PSK modulation for Underwater Communication and One-Way Travel-Time Ranging with the Low-Cost Subsea Software-Defined Acoustic Modem

What limits most the use of low-cost underwater unmanned vehicles is the lack of affordable and low-power acoustic modems and positioning systems able to provide satisfactory performance, such as accurate distance measurement, a transmission range of at least several hundred meters, and a data rate of a few kilobits per second.In fact, although low-cost modems are now available in the market, they usually provide a data rate of only a few hundred bits per second and may not be able to adapt their communication parameters such as modulation and coding schemes nor perform complex tasks such as One-Way Travel-Time (OWTT) ranging or online data collection and processing from attached sensors.In contrast, the Subsea underwater acoustic software-defined Modem (SuM), recently developed by the University of Padova and SubSeaPulse SRL, is a low-cost platform composed of a newly developed Raspberry Pi HAT analog frontend, which brings underwater acoustic data transmission and positioning capabilities over the widely used Raspberry Pi platform, thus exploiting its great flexibility.In this paper we present its inaugural sea trial campaign in fresh and salt