Fundamental limits on acoustic source range estimation performance in uncertain ocean channels

Matched‐field methods which exploit complex multipath propagation models to localize underwater acoustic sources are particularly sensitive to errors in the assumed environmental parameters. In this paper, the Cramer–Rao lower bound (CRLB) is used to determine fundamental limits on the accuracy of range estimates obtained in the presence of uncertain environmental parameters. Theoretical results obtained using an adiabatic normal mode propagation model and a realistic model of sound‐speed profile uncertainty indicate that without prior statistical knowledge of the environmental parameters, the CRLB may diverge even when the number of unknowns is less than the number of acoustic modes. When the prior probability distribution of the environmental parameters is available, however, the CRLB indicates a significant improvement in range estimation performance is possible. Numerical evaluation of the bound on range estimation in the presence of sound‐speed profile uncertainty is performed both for an ideal waveg...