Alert! How Fraunhofer IIS technology warns of crises via DAB+
In the event of a crisis, fast and reliable warning systems are particularly important. To test Germany's alarm systems, a warning day is held every year. The next one in Bavaria is scheduled for 12 March 2026. On this day, various communication systems for warning the population will be tested, including the DAB+ digital radio standard. To this end, Fraunhofer IIS has played a key role in developing a technology that can also be used in the nationwide test alarm in Bavaria: Automatic Safety Alert (ASA). It enables warning messages to be sent even when mobile phone or internet connections are down. But how does the system work – and how is it used in the event of a disaster?
11 September 2025, 11 a.m. A shrill beeping sound pierces the air throughout Germany. Since 2020, an annual test warning has been carried out to ensure that the warning system is functioning properly in the event of a crisis. Most people receive the message via a loud beep on their mobile phones. But what happens if the mobile network fails – a conceivable scenario in the event of a disaster? This is where ASA comes in.
ASA – disaster warning with the help of geofencing
ASA technology transmits warning messages via DAB+ radios even when mobile phone networks or the internet are down. Other warning options, such as apps or cell broadcast messages on our smartphones, are always dependent on a mobile phone connection. Another special feature of ASA is that radios equipped with the technology have a localisation function. This allows affected areas to be warned in a targeted manner while avoiding over-alerting the population. A software module processes the localisation data and can activate the radio from standby mode if necessary or automatically change the programme so that the hazard warning reaches users at all times.
The warning messages are regionally adapted and transmitted via so-called geocodes – twelve-digit number sequences that each describe an area of approximately one square kilometre and must be stored once by consumers in their radio as location information. Users can view these codes on the ASA website and enter them into their radio.
To enable ASA radios to quickly recognise whether the current group of radio stations on a DAB+ frequency (the so-called ensemble) supports warning messages, ASA-enabled ensembles send a ‘heartbeat’ signal once per second. In the event of an alarm, this signal also contains information on the respective warning level.
‘The working group I lead at Digitalradio Deutschland e.V. has decided to initially only broadcast priority level 1 warnings via the ASA system, because this switchover function is very invasive; we only use it in situations where time is of the essence,’ explains Olaf Korte, group manager for broadcast applications at Fraunhofer IIS. The radio is therefore only activated automatically at warning level 1, the highest of the three levels provided for in the nationwide Modular Warning System (MoWaS). At warning levels 2 and 3, as before, only devices that are switched on would be informed as part of the normal radio programme in order to avoid unnecessary disturbance, for example at night.
Accessible warnings with ASA
All devices with integrated ASA technology are marked with the ASA logo. Warnings are issued either as voice announcements by radio announcers or via text-to-speech (TTS) technologies, which automatically convert text messages into spoken language. In addition to acoustic signals for listeners, messages can be displayed in detailed text form as Journaline text on the radio display for deaf people using the extended warning function EWFplus – on selected devices even via a flashing signal. ASA with EWFplus can therefore offer a largely barrier-free warning system.
ASA as the standard for disaster warning
Olaf Korte's team has been working on integrating warning functions into digital broadcasting since around 2010 and has been involved in standardisation for 30 years. ASA was introduced as an international standard and is based on standards from the European Telecommunications Standards Institute (ETSI). The first certified receivers have been commercially available since mid-2025. The technology is now an important part of the warning mix, which continues to consist of sirens, warning apps and cell broadcasts.
An initial test run with ASA transmissions via DAB+ took place on the nationwide warning day in September 2024. In September 2025, ASA-certified receivers were tested in use for the first time: The warning messages via the Ingolstadt radio station even integrated the entire warning chain for the first time, including the Federal Office for Civil Protection and Disaster Assistance (BBK) and the Modular Warning System. ASA is connected directly to MoWaS, which ensures that only authorised warning messages are disseminated – thus ruling out uncontrolled transmission.
ASA is expected to be tested again in 2026 during a nationwide test alarm in Bavaria. However, comprehensive coverage is not yet available: the infrastructure for DAB+ warning transmission is being gradually expanded in Germany and thus also in Bavaria.
Another important milestone is the launch of regular ASA operations in the first nationwide DAB multiplex, which is currently planned for the next nationwide warning day on 10 September 2026. In other European countries, such as Austria, the implementation of the technology is still in the development phase. Olaf Korte and his team are looking to the future with hope and striving to establish a reliable warning system using ASA technology at both the national and global levels.
