Warping based lag-Doppler filtering applied to motion effect compensation in acoustical multipath propagation.
Résumé
The estimation of an impulse response of a propagation channel is necessary for a large number of underwater applications: underwater communication, sonar detection and localization, marine mammal monitoring, etc. Basically it informs us about the distortions of transmitted signal in underwater channels and enables geoacoustic inversion. The propagated signal is usually subject to additional and undesirable distortions due to the motion of the transmitter-channel-receiver configuration. This paper points out the effects of the motion while estimating the IR by matching filtering between the transmitted and the received signals. A methodology to compare the IR estimation in motionless and motion contexts is presented. Based on this comparison, a warping-based lag-Doppler filtering method in the wideband ambiguity plane for motion effect compensation is proposed. It aims at reducing the distortions due to the motion phenomena and accurately estimating the IR of the channel. The proposed methodology is applied to real data sets issued from BASE'07 campaign (NURC, SHOM, and FWG, South of Sicilia, 2007). Motion compensated estimations of IRs are computed from sources transmitting broadband linear frequency modulations moving up to 12 knots in the shallow water environment of the Malta plateau.