Barankin bound for source localization in shallow water

Matched-field methods are known to have a severe ambiguity problem. In low signal-to-noise-ratios (SNRs), where the estimator cannot distinguish between the ambiguity function peak near the true source location and ambiguous ones, its mean square error deviates radically from the Cramer-Rao lower bound (CRLB). The Barankin bound for the source localization problem in an uncertain shallow water environment is derived. In particular, a method of selection of the test-points for evaluation of the bound is presented. The bound is evaluated using a "general mismatch" benchmark scenario. The results presented predict the threshold SNR below which the performance degrades dramatically. Channel uncertainties in the benchmark scenario are shown to increase this threshold SNR by as much as 3 dB.