M.S.Ramaiah School of Advanced Studies 1
Final Project Presentation
Vinay DivakarCWB0912001 , FT-12
M. Sc. [Engg.] in Electronic Systems Design
Engineering
Proposed Academic Guides :
Mr. Sreekrishna R.
Ms. Preetham Shankpal
Underwater Acoustic Modem.
Design and Development of Underwater Acoustic
Modem for Shallow Waters and Short Range
Communication
M.S.Ramaiah School of Advanced Studies
Introduction A modem is responsible for transmitting and receiving data.
In air electromagnetic waves are used for the transmission and
reception of the data, however EMW cannot be used for data
transmission underwater, since the bandwidth is severely limited to
KHz range.
RF signals are easily absorbed underwater.
And the antenna required to transmit RF signals at KHz will be
very large with high power consumption, therefore acoustics was
seen as the most reliable choice of underwater communications.
2Underwater Acoustic Modem.
M.S.Ramaiah School of Advanced Studies
Introduction continued
Due to the unique characteristics of water, its not been an easy task to
set up UWSN’s.
Available BW’s for different ranges in UWA channel
3Underwater Acoustic Modem.
Range [Km] Bandwidth [BW]
KHz
Very Long 1000 <1
Long 10 - 100 2 - 5
Medium 1 - 10 ~10
Short 0.1 - 1 20 -50
Very Short <0.1 <0.1
Table 1. BW available at different ranges[4]
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Summary of Literature ReviewAuthors Data Rate Bit Error Rate
(BER)
Signal-to-Ratio
(SNR)(dB)
Ratings Range
B. Benson et al 200 bps 10-2 10dB Transmit:2W to
40W
Receive:
375mW(Standby)
& 750mW(active)
<350m
Jack Wills, Wei Ye
and John
Heidemann
- 10-5 - 5V 50m
Saunvit Pandya et
al
- - 20.2dB(air)
250dB(underwater)
5V 155cm(air)
20cm(underwater)
Raja Jurdak et al 24 bps - 6.95dB - 13m
Heungwoo Num
and Sunshin
100 bps - - 3.3V 3m
Jun-Ho-Jeon and
Sung-Joon-Park
48 Kbps(watertank)
5 Kbps(Pond)
1 Kbps(Pond)
1 Kbps(offshore)
- - 14.8V 1m
1m
30m
20m
Underwater Acoustic Modem. 4
M.S.Ramaiah School of Advanced Studies
Existing systemsThe significant deficiencies identified in the existing underwater commercial acoustic
modems such as Linquest and Benthos[15] are as follows
• The physical structure of these commercial modems is bulk and also heavy in
weight
• Since these modems are basically designed for long range communication,
therefore they consume immense amounts of power, hence the overall power
consumption is high
• The cost of development of one such commercial modem is very high, therefore
not a cost effective option for deployment of underwater sensor networks
• These modems are generally designed for deployment in the deep oceans, thus
making it difficult to access these modems, and frequent charging or replacement
of the batteries is necessary which includes high maintenance cost.
Underwater Acoustic Modem. 5
M.S.Ramaiah School of Advanced Studies
Target SystemTo overcome the stated deficiencies,
• The target system should be designed for short range communication (<100 m).
• The target system should be designed for shallow waters of depth (<100m).
• The cost of development per node should be low for making it reliable for
deployment of underwater sensor network using several such low cost nodes.
• The target system should be small in size i.e. the size per node should be small.
• The overall power consumption per node or system should be low in order to
increase the lifetime of the system, and reduce the maintenance cost
• The system should be able to efficiently transmit and receive data adapting the
underwater environmental characteristics.
Underwater Acoustic Modem. 6
M.S.Ramaiah School of Advanced Studies
Problem Definition• The customer problems with existing modems are, they are
designed for long range communication and for deep waters.
Therefore the power consumption and the maintenance cost is
high.
Hence the chosen problem is to, Design and Development of
Underwater Acoustic Modem for shallow waters and short range
communication
Underwater Acoustic Modem. 7
M.S.Ramaiah School of Advanced Studies
Aim of the Project
The aim of the project is to Design and Develop a Underwater
Acoustic Modem for shallow waters (<100m) and short range
(<100m) communication.
