Deterministic maximum likelihood DOA estimation in heterogeneous propagation media

In a number of array signal processing applications, such as underwater source localization, the propagation medium is not homogeneous, which causes a distortion of the wavefront received by the array. In this paper, we consider the direction-of-arrival (DOA) estimation problem for such distorted wavefronts. In previous approaches, the so-called multiplicative noise scenario is considered based on the assumption that the distortion is random and can be parameterized by a small number of parameters. To gain robustness against mismodelling we assume a scenario in which the wavefront amplitude is distorted in a completely arbitrary way. We derive the maximum likelihood (ML) estimator of the DOA and show it can be obtained by means of a simple 1D search. The Cramer-Rao bound (CRB) for the problem at hand is derived. Numerical simulations illustrate a good performance of the estimator and show that its accuracy is comparable with that of estimators which require knowledge of the form of amplitude distortions.