Analysis of the Underwater Multi-Path Reflections on Doppler Shift Estimation

For underwater target localization and tracking, accurate Doppler shift estimation is very important. In this letter, the analysis of the multi-path effect on Doppler shift estimation accuracy is conducted for the narrow-band acoustic underwater channels. We conducted comprehensive analysis on the performance of a widely used low-complexity Doppler estimation algorithm, and showed that the mean square estimation error decreases with sample length quadratically. Then we derived the Cramér-Rao lower bound, which also decreases quadratically with sample length. As a result, we concluded that the impact of multi-path effect is negligible for a sampling length of several seconds. The theoretical results are verified by numerical simulations.