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M.S.Ramaiah School of Advanced Studies
Project Objectives• To conduct literature review on acoustic signals, existing underwater acoustic
modems, underwater channel characteristics, modulation schemes, error
detection and correction schemes.
• To arrive at a system level specifications and functional block diagram of the
low rate underwater acoustic transceiver system.
• To model the underwater acoustic channel and integrate noise models to the
designed acoustic modem for analysing the system performance.
• To design, model and simulate the underwater acoustic modem using
appropriate simulation tool for the desired specifications.
• To realize the designed system in hardware for low data rate communication
• To test and analyse the performance of the developed system
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Concept Development
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Fig 1. Divergent and Convergent Thinking
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Design SpecificationsParameters Specification
Modulation Scheme BFSK
Receiver Non-coherent BFSK Detection
Error Protection and Detection Cyclic Redundancy Check (CRC-6420)
Bandwidth (BW) 3200 Hz
Frequency Separation (Δf) 1 KHz
Data rate (N) 1600 bps (1300bps + Redundancy)
Redundancy Bits ~300 bps
Transmit signal Power (P) 0.1 W
Sampling Time ,Ts 1/1600
Symbol period,Tsym 0.625 ms
Frames per second 100 Fps
Operating Range (R), meters Below 100 m
Operating Depth (D), meters Below 100 m
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Table 1- Design specifications
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Advanced Development
Underwater Acoustic Modem. 12
Fig 2. Detailed Block Diagram
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Underwater/Aquatic Channel Block
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Fig 3. Underwater Channel Block Description
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Underwater Channel Model• Propagation Delay block
• Path Loss (Absorption Loss + Spreading Loss)
• AWGN
• Ambient Noise (Turbulence, Wave, Shipping and Thermal)
• Multipath delays for surface and sea bottom reflections
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Complete Underwater Channel
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Fig 4. Underwater Acoustic Channel
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Propagation Delay Block
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Fig 5. Propagation Delay underwater
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Spreading Loss
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Plspreading (r) = k*10*log (r) (dB)
r: Range in meters (m)
k: Spreading Factor (bounded=1, unbounded = 2)
Fig 6. Spreading Loss
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Absorption Loss
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Fig 7. Boric Acid Component
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Absorption Loss contd…
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Path Loss
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Fig 8. Path Loss (Absorption + Spreading Loss
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Ambient Nosie
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Ambient Noise contd…
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Fig 9. Ambient Noise Models
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Multipath Delays
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• 1st delay due to reflection from surface (4ms)
• 2nd delay due to reflection from sea bottom (15ms)
Fig 10. Multipath Delays
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Multipath Delays contd…
The parameters of the two delay signals used in the simulations are as
follows;
• Delayed Signal1 : Time shift, T1 : 9600 samples (4Ts)
Phase shift, ⱷ : 20 degrees
Frequency shift, FD1: 20 Hz (2 m/s)
Gain, α1: 0.25
• Delayed Signal2 : Time shift, T1 : 24000 samples (15Ts)
Phase shift, ⱷ : 30 degrees
Frequency shift, FD1: 40 Hz (4 m/s)
Gain, α1: 0.5
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M.S.Ramaiah School of Advanced Studies
System Model in Matlab/Simulink
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Fig 11. System Model
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Model ExperimentsThe Systems End to End performance is simulated for different
mediums;
• Model 1 – System with AWGN
• Model 2 – System with AWGN + Path Loss
• Model 3 – System with AWGN + Path Loss + 2 Multipath delays
• Model 4 – System with AWGN + Path Loss + 2 Multipath delays
+ Shipping Noise (complete underwater channel)
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M.S.Ramaiah School of Advanced Studies
Model 1 -AWGN
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Fig 12. System with AWGN
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Simulation Results – Model 1
• Eb/No vs BER • System is showing excellent
performance for AWGN medium
BER Eb/No (dB)
10-5 11
10-4 10
10-3 9
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Fig 13. ber vs eb/no for AWGN
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Model 2-AWGN + Path Loss
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Fig 14. System with AWGN + Path Loss
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Model 2 – Simulation Results• Depth – 10 m • System operates well upto a range
of 30 m, Eb/No required is 19 dB
for BER 10-4
Depth (m) Range (m) BER EbNo
(dB)
10 50 10-3 22
30 10-3 18
10-4 19
10 10-5 20
10-4 19
10-3 18
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Fig 15. Depth 10m
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Model 2 – Simulation Results contd…
• Depth – 30 m • System operates well upto a range
of 100 m, Eb/No required is 12
dB for BER 10-5
Depth (m) Range (m) BER Eb/No
(dB)
30 100 10-5 12
10-4 11
10-3 10
50, 30 and
10
10-5 11
10-4 10
10-3 9
Underwater Acoustic Modem. 31
Fig 16. Depth 30m
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Model 2 – Simulation Results contd…
• Depth – 50m • An Eb/No of 6 dB can attain a
transmission range upto 100m for
a BER of 10-4.
