In this work we present the results of a measurement
campaign carried out in the Mediterranean sea aimed at
characterizing the underwater acoustic channel in a wideband at
ultrasonic frequencies centered at 80 kHz with a width of 96 kHz,
covering two octaves from 32 to 128 kHz. So far, these type of
wideband measurements are not found in the literature. Periodic
orthogonal frequency division multiplexing (OFMD) sounding
signals using Zadoff-Chu sequences have been specially designed
for this purpose. The collected data has been post-processed to
estimate the time-variant impulse and frequency responses and
relevant parameters for system design like the time coherence,
bandwidth coherence, delay spread and Doppler bandwidth. The
statistical behavior of the channel gain random fluctuation has
also been analyzed. This information has been extracted for both
the global channel and each path separately. The wide bandwidth
of the measurements have allowed the characterization of the
channel in a scarcely explored ultrasonic band with an accuracy
that is far beyond what is reported in previous works.
