5G-SPECTRA: Satellite Performance Evaluation for Coexistence with Terrestrial Radio Applications

The 5G-SPECTRA project was a continuation of Magister’s previous TN/NTN coexistence simulation studies. During this project, Magister developed simulation tools for evaluating more specifically how satellites can best coexist with terrestrial 5G.

In response to the ESA’s invitation to tender, Magister undertook the 5G-SPECTRA project in partnership with Satellite Applications Catapult and the University of Surrey in England. The project focused on radio specification studies for 5G non-terrestrial networks.

Within 5G-SPECTRA, Satellite Applications Catapult and the University of Surrey identified coexistence interference scenarios, frequency bands, and network use cases. 

Magister, on the other hand, developed simulation tools for analyzing these scenarios. The goal was to examine the extent of the adjacent NTN/TN channel interference in various situations. The simulation results will be contributed to the 3GPP Technical Specification Group Radio Access Network (TSG RAN), RAN4 related RF specifications.

But what does coexistence mean here, exactly?

“It means that terrestrial (TN) and NTN networks can coexist and overlap not only in the same geographical coverage area”, Magister’s former CEO Jani Puttonen replied, “but also on the same or adjacent radio frequency.”

The 5G-SPECTRA project started in February 2023 and was completed in May 2024.

Better coverage with coexistence

Coexistence has become an increasingly pressing issue. More and more of the SatCom industry has shifted from geostationary satellites to non-geostationary (NGSO) satellites, such as low-earth orbit (LEO) satellite constellations.

“There is a significant propagation delay with a geostationary satellite orbiting at 36,000km”, Puttonen pointed out.

“That’s why they’re bringing in these LEO constellations. The delay is shorter and the localized capacity greater. However, they require hundreds of satellites to have constant coverage of the same area.”

Coexistence must be addressed, since these LEO satellite constellations are not geostationary. At times, they might be over areas with high traffic demand that already have TN coverage. In that case, they would complement the TN capacity. However, at other times, they may be over areas with no TN – such as the sea or mountains. In that case, they would provide all the capacity, and “fill the gaps” of TN coverage.

“Without regulatory and standardization efforts that allow NTNs to coexist with TNs, there simply won’t be any 5G NTN-based SatCom systems”, Puttonen stated.

“TN stakeholders won’t allow 5G NTNs to be developed if they interfere with existing networks. Currently, TN stakeholders have their own simulation tools, but the SatCom industry players necessarily do not. Magister aims to provide the SatCom industry with its own simulation tools so it can independently evaluate various coexistence scenarios”.

Co-channel coexistence refers to a situation where networks use the same frequency band. It is usually determined by regulatory bodies that specify the locations and other constraints for SatCom systems using specific frequencies.

However, it is another kind of coexistence that Magister is now focusing on – when networks use adjacent frequency bands. 

“You might think that there would be no interference if they are on neighbouring frequencies. However, there will be leakage because of non-ideal RF filters.”

The simulation results help in standardization

In the project, Magister simulated scenarios for different kinds of NTN and TN scenarios to see the extent of the adjacent channel interference in various situations.

“From these simulation results, we would then be able to define a set of constraints. They ensure that the magnitude of interference is not too high to cause significant performance loss,” Puttonen explained.

These simulation results will be shared with the standardization bodies that decide on the specifications for 5G NTN radio performance.

According to Puttonen, the SPECTRA project was a nice continuation of Magister’s previous TN/NTN coexistence simulation studies.

“Previously, we have focused on TN/NTN coexistence scenarios in FR1 (2-6GHz) for handheld mobile devices. However, in 5G-SPECTRA, we are complementing these by either focusing on scenarios in FR1 for IoT devices or in FR2 (20-30GHz) for directional terminals. Throughout the course of the project, we compare these two alternatives and decide which will be the most useful to focus on, even though our simulation tools could eventually be used for either”, Puttonen summarized.

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