The nation's top technology companies have spent millions of dollars and nearly two years building devices, poring over laptops and working in federal labs trying to come up with a new way of providing high-speed Internet to bandwidth-hungry cities as well as hard-to-reach rural regions.
Last week, the companies moved from lab to field.
Engineers from the technology heavyweights, including Motorola and Philips, lugged their laptops, antennas and other equipment to parks, homes and high-rises around the Washington area, hoping to prove to the Federal Communications Commission that the unlicensed airwaves between television stations, known as white spaces, could provide a new form of mobile Internet service.
Using white spaces will offer "a way to provide broadband across long distances at much faster speeds than cell phone networks and WiFi," said Jake Ward, spokesman for the Wireless Innovation Alliance, which includes Google, Microsoft, Hewlett-Packard and Dell. The group is trying to convince regulators that using the airwaves will provide broadband to rural schools, beam high-definition online video to low-income households and let consumers stream music while sitting in highway traffic.
First out of the gate was a team from Motorola. On a recent steamy day in the middle of PatapscoValleyState Park about 10 miles west of Baltimore, Dave Gurney, an engineer for the company, set up shop in a parking lot surrounded by dense forest.
A large black box the size of a suitcase hooked up to a laptop sat near the base of a tree-covered hill. An antenna perched on a tripod rested a few feet away. A group of engineers stared intently at the contraption, as if it were about to spring to life.
"It's done!" Gurney said. He held his breath as the men leaned in further and quickly jotted down a cryptic list of numbers. Then he ran the test again.
The stakes are high for this mysterious black box. Tech giants and Silicon Valley start-ups are betting that using white spaces could extend the Internet's reach. They also hope it will spark a new wave of portable devices.
But the idea faces big hurdles. Broadcasters use adjacent airwaves to beam TV shows to viewers, and they say the technology could interfere with over-the-air signals. Wireless microphone users, from pop stars to mega-church ministers, say using white spaces could blot out their sounds.
White-space backers say their devices will be able to detect and avoid frequencies being used by broadcasters and wireless mics. Critics say the devices are not reliable enough.
The FCC is trying to settle that debate. For more than a year, the agency has been testing prototypes with mixed results. An early prototype built by Microsoft failed to operate in the FCC's lab. Microsoft later determined the device was broken.
The FCC is now testing other prototypes built by Philips and Motorola as well as Silicon Valley start-up Adaptrum and Singapore-based Institute for Infocomm Research. The Motorola device connects to a database of TV stations operating within 124 miles and scans the airwaves nearly every second for other signals that may pop up unexpectedly, such as a wireless microphone.
If the device senses that it is within or close to a TV station's coverage area, it is supposed to avoid that station's frequency. It then ranks empty frequencies by their proximity to existing signals. If a new signal suddenly appears, the white-space device should automatically switch to another open channel.
Gurney ran the scan twice and recorded the results. He then covered the machine in bubble wrap, rolled it across the parking lot and ran the test again. Signal strengths can change by location, depending on how many trees, hills and people are nearby.
"We're testing multiple times to make sure the results are consistent," he said.
But the results can be hard to decipher. At the first location, Motorola's device indicated that channel 51, for example, was open and available. At the second location, the device picked up a weak signal on the channel, suggesting it was already in use.
Motorola's engineers say that means the signal changed slightly between locations, and the device would be able to avoid that channel as soon as it was detected. But Bruce Franca, vice president of policy and technology for the Association for Maximum Service Television, a broadcasting industry group, is skeptical.
"The results of every single test were different," he said. "The device failed to recognize that certain channels are actually being occupied by TV signals. ... Clearly this is not ready for prime time."
Shure, which makes microphones and other audio equipment used in Broadway shows and sports games, argues the tests have not proven that the prototypes can consistently detect TV signals, let alone wireless microphones that hop on frequencies without notice.
The FCC plans to test the white-space devices at an entertainment venue in the next few months. The National Football League has offered the Baltimore Ravens' stadium or the Washington Redskins' park as possible venues. And the RecordingAcademy, which puts on the Grammy Awards, has offered up the Lollapalooza music festival in Chicago next month for testing.
"That's where the rubber will meet the road," said Mark Brunner, senior director of brand management at Shure.