Doppler Shift Estimation for Downlink OFDM Signals in Underwater Acoustic Integrated Sensing and Communication Networks

Underwater acoustic integrated sensing and communication networks (UAISACNs) using orthogonal frequency division multiplexing (OFDM) signals play an important role in the underwater missions due to their suitability to combine the sensing and communication applications simultaneously. However, the UAISACNs exhibit serious performance degradation when existing the Doppler shift. In order to handle this challenge, a Doppler shift estimation scheme is proposed for downlink OFDM signals of the UAISACNs in this paper. Firstly, the received signals are preprocessed via utilizing the property of the known sequence employed in the frame structure of transmitted signal in our presented work. Then, the composite fading coefficient has been derived by combining the second statistic with the fourth statistic of these preprocessed signals. Finally, based on the aforementioned derived composite fading coefficient, a maximum likelihood Doppler shift estimator is Proposed for the downlink OFDM signals of the UAISACNs. Simulation results are provided to show the benefits of the proposed scheme.