible, reliable underwater communication between
UWA-SNodes and UUVs is required.
UWA-SNodes and UUVs should have self-configuration capabilities that allow them to network
themselves. They should manage the operations by sharing location information,
configurations, and movements, in order to send monitored data to an on-shore location.
5.2 Application domain of UWASN
A UWASN can realize unexplored underwater applications, increasing the capacity for
detecting and forecasting changes in time-varying oceanic environments. Table 1 shows the
UWASN market segments and their current and future potential applications.
Annex A provides a description of the selected application of UWASN.
Table 1 – UWASN market segments and their current and future applications list
Market segment Description
Early warning system for detection of disasters and tsunami, and providing
warnings
Studying the effects of oceanic earthquakes (seaquakes)
Climate recording
Pollution control
Scientific applications
Oil/gas fields exploration
Detecting climate change
Improving weather forecasting
Studying marine biology
Ocean circulation studies
Discovery of natural resources
Temperature monitoring in runtime
Business applications Chemical and biological changes
Detection of pipeline leakages
Seismic monitoring allowing reservoir management approaches
Assisted navigation
Identifying hazards in the seabed
Identifying submerged wrecks
Identify the mooring positions
Civilian applications
Underwater hazard avoidance
Defining seabed pipeline routes
Identifying underwater oilfields
Defining paths for the layering of underwater cables
Aquaculture and farming
Aqua applications
Remote control-monitoring of costly devices

– 12 – ISO/IEC 30140-1:2018 © ISO/IEC 2018
Market segment Description
Strategic surveillance
Monitoring port facilities
Securing foreign harbours
Military applications Mine countermeasures
Submarine monitoring
Intruder detection
Ocean bottom imaging and mapping

6 Characteristics of UWASN in terms of the effects of propagation variability
6.1 Underwater acoustic communication
Underwater acoustic communication method is used for underwater data transfer. It can
establish acoustic communication with the help of transducers. Due to time variations of the
channel, limited bandwidth, multipath propagation, and strong signal attenuation, underwater
communication is difficult. Because of the high conductivity of seawater, acoustic
communication works far better than the RF communication.
Concerns that should be examined while planning UWASN system are:
– attenuation of water limits sound’s propagation distance;
– path dependent, low propagation speeds of the sound, varying in the interval of
(1 500 ± 120) m/s;
– echoes and interferences caused by multipath(s) due to sea bottom and sea surface
reflections, as well as between the layers of water body with different densities;
– acoustic signal disturbed by different characteristics of underwater channel and Doppler’s
effect not only from motion of transmitter and receiver but also from time-variability of the
surface and water column [5];
– noise level in underwater can corrupt or block parts of signal.
Sound is produced when an object vibrates and transmits motion to the surrounding physical
medium. This results in the propagation of vibrations, where the particles in the medium
oscillate in the same direction as the propagation.
6.2 Acoustic signal strength attenuation
A sound’s intensity is reduced with distance through the medium in which it travels. In
idealized materials, a sound’s signal amplitude weakness because of wave spreading.
Attenuation is another reason for weakening of sound.
a) Absorption
Converting sound energy into some other form is called absorption. Acoustic waves are
converted to heat due to absorption [6].
b) Sound speed profiles
The speed of sound in water depends on several parameters such as temperature, salinity
and pressure [7]. In general, sound speed in water increases with increasing water
temperature, salinity and pressure.
6.3 High propagation delay
Sound’s slow underwater propagation speed can be differentiated from electromagnetic
propagation. Sound's underwater speed is influenced by underwater properties such as
pressure, salinity, and temperature, which are openly associated with depth. The salinity of all

shallow seawater associated with rivers, and some seawater with ice in the Antarctic or Arctic,
can change. Near the sea surface, sound’s underwater speed is more than four times faster
than its speed in air.
The bending of a sound signal is caused by underwater inhomogeneity characteristics. This
commonly occurs in the vertical way because of three factors: (1) water temperature changes
due to the non-uniform heating by the sun’s rays, (2) salt concentration changes, and (3)
hydrostatic pressure changes due to depth. The sound curvature direction is influenced by the
sound velocity distribution of the medium. Sound signals are bent downward in summer
because the upper layers of water are warmer than lower layers. Sound signals are bent
upward in winter because the temperature of lower water is retained. Therefore, the range of
sound propagation is greater in winter than in summer.
6.4 Multipath
In underwater environment, the signal propagates from the transmitter to the receiver via
either direct or multipath propagation. Additionally, the mechanisms of the multipath formation
in the ocean depend on channel geometry, signal frequency, sound speed profile, range of
transmission, and depth of water.
Owing to reflection or refraction of the acoustic waves, there would likely be underwater
multipath(s) of acoustic waves. As acoustic waves bounce, either at the surface or bottom of
the sea or from water turbulence, and reach the receiver, reflections of the acoustic waves
occur, resulting in multipath propagation of the acoustic waves. This kind of reflection is
common in shallow water. Acoustic wave refractions usually occur in deep water environment,
where the speed of sound changes with depth.
Since horizontal communication takes place in underwater, multipath propagation should be
considered. Water surface reflections, bottom reflections, and water turbulence reflections
can generate the multipath. To reduce multipath effects, directional remote transducers can
be used. However, if there are obstacles nearby, the modem will experience dynamic
multi-pathing that is rapidly fluctuating due to reflections, and the performance of the modem
drops dramatically. Therefore, the multipath powers a constant trade-off between a modem’s
cost and its reliability [8].
6.5 Propagation loss
Propagation loss is collective impact of attenuation, absorption loss, and geometric spreading.
In water, sound travels more than four times quicker than in air. Sounds are transmitted as a
pressure wave in water, like in open air. Sound pressure is measured in decibels (dB) with
reference to one micropascal (µPa). The noise sources in UWASN channels are separated
into ambient noise and man-made noise.
– Attenuation
Attenuation is created through absorption while transforming acoustic energy to heat. It is
increased by frequency and distance. At a rough ocean bottom and surface, attenuation is
initiated by scattering. Attenuation is also started by refraction and is also influenced by
water depth.
– Geometric spreading
This is the spreading of sound energy by waves. It is frequency independent and
increases with propagation distance. The common geometric spreading approximations
are cylindrical spreading and spherical spreading.

