Passive Time Reversal Acoustic Communications Through Shallow-Water Internal Waves

During a 12-h period in the 2006 Shallow Water Experiment (SW06), binary phase shift keying (BPSK) signals at the carrier frequencies of 813 and 1627 Hz were propagated over a 19.8-km source-receiver range when a packet of strong internal waves passed through the acoustic track. The communication da...

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Bibliographic Details
Published in:IEEE journal of oceanic engineering 2010-10, Vol.35 (4), p.756-765
Main Authors: Aijun Song, Badiey, Mohsen, Newhall, Arthur E, Lynch, James F, DeFerrari, Harry A, Katsnelson, Boris G
Format: Article
Language:English
Subjects:
Acoustic communications
Acoustics
Channel estimation
Channels
Coherence
Decision feedback equalizers
Feedback
Fluctuation
Internal waves
Marine
Performance degradation
Radar tracking
Receivers
time reversal processing
Tracking
Waveguides
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Summary:During a 12-h period in the 2006 Shallow Water Experiment (SW06), binary phase shift keying (BPSK) signals at the carrier frequencies of 813 and 1627 Hz were propagated over a 19.8-km source-receiver range when a packet of strong internal waves passed through the acoustic track. The communication data are analyzed by time reversal processing followed by a single-channel decision feedback equalizer. Two types of internal wave effects are investigated in the context of acoustic communications. One is the rapid channel fluctuation within 90-s data packets. It can be characterized as decreased channel coherence, which was the result of fast sound-speed perturbations during the internal wave passage. We show its effect on the time reversal receiver performance and apply channel tracking in the receiver to counteract such fluctuation. The other one is the long-term (in the scale of hours) performance degradation in the depressed waveguide when the internal waves passed through the acoustic track. Even with channel tracking, the time reversal receiver experiences average 3-4-dB decrease in the output signal-to-noise ratio (SNR). Such long-term performance degradation is explained by the ray approximation in the depressed waveguide.
ISSN:0364-9059
1558-1691
DOI:10.1109/JOE.2010.2060530