6G faces a spectrum-sharing future

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(Source: Kirill Ivanov/Alamy Stock Photo)

Spectrum sharing is set to become a central element of 6G planning in order to meet growing demand for increasingly scarce resources, according to a 6G Forum panel featuring representatives from the National Telecommunications and Information Administration (NTIA), AT&T, LitePoint and the Dynamic Spectrum Alliance. (See Can the telecom industry pave a smoother path to 6G?)

In the US, the NTIA has been tasked to identify at least 500MHz for commercial auction to support wireless broadband, including 5G and 6G, before 2030, while legislation sets a broader goal of 800MHz by 2034. (See Here's the latest on US efforts to find spectrum for 6G.)

Derek Khlopin, the NTIA's deputy associate administrator for spectrum, said studies cover several bands, including portions of the 1.6GHz, 2.7GHz, 4.4GHz and 7GHz ranges. However, he noted that making spectrum available may not always mean it can immediately be cleared of existing users.

Indeed, certain federal systems could remain in bands "for a significant amount of time," requiring ongoing sharing or other protections. "There will be more sharing necessary because the demands certainly aren't stopping, not just from the mobile community, but from other spectrum users as well on the commercial side," Khlopin said.

He described the likely outcome as "a bit of a mixed bag": some systems may move, while others may be accommodated through arrangements such as static exclusion zones or dynamic access. Here, he cited CBRS as a "great model," and suggested better data and AI scheduling tools could help make sharing more efficient.

Testing times, and the benefits of MRSS over DSS

For mobile operators, it is important that shared spectrum can be made predictable enough for their needs. Khushboo Kalyani, product marketing manager at LitePoint, said regulators and standards bodies need to define interference conditions – including power limits, signal leakage, waveforms and frequency offsets – so device makers and test vendors can evaluate equipment against them.

"There could be 100 different real-world situations that a device comes through. You essentially cannot test against that," she said. Instead, the industry could select test cases that characterize performance under shared or interfering conditions.

That testing challenge could grow as 6G adds bands, sharing arrangements, modulation schemes and antenna configurations. Kalyani warned that the combinations could multiply the test matrix, extending development time and affecting manufacturing costs. "You're essentially now going to be testing a combination of combinations," she said. She expects the industry to focus on practical subsets of scenarios rather than trying to test every possible configuration.

The panel also discussed sharing between generations of cellular technology. Milap Majmundar, AVP, emerging network, spectrum technologies and standards at AT&T Labs, said newer multi-RAT spectrum sharing (MRSS) technology could avoid some of the previous shortcomings of earlier 4G/5G dynamic spectrum sharing (DSS).

He said DSS faced overhead from control channels and the need for 5G to work around LTE reference signals. In contrast, "[New Radio/NR] does not have these fixed common reference signals," he said, providing greater flexibility to the newer air interface.

"I'm actually quite optimistic that we will be able to make, as an industry, 5G/6G MRSS to be much more efficient than what we had with 4G/5G DSS," Majmundar said.

The 6GHz debate

Meanwhile, Martha Suarez, president of the Dynamic Spectrum Alliance, argued that 6G planning should also incorporate other technologies such as Wi-Fi and non-terrestrial networks.

"I agree with the concept that 6G should have sharing as part of the concept itself. I think it's harder now to find exclusive bands for everything,” she said, adding that spectrum could be shared across applications depending on deployment and local needs.

Suarez pointed to the proposed UK approach for upper 6GHz in which mobile operators would have access when they need the band, while Wi-Fi could use it when it is not in use. She said such models could help balance investment certainty with more intensive spectrum use. "Those models could also be considered," she said. (See US unlicensed 6GHz isn't changing: The mobile industry needs to move on and UK wants mobile and Wi-Fi to share upper 6GHz spectrum.)

She also noted that the US has opened the full 6GHz band for Wi-Fi, which she viewed as a strong decision, and encouraged other countries to consider the benefits of that approach.

In contrast, "Europe has a somewhat different path, and they think that they will need part of the upper 6GHz band for future networks. But we are encouraging them to have some type of sharing," Suarez said. (See Mobile operators beat Wi-Fi for upper 6GHz in Europe.)

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