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Sensors 2017, 17(4), 937; doi:10.3390/s17040937

Improving Passive Time Reversal Underwater Acoustic Communications Using Subarray Processing

School of Marine Science and Technology, Northwestern Polytechnical University, Xi’an 710072, China
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Academic Editor: Jaime Lloret Mauri
Received: 3 January 2017 / Revised: 11 April 2017 / Accepted: 19 April 2017 / Published: 24 April 2017
(This article belongs to the Section Sensor Networks)
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Abstract

Multichannel receivers are usually employed in high-rate underwater acoustic communication to achieve spatial diversity. In the context of multichannel underwater acoustic communications, passive time reversal (TR) combined with a single-channel adaptive decision feedback equalizer (TR-DFE) is a low-complexity solution to achieve both spatial and temporal focusing. In this paper, we present a novel receiver structure to combine passive time reversal with a low-order multichannel adaptive decision feedback equalizer (TR-MC-DFE) to improve the performance of the conventional TR-DFE. First, the proposed method divides the whole received array into several subarrays. Second, we conduct passive time reversal processing in each subarray. Third, the multiple subarray outputs are equalized with a low-order multichannel DFE. We also investigated different channel estimation methods, including least squares (LS), orthogonal matching pursuit (OMP), and improved proportionate normalized least mean squares (IPNLMS). The bit error rate (BER) and output signal-to-noise ratio (SNR) performances of the receiver algorithms are evaluated using simulation and real data collected in a lake experiment. The source-receiver range is 7.4 km, and the data rate with quadrature phase shift keying (QPSK) signal is 8 kbits/s. The uncoded BER of the single input multiple output (SIMO) systems varies between 1 × 10 1 and 2 × 10 2 for the conventional TR-DFE, and between 1 × 10 2 and 1 × 10 3 for the proposed TR-MC-DFE when eight hydrophones are utilized. Compared to conventional TR-DFE, the average output SNR of the experimental data is enhanced by 3 dB. View Full-Text
Keywords: underwater acoustic communications; passive time reversal; adaptive multichannel equalization; channel estimation underwater acoustic communications; passive time reversal; adaptive multichannel equalization; channel estimation
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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He, C.; Jing, L.; Xi, R.; Li, Q.; Zhang, Q. Improving Passive Time Reversal Underwater Acoustic Communications Using Subarray Processing. Sensors 2017, 17, 937.

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