Mixed Signals

Jammers meant to foil roadside bombs in Baghdad jeopardize troop safety.

The trademark image of Baghdad: an Iraqi insurgent, radio or cell phone in hand, lurking in sight of a military convoy. The insurgent pushes a button; an improvised explosive device detonates.

In reaction, the United States has rushed out billions of dollars of promising anti-IED technologies over the past three years, including radio frequency jammers meant to interrupt the signal between the triggerman and the bomb. But like most rushed technology fixes, solutions have caused unanticipated problems, sometimes leaving warfighters worse off than before.

The military calls the problem CREW (short for Counter Radio Controlled IED Electronic Warfare) fratricide. When multiple jammers cancel out each other's signal, it leaves troops unprotected. The result is casualties-and not just from interference with anti-IED efforts. Radio communications are severely degraded by the jammers. Blue Force Tracking, the military's system for locating friendly forces, gets disrupted to the point of complete loss. Jammers also have interfered with the radio signals from ground control stations to unmanned aerial vehicles flying over Baghdad, causing some to crash.

Because of the myriad makes and models of radio frequency jammers operating in Baghdad, plus the Iraqi army's devices, the city contends with the dirtiest radio frequency spectrum on earth, says an Army officer speaking on condition of anonymity.

A world away, military radio engineers and wonks met in Maryland late last year to discuss solutions. "It used to be that the U.S. could take the radios, turn them on and jump into any theater," said John G. Grimes, assistant secretary of Defense for networks and information integration and chief information officer, at the conference keynote. "I'm here to tell you that doesn't happen anymore."

Lately, the military has taken to deploying Navy specialists in electronic warfare to Iraq to help Army units manage the messy radio frequency environment there. The Defense Information Systems Agency also merged its two spectrum organizations into one last year to get a better handle on the electromagnetic spectrum and help de-conflict radio frequency signals.

Part of the problem is that the military does not have a single authoritative source to track use of radio frequencies, says Paige Atkins, director of the new Defense Spectrum Organization. Frequency assignments can be made dynamically as new technology comes online in different geographical areas. DISA draws on a number of military databases to form a picture of frequencies in use, but not all those databases are updated in real time, she adds.

That means signal conflicts can force a commander in the field to decide among calling for air support by radio, operating radar or using a jamming device. "We have had some folks who have had to make that decision," says Atkins.

The agency must become more agile in its processes, she says. A possible solution is to develop a standard for reporting spectrum use across the military. Atkins says that could be accomplished with standardized Extensible Markup Language meta-data tags. But critics of metadata note that real life isn't always conducive to carefully tagging each bit of data for inclusion into a far away database.

The spectrum problem is only going to get worse. At the heart of modern military doctrine lies net-centric warfare, a new way of fighting battles that depends on pulling in and pushing out information from the field and headquarters. Superior information gathered from sensors, radars, UAVs and individual soldiers will collectively create a layer of virtual armor around the American military. But if the radio spectrum goes down, so does the ability of soldiers to fight effectively. The more the military depends on radio spectrum, the more fragile the asset becomes.

"At some point very soon, we're going to have a tremendous spectrum crunch" unless management and technology improve, said Richard Russell, associate director of the White House Office of Science and Technology Policy, who also was at the conference.

New technologies out of the United States' control likely will make things even worse. Take WiMax, a nascent wireless broadband standard that creates a high-speed wireless connection that extends for tens of miles. Manufacturers can deploy it across several patches of spectrum, including those in the 3.5 gigahertz range, a frequency spread used for U.S. military radar. At that range, WiMax conflicts with radars and radars conflict with WiMax.

Critics add to the list of threats a White House policy that allows the auction of federally licensed spectrum. The Federal Communications Commission recently sold about 90 megahertz of spectrum (previously held by both civilian and military agencies), raising almost $14 billion as of September 2006. Russell defended the sale at the conference, saying that it forced agencies to assign a concrete dollar value to spectrum licenses. Agencies sometimes hold on to licenses without knowing their true value, he says. And the private sector now can innovate further with their newfound spectrum, he adds.

Meanwhile, technology doesn't stand still. The problems technology causes usually get technological solutions, for good or for ill. Ever since engineers learned how to send signals through the air, they've been honing ways to slice up signals with ever sharpened electronic knives. Maybe in the future, the many demands on spectrum could be accommodated through advanced multiplexing techniques, "which would allow us not to relinquish spectrum but share it," Atkins says. "The only potential issue would be to assess if . . . those devices cause interference to our own systems."