UNDERWATER COMMUNICATION USING SONAR AND ACOUSTIC WAVES

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CONTENTINTRODUCTIONHISTORYSONAR WAVESACOUSTIC UNDERWATER COMMUNICATION ARCHITECTUREBASICS OF ACOUSTIC UNDERWATER COMMUNICATIONFACTORS INFLUENCE ACOUSTICUNDERWATER COMMUNICATIONSRECENT ACTIVITIES SHOWS THE IMPORTANTANCE OF ACOUSTIC UNDERWATER COMMUNICATIONADVANTAGES, DISADVANTAGES AND APPLICATIONCONCLUSION REFERENCES

INTRODUCTIONThere are lots of uses of underwater environment like oceanographic monitoring, scientific exploration, disaster monitoring and also especially for oil/gas field exploration.In ocean could be highly time varying and spatial-varying, hence, posing major challenges to the design and development of effective communication systems for underwater applications.Sonar and electromagnetic waves are different in nature. Sonar waves are caused by a physical vibration of particles and electromagnetic waves are caused by interference in an electromagnetic field.

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HISTORYBefore sonar the only technology people used was to actually listen to the water with different devicesIn 1822 Daniel Colloden used an underwater bell to find the calculations of the speed of sound underwater in Switzerland; this was a step towards sonar In 1906 Lewis Nixon was the first to invent Sonar.He invented it to detect icebergsThe picture to the right depicts its early and simple use

SONAR WAVESSONAR stands for SOund NAvigation and Ranging.

It is a device that is used mainly for the detection and location of underwater objects by reflecting acoustic/sound waves. There are basically two types of sonar communicationActive sonar communication system Passive sonar communication system

Active sonar communication system Half duplex active sonar communication

Full duplex active sonar communication

Passive Sonar Communication System

ACOUSTIC UNDERWATER COMMUNICATION ARCHITECTURE

In underwater network system, a group of sensor nodes are anchored to the bottom of the ocean or may be interconnected to one or more underwater gateways by wireless acoustic linksThe horizontal transceiver is used by the underwater gateways to communicate with the sensor nodes to send commands and configuration data to the sensors and/or collect monitored data

1 D ArchitectureSensor nodes are anchored to the bottom of the ocean with deep ocean anchors. By means of wireless acoustic links, underwater sensor nodes are interconnected to one or more underwater sinks Sensors can be connected to sinks by means of direct links or through multi-hop paths

CHALLENGES IN 2-D ARCHITECTURESensing coverage: Sensors should collaboratively regulate their depth in order to achieve full column coverage, according to their sensing ranges. Hence, it must be possible to obtain sampling of the desired phenomenon at all depthsCommunication coverage: Since in 3D underwater networks there is no notion of uw-sink, sensors should be able to relay information to the surface station via multichip paths

3-D ArchitectureSensor nodes float at different depths in order to observe a given phenomenon. The possible solution to achieve different depths would be to attach each UW-sensor node to a surface buoy, by means of wires Multiple floating buoys may obstruct ships navigating on the surface

BASICS OF ACOUSTIC UNDERWATER COMMUNICATIONAcoustic waves enable communications over long-distance since they suffer from relatively low absorption. Underwater Acoustic communications are also affected by high path loss, noise, multipath, high and variable propagation delay and Doppler spreadDepending on their range, underwater acoustic communication links can be classifieds very long, long, medium, short and very short

RECENT ACTIVITIESthe oil-rig explosion in the Gulf of Mexico in the Summer of 2010 could have been prevented by acoustic sensing/actuating systems that can be triggered by acoustic control signals.In 2013 an inventor in the United States unveiled a "spider-sense" bodysuit, equipped withultrasonic sensorsandhaptic feedbacksystems, which alerts the wearer of incoming threats; allowing them to respond to attackers even when blindfolded

ADVANTAGES

is used to find and identify objects in water. It is also used determine water depth (bathymetry).Sonar was first used during World War I to detect submarines.The technology steadily improved, and by World War II, was used once again for militarypurposes.

DISADVANTAGES

Multipath propagationFormation of shadow zonesSmall propagation speed NoiseLimited band width

APPLICATION

Military application:MinesAircraftUnderwater securityCivilian application:FisheriesVehical locationScientific application:Biomass estimationWave mesurement

CONCLUSION

At last we find out that acoustic waves are best medium for underwater communication. The 3-D architecture is a better way to communicate underwater.But in acoustic waves there are many factors, which affect the underwater communication. To remove the effects of factors, which influence the underwater communication further research going on .so we can summarize in one line that acoustic waves are better medium for underwater communication

REFERENCES

[1] J.Heidemann, Yuan Li, Affan Syed, Underwater Sensor Networking:Research Challenges and Potential Applicat ion, USI/ISI Technical Report ISI-TR-2005-603, 2005 [2] AntonioMansillaFabregat , Desenvolupament , proves decampianlisideresultats en unaxarxa de sensors, Master in Science in Telecommunicat ion Engineering &Management .UniversitatPolitecnica De Catalunya, 2008. [3] D.Pompili,T.Melodia,andI.F.Akyildiz. Three dimensional and two dimensional Development Analysis foe underwater Acoustic Sensor Network.Ad Hoc networks, 7(4); 778-790, June2009. [4] L. Freitag and M. Stojanovic, Acoustic communications for regional undersea observatories, in Proceedings of Oceanology International, London, U.K., mar 2002.

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