Underwater wireless communication networks (UWCNs) consist of sensors and autonomous underwater vehicles (AUVs) that interact, coordinate and share information with each other to carry out sensing and monitoring functions.

1. Presented BY : Akash
Department of ECE
Amrita Vishwa Vidyapeetham, Coimbatore
Underwater Wireless
Communication

2. Organization Of The Presentation
❖ Introduction
❖ History
❖ Necessity of Underwater Wireless Communication
❖ Factor influencing acoustic communication Features
❖ Hardware platform Interfaces
❖ Acoustic Modem
❖ Data Transmission in modem
❖ Advance modems Available
❖ Underwater Acoustic Sensor Networks(UW-ASN)
❖ UW-ASN Communication Architecture
❖ Appilications
❖ Limitations
❖ Conclusion
❖ Reference

3. Introduction
Underwater wireless communication is the wireless communication in
which acoustic signals (waves) carry digital information through an
underwater channel. Electromagnetic waves are not used as they
propagate over short distances. Over the past decades, heavy cables
were used to establish a high speed communication between remote
end and the surface. To overcome such difficulties, underwater wireless
communication has come into existence.

4. 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 wote 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 summarised 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.

5. NECESSITY OF UNDERWATER WIRELESS COMMUNICATION
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.

6. FACTORS INFLUENCING ACOUSTIC COMMUNICATION
★ Path loss: Due to attenuation and geometric spreading
★ Noise: Man-made noise and ambient noise(due to hydrodynamics)
★ Multipath propagation.
★ High propagation delay.
★ Doppler frequency spread.

7. HARDWARE PLATFORM INTERFACES
● 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.

8. ACOUSTIC MODEM
● Employ advanced modulation scheme and channel equalization for improved
signal to noise ratio.
● Employ high performance error detection and correction coding scheme which
reduces bit error rate to less than 10- 7
Parts of an acoustic modem:
● DSP Board
● AFE(Analog Front End) Board
● DC/DC Converter

9. DATA TRANSMISSION IN MODEM
When no data is being transmitted, the modem stays in sleep mode, it
periodically wakes up to receive possible data being transmitted by far end
modem. This results in low power consumption. Similarly when the data is to
be transmitted , the modem receives data from its link in sleep mode and then
switches to transmit mode and transmit the data.

10. ADVANCED MODEMS AVAILABLE

11. UNDERWATER ACOUSTIC SENSOR NETWORKS (UW-ASN)
● Group of sensors and vehicles deployed underwater and networked via acoustic
links, performing collaborative tasks.
● Equipment
➔ Autonomous Underwater Vehicles (AUVs)
➔ Underwater sensors (UW-ASN)

12. UW-ASN COMMUNICATION ARCHITECTURE
2-D ARCHITECTURE

13. 3-D ARCHITECTURE

14. APPLICATIONS
● Seismic monitoring
● Pollution monitoring
● Ocean currents monitoring
● Equipment monitoring and control
● Autonomous Underwater Vehicles (AUV)
● Remotely operated vehicle(ROV)
● Acoustic navigation technology for multiple AUVs.
● Solar Powered AUVs

15. LIMITATIONS
● Battery power is limited and usually batteries can not be recharged easily.
● The available bandwidth is severely limited.
● Underwater sensors are prone to failures because of fouling, corrosion, etc.
● Highly affected by environmental and natural factors such as heterogeneities of
the water column, variations of sound velocity versus depth, temperature and
salinity, multiple and random sea reflections and significant scattering by fish,
bubble clouds and plankton.

16. CONCLUSION
Despite much development in this area of the underwater wireless
communication, there is still an immense scope so more research as major
part of the ocean bottom yet remains unexploded. The main objective is to
overcome the present limitations and implement advanced technology for
oceanographic research and cope up with the environmental effects on the
noise performance of acoustic systems to compete with the future challenges
like effective transmission of audio and video signals etc.

17. References
● Underwater Wireless Communications - Milica Stojanovic
● Wireline Quality Underwater Wireless ... - LinkQuest
● Intelligent agent based information routing in wireless body sensor ...

18. Thank You!