RESEARCH PROPOSAL: UNDERWATER ACOUSTICS AND COMMUNICATION

LT CDR FARJAD DILDAR GHUMAN PN (P.No 7500)

 TABLE OF CONTENTS
1. INTRODUCTION
2. ABSTRACT
3. BACKGROUND
4. RESEARCH METHODOLOGY
5. SIMULATION OF UNDERWATER ACOUSTIC NETWORK USING AQUA-3D
VISUALIZATION TOOL IN UBUNTU 16.04 LTS
6. PROPOSED OPTIMIZED UNDERWATER ACOUSTIC NETWORK
7. PROPOSED 4D-UNDERWATER SENSOR NETWORK
8. BENEFITS OF THE PROPOSED TECHNIQUES FOR PN
9. CONCLUSION
10. RELEVANT PAST EXPERIENCE OF OFFICER
11. LIST OF REFERENCES
 RESEARCH PROPOSAL: UNDERWATER ACOUSTICS AND COMMUNICATION
LT CDR FARJAD DILDAR GHUMAN PN (P.No 7500)
INTRODUCTION
1. Underwater communication can be accomplished by three main possible methods
which include acoustic, RF and optical sources. Acoustic waves play an imperative role
in covering appreciable distances whereas RF energy could only cover more distances
in case of extra low frequencies from 30 to 300 Hertz [1] . Optical waves can travel in
blue-green regions, but are prone to attenuation and scattering, and are limited to
distances on the order of a few hundred meters [2] . Thus, acoustic waves is perhaps the
feasible solution for communicating underwater. Underwater acoustic communication has
multiple applications in commercial sector such as off-shore oil and gas industry, pollution
and climate monitoring in environmental systems, collection of scientific data recorded at
ocean-bottom stations, unmanned underwater vehicles, speech transmission between
divers and mapping of the ocean floor for detection of objects and discovery of new
resources. However, underwater acoustic communication channels have signal
dispersion in both time and frequency domain [3].

2. Underwater acoustic communication systems are evolving with scope of their

applications increasing in military sector. The real-time communications between
submarines, Unmanned Underwater Vehicles (UUVs) and different base stations can be
made free from wires to enhance their range of operations. Underwater wireless acoustic
communication is quite effective with the wireless connectivity containing multiple nodes
whether mobile or stationary deployed underwater for innumerable applications known as
Underwater Acoustic Network [4] . Wireless connectivity is enabled by the means of
acoustic modules deployed underwater. Acoustic modems in these deployed nodes can
sense the data as per application desired. In defense sector Underwater Acoustic
Network can enable us to perform undermentioned tasks particularly in ASW:
a. Underwater Intelligence Gathering
b. Underwater Reconnaissance
c. Maritime Security and Surveillance
d. Search and Rescue Operations
e. Climate Monitoring/Oceanography
f. Telemetry Systems
ABSTRACT
3. Underwater architecture of sensor networks and all its layers from physical to
application are adopting drastic changes with the advancement in military systems. An
underwater acoustic wireless sensors network can be simulated via different simulators
and is shown utilizing the Aqua-3D visualization tool in Ubuntu 16.04 LTS. In this proposal
an efficient physical layer of underwater sensor network is being proposed along with
localization technique for sensing nodes keeping time delay, energy consumption and
localization error to its minimum.
BACKGROUND
4. Communication in the underwater acoustic channel has always been a challenge
due to various factors. One of the main reasons is absorption of high frequency sounds
by the seawater which relentlessly degrades the available bandwidth. Additionally,
extended multi-paths, rapid time-variation, fading and Doppler shifts are also experienced
in underwater channels. Primitive underwater acoustic communications systems utilized
incoherent modulation techniques due to simplicity and reliability but these techniques
proved to be inefficient. Underwater acoustic communications involve all propagation
theories which are brought under consideration [5]. Transmission, reception and data
acquisition involves the bit error rate, throughput and bandwidth which are dependent
upon the modulation techniques [6].
5. The increasing role of PN in western AOR such as Gwadar, Ormara and Creeks
and advancement of PMSA along with formulation of RSS and LSS sites requires more
stringent security measures in underwater warfare to counter most of the imminent threats
such as mine deployment and hostile submarine. This can be effectively done with the
underwater sensor networks deployed on the coastal belt with its architecture layers
optimized and can be utilized for various applications.

