Accurate Doppler estimation for underwater acoustic communications

In underwater acoustic transmissions, Doppler effect can be caused by propagation medium movements or by the relative velocity between the transmitter and the receiver. It often yields additional difficulties for processing received signals. The purpose of this paper is to present a new algorithm for Doppler frequency estimation. The algorithm is based on cross-correlation among training sequences located at the beginning and at the end of transmitted data frames. From these training sequences two phase estimates are calculated: a coarse one and a precise one. The precise estimation has much smaller ambiguity range than the coarse one, but it yields higher precision for the estimated Doppler frequency. We show that a convenient combination of the coarse and precise phases leads to a good Doppler estimation within the speed range under consideration in the dedicated application.