The Subsea Software-Defined Acoustic Modem v2: Extended Capabilities and Sea Test

The variety of technological applications that can benefit underwater missions, such as diver coordination and surveillance of critical areas with Autonomous Underwater Vehicles (AUVs), calls for the development of a flexible underwater communication platform that can be customized according to the user needs. Building on the architecture of the low-cost SuM software-defined acoustic modem developed for research purposes, we introduce SuM2, a new and more sophisticated acoustic device designed for operational conditions. SuM2, while maintaining interoperability with JANUS digital communication, enhances both the hardware and software architecture of the original SuM modem by introducing higher transmission power, an improved analog front-end, support for Single-Sideband (SSB) analog voice and advanced digital transmission features including multiplexed data streams and optional CSMA-like medium access. Sea trials demonstrate interoperability with commercial communication devices, reliable communication at ranges up to 3.3 km, and bit rates up to 19.2 kbps at short range. The results confirm that SuM2 achieves a significantly extended communication range compared to its predecessor while retaining full software-defined flexibility and compatibility with commercial SSB devices and NATO standards. The presented architecture establishes SuM2 as a versatile and affordable acoustic modem suitable for both research and operational deployments.