RESEARCH METHODOLOGY
6. The subject research consists of following parts:
a) Simulation/designing of underwater acoustic network utilizing the Aqua-3D
visualization tool in Ubuntu 16.04 LTS on Aqua-sim underwater network simulator.
b). An efficient and up to date physical layer has been proposed which
incorporates the channel equalization, spatial modulation along with time reversal
mirrors and phase conjugation techniques which are fruitful for effective
underwater acoustic communication.
c). 4D underwater network sensor has also been proposed addressing the
inherent localization issues.
SIMULATION OF UNDERWATER ACOUSTIC NETWORK USING AQUA-3D
VISUALIZATION TOOL IN UBUNTU 16.04 LTS
7. After comparing in [7], the Aqua sim being the most viable option is chosen for
simulation of acoustic communication network. It enables us to visualize the data packet
collision in greater latency acoustic networks along with attenuation in propagation
channels. It supports 3D splitting of nodes and is an advanced block of NS-2 simulator
[8] .In setup phase, the sensing nodes are dynamically split at random locations and out
of the complete network few nodes are considered which enable the traffic to start and
send packet towards the node located at surface. Different routing protocols can be
selected and used to analyze the selected parameters. Traffic initialization and ending is
enabled with the help of random digit generator[8] .Simulation is run for several times and
finally the average is acquired to avoid errors in calculations. Metrics involved in
simulation are latency, reliability, throughput and energy utilized.
8. The simulation involves physical layer which includes attenuation and collisional
models. MAC layer involves Broadcast, Aloha, Tu (Modified T) and R-MAC (Reservation
based) protocols whereas the Network Layer protocols involved in aqua sim are vector
based routing, depth based routing and Hop by Hop vector based methods [9]. It contains
environmental, playback, control and information panel for its basic functionalities.
Moreover, six types of events of network can be visualized which include sending,
reception, dropping and collision of packets, enqueuer and dequeuer

Figure 1 Aqua 3D Visualization Environment [10]

Figure 2 Aqua 3D Graphical User Interface[10]

PROPOSED OPTIMIZED UNDERWATER ACOUSTIC NETWORK

9. An optimized underwater acoustic network with modernized solution for physical
layer is given as under:
a) Optimization and Modernized Solution for Physical Layer
In optimization of physical layer adaptive modulation techniques have been
utilized [11]. However, MIMO (Multiple Input Multiple Output) and OFDM
(Orthogonal Frequency Division Multiplexing) [12] amalgamation has proven to be
an effective solution which resolves the issues arising due to single carrier Inter
Symbol Interference. The approximate computing improving approximate
communications through deployment of Wireless Networks On Chip can increase
energy efficiency in MIMO-OFDM systems. The Doppler shift issues can be
lessened by null carriers with synchronization of the phases and consideration of
an adaptive approach amongst the OFDM blocks. Peak to average power ratio is
another issue lowering efficiency of amalgamated MIMO-OFDM systems which is
catered by initialization codes, targeted mapping techniques, clipping and proper
intrusion of interleaves. Channel estimation of the received signals of MIMO-
OFDM systems are improved by Minimum Mean Squared Error estimation. After
estimation for equalization technique Time Domain per tone equalization can be
inculcated for the maximization of the signal to interference noise ratio. For
detection the super detection techniques can be utilized and finally after acquiring
the information, the equalizer is used for the reliable detection [12] . Stepwise
analysis of MIMO-OFDM combined system is as follows:

1) Channel Equalization Long delay spread and a high Doppler

spread are issues faced in shallow water. Phase shift keying (PSK) along
with adaptive Decision Feedback Equalizers (DFE) and spatial diversity
combined are effective but computationally complex. The underwater
acoustic channel has a higher delay spread, the multipath are often non-
continuative. Hence utilizing a sparse equalizer with tap placement to
reduce the number of required taps may be consumed. This would lower
the complexity, track efficiently and magnify performance with Sparse
Partial Response Equalizers (SPRE) when combined with Belief
propagation (BP) detector, the inter-symbol interference (ISI) from the
SPRE can be utilized for multipath diversity. Blind DFE when combined with
an appropriate repeated procedure provides good performance on short
data transmissions.

2) Time Reversal Mirrors and Phase Conjugation Linearity in

wave equation allows the sound to be transmitted from one location and
received at other locations, reversed and retransmitted, focuses back at the
original source location. This is the technique behind Time Reversal Mirrors
(TRM) or active phase conjugation. TRM reduces longer delay spreads of
channel while spatial focusing would enhance signal-to-noise ratio (SNR).
Both the spatial multiplexing and low probability of intercept (LPI)
communications are hence achieved. A closely related idea – Passive
Phase Conjugation (PPC) uses the cross-correlation of two signals
transmitted instantly from the transmission side.

3) Spatial Modulation Literature has shown that the capacity of

a physical channel increases linearly with the minimal number of transmit
and receive antennas. This increase also enhances achievable data
packets through the use of Multiple Input Multiple Output (MIMO)
processing techniques with coding such as space-time. Optimal detection
 technique such as Maximum Likelihood Sequence Estimation (MLSE)
increases performance with increasing of antennas.

