Germany's TETRA Critical Communications Network Faces Toughest Test in Decades

Thuringia wildfire pushes Digitalfunk BOS to unprecedented operational limits — and the network holds.

In early July 2025, a major wildfire broke out on the Saalfelder Höhe near the district of Gösselsdorf in the Saalfeld-Rudolstadt county of Thuringia, Germany. Fuelled by weeks of drought and near 40°C temperatures, the blaze spread rapidly across steep, topographically challenging terrain encompassing valleys, old mining shafts, embankments, and forested hillsides — ultimately burning an area of 270 hectares. It became the largest wildfire in Thuringia in more than 30 years.

The incident served as a significant operational test for Germany's Digitalfunk BOS Network — the nationwide TETRA-based digital radio network for public safety and security agencies. Once again, the network demonstrated its resilience under extreme conditions, with cross-organisational and cross-border communications playing a decisive role in the successful management of the incident.

Rapid Escalation

At 14:24 on 2 July 2025, the Jena emergency coordination centre dispatched a large-scale response to the scene under the category "large vegetation fire." Initial units from volunteer fire brigades were met with a rapidly escalating fire front, driven by strong winds and reaching heights of approximately five metres. Crown fires developed quickly, accelerating the spread across steep slopes.

By 17:30 that same afternoon, the county authority declared a formal state of disaster (Katastrophenfall) for the Saalfeld-Rudolstadt district. Units from neighbouring districts — Sonneberg, Saale-Holzland-Kreis and Ilmkreis — as well as the Federal Agency for Technical Relief (THW) and Thuringia Police were already mobilised. The Thuringia Police helicopter deployed its external water container on the first day. At peak operations, up to 750 responders from all public safety and security agencies (BOS) were on duty in shift rotations.

Given that adequate close-range water supplies could not be guaranteed, extended hose lines stretching up to 14 kilometres were established to distant water extraction points, alongside tanker shuttle operations. Four relief contingents from the Free State of Bavaria were also deployed, along with helicopters from Thuringia Police, Bavaria Police, and the Federal Police — at times, three aircraft operating simultaneously.

Communications Under Pressure

With the activation of the incident command structure, the Authorised Office (Autorisierte Stelle, AS) in Erfurt was immediately notified and commenced operational support. The BDBOS deployed its dedicated "Special Operational Structure for Wildfires" (Besondere Aufbauorganisation Waldbrand), enabling overregional coordination and the provision of additional network resources.

Two TMO cross-border talkgroups (TBZ-Sprechgruppen) were approved and reserved at an early stage by the Federal Authorised Office. These were used for inter-state communications with Bavarian units, as well as for aerial coordination and water-drop operations by the deployed helicopters.

Due to the topography and the breadth of operational sectors, up to 20 TMO talkgroups were ultimately established and used — covering incident command, individual firefighting sectors, water supply operations, shuttle logistics, aerial coordination, and fuel and supply logistics. In sectors with limited TMO coverage, particularly in the Königsthal valley area situated below the fire on the steep slope, Direct Mode Operation (DMO) talkgroups were used, supplemented in several sectors by multiple DMO repeaters to overcome terrain obstacles.

The three TETRA base stations covering the operational area were each equipped with two carriers. As the area is rural rather than urban, the number of available time slots was limited. Despite this, overall network availability across the operational area reached approximately 98 percent. Only in the Königsthal valley sector was TMO connectivity restricted, and a request for a mobile base station was temporarily submitted to AS Thüringen, though subsequently withdrawn as the situation in that sector stabilised.

During peak periods, base stations experienced high load, resulting in queuing. Operational coordinators reinforced correct radio discipline: responders were advised to hold the Push-to-Talk (PTT) button until a voice channel was allocated rather than releasing and re-pressing, which extends waiting times, and to avoid switching handsets off and on, which generates additional network load.

Statistical Highlights

The four most intensive days of the incident drove communications activity to levels unprecedented in Thuringia:

• 140,000 SDS messages were transmitted — averaging 30,000 per day, a tenfold increase over the normal daily load of approximately 3,000.
• 20,000 group calls were made, compared to approximately 30 per day under normal conditions — peaking at over 5,000 per day during the operation.
• 12,000 minutes of voice radio traffic were logged — equivalent to 200 hours, or more than eight continuous days of communication.

BDBOS noted that such sustained communication volumes would have been unachievable within the capacity constraints of analogue radio systems.

Resolution

On 6 July 2025, following the containment of the fire's spread, "fire under control" was declared. The state of disaster was formally lifted by the Saalfeld-Rudolstadt county administrator on 8 July 2025 at 10:00. Following the extinguishing of several hundred hotspots, "fire out" was officially reported to the Jena coordination centre on 14 July 2025 at 08:00.

Picture: Courtesy of  Landratsamt Saalfeld-Rudolstadt, Amt für Bevölkerungsschutz