Underwater Acoustic Modem. 32
Depth (m) Eb/No
(dB)
Range (m) BER
50
6
10 10-4
30 10-4
50 10-4
100 10-4
Fig 17. Depth 50m
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Model 3-AWGN + Path Loss + Multipath
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Fig 18. System with AWGN + Path Loss +2 Multipath delays
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Model 3 - Simulation Results• Depth – 10m
• As multipath induced, system
cannot operate for a depth of 10m
anymore, performance totally
degraded
Depth (D)
in meters
Range in
meters
Eb/No BER
10
10 22 10-2
30 22 10-2
50 22 10-2
Underwater Acoustic Modem. 34
Fig 19. Depth 10m
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Model 3 - Simulation Results contd…
• Depth – 50m • System can achieve a BER of
10-3 for a Eb/No of 19 dB, with a
transmission range of 10m.
Depth (D)
in meters
Range in
meters
Eb/No BER
50
10 24 10-4
19 10-3
30 25 10-3
50 25 10-3
Underwater Acoustic Modem. 35
Fig 20. Depth 50m
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Model 3 - Simulation Results contd…
• Depth - 100m • BER of 10-3, range upto 30m for
Eb/No of 16 dB
Depth (D)
in meters
Range in
meters
Eb/No BER
100
10 18 10-5
16 10-4
12 10-3
30 24 10-4
16 10-3
50 25 10-3
Underwater Acoustic Modem. 36
Fig 21. Depth 100m
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Model 4 – underwater channel with shipping noise
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Fig 21. System with AWGN + Path Loss + Multipath + Shipping noise
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Model 4 - Simulation Results
• Depth – 10m• BER is high & system
performance degraded
Depth
(m)
Range
(m)
Shipping
Factor
(S)
Eb/No
(dB)
BER
10 10 0 23 10-2
0.5 25 10-2
1 17 10-1
Underwater Acoustic Modem. 38
Fig 22. Depth 10m
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Model 4 - Simulation Results contd…
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• Depth – 30m
• Ranges – 10m, 30m, 50m
• S – 0, 0.5, 1
Fig 23. Depth 30
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Model 4 - Simulation Results contd…
Depth (m) Range (m) Ship Factor (S) Eb/No (dB) BER
30 10 0 22 10-5
20 10-4
17 10-3
0.5 23 10-5
21 10-4
18 10-3
1 4 10-1
30 0 22 10-4
0.5 22 10-3
1 5 10-1
50 0 23 10-2
0.5 23 10-2
1 6 10-1
Underwater Acoustic Modem. 40
• system shows good performance for a range of 10 m and 30m, however the
system performance degrades as the shipping activity is at peak
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Model 4 - Simulation Results contd…
Underwater Acoustic Modem. 41
• Depth – 50m
• Ranges – 10m, 30m, 50m
• S – 0, 0.5, 1
Fig 24. Depth 50m
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Model 4 - Simulation Results contd…
Depth (m) Range (m) Ship Factor (S) Eb/No (dB) BER
50 10 0 18 10-5
15 10-4
13 10-3
0.5 18 10-5
21 10-4
16 10-3
1 13 10-2
30 0 18 10-5
16 10-4
13 10-3
0.5 20 10-5
18 10-4
14 10-3
1 13 10-1
50 0 21 10-5
18 10-4
14 10-3
0.5 23 10-5
21 10-4
17 10-3
1 6 10-1
Underwater Acoustic Modem. 42
M.S.Ramaiah School of Advanced Studies
Model 4 - Simulation Results contd…
Underwater Acoustic Modem. 43
• Depth – 70m
• Ranges – 10m, 30m, 50m
• S – 0, 0.5, 1
Fig 25. Depth 70m
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Model 4 - Simulation Results contd…
Depth (m) Range (m) Ship Factor (S) Eb/No (dB) BER
70 10 0 14 10-5
12 10-4
10 10-3
0.5 15 10-5
13 10-4
11 10-3
1 17 10-2
30 0 15 10-5
13 10-4
11 10-3
0.5 15 10-5
14 10-4
14 10-3
1 20 10-2
50 0 16 10-5
14 10-4
11 10-3
0.5 17 10-5
15 10-4
11 10-3
1 22 10-2
Underwater Acoustic Modem. 44
M.S.Ramaiah School of Advanced Studies
Performance behavior of system
• Model 1 - The system provides excellent performance of BER 10-5 for a signal
strength of 11 dB, for AWGN channel.
