New splitting method: Fraunhofer IIS brings satellites into the 5G era

Global mobile communications that reliably reach every remote region, leaving no gaps on the map? Satellites play a key role in achieving this goal. In the future, however, not all satellites will be powerful enough to act as complete base stations.

As part of the TRANTOR project funded by the European Commission, Fraunhofer IIS has now researched a splitting method that allows satellites of different classes to be integrated into the 5G network despite that shortcoming.

With 5G, communication on the ground is to merge with space for the first time to form non-terrestrial networks, in which satellites can completely take over the role of base stations. However, the technical challenges to be resolved are enormous: the existing mobile communications standards are not designed to allow signals to cover thousands of kilometers with the associated latency. Although the satellites themselves are increasingly being equipped with intelligent on-board processors, they are still reaching their performance limits. “After all, the industry is focused on building cost-effective satellites with robust and energy-efficient components,” explains Rainer Wansch, Head of the RF and SatCom Systems Department at Fraunhofer IIS.

Splitting the base station

Fraunhofer IIS has successfully demonstrated in the lab how satellites can be integrated into mobile communications, even if their performance falls short. To do this, the researchers split a 5G base station in half, so that only part of the signal processing is moved into space while the rest remains on the ground. This allows the satellites to be active players in the network and support wireless communications while minimizing the use of computing power, energy, and resources.

Another advantage of the splitting approach is that it greatly increases flexibility within the communication infrastructure. “Our splitting method opens the door to new and more complex architectures,” Wansch says. That’s because splitting makes it possible to distribute and design functions and tasks variably across different satellite orbits and performance classes. This is particularly relevant for the development of future 6G mobile communications, which are set to integrate not only satellites but also airborne platforms such as drones or aircraft.

For the experiment, Fraunhofer IIS used a channel emulator to realistically recreate the extreme conditions of space. This made it possible to simulate the connection to a geostationary satellite located at an altitude of 36,000 kilometers. Fraunhofer IIS used the DVB-S2X satellite communication standard to connect the base station and link the two split components together. Finally, part of the base station ran on a commercially available field-programmable gate array (FPGA), which could conceivably be used on future satellites.

Dense, universal, resilient

This demonstration of the splitting method is Fraunhofer IIS’s contribution to the TRANTOR project, which the European Commission is funding to prepare the transition of satellite communications from 5G to 6G. By consistently integrating satellites into mobile networks, research and industry hope to create a dense and universally available communications network that is highly resilient, even in crisis situations. Fraunhofer IIS is currently working on this in numerous other research projects; it’s also involved in 5G standardization through its role on the 3rd Generation Partnership Project (3GPP). Last year, the research institute was appointed to the Steering Board of the newly founded NTN Forum of the European Space Agency (ESA).