Detection, synchronization, and Doppler scale estimation with multicarrier waveforms in underwater acoustic communication

We propose a novel method for detection, synchronization, and Doppler scale estimation for underwater acoustic communication using orthogonal frequency division multiplex (OFDM) waveforms. The method involves transmitting two identical OFDM symbols together with a cyclic prefix, while the receiver uses a bank of parallel self-correlators matched to different Doppler scaling factors on waveform dilation or compression. We characterize the receiver operating characteristic in terms of probability of false alarm and probability of detection, and analyze the impact of Doppler scale estimation accuracy on the data transmission performance. We have tested the proposed method with real data from an experiment at Buzzards Bay, MA, Dec. 15, 2006. Using only one OFDM preamble, the proposed method achieves performance similar to an existing method that uses two linearly-frequency-modulated (LFM) waveforms, one as a preamble and the other as a postamble. Avoiding the need of buffering the whole data packet before data demodulation, the proposed method enables online receiver operation.