• Model 2 – For a depth of 10m, the system can operate upto a range of 30m for a
signal strength of 19 dB. As the depth increases to 50m, systems range extends
to 100m for a low signal strength of 6 dB
• Model 3 – Multipath are very significant shallow waters, therefore for a depth
of 10m, the systems performance is degraded with high BER. For a depth of
50m, system operates efficiently for range of 10m, BER of 10-4 for signal
strength of 19 dB. For a depth of 100m, the system can achieve a BER of 10-4
for Eb/No of 18 dB with range 10m.
• Model 4 – For a depth of 10m, the system performance is degraded. For a depth
of 30m, with s-0, 0.5, the system can operate efficiently upto a range of 30m
with BER 10-4 for EbNo of 20 dB. For a depth of 50 m ,the system shows
excellent performance for a range upto 30m with BER of10-4, for EbNo of 18
dB. For a depth of 70m, the system is operating at its best for a range up to
50m, BER 10-5 for a Eb/No of 17 dB.
Underwater Acoustic Modem. 45
M.S.Ramaiah School of Advanced Studies
Challenges faced• Modeling and integrating the complex characteristics resembling the
underwater acoustic channel.
• Identifying the appropriate frequency separation (Ϫf) required in a Bandwidth
of 3.2 KHz for BFSK. Therefore the system was simulated for different Ϫf of
2.5KHz, 2KHz and 1 KHz, thus the system provided an optimum performance
for 1KHz.
• The systems performance degraded when multipath was introduced, for a
CRC-4. Therefore the system was simulated for different CRC’s, such as
CRC-6, CRC-8 and CRC-16. Hence CRC-6 was used to increase the
redundancy between packets in order to minimize ISI effects and achieve an
optimum performance.
Underwater Acoustic Modem. 46
M.S.Ramaiah School of Advanced Studies
ConclusionFrom the simulation results, it is concluded that;
• The performance of the system improves as the depth increases, since, as the
depth increases the affects of multipath, absorption loss and shipping noise is
minimized.
• From the Table, seen that, system achieves excellent performance for a depth
of 30 m and above, up to a range of 50m with a BER of 10-4 for a maximum
required Eb/No of 20 dB, for a low shipping factor of 0 and 0.5.
Underwater Acoustic Modem. 47
Depth (m) Range (R) Eb/No (dB) BER
10 10 23 10-2
30 30 20 10-4
50 30 18 10-4
70 50 17 10-5
• The systems performance is degraded when operated at a depth of 10m
and the system cannot operate efficiently while the shipping activities
are at peak i.e. S-1.
Table – Final System Performance Specifications
M.S.Ramaiah School of Advanced Studies
Conclusion• The system performed efficiently for a depth of 10m up to model-2, but the
introduction of multipath (4ms and 14.33ms), degraded the signal strength
drastically while the systems performance degraded. Therefore multipath
significantly affects the performance of the system for shallow waters.
• The requirement of Eb/No to achieve a BER of 10-4 can be further reduced by
increasing the depth of the system placed underwater, above 100m, but this
will conflict with the requirement of the system to operate at shallow waters.
• Therefore using the CRC-6 scheme and Non-coherent BFSK scheme to design
an underwater acoustic modem, can achieve a good performance operating at
shallow depths of 30m, 50m and 70m, providing a transmission range up to
50m.
Underwater Acoustic Modem. 48
M.S.Ramaiah School of Advanced Studies
Future Work
• Errors can be minimized further by using, error correction by
retransmission of the non-critical data frames using the Selective ARQ
(Automatic Repeat Request) protocol.
