Characterization of overspread acoustic communication channels
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چکیده
The underwater acoustic communication channel is regarded as a difficult channel, owing to its bandlimited character, long delay spread, and time variability. In order to characterize the delay-Doppler spread, in situ measurements of the time-varying impulse response are required. This can be realized by transmitting and recording dedicated probe signals such as a pseudorandom binary sequence or a chirp ping train. Unfortunately, when the channel is overspread, i.e., the product of delay spread and Doppler spread is greater than one, channel soundings are compromised. This paper investigates which parameters can still be extracted from an overspread channel, and what type of probe signal is preferred. To this end, at-sea channel soundings are used as well as synthetic data generated with a channel simulator. It appears that the Doppler spectrum can be measured properly in many environments , but not the power delay profile. As the extent of the delay-Doppler spread increases, binary-sequence and chirp soundings lead to markedly different channel estimates.
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تاریخ انتشار 2010