Improving Delay Estimation in Underwater Acoustic Applications by the Additional Use of Cross-Cross-Correlation.

Next generation space-terrestrial-ocean integrated mobile networks providing global internet access that extend to the undersea are based on heterogeneous networks. In underwater applications, a key role is played by the acoustic positioning. In particular, this task can be accomplished making use of multiple passive sensors that estimate the differential signal delays employed for positioning. This paper exploits a methodology aimed at improving delay estimation by means of cross-cross-correlation, i.e., the cross-correlation between all the multi-sensor cross-correlations. The resulting equation system is formulated as a least squares (LS) minimization problem, whose solution is efficiently found resorting to the pseudo-inverse technique, ensuring a fast execution of the algorithm, without using statistical information on random signal spectra. The performance of the devised method is numerically analyzed for an extensive range of operating parameters to demonstrate the validity of the proposed approach in comparison with classic counterparts and theoretical optimum bounds.