• In order to correct some critical data, an error correcting scheme can be
used in conjunction with CRC, to correct critical data on spot and transmit.
This will provide excellent error detection as well correction capabilities.
Underwater Acoustic Modem. 49
M.S.Ramaiah School of Advanced Studies
Hardware Details
Transmitter :
• Input Data – Terminal 1 from PC
• Level Converter – Max 232
• Microcontroller-CRC
• Ultrasound Transducer (40 KHz)
Receiver:
• Ultrasound Transducer (40 KHz)
• Microcontroller-CRC
• Level Converter
• Output Data – Terminal 2 to PC
Underwater Acoustic Modem. 50
M.S.Ramaiah School of Advanced Studies
Block Diagram of System
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Fig 26 – Hardware System Block Diagram
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Hardware Setup
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Transmission Process
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Data Reception Process
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M.S.Ramaiah School of Advanced Studies 55
ReferencesBenson.B, Y.Li, Kastner, Faunce, Domond, Kimball and Schurgers (2010).
‘Design of Low-Cost Underwater Acoustic Modem for Short Range Sensor
Networks’. Oceans 2010 IEEE, San Diego.
Akyilidz, Pompili, Melodia (2005)‘Underwater Acoustic Sensor Networks :
research Challenges’ Elsevier, Ad Hoc Networks3,257-279,February.
Wills, Wei Ye and Heidemann (2006) ‘Low-Power Acoustic Modem for Dense
Underwater Sensor Networks’. USC information Sciences Institute.
Jullo Diago Miranda Xavier (2012) ‘Modulation Analysis for an Underwater
Communication Channel’. FEUP, October.
Gunilla Burrowes and Jamil.Y.Khan (2011) ‘Short-Range Undewater Acoustic
Communication Networks’. InTech, ISBN: 978-953-307-432-0, Australia.
Underwater Acoustic Modem.
M.S.Ramaiah School of Advanced Studies
ReferencesJurdak, Agmas, Beldi and lopes (2007) ‘Software Modems for Underwater
Sensor Networks’. Oceans 2007 IEEE, ISBN-978-1-4244-0635-7, 1 – 6.
Saunvit Pandya, Jonathan Engel, Jack Chen, Zhifang Fan, Chang Liu (2005)
‘CORAL: Miniature Acoustic Communication Subsystem Architecture for
Underwater Wireless Sensor Networks’. SensorsIEEE.
Heungwoo Nam and Sunshin An (2007) ‘An Ultrasonic Sensor Based Low-
Power Acoustic Modem for Underwater Wireless Sensor Network’. IEEE
Secon, 2010, 1-3.
Babu, Dr. Rao (2011) ‘Evaluation of BER for AWGN, Rayleigh and Rician
Fading Channels under various Modulation Schemes’. International Journal
of Computer Applications, Volume 26-9.
56Underwater Acoustic Modem.
M.S.Ramaiah School of Advanced Studies
ReferencesBabu, Dr. Rao (2011) ‘Evaluation of BER for AWGN, Rayleigh and Rician Fading
Channels under various Modulation Schemes’. International Journal of Computer Applications, Volume 26-9.
Jeon and Park (2010) ‘Implementation of a Low-Power Acoustic Modem for Underwater Wireless Sensor Networks’. IEEE Seacon.
Nejah NASRI , Laurent ANDRIEUX , Abdennaceur KACHOURI , and MounirSAMET (2009), ‘Behavioral Modelling and Simulation of Underwater Channel” WSEAS TRANSACTIONS on COMMUNICATIONS , February.
Forouzan (2007) ‘Data Communications and Networking’. 4th ed, New York McGraw-Hill.
Haykins (2001) ‘ Communication Systems’. 4thed, U.S.A, McMaster University.
LinkQuest, Inc., Underwater Acoustic Modems,
http://www.link-quest.com/html/uwm hr.pdf
Underwater Acoustic Modem. 57
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Activity Weeks 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Pre-Project
Presentation
Literature
Survey
Concept
Exploration
Concept
Selection
Underwater
Channel
Modelling
Design and
Modelling of Tx
& Rx
Model
&Simulations
Model Analysis
Interim Review
Model
Optimization
Preparation of
Final Report
and
Presentation
Final
Presentation
Project Schedule
M.S.Ramaiah School of Advanced Studies 59
Thank You
Underwater Acoustic Modem.
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