Performance Analysis of Single-Receiver Matched-Mode Localization

Acoustic propagation in shallow water at low frequency is characterized by a few propagating modes. When the source is impulsive or short enough, the modes can be extracted from the signal received on a single sensor using a warping operator. This opens the door to single-receiver matched-mode processing (SR-MMP) as a means to estimate source location and/or ocean environmental parameters. While the applicability of SR-MMP has been demonstrated through several experiments, prediction of its achievable performance has not been fully investigated. In this paper, performance analysis of SR-MMP is carried out using numerical simulations of a typical shallow water environment, incorporating possible environmental mismatch as well as degradations resulting from nonideal modal filtering. SR-MMP is a nonlinear estimation problem that presents three regions of operation: the high SNR asymptotic region driven by local errors, the intermediate SNR threshold region driven by sidelobe ambiguities and the low SNR no-information region. The method of interval errors, which gives computationally efficient and reliable mean squared error performance prediction, is used to conduct the analysis. The results suggest that the SR-MMP performance depends strongly on the source/receiver depth. A significant loss in performance is observed when the receiver is located at a node common to two modes. Receiver depth must therefore be chosen with care. SR-MMP seems to be quite robust to mismatch on the seabed properties alone but does not handle well the combined effect of seabed and water column mismatches. Nonideal modal filtering has a moderate impact on performance.