Multichannel equalization by decision-directed passive phase conjugation: experimental results

An adaptive technique for underwater acoustic communication using passive phase conjugation (PPC) is developed. Multipath channel-parameter identification is accomplished by decision-directed model building and finite-window block-updated least squares computed by LSQR (an iterative linear systems s...

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Bibliographic Details
Published in:IEEE journal of oceanic engineering 2004-07, Vol.29 (3), p.824-836
Main Authors: Flynn, J.A., Ritcey, J.A., Rouseff, D., Fox, W.L.J.
Format: Article
Language:English
Subjects:
Acoustic modem
Acoustic scattering
Algorithms
Arrays
Blocking
Buildings
Channels
coherent underwater communications
Communication channels
Computation
Computational efficiency
Computer architecture
Decision feedback equalizers
Decisions
digital communications
Equalization
fading
Least squares methods
Linear systems
Marine
multichannel equalization
Phase conjugation
shallow water
time reversal
time-varying channel estimation
Underwater acoustics
Underwater communication
waveguide
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Summary:An adaptive technique for underwater acoustic communication using passive phase conjugation (PPC) is developed. Multipath channel-parameter identification is accomplished by decision-directed model building and finite-window block-updated least squares computed by LSQR (an iterative linear systems solver). The resulting channel estimates are then used by the PPC processor to generate decisions for use in the next processing block. This architecture effectively accomplishes array equalization with low computation cost in shallow-water environments that exhibit rapidly fluctuating multipath scattering. The performance on shallow-water acoustic communications channels is demonstrated at ranges of 0.9-4.6 km under windy surface conditions and shipping noise, using measured wide-band telemetry data with binary phase-shift keying signaling. The algorithm is evaluated with sparse receiver apertures using subsets of a 14-element array.
ISSN:0364-9059
1558-1691
DOI:10.1109/JOE.2004.831618