This study explores the performance of different modulation schemes for underwater acoustic communications, which are crucial for efficient data exchange in Uncrewed Underwater Vehicles (UUV) used in various maritime applications.
We conducted sea trials in the Venetian Lagoon and the Gulf of La Spezia using a low cost software-defined acoustic modem developed by the University of Padua and SubSeaPulse SRL. Our analysis compares the performance obtained using the JANUS waveform with that recorded using Binary Phase Shift Keying (BPSK). Despite JANUS ensures superior Packet Delivery Ratio (PDR), BPSK achieves greater throughput over shorter distances. Specifically, JANUS consistently provides high PDR across different environmental conditions, making its use ideal for scenarios where reliable communication is required. Conversely, BPSK modulation provides significantly higher data rates, even though reaches a lower PDR. This makes BPSK suitable for applications where throughput is more critical. These findings
highlight the trade-offs between communication reliability and data rate, guiding the selection of modulation techniques for specific underwater scenarios. This research contributes to the ongoing development of efficient underwater communication networks, which are essential for the advancement of autonomous marine technologies.

Keywords: Underwater communications; acoustic modem; software defined modem; JANUS; MPSK; sea-trial.