Drone flights – are we blind at lower altitudes? ISAC: Regain control with mobile communications!

Professor Thomä, why is U-Space so important for our resilience and safety?

U-Space is a term commonly used in Europe to refer to the airspace used by unmanned aerial vehicles. Traffic management systems (Unmanned Traffic Management, UTM) already exist for the commercial use of U-Space. In just a few years, U-Space has developed into a highly dynamic field.  Drones offer incredibly valuable opportunities for efficient and high-quality inspections of power lines, wind turbines, and large solar parks, for example. They also support agriculture and can help save lives in rescue operations. In addition, there are drones that are flown by private individuals purely for recreational purposes. This naturally leads to a massive increase in the number of drones in U-Space, but it also poses risks, as not all drone operators adhere to the rules.

Where do you see the greatest risks today?

When we talk about risky drone flights, we are essentially talking about unauthorized flights in the vicinity of critical infrastructure, military properties, airports, or security-relevant industrial complexes. This is now well known, as evidenced by the regular airport closures across Europe. However, the issue is much broader, as other areas of critical infrastructure are also affected. The most vulnerable points are generally those where infrastructure is widely distributed. This includes facilities for the generation and distribution of energy – especially renewable energy – telecommunications sites, and transportation hubs. We are talking about objects that are often decentralized, relatively freely accessible, and therefore difficult to protect. When you consider, for example, that substations today are typically protected only by a chain-link fence and a warning sign saying “Caution: High Voltage” – whereby the word “protection” sounds like a mockery given the threat situation – then this borders on naivety. As for the specific risks posed by drones: Drone flights can be used for espionage, sabotage, or provocation. A few years ago, this was theoretical at best. But today, with Russia waging a terrible war on part of Europe, hybrid warfare reaching new heights, and geopolitical upheavals unfolding before our eyes, it is incredibly relevant. Moreover, the authorities assume that this threat will continue to escalate.

For decades, we have relied on radar technology for airspace surveillance – but is this sufficient in light of the new threat situation?

Conventional airspace surveillance is not designed for comprehensive surveillance of U-space. The available drone defense systems are also only suitable for monitoring individual locations, such as power plants or airports. They can be set up locally and temporarily for special events such as a G7 or NATO summit. However, they are not networked over a large area and are not designed for permanent and nearly comprehensive operation. There is no way to combine data across regions to create a comprehensive picture of the lower airspace. Furthermore, radar sensors can only be used to a very limited extent, primarily for regulatory reasons. However, we need a system that can also detect and identify passive drones. Radar sensors are absolutely essential for this. Hobby drones are not particularly interesting in case of doubt, but in the current sensitive situation – even without malicious intent on the part of the pilot – they always initially create a potential threat. Protective systems are therefore under strain in any case. Drones that are proven to pose a targeted threat must therefore first be distinguished from harmless hobby drones. To do this, heterogeneous sensor data must be collated and condensed. The information obtained must then be reliably passed on in real time to authorities or operators of critical infrastructure. In short, we need a national, networked sensor system with high resolution and fast response times. Dedicated radars, which are extremely expensive to purchase and operate and also require radio bands that are not available nationwide, are unsuitable for this purpose. We should therefore urgently exploit the technological potential of mobile phone networks.

What role can mobile phone networks play?  

The main advantage is that mobile networks already have a dense coverage. The entire federal territory is almost completely covered by mobile communications – except for a few white spots, which are actually located far away from any relevant infrastructure. Mobile networks in Germany have the necessary infrastructure, power supply, and network connection, and are regularly maintained on site or tested for functionality via remote control. This gives us a virtually perfect platform that can be used to monitor U-Space. This is where the key technology of Integrated Sensing and Communication (ISAC) comes into play. ISAC integrates the sensor technology directly into the communications network. The signals that are normally transmitted by mobile phone base stations for communication purposes can, together with additional sensors, also be used for radar detection of objects in the airspace. Other threats to critical infrastructure that do not originate from drones can also be detected with ISAC. The existing mobile network and the additional sensors create an efficient and comprehensive system of networked communication and sensor technology. And this is far more than just a pipe dream: ISAC is already being standardized by 3GPP—an international cooperation of standardization bodies that develops technical specifications for mobile communications standards worldwide—as part of 5G Advanced and is considered a key feature of future 6G networks. However, pragmatic approaches already allow solutions to be found for urgent tasks to improve security in public spaces within the framework of the existing network.

When you say that ISAC is already technically feasible because it can be built on the existing mobile network, mobile network operators will certainly not shout “Hurray!” if they have to make additional investments. What about the economic viability of the overall concept?

