Wideband Ultrasonic Acoustic Underwater Channels: Measurements and Characterization

TL;DR

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.

Abstract

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.

Figures (15)

• Figure 1: Measurement scenario.
• Figure 2: Measurement equipment at the receiver side.
• Figure 3: Block diagram of the measurement system.
• Figure 4: Partial spectrum of the received signal for the (a) first carriers and (b) last carriers. The frequency response of the filters $g_i[n]$ used for channel estimation is superimposed in orange color.
• Figure 5: Block diagram of the signal processing system for the channel frequency response estimation based on a bank of filters.