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Coherence as a criterion for multichannel combining in low SNR communications in an upwelling environment

F. B. Louza and S.M. Jesus
LARSyS, University of Algarve, 8005-139 Faro, Portugal

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Ref.: OCEANS MTS/IEEE, Singapore (Malaysia), April 2020

Abstract: Establishing low signal-to-ratio (SNR) communications is a challenging task which aims at being undetected and may contribute to reduce underwater acoustic pollution minimizing impacts over marine life. In order to improve system reliability, the SNR at the receiver needs to be augmented, which is normally done by temporal and spatial coherent averaging. Much effort has been done to measure and understand coherence in shallow water [1,2]. However, in an upwelling shallow water environment, signals fluctuate rapidly with time due to short time scale oceanographic phenomena [3]. In the vicinity of busy harbors and areas of industrial construction, high noise levels may hamper efforts to recover acceptable SNR of weak communication signals. These factors influence the time of integration which is related to the effective bit rate of the communication system. The main goal of this study is to understand the impact of both temporal (TCOH) and spatial coherence (SCOH) over low SNR communications in a challenging channel and how to use coherence as a criterion to perform multichannel combination. Moreover, to compare results in terms of Bit Error Rate (BER) from data collected during the BioCom’19 experiment [4], using two independent arrays with four hydrophones each.



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