'Splitting method' brings less-powerful satellites into 5G era

Satellites are playing a key role in achieving the goal of global mobile communications that reliably reach every remote region, leaving no gaps on the map. In the future, however, not all satellites will be powerful enough to act as complete base stations. The Fraunhofer Institute for Integrated Circuits IIS has now developed a splitting method that allows satellites of different classes to be integrated into the 5G network despite this 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 kilometres with the associated latency. Although the satellites themselves are increasingly being equipped with intelligent onboard 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,” said Rainer Wansch, Head of the RF and SatCom Systems Department at Fraunhofer IIS.

Fraunhofer IIS has 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 minimising the use of computing power, energy and resources.

Another advantage of the splitting approach is that it greatly increases flexibility within the communication infrastructure, with Wansch saying, “Our splitting method opens the door to new and more complex architectures.” This is 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 km. 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.

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.

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