Massive MIMO, adaptive beam forming spiff up 12 GHz band

Advances in wireless technology are getting some love in the fight over whether the 12 GHz band should be used for 5G.

In its latest arguments before the FCC, long-time 12 GHz 5G proponent RS Access points (PDF) to a report that identifies recent technology advances for making the 12 GHz band so desirable for 5G, including Massive MIMO, beamforming and 5G carrier aggregation.

In support of the 12 GHz band offering a “huge technical advantage,” RS Access points to engineering firm Roberson and Associates’ findings that the 12 GHz band is a great “Goldilocks” band combining the best of C-band and millimeter wave (mmWave) characteristics in the areas of capacity, coverage, path loss and equipment development.

RS Access is putting a renewed focus on its quest to get the 12 GHz band teed up for 5G. The firm, which has ties to Dell Technologies founder Michael Dell, owns MVDDS licenses in the band, which could be used for 5G, a more lucrative use than the original intent for the spectrum. Dish Network is another big player in RS Access’ corner – one that is at direct odds with biggies like Elon Musk’s Starlink, which also wants to use the 12 GHz band, but for other purposes. RS Access thinks they can all co-exist.

RELATED: RC Access: Studies show ‘win-win’ for 12 GHz band

In a September 17 meeting with FCC staff, RS Access representatives reviewed the history of the proceeding and claimed to be the only party that has submitted detailed engineering and economic studies demonstrating that satellite and terrestrial 5G services can coexist “while unleashing tremendous social value.”

Its opponents, led by SpaceX, have provided “no science-based analysis or rebuttal of their own; they have instead offered rhetoric and misrepresentation that distract from the serious policymaking issues before the Commission,” RS Access CEO V. Noah Campbell wrote to the FCC.

Indeed, SpaceX has come out with guns blazing in recent FCC filings (PDF) of its own, saying RS Access’ arguments are “fatally flawed” and demonstrate a “disturbing lack of understanding of how customers are actually served using the 12 GHz band.” Even more troubling, according to SpaceX, is RS Access “callously concludes that the Commission should give DISH and RS Access new rights for free, even if such a donation would deny next-generation satellite broadband service to tens of thousands of otherwise unserved Americans across the country.”

RELATED: T-Mobile sharpens argument for 12 GHz auction

12 GHz: How valuable is it?

In a recent interview with Fierce, Roberson and Associates founder and CEO Dennis Roberson said some of the things he’s heard about the 12 GHz band remind him of the types of comments people made about other spectrum bands many years ago. (Roberson has been chair of the FCC's Technological Advisory Council for the past eight years.) 

However, in his view, the 12 GHz is a lot closer to the 3.7 GHz C-band than it is to the 28 GHz band, which is considered mmWave, and he’s not just talking about where the numbers land in sequence.

The characteristics of 12 GHz are much more akin to what’s currently considered high mid-band 5G spectrum.  Advances in technology over the past five years have made it more efficient, including when compared with mmWave, where the road has been “bumpy,” but engineering improvements are being made, he said.   

Over the past five years, Massive MIMO antennas have emerged and the ability to do beam forming is far more practical. Massive MIMO is something T-Mobile is taking advantage of, and it’s a good bet that AT&T and Verizon will take full advantage of it in C-band. But those techniques also are applicable to the 12 GHz band, he added.

Unfortunately, certain tools get a lot more cumbersome when you get to mmWave, Roberson added. As the antenna shrinks at the higher spectrum in dense configurations, the energy also is concentrated in a smaller area and that generates a lot of heat. But that’s not a problem in the lower 12 GHz band, he said.

If you look at the 280 megahertz of spectrum in the C-band compared with the 500 megahertz available in the 12 GHz band and the 800 megahertz at mmWave, “the surprising fact is that you get a lot more throughput out of the 12 GHz than you would in the millimeter wave,” even though there’s considerably more spectrum available at mmWave frequencies, he said.

For example, his firm found that 1 MHz of 12 GHz spectrum can carry 3.76 times as much data as 1 MHz of 28 GHz spectrum (under peak throughput conditions). In addition, they estimate that 500 MHz in the 12 GHz band could support aggregate downlink throughput of 20 Gbps, which is markedly higher than an estimated 15.1 Gbps feasible using the 280 MHz of spectrum in the 3.7 GHz band or the estimated 9 Gbps using the 800 MHz of spectrum in the 28 GHz band.  

Those aren’t the only differences. 5G deployments will require a lot more base stations at mmWave frequencies than in the 12 GHz band, and semiconductors and other network elements can be produced at lower cost in the 12 GHz band than in mmWave frequencies, according to Roberson.

Carr: Comes down to engineering

Ultimately, it will be up to the FCC, which is still acting without a permanent chair and awaiting a fifth commissioner appointee.

During an American Enterprise Institute event last week, Commissioner Brendan Carr was asked about the topic. He said the 12 GHz band “really comes down to engineering” for him. In a nutshell, “we have incumbent terrestrial providers that have 12 GHz licenses that want to do more with those licenses, that want to get into the 5G game with that 12 GHz spectrum,” he said.

On the other side of the equation, “we have this spectrum that is currently being used for a lot of these low earth orbit satellite operations,” including the type that SpaceX does. “There's going to be an engineering battle of experts as to: Can we do all of it? Which is obviously the preferred policy outcome," he said.

"If we can get greater terrestrial use out of 12 GHz while not causing harmful interference or interfering with these low earth orbit satellite connections, that's great. We'll simply have the proceeding and see where the engineering comes down," he said.