Experimenting Various JANUS Frequency Bands with the Subsea Software-Defined Acoustic Modem

The use of traditional commercial acoustic modems is typically confined to Oil & Gas and military scenarios, as their high power consumption and steep cost make them inaccessible for many other applications, such as aquaculture, diver communication and low-cost underwater vehicle swarm. While low-cost acoustic modems are gradually entering the market, flexible research platforms like software-defined acoustic modems (SDAMs) remain prohibitively expensive for small research groups and startup companies, who, on the other hand, often drive innovation and generate new ideas. As a result, the development of these technologies, which currently find application in a few specialized contexts, remains constrained. When considering experimentation, what has empowered do-it-yourself practitioners and students approaching circuits and embedded systems is the availability of user-friendly and affordable prototyping boards like Arduino and Raspberry Pi. Following this paradigm, we developed the first Raspberry Pi HAT acoustic frontend for underwater acoustic testing and experimentation, and hence realized the low-cost Subsea softwaredefined acoustic Modem (SuM). In this paper we present its evaluation when used with the JANUS waveform at different frequencies bands, in both salt and fresh water. Given that we succeeded in proving its technological maturity in sea trials, we believe this modem can be both a valuable platform for industrial applications and a game changer to encourage other research institutes to experiment underwater communications.