Abstract
Underwater sound propagation is very sensitive to geometric and environmental variations. The geometric variations are the motion of the source and/or receiver, while the environmental variations are due to surface motion and water column variations. In order to reduce the effects of these variations, it is necessary to understand their effects on sound propagation. In this paper, some water column variations are reported, and their effect on the underwater sound propagation is studied. These water column variations were observed during an experiment in the TrondheimFjord on 22 September 2016. Strong amplitude variations were observed in the channel impulse response during the experiment. The Doppler analysis was performed on the channel impulse response, which showed strong Doppler variations. The amplitude and Doppler variations suggested the presence of water column variations. To demonstrate the performance of the communication system, the time reversal combiner was implemented. The system performance was demonstrated by computing the mean squared error between the transmitted signal and the output of the combiner. The performance of the combiner degraded by ~2.5 dB in the presence of water column variations. Due to these variations, the amplitudes of the arrivals changed rapidly, which posed a great challenge for the time reversal combiner. These amplitude variations affected the focusing of the combiner and hence induced intersymbol interference and performance degradation. This work provides an insight into the effects of water column variations on underwater sound propagation and underwater acoustic communications.
Highlights
IntroductionThe underwater acoustic channel is a bounded medium with the sea surface and the sea bottom
The underwater acoustic channel is a bounded medium with the sea surface and the sea bottom.In this bounded medium, the acoustic signals propagate through multiple paths including the direct path, surface reflected path, bottom reflected path, and other paths with multiple interactions from the surface and/or bottom
This paper reports some water column effects that were observed during an experiment and studies their effects on the underwater sound propagation and underwater acoustic communications
Summary
The underwater acoustic channel is a bounded medium with the sea surface and the sea bottom. This paper reports some water column effects that were observed during an experiment and studies their effects on the underwater sound propagation and underwater acoustic communications. The typical pixel difference of 5 dB, wave width of 11 km, and four wave crests have been reported for Norwegian waters The effects of these water column variations on the underwater sound propagation have been studied in the literature. The effects of water column variations on sound propagation and underwater acoustic communications are studied. The main work of this paper is: (1) to study the effects of water column variations on underwater sound propagation using channel IR analysis, (2) to study the effects of these variations on underwater acoustic communications.
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