The Federal Communications Commission today enacted a set of rules governing the sale and deployment of wireless signal boosters, devices consumers use to improve cell phone signals. More than 2 million of these devices are in use across the country, and until now consumers who bought them could just turn them on and let them work their magic.

Not anymore. Anyone who buys one of these devices from now on must seek the permission of carriers. Even the 2 million devices already in use must be turned off immediately unless their owners register them. The FCC states in an FAQ:

Did the FCC recently adopt new rules for signal boosters? Yes. The FCC recently adopted new rules to improve signal booster design so these devices won’t cause interference to wireless networks. The FCC also adopted new rules about what cell phone users need to do before using a signal booster. I already have a signal booster; do I need to do anything under the new rules? Yes. Under the FCC’s new rules, you (1) need your wireless provider’s permission to use the booster, and (2) must register the booster with your wireless provider. Absent your provider’s permission, you may not continue using your booster.

For practical purposes, there is a good chance you could keep using that device without getting any threatening legal letters. But technically, the FCC could issue fines to customers who fail to comply, Public Knowledge Legal Director Harold Feld told Ars. There's no word yet on what will happen to consumers who fail to register or whether carriers would actively seek them out.

(UPDATE: The FCC has already changed the language on that FAQ, indicating that the onus may not be on owners of existing devices to register with carriers. The FCC deleted the sentence that says "Absent your provider's permission, you may not continue using your booster." Instead, it now says, "If a wireless provider or the FCC asks you to turn off your signal booster because it is causing interference to a wireless network, you must turn off your booster and leave it off until the interference problem can be resolved. When the new rules go into effect, you will be able to purchase a booster with additional safeguards that protect wireless networks from interference." For buyers of new devices, the FAQ does still say that "[b]efore use, you must register this device with your wireless provider and have your provider's consent.")

There are good reasons for the FCC to regulate these devices. They could cause interference with cellular networks, even if the ones today generally haven't been too problematic. Everyone from consumer advocates to booster device makers, carriers, and the FCC agrees that standards to prevent interference are good. But Feld, other consumer advocates, and the makers of these devices say it's unfair to consumers to make them register with carriers.

Carriers aren’t ready to detail registration policies

Major carriers haven't said how the registration process will work, but one conceivable outcome is that they could charge customers an extra fee to use boosters, like they do with other devices that improve signals.

Wireless boosters are "saving the carriers money by not making them build more towers, but now they can charge you for improving the holes in their own network," Feld said.

Requiring a specific carrier's permission is odd, because a wireless booster can be used to improve signals on just about any network, said Michael Calabrese, director of the Wireless Future Project at the New America Foundation. Calabrese helped advise the government on its recent spectrum sharing plan. "97 percent of the boosters sold are wideband boosters, meaning they amplify the signals of all carriers equally," Calabrese told Ars. "For some reason, the commission has delegated authority to the carrier."

(UPDATE: After this story ran, we got a more positive take on the registration requirement from Wilson Electronics, a signal booster manufacturer. "We don't see registration having a surcharge added to it-—or being an end-all scenario," the company said. "90+ carriers already gave blanket approval to boosters that meet the specs. And the [FCC] commissioners were clear about the registration not being cumbersome. They also mentioned that they suspect few people will actually register the products given that consent will already be given." Wilson did oppose the registration requirement, but said on the whole the ruling was good and should only affect poorly designed products. Wi-Ex, maker of zBoost boosters, said "consumers do not have to power down the zBoost consumer products. Our Boosters do not interfere with the wireless providers' networks—consumers can continue using them and look for the notice their provider will send them regarding registration of the product with them.")

If carriers are stingy with device approvals, households with subscriptions to multiple carriers could have to purchase one booster for each carrier—even though there's no technical reason preventing a single booster from covering phones from multiple carriers.

Even though consumers have to register devices they already bought, booster manufacturers were given one year to clear out existing inventory before they have to sell new hardware that meets the interference rules. If they can keep selling existing devices, it's difficult to imagine they've caused cellular providers too much trouble.

FCC commissioner Robert McDowell said, "wireless service providers have experienced some harmful interference with boosters interacting with their networks." McDowell also lauded boosters for improving signals, even in tunnels where cellular connections are often disrupted.

Commissioner Mignon Clyburn said for millions of people, cellular service disruptions "are more than rare, trivial annoyances." Commissioner Jessica Rosenworcel said that 41 percent of children live in homes served only by cell phones and not landlines, making boosters one option for ensuring that emergency calls and doctor's calls can be completed.

