Underwater acoustic communication
Underwater acoustic communication is a technique of sending and receiving message below water. There are several ways of doing such communication but the most common is using
hydrophones. Under water communication is difficult due to factors like multi-path propagation, time variations of the channel, small available bandwidth and strong signal attenuation, especially over long ranges. In underwater communication there are low data rates compared to terrestrial communication, since underwater communication uses acoustic waves instead of electromagnetic waves.
Use of vector sensor receivers
A vector sensor is capable of measuring important non-scalar components of the acoustic field such as the wave velocity, which cannot be obtained by a single scalar pressure sensor.
In recent decades, extensive research has been conducted on the theory and design of vector sensors [Proc. AIP Conf. Acoustic Particle Velocity Sensors: Design, Performance, and Applications, Mystic, CT, 1995.] [A. Nehorai and E. Paldi, “Acoustic vector-sensor array processing,” IEEE Trans. Signal Processing, vol. 42, pp. 2481-2491, 1994.] . Many vector sensor signal processing algorithms have been designed [K. T. Wong & H. Chi, "Beam Patterns of an Underwater Acoustic Vector Hydrophone Located Away from any Reflecting Boundary," IEEE Journal of Oceanic Engineering, vol. 27, no. 3, pp. 628-637, July 2002.] [P. Tichavsky, K. T. Wong & M. D. Zoltowski, "Near-Field/Far-Field Azimuth & Elevation Angle Estimation Using a Single Vector-Hydrophone," IEEE Transactions on Signal Processing, vol. 49, no. 11, pp. 2498-2510, November 2001.] [K. T. Wong & M. D. Zoltowski, “Self-Initiating MUSIC-Based Direction Finding in Underwater Acoustic Particle Velocity-Field Beamspace," IEEE Journal of Oceanic Engineering, vol. 25, no. 2, pp. 262-273, April 2000.] [K. T. Wong & M. D. Zoltowski, “Root-MUSIC-Based Azimuth-Elevation Angle-of-Arrival Estimation with Uniformly Spacedbut Arbitrarily Oriented Velocity Hydrophones," IEEE Transactions on Signal Processing, vol. 47, no. 12, pp. 3250-3260, December 1999.] [K. T. Wong & M. D. Zoltowski, “Extended-Aperture Underwater Acoustic Multisource Azimuth/Elevation Direction-Finding Using Uniformly But Sparsely Spaced Vector Hydrophones," IEEE Journal of Oceanic Engineering, vol. 22, no. 4, pp. 659-672, Oct. 1997.] [K. T. Wong & M. D. Zoltowski, “Closed-Form Underwater Acoustic Direction-Finding with Arbitrarily Spaced Vector-Hydrophones at Unknown Locations," IEEE Journal of OceanicEngineering, vol. 22, no. 3, pp. 566-575, July 1997.] . They have been mainly used for underwater target localization and
Earlier underwater acoustic communication systems have been relying on scalar sensors only, which measure the pressure of the acoustic field. Vector sensors measure the scalar and vector components of the acoustic field in a single point in space, therefore can serve as a compact multichannel receiver. This is different from the existing multichannel underwater receivers [T. C. Yang, “Temporal resolutions of time-reversal and passive phase conjugation for underwater acoustic communications,” IEEE J. Oceanic Eng., vol. 28, pp. 229–245, 2003.] [M. Stojanovic, J. A. Catipovic, and J. G. Proakis, “Reduced-complexity spatial and temporal processing of underwater acoustic communication signals,” J. Acoust. Soc. Am., vol. 98, pp. 961–972, 1995.] , which are composed of spatially separated pressure-only sensors, which may result in large-size arrays.
In general, there are two types of vector sensors: inertial and gradient [T. B. Gabrielson, “Design problems and limitations in vector sensors,” in Proc. workshop Directional Acoustic Sensors (CD-ROM), New Port, RI, 2001.] . Inertial sensors truly measure the velocity or acceleration by responding to the acoustic medium motion, whereas gradient sensors employ a finite-difference approximation to estimate the gradients of the acoustic field such as velocity and acceleration.
In the example of vector sensor communications shown, there is one transmitter pressure transducer, shown by a black dot, whereas for reception we use a vector sensor, shown by a black square, which measures the pressure and the "y" and "z" components of the velocity. This is a 1×3
single-input multiple-output(SIMO) system. With more pressure transmitters, one can have a multiple-input multiple-output(MIMO) system also.
* [https://www.ensieta.fr/e3i2/images/E3I2/Publi/publi/JARROT_05a.pdf A paper on denoising of underwater signals]
* [http://www.eie.polyu.edu.hk/~enktwong/ Click here to download references (3)-(8)]
Wikimedia Foundation. 2010.
Look at other dictionaries:
Underwater acoustics — The field of underwater acoustics is closely related to a number of other fields of acoustic study, including sonar, transduction, acoustic signal processing, acoustical oceanography, bioacoustics, and physical acoustics.HistoryUnderwater sound… … Wikipedia
Communication with submarines — is difficult because radio waves do not travel well through thick electrical conductors like salt water. The obvious solution is to surface and raise an antenna above the water, then use ordinary radio transmissions. Early submarines had to… … Wikipedia
Underwater archaeology — is the study of past human life, behaviours and cultures using the physical remains found in salt or fresh water or buried beneath water logged sedimentMuckelroy, K., Maritime archaeology. Cambridge University Press 1978. ISBN 0 521 29348 0] . It … Wikipedia
Thales Underwater Systems — (TUS), formerly known as Thomson Marconi Sonar, is an international defence manufacturer specialising in sonar systems for submarines and surface warships, and airborne sonar systems as well as communications masts and systems for submarines. TUS … Wikipedia
Ray tracing (physics) — In physics, ray tracing is a method for calculating the path of waves or particles through a system with regions of varying propagation velocity, absorption characteristics, and reflecting surfaces. Under these circumstances, wavefronts may bend … Wikipedia
Sonar — This article is about underwater sound propagation. For atmospheric sounding, see SODAR. For other uses, see Sonar (disambiguation) … Wikipedia
warning system — ▪ military technology Introduction in military science, any method used to detect the situation or intention of an enemy so that warning can be given. Because military tactics from time immemorial have stressed the value of surprise… … Universalium
Military equipment of Turkey — The military equipment of Turkey includes a wide array of arms, artilleries, large surface vessels, cannons, armored vehicles, mortars, unmanned vehicles and many different equipments. Contents 1 Historical development 1.1 General 1.2 1923 1950 … Wikipedia
Guðlaugur Kristinn Óttarsson — (Born December 11, 1954 in Reykjavík, Iceland), guitar player and engineer. He is a mathematician, an inventor, a practising polytechnic engineer, lecturer and the author of several scientific papers.Childhood: first contact with science and… … Wikipedia
Cetacean intelligence — denotes the cognitive capabilities of the Cetacea order of mammals, which includes whales, porpoises, and dolphins. Contents 1 Brain size 2 Brain structure 3 Problem solving ability … Wikipedia