N. Martins nmartins@ualg.pt
S.M. Jesus sjesus@ualg.pt
SiPLAB-FCT, Universidade do Algarve,
Campus de Gambelas,
PT-8005-139 Faro, Portugal.
Comments: download pdf
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Ref.: IEEE Journal of Oceanic Engineering, Vol. 31 (3), pp.646-656, 2006.
Abstract
A time-frequency blind estimator of the ocean acoustic multipath
channel response is presented. Both the acoustic channel response and
the source input signal are assumed deterministic, and the source
signal is assumed highly non-stationary. The estimator relies on the
time-frequency representation of the received signal, permitting the
separation between the channel and the source signal. First, the
unstable initial acoustic arrivals allow the estimation of the source
signal instantaneous frequency, by maximization of the radially
Gaussian kernel distribution; then, the Wigner-Ville distribution of
the received signal is windowed and integrated, where the observation
window is defined by the instantaneous frequency estimate, allowing the
recovery of the channel impulse response. This last step constitutes an
approximation to the conventional matched-filter. Results obtained on a
real underwater acoustic data set acquired during the INTIMATE 96
experiment, where the acoustic channel was driven by an LFM signal,
show that the channel s detailed structure could be accurately and
consistently recovered, with the quality of the channel estimates
ranging from 0.796 to 0.973, as compared to the matched-filter result.
Time-frequency processing is shown to provide a viable approach to the
blind estimation of the ocean acoustic channel excited by a
deterministic non-stationary source signal.
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