Abstract
Underwater acoustic (UWA) communication is an essential part of many
civilian and military applications. For UWA sensor networks, the sensing
information can only be interpreted meaningfully when the location of
the sensor node is known. However, node localization is a challenging
problem. Global Navigation Satellite Systems (GNSS), which are often
used in terrestrial applications, do not work underwater. In this paper,
we propose and investigate techniques for localization of a
single-antenna UWA communication receiver with respect to one or more
transmit antennas. These techniques are based on the matched field
processing. Firstly, we demonstrate that a non-coherent ambiguity
function (AF) allows significant improvement in the localization
performance compared to the coherent AF previously used for this
purpose, especially at high frequencies typically used in communication
systems. Secondly, we propose a two-step (coarse-to-fine) localization
technique. The second step provides refined spatial sampling of the AF
in the vicinity of its maximum found on the coarse space grid covering
an area of interest (in range and depth), computed at the first step.
This technique allows high localization accuracy and reduction in
complexity and memory storage, compared to the single step localization.
Thirdly, we propose a joint refinement of the AF around several maxima
to reduce outliers. For validation of the proposed techniques, we run
numerical experiments in different UWA environments, with different
parameters for the spatial sampling, number of transmit antennas and
different accuracy for the estimation of the acoustic channel response.