Underwater communications for moving source using geometry-adapted time reversal and DFE: UAN10 data

This work presents an improved version of our previously proposed technique, i.e. the combined geometry-adapted passive Time Reversal (pTR) and Decision Feedback Equalizer (DFE) for underwater communications between a moving source and a fixed receiver array (implying a range change) [1]. Since the geometry change can be compensated by employing a proper frequency shift on the probe Impulse Response (IR) in the pTR processing, the geometry-adapted pTR is called Frequency Shift pTR (FSpTR). A slot-based FSpTR processing is performed, where frequency shifts applied to the IRs can change over slots to compensate for geometry changes over time. The FSpTR output is the concatenation of slots of the processed signals. With different frequency shifts for consecutive slots, there are phase jumps in the FSpTR output. In this work, we propose a new phase-jump correction method, which is stable with respect to IR time-window selection. After the phase correction, a standard phase synchronization method and the DFE can then be applied subsequently to the FSpTR processing to further improve the performance. The developed technique is named FSpTR-DFE. Experimental data collected off Pianosa island, Italy in September 2010 for Underwater Acoustic Network (UAN) project, is called UAN10 data and used in the evaluation of the FSpTR-DFE performance. An information rate up to 2400 bps and BPSK signaling are considered. The results show that the FSpTR-DFE technique outperforms the FSpTR as well as the technique combining the conventional pTR with DFE when there exist strong range changes.