Flumo: Flexible Underwater Modem

The last years have seen a growing interest in underwater acoustic communications because of its applications in marine research, oceanography, marine commercial operations, the offshore oil industry and defense. High-speed communication in the underwater acoustic channel has been challenging because of limited bandwidth, extended multipath, refractive properties of the medium, severe fading, rapid time variation and large Doppler shifts. In this paper, we show an implementation of a flexible Software-Defined Acoustic (SDA) underwater modem, where modulation parameters are completely tunable to optimize performance. In particular, we develop the system architecture following two key ideas. First, the modulation/demodulation part runs fully in software and is completely decoupled from the rest of the system. The system can be used to send/receive modulated signals from different system and, on the other side, it can be used to modulate signals that are sent from different system. Second, we provide to the users a flexible and tunable system where the different communication parameters can be adjusted in order to reach the best performance in every scenario. The proposed modem, that also supports the JANUS standard, has been validated experimentally in two different controlled testbeds and also through the Watermark simulator, which provides a realistic and repeatable co-simulation environment.