– 14 – ISO/IEC 30140-1:2018 © ISO/IEC 2018
6.6 Noise
There are two types of noise sources in UWASN channels: (1) ambient noise; and
(2) man-made noise.
1) Ambient noise
This is associated with the seismic and biological activities of water, and it is also related
to water movement due to rain, wind, storms, etc.
Ambient noise affects the received signal-to-noise ratio (SNR) and also affects the
required transmitter power. UWASN should consider these situations. Ambient noise in the
monitoring water body should be considered for selecting receivers due to its impact on
the received SNR and for sizing transmitter power [9].
2) Man-made noise
In water, man-made noises are produced by shipping activity and various kinds of
underwater devices such as pumps. Marine worksites locations have more noise.
7 Differences between UWASN and terrestrial sensor network
7.1 Types of underwater communication technologies
The design of the underwater communication system should consider the multipath and
limited bandwidth of the underwater medium. Current underwater communication systems use
optical, radio or acoustic transmission. Depending on application and design requirements,
these methods have advantages and limitations.
a) Acoustic waves:
In underwater environments, because of lower attenuation compared to air, acoustic
waves are used for communication. Underwater acoustic wave usage is affected by the
multipath, water temperature, and ambient noise. Nevertheless, the currently favourable
technique is to use acoustics for underwater communication [10].
b) Radio waves:
Radio waves are electromagnetic waves. The underwater speed of EM waves is
approximately 200 000 times faster than acoustics; for this reason, network latency is
impressively compact. EM waves are not sensitive compared with acoustics for multipath
effects in shallow water [11].
RF can work underwater only for short distances; for long distance underwater
communication, radio waves cannot work efficiently.
c) Optical waves:
Free-space optical (FSO) waves in the blue-green wavelengths contain 10 Mbps to
150 Mbps of high-bandwidth communication in the 10 m to 100 m or longer range.
The important features of optical, acoustic, and radio waves for a UWASN in a seawater
environment are given in Table 2 [6].

Table 2 – Summary of the features of acoustic, radio,
and optical waves in seawater environments
Feature Acoustic Radio Optical
Attenuation Low Moderate High
Effective range several kilometres several metres several metres
Propagation delay High Low Low
Bandwidth-limited
Power-limited
Heavy constraints Interference-limited Environment-limited
Environment-limited.
Environment-limited.
Table 3 shows the benefits and limitation of three underwater communication technologies
using the three types of waves introduced in Table 2.
Table 3 – Differences between underwater communication technologies [10][12]
Technology Benefits Limitations
High bandwidth at very close range Range is limited in water
Simply able to cross seabed, air, and water Has limited wave propagation
boundaries characteristics that arise from the high
RF attenuation due to the conductivity of water
Not affected by turbidity and pressure gradients
Works in non-line-of-sight, not affected by
sediments and aeration
Range is up to some kilometres While transmitting by air or underwater,
heavy reflections and attenuation
Verified technology
Limited bandwidth
Acoustic
Unfavourably affected by salinity, pressure,
and ambient noise gradients
Performance is poor in shallow water
Very high bandwidth Easily transmitted by air or underwater
Vulnerable to particles, turbidity, and
marine fouling
Optical
Requires line-of-sight
Small range
Additional information to identify the differences between the underwater transmission media
mentioned in Table 3 is as follows.
Low bandwidth: This is an important factor in UWASN. The multipath, noise, transmission loss,
Doppler spread, and high propagation delay markedly affect underwater communication. The
above issues control the variability of the underwater medium, which makes the medium
bandwidth both limited, and intensely reliant on the frequency and range. Systems that are
short range and operating over 10 m may require 100 kHz of bandwidth more, but lengthy
range systems operating at more than 10 km may require bandwidth of a few kilohertz.
Range can be a factor in classifying underwater acoustic communication links.
Data rate: Instead of electromagnetic waves like terrestrial networks, UWASN use acoustic
waves. For this reason, as compared to terrestrial networks, data rates are low in a UWASN.

– 16 – ISO/IEC 30140-1:2018 © ISO/IEC 2018
7.2 Housing case
A waterproof housing case is needed for UWA-SNodes for preventing corrosion and failure
(see 9.4).
7.3 Costs associated with sensor nodes
The deployment cost of a UWA-SNode is very high compared to terrestrial sensor node and
battery change is also required for reuse. Most of the UWA-SNodes except disposable nodes
require nodes replacement technology, known as node reclamation [13].
7.4 Omni-directional and directional transducers for data transmission and reception
In a UWASN, omni-directional and directional transducers are needed for data between the
transmitter and receiver. The underwater cluster network is a small network and uses the
omni-directional transducer as shown in Figure 2.
The directional transducer has limitations in terms of mobility. This transducer radiates
equally and receives equally in all directions of the cluster. Underwater relay nodes using the
directional transducer by which the data is received from the UWA-CH are transmitted toward
the UWA-GW. This is because the communication link between the
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