SEMINAR REPORT ON

UNDERWATER WIRELESS COMMUNICATION

UNDER GUIDANCE OF

ER. SUNIL BISOI

By:-

SUSHOBHAN BEHERAMALIRoll No:-116102, Sec:- BRegd. No:- 1101211423Branch:- ENTC

INTRODUCTION

Underwater wireless communication is thewireless communication in which acoustic signals(waves) carry digital information through anunderwater channel. Electromagnetic waves arenot used as they propagate over short distances.Over the past decades, heavy cables were usedto establish a high speed communicationbetween remote end and the surface. Toovercome such difficulties, underwater wirelesscommunication has come into existence.

NECESSITY OF UNDERWATER WIRELESS COMMUNICATION

Wired underwater is not feasible in all situations asshown below-:

• Temporary experiments

• Breaking of wires

• Significant cost of deployment

• Experiment over long distances.

To cope up with above situations, we requireunderwater wireless communication.

FACTORS INFLUENCING ACOUSTIC COMMUNICATION

• Path loss: Due to attenuation and geometricspreading.

• Noise: Man-made noise and ambient noise(due tohydrodynamics)

• Multi-path propagation

• High propagation delay

• Doppler frequency spread.

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, highperformance implementations for DSP applications

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

DATA TRANSMISSION IN MODEM

When no data is being transmitted, the modem stays insleep mode, it periodically wakes up to receive possibledata being transmitted by far end modem. This results inlow power consumption. Similarly when the data is to betransmitted , the modem receives data from its link insleep mode and then switches to transmit mode andtransmit the data.

ADVANCED MODEMS AVAILABLE

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)

Autonomous Underwater Vehicles (AUVs)

It is a robot which travels underwater without requiring input from an operator.

Applications Of AUV

Until relatively recently, AUVs have been used for a limited number of tasks dictated by the technology available. With the development of more advanced processing capabilities and high yield power supplies, AUVs are now being used for more and more tasks with roles and missions constantly evolving.

Commercial

The oil and gas industry uses AUVs to make detailed maps of the seafloor before they start building sub sea infrastructure; pipelines and sub sea completions can be installed in the most cost effective manner with minimum disruption to the environment. The AUV allows survey companies to conduct precise surveys of areas where traditional bathymetric surveys would be less effective or too costly. Also, post-lay pipe surveys are now possible.

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

LIMITATIONS

• Battery power is limited and usually batteries cannot 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 watercolumn, variations of sound velocity versusdepth, temperature and salinity, multiple andrandom sea reflections and significant scatteringby fish, bubble clouds and plankton.

CONCLUSION

Despite much development in this area of theunderwater wireless communication, there is stillan immense scope so more research as major partof the ocean bottom yet remains unexploded. Themain objective is to overcome the presentlimitations and implement advanced technologyfor oceanographic research and cope up with theenvironmental effects on the noise performance ofacoustic systems to compete with the futurechallenges like effective transmission of audio andvideo signals etc.

References

• www.ieee.org/organizations/pubs/newsletters/oes/html/spring06/underwater.html

• www.link-quest.com/html/oceans2000.pdf/

• www.gleonrcn.org/pgm-download_media.php?name=Aquanode.pps

• www.cs.virginia.edu/sigbed/archives/akyildiz.pdf

QUERIES

THANK YOU