5G takes a big step toward lower 3GHz band

The US Department of Defense (DoD) on Wednesday released a redacted version of its Emerging Mid-Band Radar Spectrum Sharing (EMBRSS) feasibility assessment, which could move the 5G industry forward in its efforts to get a chunk of the lower 3GHz band.

The wireless industry's main trade association, CTIA, cheered the move. "We look forward to working with all stakeholders to identify ways to make more spectrum available for full-power, licensed commercial use domestically as soon as possible, while also supporting the needs of our military and national security," wrote Umair Javed, CTIA's SVP of spectrum, on the association's website. 

The DoD's 236-page EMBRSS report makes clear that the Pentagon is very interested in protecting existing US military operations in the lower 3GHz band, which stretches from 3.1GHz-3.45GHz (it is also referred to as 3100-3450MHz). However, the agency does hold open the possibility of freeing up some of the spectrum for 5G.

"This report ... concludes that shared Federal and non-Federal use of the 3100-3450MHz band for shared Federal and non-Federal use is feasible if, and only if, the listed conditions enumerated in Section 8.4 of this report are fully proven through rigorous, in-depth, real-world full scope operational testing with Joint Force assets and implemented in advance of any auction," the report states.

The caveats

Section 8.4 of the feasibility assessment outlines the stipulations the Pentagon would have on releasing spectrum in the lower 3GHz band for 5G.

"Sharing of the 3100-3450MHz band between Federal and commercial systems is not feasible unless certain regulatory, technological, and resourcing conditions are proven and implemented," the report states.

It continues, noting that a "coordination framework must facilitate spectrum sharing in the time, frequency, and geography domains as well as stringent adherence to all the following conditions:

But the DoD report adds that even if the conditions are met, "spectrum sharing between Federal and non-Federal users in the 3100-3450MHz band will remain challenging. DoD is concerned about the high possibility that non-Federal users will not adhere to the established coordination conditions at all times; the impacts related to airborne systems, due to their range and speed; and required upgrades to multiple classes of ships. Developing a DSS [dynamic spectrum sharing] capability presents a massive engineering challenge."

A sharing event 

The DoD also said this week that it will hold an event on April 8 to "unveil a new initiative for collaborative spectrum study and experimentation. Efforts within this initiative, which will be coordinated through the National Spectrum Consortium, will examine technical approaches to dynamic spectrum sharing with the goal of building trust among stakeholders and accelerating solution deployment."

When questioned about the event by Light Reading, a DoD official offered a few more insights into what the Pentagon might announce.

"DoD is excited to discuss work that is about to begin in support of the National Spectrum Strategy during this event," wrote Paul Brooks, a representative of the Office of the DoD Chief Information Officer. "We are committed to ensuring the US remains at the cutting edge of 5G/NextG technology and fully intend to approach this in a collaborative and transparent way that encourages industry innovation while maintaining critical national security capabilities."

The 5G industry has been eyeing spectrum in the lower 3GHz band for years. US military officials, in past remarks on the topic, have resisted calls for the DoD to release any spectrum in the lower 3GHz band. Instead, they've only been open to spectrum sharing scenarios.

The situation has generated plenty of interest among players in the private sector. For example, startup Digital Global Systems (DGS) recently exited stealth mode with technology it said would support spectrum sharing, including in the lower 3GHz band.

However, recently a top official at the DoD said the agency would consider moving some of its airborne radar operations off the lower 3GHz band in order to free it up for 5G operations.

"We're also going to look at some other aspects, potentially some limited, paid-for relocation, perhaps for future airborne radars," said DoD CIO John Sherman at an NTIA event earlier this year. "We're going to check this out here, and really try to turn over every rock we can on this, because we know the criticality … about the very close unity of commercial and military success."

But Sherman reiterated the Pentagon's preference for spectrum sharing – rather than relocation – in the lower 3GHz band.

Regulatory moves

The potential for "paid-for relocation" is important because the US 5G industry is keen to move military users off the lower 3GHz band so it can be repurposed for commercial operations. Paying for such a shift is a familiar concept in the telecommunications industry as spectrum auction revenues are often used to relocate incumbent users to other bands. In general, the 5G industry does not want to share the band with the DoD.

After almost two years of work, the DoD's EMBRSS report was finished late last year but was not publicly released until now.

The report has already been overtaken by more recent events. The Biden administration released its national spectrum strategy late last year. That document puts the NTIA squarely in charge of handling spectrum coordination between federal and commercial users.

And the NTIA's spectrum strategy implementation plan, released earlier this year, calls for ongoing studies on how to shift federal users out of the lower 3GHz band in order to free it up for commercial use. However, the government's study of the job won't be done until 2026.

"We're pleased that the administration's National Spectrum Strategy is correcting the incomplete EMBRSS study by considering proven sharing techniques such as retuning, relocating and repacking federal systems as well as other robust sharing mechanisms," wrote Javed, the CTIA official.