In addition to consumer-strength boosters for homes, small offices, and vehicles, there are industrial-strength wireless boosters designed for airports, hospitals, stadiums, etc. Industrial-strength boosters have to meet stricter interference standards because they transmit at higher power levels than consumer-grade ones, and anyone who operates an industrial-class booster will need an FCC license.

Carriers both large and small have reportedly assured the FCC that they won't be unreasonable in providing approval for use of consumer-grade boosters.

We've asked Verizon Wireless, AT&T, T-Mobile, and Sprint to provide information on how the registration process will work and whether consumers will have to pay any extra fees when using wireless signal boosters. We haven't gotten any specific answers, but that's not surprising. AT&T pointed out to us this afternoon that the FCC hadn't even released the text of its order yet. (The FCC has since released the order.)

The FCC booster FAQ we mentioned earlier says, "Most wireless providers consent to the use of signal boosters. Some providers may not consent to the use of this device on their network." In other words, carriers generally allow it, but they're not legally required to.

AT&T told us that it's "pleased that the FCC has adopted technical standards designed to protect our customers from interference caused by signal boosters while allowing well-designed boosters to remain in the marketplace. For these standards to be most effective, however, it is important that they are coupled with appropriate enforcement and consumer outreach.”

Similarly, T-Mobile said it "supports the FCC’s decision today to facilitate the deployment of well-designed third-party signal boosters that can improve wireless coverage, provided they meet technical criteria to prevent interference and that consumers obtain consent from their service provider. T-Mobile will have more to say on this topic once we’ve had a chance to review the FCC’s Report and Order.”

Sprint declined comment today, but has publicly supported the FCC rules. Verizon told us "Our goal is always to make things as simple as possible for customers, and will work to do so here as well."

FCC says it took the best deal it could get

After the FCC unanimously approved the new rules today, FCC Chairman Julius Genachowski was asked why the carrier-consent provision became part of the final order. He said that carriers have agreed to play nice, so the FCC let them decide which devices consumers get to use. He said the FCC could revisit its decision later on if carriers end up acting unreasonably.

"One of the things that helped facilitate an outcome here was the commitment by a number of carriers to provide that consent," Genachowski said. "Our goal is to put in place clear rules of the road that enable and authorize signal boosters for consumers as quickly as possible, but as part of a framework that prevents interference. We all said, 'You know what, this is the fastest way to get from A to B. Meanwhile, we're going to monitor this.' We expect it to work but we haven't ruled out other options for the future if for some reason it doesn't."

Feld accused the FCC of rolling over for carriers by giving them the right to reject wireless boosters that customers want to use. Calabrese called it "profoundly anti-consumer." Besides charging monthly fees, Calabrese said carriers could strike exclusive deals with device makers to make sure they get a cut of each device sale.

"They could change their mind at any point, and enter into a royalty agreement with a particular booster maker," he said.

Feld explains that the boosters take your cellular signal and increase its power so that it reaches a cell tower (whereas femtocells work by taking your cellular signal and dumping it onto your home wireline network). Wireless boosters could be particularly useful in rural areas and in emergency situations, when one tower is down but the booster allows a connection to a further tower, he said.

"What's particularly irritating is we've got about 2 million people who bought these devices in good faith," Feld said. "The FCC is requiring them to go and register with their carriers and get permission [to keep using them]."

Prior to the FCC decision, the CTIA Wireless Association said the commission should take the stance that "commercial wireless providers must consent to the use of signal boosters on their networks prior to their operation."

"For the past decade, manufacturers of signal boosters have marketed and sold these devices without properly informing consumers of the need to work with affected licensees prior to operating devices," the CTIA said.

Wireless signal booster maker Wilson Electronics pleaded its case with the FCC too, arguing that the registration requirement is nonsensical, given that new devices won't even hit the market unless they meet interference requirements. Wilson's boosters are designed for use in the home, offices, and vehicles, with devices costing anywhere from $140 to several hundred dollars.

"Now that the Commission is on the verge of adopting network protection standards that were collaboratively developed by carriers and manufacturers to safeguard wireless networks, it would defeat the purpose of the rulemaking for the Commission to decide to empower carriers to deny consumers access to robust boosters that have been designed to meet those very standards," Wison wrote in a letter to the FCC on Feb. 12.

Expanding Wi-Fi

The FCC today also approved a Notice of Proposed Rulemaking to expand the amount of spectrum available to Wi-Fi in the 5GHz band by 195MHz, or about 35 percent. While the wireless booster decision was a final order, the spectrum one was preliminary and generally uncontroversial. The FCC is just beginning what might be a two-year process to expand the 5GHz band. Some interference concerns will have to be addressed. Read our previous coverage for more details.