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Nachrichten, Termine, Experten
Amid geopolitical turmoil, protecting critical maritime infrastructure is more important than ever. The Fraunhofer Institute for Communication, Information Processing and Ergonomics FKIE is working together with maritime security research partners to develop innovative solutions for underwater acoustic communication and robust networks.
Conventional communications such as cellular networks, Wi-Fi and GPS do not work underwater because water severely attenuates electromagnetic waves. Fraunhofer FKIE therefore uses sound waves, or acoustics, for this task. But acoustic communication comes with physical limitations: Sound travels through water at only about 1,500 meters per second—roughly 200,000 times more slowly than light travels through air. Bandwidth poses another challenge: The greater the required transmission range, the lower the frequency needs to be. At ranges of around ten kilometers, net data rates often fall below 200 bits per second. The signal is also constantly disrupted by reflections from the water’s surface or the sea floor and fluctuations in temperature and salinity. Fraunhofer FKIE is working closely with partners to address these challenges by developing intelligent, self-configuring acoustic networks for underwater sensors and uncrewed submersibles (AUVs, short for autonomous unmanned vehicles).
From a single node to the underwater internet
But how does this underwater network work? Its backbone consists of flexible, rugged sea floor nodes equipped with sensors. These can transmit and receive data across high and low-frequency bands. A gateway buoy plays a key role by bringing the data above the surface, where it uses radio waves to transmit signals to ships or to shore. Autonomous underwater vehicles serve as mobile sensors and provide connectivity. The nodes can adjust their data rates, transmission power and other parameters, adapting dynamically to changing communication needs and environmental conditions such as rough seas or noisy vessels. This resilient network enables the uncrewed operation of sensors for intelligence gathering, surveillance and reconnaissance. It supports government and military defense missions as well as civilian protection, such as monitoring offshore wind farms and pipelines or collecting environmental data. In addition to detecting submarines, the acoustic network enables uncrewed mine hunting missions from a safe distance while operators remain protected aboard the mothership.
“Our goal was to replace rigid point-to-point connections with dynamic acoustic networks. Because conventional IP networks are unsuitable for extremely narrowband channels, we are developing entirely new protocol architectures,” says Fraunhofer FKIE research scientist Dimitri Sotnik. “We achieved this with the GUWAL standard and the GUWMANET protocol, which we established in collaboration with Bundeswehr technical center 71 (WTD 71).”
The GUWAL (Generic Underwater Application Language) standard specifies the format for requesting and transmitting sensor data and exchanging commands with autonomous underwater vehicles (AUVs). Designed specifically for efficient data compression and preprocessing in underwater communications, the format uses packets that are just 128 bits long. The GUWMANET (Gossiping in Underwater Acoustic Mobile Ad-hoc Networks) network protocol builds on GUWAL and provides the foundation for standardized underwater data exchange, such as querying sensor data or sending control commands to autonomous underwater vehicles. In sea trials, the protocol achieved a packet delivery rate of about 90 percent. “Because underwater links and nodes are vulnerable to sabotage, jamming (acoustic interference) and eavesdropping, we are building cybersecurity safeguards directly into the protocol to ensure the integrity of transmitted situational data and commands,” says the researcher.
GUWMANET supports multihop communication, a key technology for underwater applications. Because range is a function of data rate, not all network nodes can exchange data directly; instead, data must be relayed from node to node. The system must therefore automatically find routes to the destination and adapt them to constantly changing conditions. “GUWMANET can be configured so that only certain seabed nodes or AUVs communicate with one another while the others simply listen in. The buoy can also join the conversation. It has an acoustic transducer mounted on the underside for underwater communication,” says Sotnik. The gateway buoy prototype has already been deployed in large-scale NATO exercises near Lisbon, Portugal, where it forwarded GUWAL underwater data packets to a maritime operations center on shore. The GUWMANET protocol has also been successfully tested in numerous NATO operations.
Coordinating underwater swarms to protect ports and ships
GUWMANET also serves as the primary protocol for underwater communications and network routing in European defense project SWAT-SHOAL (SWArm and Teaming operation of manned and unmanned underwater vehicle SHOAL). The project aims to develop a swarm-based “system of systems” integrating crewed and uncrewed naval units. Working as a team, these units will provide greater performance and efficiency across a wide range of underwater missions involving mobile threats below the surface. The system enables different vehicle types to handle more complex scenarios as a cohesive team or to organize themselves in a group in which each entity is assigned a specific task. “In SWAT-SHOAL, we are exploring how to control multiple underwater vehicles so they travel in formation and carry out a mission together—such as protecting ships,” Sotnik explains. So far, the swarm technology has been evaluated in harbor trials, but several weeks of sea trials will begin shortly, allowing the project partners to test the entire process from mission planning through reconnaissance.
https://www.fraunhofer.de/en/press/research-news/2026/november-2026/buoys-the-co...
Communication technologies are tested during a sea trial.
Copyright: © Fraunhofer FKIE
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Communication technologies are tested during a sea trial.
Copyright: © Fraunhofer FKIE
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