PROPOSED 4D UNDERWATER SENSOR NETWORK

10. Steps for designing of localization technique proposed in 4D-UWSN is given as
follow:
a. Designing of 4D-UWSN is accomplished by fixed 3D-UWSN which are
sensors anchored at different depths and mobile UWSNs (Remotely Operative
Underwater Vehicles(ROVs)) for data collection from anchor nodes and data
forwarding to the remote station. After transmission of data to ROV, the sensors
nearer to ROV and having larger info can use RF transmission whereas the
sensors having lesser data and at distance far from ROV can use acoustics links.
Imaging sonars and metal detectors amalgamated with Autonomous Underwater
Vehicles(AUVs) can contribute in underwater reconnaissance which can be a
feasible economic solution for protection of naval forces.

b. Collecting data amongst nodes in networks is the ultimate task of its

existence however, it becomes useless in the absence of locations of the nodes.
Localization is a method finding location of nodes and allowing effective
communication underwater[13] . Two types of nodes are usually in use in primitive
communication underwater being beacon and ordinary nodes. Beacon nodes are
anchor nodes and localized due to fix position of the sink and nodes. Other nodes
are mobile due to water currents. The mobility can be observed by kinematic
mobility model. To visualize the targeted region, a cluster will be formed at the start
by using a geometrical object such as trapezoid. Framework of this proposal
consist of following:

1) Trapezoid Formation Agent (TFA) is responsible for division of

complete network into slabs/ trapezoids of numerous shapes. TFA will travel
across the straight trajectory at different depths of the sea for gathering
trapezoidal information and find algorithm on the Sink Knowledge Base
(SKB). Node related information will be saved at the Node Knowledge Base
(NKB).

2) After first phase we will involve the deployment and activation of

Localization Agent (LA) by the destination. It will also install Autonomous
Underwater Vehicle (AUV) at fixed depth of the sea surface.

3) Third phase involves activation of Localization Agent (LA), the AUV

will move along the fixed straight trajectory and informs real-time locational
information beacon messages at specified points on the present trajectory.

4) The Anchor Agent (AA) at anchor node position gets these

messages and calculates the strength of incoming signals.

5) Re-localization of anchor node is based on the real-time locational

data of the broadcast node and signal strength.
 6) Every associated anchor node’s trapezoid, the trilateral method is
employed which enables to find position.

7) All agents update data packets onto the SKB and NKB.

c. The proposed work resolves the generic problem of localization

experienced in Underwater Sensor Networks data structural algorithms and hence
it applies to the applications which consider the localization issue. This proposed
scheme is augmented by node agents and knowledge base. Inspiration for subject
proposal has been taken by the idea presented by [14] i.e., identifying the sensor
location with the constraints in bandwidth and more errors. From the results, it is
obvious that localization error and energy consumption have been reduced. Each
layer helps the layer above and below it. Network layer address the problems of
both the MAC and Transport layer.

BENEFITS OF PROPOSED TECHNIQUE FOR PN

11. Following are the benefits accrued by our proposed techniques.
a. Practically implementing the Underwater Acoustic Networks require huge
cost transmission and loss of data packets which are simply visualized from the
Aqua 3D visualization tool after simulating it on Aqua Sim utilizing Ubuntu 16.04
LTS. Many simple design changes can be implemented without any cost.
b. Remote monitoring and tracking of hostile submarines with the deployed
underwater wireless sensor network while knowing the location of all the nodes in
the network.

c. Real-time communications and data sharing amongst all the nodes in the
network.

d. Cost effective solution as all nodes do not require GPS and location is
known to the base station.

e. Underwater communication network can be deployed for telemetry

applications.

f. Maritime security and surveillance along with search and rescue operations
with the deployment of underwater Wireless Sensor Network.

CONCLUSION
12. Underwater sensors were the devices which were advocated primarily for the
military applications due to its ability to do something beyond the capability of ordinary
under water vessels. Underwater sensor network can provide the sensitive data from the
most vulnerable enemy areas without disclosing their presence. Need for the localization
of the nodes increases manifolds in case of military application. Moreover, the localization
needs to be computationally feasible. Proposed Technique will provide an economical
way to accurately predict the location of the nodes and ultimately giving correct data from
the enemy lines. Moreover, it can be a massive addition to the capabilities of Underwater
Warfare of Pakistan Navy.

RELEVANT PAST EXPERIENCE OF OFFICER

13. Following are the relevant experience/ expertise of the proposing officer pertaining
to the above mentioned research area.
a. During the course completion of Master program at NUST PNEC Karachi
the officer is also performing the duties of WESMC manager since 2018 and
reiteratively taught the subjects like Hydro-acoustic & Sonar Engineering and
Underwater Warfare.
b. The officer completed his Master program from NUST PNEC in
Communications Engineering and has worked on sensor network simulator
namely OMNET+ designing an optimized LEACH algorithm for Wireless Sensor
Networks enhancing its energy efficiency as energy being one of the critical design
issues in Wireless Sensor Networks for MS thesis.
c. Academic Record: The officer was awarded PNA Dirk being second best
cadet in academy and secured 3.67 CGPA in BE(Electronics) securing third
position in his class. Whereas, in Master program currently the officer has secured
4.0 CGPA.
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