MADAN MOHAN MALAVIYA ENGINEERING COLLEGE GORAKHPUR

SESSION – 2011-12SEMINAR REPORT ON

UNDERWATER WIRELESS COMMUNICATION

SHUBHAM SRIVASTAVA ELECTRONICS & COMMUNICATION ENGG.

B.TECH. 3RD YEARROLL NO. 0904231065

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 propogate 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.

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.

FACTORS INFLUENCING ACOUSTIC COMMUNICATION

• Path loss: Due to attenuation and geometric spreading.

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

• Multi-path propogation• High propogation 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, TransducersSignal modulationHardware:

Software Defined Acoustic Modem (SDAM) Reconfigurable hardware known to provide, flexible, high

performance 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 MODEMWhen 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.

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)

UW-ASN COMMUNICATION ARCHITECTURE

2-D ARCHITECTURE

3-D ARCHITECTURE

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 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.

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.

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

THANK YOU

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