Sl. Li et Pm. Schultheiss, DEPTH MEASUREMENT OF REMOTE SOURCES USING MULTIPATH PROPAGATION, IEEE journal of oceanic engineering, 18(4), 1993, pp. 379-387
A submerged acoustic source radiates narrowband Gaussian noise. Its si
gnal propagates to a remote, large aperture vertical array over a mult
ipath channel whose characteristics may or may not be fully known. The
primary concern of this paper is the accuracy of source depth estimat
es obtainable from the array output. Cramer-Rao bounds for the depth e
stimate are calculated. When the velocity profile is known exactly the
value of the bound is quite insensitive to the precise form of the ve
locity profile. A bound calculated from a constant velocity profile yi
elds an excellent approximation for many situations likely to be encou
ntered in practice. Introduction of an unknown parameter into the velo
city profile has little effect on the Cramer-Rao bound for depth. Howe
ver, a maximum likelihood estimator of depth working with an inaccurat
e value of the unknown parameter performs poorly. To obtain satisfacto
ry performance one must estimate the unknown parameters along with the
source depth. Simulations demonstrate the success of this approach.