Ranging using spectral information

Information inequality is used to place lower bounds on the variance of unbiased spectrum-based range estimates. Bounds are also presented for the case of imprecisely known source spectrum shape and signal propagation model. A closed-form range estimator is developed for the case of deep ocean acoustic waves, and is shown to approach the information inequality for signals with large in-band signal-to-noise ratio. It is shown that spectrum-based range estimates are more accurate than those based on signal arrival times for sources far (at least a few array lengths) from a sensor array