Spectrum Allocation to Get a Strategic Overhaul

Cell phone communications, GPS navigation, television, and national defense systems have one thing in common: They all rely on access to the radio spectrum. But the usable spectrum is limited, and demand for it is growing.

As a result, the federal government is modernizing its approach to spectrum management. Its aim is to allocate and administer spectrum resources in ways that support the expansion of wireless services and technologies while protecting the operation of critical activities—including aviation, emergency response, and national defense.

MITRE, operator of six federally funded R&D centers, is performing advanced research, analysis, and testing to support the effective implementation of the government’s plans. 

Finding Innovative Solutions to the Spectrum Shortage

“The rapid growth of wireless communications has created a radio spectrum shortage, and the traditional ways of allocating spectrum can’t meet this new demand,” explains MITRE Chief Scientist Leila Ribeiro, Ph.D., an expert in wireless communications and spectrum evolution. “MITRE is working across government and industry to find innovative ways to share spectrum.”

That’s a complex undertaking.

Historically, spectrum has been managed with bands—or specific frequency ranges—reserved for certain users and applications. Today, repurposing is needed to more efficiently and dynamically utilize the available spectrum.

Traditional approaches to allocating additional commercial spectrum have included relocating government users out of a band, or compressing them into a portion of the band, to free up spectrum that can then be auctioned off to commercial users. However, the relocation approach is becoming increasingly difficult due to increased congestion. 

More innovative approaches allow multi-user access to spectrum. These can range from static coexistence to dynamic spectrum sharing (DSS), where multiple users take turns using a specific frequency band based on shifting priorities.

MITRE is looking at all options, from relocation to DSS, to support the national spectrum modernization goals. 

“But spectrum repurposing has to be done right,” Ribeiro says. “If it isn’t, it can result in a loss of functionality that could harm national security. It could affect GPS. Or it could degrade other critical services.”

Evaluating Spectrum Repurposing Opportunities, Band by Band

To get it right, the government is studying various bands to determine the best options for spectrum repurposing in each case. MITRE is a key contributor to the effort. 

We’ve already conducted analyses supporting several band studies. One focused on the Lower 37 GHz band, also known as the “innovation band” because of its ability to support fast and reliable connections—a must for 5G and future wireless technologies. Our work supported the government’s decision to pursue a shared-use framework in this band. 

MITRE has also been asked to lend its technical expertise to two new studies. One will examine a band that supports radar technologies vital for both national defense and military operations. 

Some of the big questions to be answered are whether the systems currently using the band can coexist with potential new commercial services, or whether some systems can be moved to neighboring bands. 

If they were moved, what would it cost to re-tune existing systems? Also, can this be done without the radar systems losing functionality and without causing harm to existing users in the landing bands? Additionally, what value should the government expect from auctioning this spectrum for commercial use? Would it be sufficient to cover the costs associated with these changes? And what would be the benefits to the economy?

“To do those kinds of analyses requires multidisciplinary expertise, which MITRE has,” Ribeiro says. “We’re bringing our expertise in radar systems, aviation and space-based operations, radio frequency engineering, and interference analysis to the effort, along with the capability to assess the value, risks, and costs of the different options for repurposing.”

Prototypes Support Dynamic Spectrum Sharing Needs

Additionally, MITRE is exploring advanced techniques that will allow the evolution of DSS to increase flexibility and improve the repurposing of spectrum in the future. That work has included the development and testing of prototypes to help cost-effectively achieve those goals.

“In the U.S., many government users cannot easily move into new bands or adapt their systems to accommodate new users,” explains Connor Freeberg, who leads MITRE’s DSS prototype development. “In some scenarios the onus is on commercial entrants to leverage the flexibility and agility of their systems to coexist with government users.”

Freeberg’s team has come up with a promising solution.

Instead of building a network of sensors across the country that could detect when the government is using the spectrum and relay that information to cellular users—an effort that could take many years and cost billions of dollars—the team explored how they could use existing cellular networks to perform that sensing function. 

“Cellular networks already have advanced capabilities that can detect different types of interference within the network and automatically mitigate it when it happens,” he explains. “What we’ve done is partner with industry to demonstrate that these same capabilities—which are improving with advancements in AI—could be used to detect government radar usage in a particular band of spectrum and institute interference mitigation techniques in near real time.”

A lab demonstration showed promising results for the network-as-a-sensor concept to be a viable DSS solution in some instances. 

“Now we’re working with our sponsors to further develop that concept,” Freeberg says. “Since MITRE works in the public interest, we’ll share what we’ve learned with government and industry.”