Lawmakers and regulators are at odds over the best way to satisfy the public’s growing demand for wireless data. Both have made finding more spectrum to expand mobile broadband networks a priority, but members of Congress are pushing for the immediate sale of a valuable chunk of federal airwaves, while the Obama administration appears more concerned with long-term planning.

Most stakeholders agree on one key point: The growing consumer demand for online video and other mobile applications has created a significant burden for wireless carriers, who claim their networks are straining to meet capacity. Those networks run on slices of spectrum, or airwaves, that the wireless carriers purchase at auction from the Federal Communications Commission for their exclusive use.

The various bands of spectrum have different characteristics depending on their frequency. Bands at lower frequencies are capable of covering much longer distances and going through walls, making them best suited for mobile uses, such as cellphone networks. The spectrum between 400 megahertz and 3 gigahertz is generally considered the most valuable, with all cellphone bands falling within that range.

Much of the spectrum not already sold to wireless companies or broadcasters is held by the government. The band of federal spectrum considered most valuable by the wireless industry is the 1755-1850 MHz band, more specifically the lower 25 MHz from 1755 to 1780. That band is used for cellular networks in some other countries and is technically appealing to the wireless industry for a host of reasons.

According to a report from the National Telecommunications and Information Administration, 19 U.S. government agencies currently deploy a wide variety of communications and surveillance tools in the 1755-1850 MHz band. Those include law enforcement surveillance tools, satellites dishes, drones, tactical radios and a host of other military uses.

The difficulty and cost of moving those federal users is uncertain and varies greatly depending on the use. Satellites can remain in the air for 20 years to 25 years, while other equipment potentially could be shifted to different bands of spectrum or replaced in a shorter time frame. The NTIA’s report estimates that it would take a decade and at least $18 billion to clear all federal users from the 1755-1850 band so it could be auctioned off.

“The hard truth is that there might be government users in that space that you just might not be able to move out for a while,” a Senate Democratic aide said. “They might need to be there for the next 10 to 15 years. That’s just the reality.”

But the prospect of waiting a decade is unacceptable to the wireless industry, which believes that next year’s spectrum auction — in which airwaves relinquished by television broadcasters will be sold to wireless carriers — is unlikely to attract enough broadcaster participation to satisfy its appetite. Several policymakers agree, as evidenced by the FCC’s announcement earlier this year that it will seek to auction the 1755-1780 MHz block at next year’s auction.

Rep. Doris Matsui, D-Calif., and then-Rep. Cliff Stearns, R-Fla., offered a bill last year directing the government to auction off the 1755-1780 block. Sen. John Thune, R-S.D., the ranking member of the Senate Commerce Committee, offered a similar amendment to last year’s defense authorization bill. Neither provision became law, but legislation isn’t necessary; Congress has already authorized the FCC to sell that spectrum as needed.

“Our nation is facing a looming spectrum crunch,” Matsui said. “In the short term, I believe pairing the 1755-1780 band with the 2155-2180 MHz band makes sense not just for revenue purposes but also for spurring innovation and consumer demand in our ever-growing digital economy.”

Passing legislation on the issue would provide federal agencies with a deadline as well as some form of carrot or stick to encourage government users to vacate the spectrum as expeditiously as possible. Supporters of auctioning the 1755-1780 MHz band argue that the NTIA’s cost estimate is inflated and that more detailed work and research is needed to determine the actual costs.

“All of this is completely doable under existing law,” the Senate Democratic aide said. “There’s a belief amongst some in commercial industry that, absent legislative mandate, government agencies won’t [vacate the spectrum]. But the president is firmly behind trying to make this happen and pushing it.”

Government users counter that their networks are programmed to run across the entire 95 MHz from 1755 to 1850, so depriving them of the lower 25 MHz would still require the replacement or reconfiguration of most equipment. The Obama administration has instead proposed an expanded regime of spectrum sharing between government and private industry, based largely on the way federal agencies currently use spectrum.

Unlike private companies, federal users never actually hold their own spectrum, they are instead given permission to use certain frequencies after coordinating with the NTIA. That means the various government networks must coexist in the same or adjacent bands without interference. Administration officials have suggested that a similar setup involving multiple commercial carriers may be more efficient than licensing the spectrum to one company for exclusive use.

Both the Pentagon and wireless industry have balked in the past at the notion of sharing airwaves, with the former concerned about potential interference with critical systems and the latter nervous about building its networks on spectrum it doesn’t own. Both sides view sharing as a fallback option, in contrast to the administration’s apparent preference for the approach.

The four major wireless carriers recently began preliminary testing with the Pentagon on potential sharing solutions, with particular focus on finding a way for commercial carriers to coexist in the 1755-1780 MHz band with government satellites. Allowing satellites to continue operating in the band while clearing other government users is expected to save as much as $3 billion from the relocation costs.

The Pentagon estimates the cost of vacating the entire 1755-1850 MHz band at roughly $12 billion. A Defense Department spokesman acknowledged that testing is under way with the major wireless carriers to examine the feasibility of sharing the spectrum while preserving certain vital government programs such as drones and air combat training systems.

“The department cannot provide details or speculate on the outcome of this effort,” the spokesman said. “However, it is important to note that this is a very good example of the cooperation that is occurring between the DOD and the commercial wireless industry.”

“We must carefully examine the benefits of both clearing and sharing spectrum over the long term,” Matsui said. “We must work to find a timely solution that addresses both our economic needs and our national security challenges.”

Republicans have expressed a broad preference for auctioning spectrum rather than sharing it among carriers, and they are particularly sensitive to concerns regarding critical defense systems. Should agencies drag their feet on vacating some or all of the 1755-1850 MHz block, GOP lawmakers will likely be quick to criticize the administration.

“Sharing sounds great, and there are various sharing technologies, but operating WiFi devices [in the same band] is very different than air combat training sharing spectrum with 4G broadband,” another Senate aide said. “That’s never been done before and probably shouldn’t be the first-choice option to pursue.”