Effect of reflected and refracted signals on coherent underwater acoustic communication: Results from the Kauai experiment (KauaiEx 2003)

The performance of a communications equalizer is quantified in terms of the number of acoustic paths that are treated as usable signal. The analysis uses acoustical and oceanographic data collected off the Hawaiian Island of Kauai. Communication signals were measured on an eight-element vertical arr...

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Bibliographic Details
Published in:The Journal of the Acoustical Society of America 2009-11, Vol.126 (5), p.2359-2366
Main Authors: Rouseff, Daniel, Badiey, Mohsen, Song, Aijun
Format: Article
Language:English
Subjects:
Acoustics
Acoustics - instrumentation
Communications Media
Exact sciences and technology
Fundamental areas of phenomenology (including applications)
Hawaii
Marine
Models, Theoretical
Oceanography - instrumentation
Oceanography - methods
Oceans and Seas
Physics
Seawater
Signal Detection, Psychological
Surface Properties
Underwater sound
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Summary:The performance of a communications equalizer is quantified in terms of the number of acoustic paths that are treated as usable signal. The analysis uses acoustical and oceanographic data collected off the Hawaiian Island of Kauai. Communication signals were measured on an eight-element vertical array at two different ranges, 1 and 2 km, and processed using an equalizer based on passive time-reversal signal processing. By estimating the Rayleigh parameter, it is shown that all paths reflected by the sea surface at both ranges undergo incoherent scattering. It is demonstrated that some of these incoherently scattered paths are still useful for coherent communications. At range of 1 km, optimal communications performance is achieved when six acoustic paths are retained and all paths with more than one reflection off the sea surface are rejected. Consistent with a model that ignores loss from near-surface bubbles, the performance improves by approximately 1.8 dB when increasing the number of retained paths from four to six. The four-path results though are more stable and require less frequent channel estimation. At range of 2 km, ray refraction is observed and communications performance is optimal when some paths with two sea-surface reflections are retained.
ISSN:0001-4966
1520-8524
DOI:10.1121/1.3212925