Closed loop Doppler tracking and compensation for non-stationary underwater platforms

A new Doppler estimation and compensation scheme is presented to enable robust communications between non-stationary underwater platforms such as Autonomous Underwater Vehicles (AUV). The underwater acoustic channel is affected by Doppler shift induced by vehicle movement and time varying multipath propagation. To this end, this paper proposes a Doppler tracking method that is adapted within a wideband beamforming array with Decision Feedback Equalisation. Doppler compensation is achieved by multirate sampling and linear interpolation. This approach ensures that both multipath and Doppler effects are mitigated simultaneously. Simulation and experimental results are presented to show the performance gain achieved for a range of platform velocity and acceleration levels. The proposed approach is capable of robust communications with typical bit error rates of similar to1/1000 at vehicle speeds of similar to2.6 m/s. The paper also compares experimental performance with an open loop Doppler block processing approach.