Defense Department pushes spectrum sharing as solution to wireless crunch

The Defense Department and wireless industry agree freeing up government owned spectrum is a good idea, but they disagree how about how to do it.

Marguerite Reardon Former senior reporter
Marguerite Reardon started as a CNET News reporter in 2004, covering cellphone services, broadband, citywide Wi-Fi, the Net neutrality debate and the consolidation of the phone companies.
Marguerite Reardon
5 min read

SAN DIEGO - The Department of Defense says it's onboard with freeing up more wireless spectrum for commercial wireless broadband use. But proposals that rely heavily on the government sharing wireless spectrum with private sector wireless carriers doesn't jive with what the industry wants.

Robert Wheeler, Major General United States Air Force, Deputy CIO Department of Defense, talks about the Defense Department's mobile strategy. CNET/Marguerite Reardon

At the CTIA's Mobilecon tradeshow here Wednesday, Major General Robert Wheeler, a deputy CIO for the Department of Defense, gave a keynote speech in which he outlined how the government agency plans to free up additional spectrum that will help the country reach President Obama's goal of releasing 500 MHz of additional wireless spectrum to the market.

While he promised that the Defense Department, which is the largest license holder of government owned spectrum, would clear or move off some spectrum to make room for commercial use, he also emphasized the prospect of sharing spectrum with commercial providers.

This is an idea that has been pushed recently by the National Telecommunications and Information Administration, the government agency in charge of overseeing wireless spectrum allocated to government agencies, and the President's Council of Advisors on Science and Technology (PCAST). These agencies have been reviewing ways in which government spectrum can be used to help alleviate the "spectrum crunch" facing commercial wireless providers.

In a report issued earlier this year, NTIA said it could cost $18 billion to completely clear the 1755MHz to 1855MHz spectrum band, which is the sliver of spectrum that is most attractive to commercial wireless broadband providers.

Wheeler reiterated the NTIA's findings, stating that it could be too expensive for the Defense Department to relocate its applications and services to other frequencies in order to give the wireless industry a completely cleared band of spectrum. And he noted that the government and the wireless industry would have to work together to come up with creative solutions to this problem.

"There isn't one solution to clearing this spectrum," he said. "There will be some vacating, but that can be expensive.

As an example, he described the difficulties that in relocating spectrum that is used for a satellite application that the Defense Department uses to train fighter pilots. He called the application "Top Gun on steroids" and said it was one of the most important training programs the government has in place. But he explained there was a problem. As he put it, the spectrum used for this satellite application is "smack dab in the middle" of the spectrum the agency is looking to clear for commercial wireless use.

And he explained that early assessments indicate it would be too expensive and take too long for the agency to move to a different frequency to make this spectrum available to commercial wireless providers.

"It's difficult if you have a satellite that's been up for 10 or 15 years," he said. "You can't change the transmit and receivers in space. So unless you want to pay to change out the equipment on the satellite you need to come up with something different."

A representative from the Department of Defense outlines the agency's strategy for freeing up 500MHz of wireless spectrum for commercial use at the CTIA's Mobilecon 2012 show in San Diego. CNET/Marguerite Reardon

The something different, he explained is to share some slivers of spectrum with commercial wireless operators.

There are three main types of sharing his agency is proposing. There's geographic sharing in which the Defense Department would continue to use its applications in certain locations in a discrete area and would allow commercial providers to use the spectrum in areas where it is not using the spectrum. There's also time-shifted sharing, which will allow commercial providers to use spectrum during certain periods of time when the government is not using a particular sliver of spectrum.

And the final type of sharing is what he called "true sharing" or cognitive sharing. In this scenario, special technology is used to sniff the airwaves to ensure that applications designed to use the same frequencies of spectrum are not using them at the same time and intefereing with each other.

This technique is used with unlicensed wireless spectrum, such as Wi-Fi. And it will be used when unlicensed "white space" spectrum is put into use. But "cognitive" spectrum sharing has not been used with licensed spectrum. And there are plenty of people in the wireless industry who believe this is not an ideal solution.

In his own speech at Mobilecon later on Wednesday, Federal Communications Commissioner Ajit Pai explained how relying on spectrum sharing, particularly cognitive sharing, would cause a whole host of issues. And he explained how it could even harm competition in the wireless market.

"Look, I'm not opposed to spectrum sharing," he said. "For example, geographic sharing by creating exclusion zones around certain areas can be a useful tool. And spectrum sharing may be a workable alternative when auctions can't be used to raise funds for relocation, such as in higher bands like the 5 GHz band. But if our goal is to incentivize investment in wireless networks, nothing beats clearing."

Pai said that auctioning free and clear spectrum gives wireless providers the most flexibility to put wireless spectrum to the best use. He explained that wireless companies may be unwilling to invest in building networks with this spectrum because there would be too much uncertainty in how and when they could use the spectrum.

He also said that spectrum sharing may encourage more political infighting between the wireless industry and government, since interference issues are likely to come up in a scenario where entities are sharing spectrum.

And he pointed out that sharing wireless spectrum could also hurt competition by making it more difficult for smaller players to use this spectrum.

"Spectrum sharing is a complicated and largely untested endeavor that requires a lot of coordination among potentially hundreds of federal users and licensees," he said. "The largest wireless providers in America may be up for that challenge. But I doubt that smaller ones who lack the time or resources are."

The wireless industry has accused the Department of Defense and the NTIA of dragging their feet when it comes to freeing up additional spectrum for commercial use.

But Wheeler said in an interview after his speech that this accusation was untrue.

"I disagree with that assessment that we've been dragging our feet," he said. "We are the ones who have been pushing for this, because we know how important it is for the country to get more spectrum into the hands of commercial carriers. But we have certain requirements that we need to deal with."

He explained that many of the government's systems that use this spectrum were put into place well before the wireless phone market even existed.

"Spectrum wasn't a problem 20 or 30 years ago when many of this technology was being deployed," he said. "So that wasn't even a consideration then."

John Marinho, vice president of technology and cybersecurity for CTIA, acknowledged that some spectrum sharing may be necessary to get additional capacity into the network right away. But he said there needs to be a plan in place to eventually clear that spectrum.

"We can't share spectrum into perpetuity," he said. "That doesn't benefit anyone. Clearing spectrum is the most ideal scenario, and we need to do that as quickly as possible."