Comparison of Doppler Estimation Methods in Mobile Underwater Acoustic Communication

Underwater acoustic (UWA) communication and networking have been of great interest in recent years and find utility in various commercial and military applications, including underwater surveillance, environmental monitoring, data-driven intelligent aquaculture, and unmanned underwater vehicles. However, due to the relatively low propagation ve-locity of sound through water, even modest velocities between transmitter and receiver translate into extreme Doppler shifts, marring transmission quality. The Doppler effect is amplified for high-frequency transmission, further complicating Doppler estimation and compensation. In this paper, we present three distinct Doppler estimation techniques based on linear frequency-modulated signals: displacement estimation, using preamble and postamble correlation; slope estimation, using the Fractional Fourier Transform (FrFT); and dilation estimation, using a novel matched filtering technique. We compare the efficacy of these three methods across three different scenarios: first, in simulation using a simplified channel model, and then in real-world UWA channels, employing both stationary and mobile node setups with software-defined Hydronet Modems.