As I said, ISAC uses existing infrastructure – locations, power supply, radio resources. That's why it requires comparatively little investment. Operation is cost-effective and sustainable. The system can be expanded and adapted as needed and in line with the threat situation. Since mobile network operators are continuously modernizing their networks, ISAC automatically benefits from this technological progress. What's more, the networks are already highly available, subject to a proven operator model, and sufficiently redundant – characteristics that security-related sensor technology urgently needs. After all, it is a declared goal of NATO to be willing and able to defend the entire NATO area. To this end, NATO members have agreed to significantly increase investment in security. Member states' defense spending is to be increased to five percent of gross domestic product (GDP) by 2035 at the latest. This includes 3.5 percent for traditional defense spending and 1.5 percent for defense-related spending. ISAC can be interpreted as such security- or defense-related expenditure. Since the protection of critical infrastructure and the threat posed by drones mean that national defense and internal security tasks can no longer be consistently separated, the Federal Ministry of the Interior and the Federal Ministry of Defense should coordinate their efforts in this area.

So the state would have to cushion the mobile network operators' expenses financially?

This brings us to the question posed above about the economic viability of sensing as a value-added service in the network. The concept is unlikely to be an immediate business case for mobile network operators for the time being. So they won't be shouting “Hurrah!” One solution could be to operate sensing as an MCx network service, similar to the new digital radio system used by authorities and organizations with security tasks (BOS). We are therefore talking about a government mandate here, not just financial support. An alternative could also be a PPP model or becoming part of future campus networks, especially if the focus is on protecting industrial facilities.

Let's move on to the technical component of ISAC: How are drones detected if they do not emit any signals themselves – i.e., remain passive?

Mobile phone base stations continuously transmit communication signals into the environment. Drones reflect these signals, and so-called “sniffers” – special reception sensors that are integrated into the mobile phone network – detect these reflections. And what makes ISAC special is that each object generates its own unique reflection – a fingerprint, so to speak. Once this fingerprint has been learned, it can be assigned to an object. With the application of AI, the classification process can ultimately be carried out efficiently. ISAC creates a spatially high-resolution situation picture via the sensor locations to be distributed across the entire area. Data fusion in the edge cloud then allows information from different locations to be combined. This makes it possible to determine the position, altitude, speed, and flight direction of even passive objects. Speed is important in order to be able to make the necessary preparations.

While Germany was recently debating whether ISAC could even be rolled out, Austria had already demonstrated its potential. Are Austrians on the fast track?

The Austrians have clearly recognized the high relevance of ISAC for civil security and are demonstrating that ISAC works. This is how the report published by A1 in mid-November 2025 under the headline “A1 launches ISAC pilot in 5G network: Next-generation intelligent drone and flying object detection” should be interpreted. That's great news and should shorten the lengthy discussions in debate-loving Germany! Austria also has a head start because certain frequencies – especially in the 26 GHz band – were allocated there earlier. For Germany, this means we must act now. From a technical perspective, we need to develop a consistent ISAC architecture across all levels – from physical detection to situation aggregation.

How can we achieve this in concrete terms?

From a regulatory perspective, the main issues are frequency policy, operator roles, and data protection. I believe the ball is primarily in the court of the federal government, the Federal Network Agency, and the mobile network operators. We need clear rules on how network operators can act as service providers. With its research program on communication systems, “Sovereign. Digital. Networked,” the BMFTR has already laid a good foundation for the development of the technological basis for future 6th generation (6G) mobile communications standards and thus also for ISAC. Specifically with the projects open6GHub, KOMSENS-6G and ICAS4Mobility. 

Now we need a funding program that addresses application scenarios, real-world laboratories, and pre-series systems—not just basic research. And with regard to Europe: In the medium term, we need a common ISAC architecture because drones do not stop at borders. The tests mentioned also provide valuable insights for European standardization. Don't forget: we are talking here about a highly efficient and, for the taxpayer, cost-effective key technology that offers greater security and a billion-dollar market. 

At the moment, all security technology providers know that the money is there for defense. What is not there is the time factor. Accordingly, everyone is shouting loudly and flooding the authorities responsible for procurement and purchasing with offers. How can the demand for the rollout of ISAC be heard, and what would be the most important next step?

ISAC is also making itself heard through its contact with the VDE. Thanks to its neutral and exclusively technology-neutral orientation, the VDE is a reliable partner for politicians. The VDE does not tell economic fairy tales. Since its foundation over 130 years ago, the VDE has also been a trusted anchor in matters of technology and its usefulness in application. Within the VDE, the Information Technology Society (VDE ITG) is particularly well-suited to deal with the topics of mobile communication and ISAC. Of course, I am also a member of the ITG. With the establishment of the new VDE Defense division, the VDE is also taking the right step at the right time. With ISAC, we need to start a systematic development process very soon – with pilot regions, cross-disciplinary research projects, and clear operator roles. Above all, we need a coordinated concept between politics, authorities, industry, and science. If we do not use the mobile communications infrastructure as a sensor platform, we will lose time and forfeit technological sovereignty. An ISAC-based situation assessment is feasible, scalable, and necessary. Now it's time to implement it.