Tests raise questions about RFID

Radio tags may interfere with military radar

NTIA 2002 Letter Opposing Increase in Active Power

Radio frequency identification systems used by the Defense Department to track and locate supplies could interfere with — and potentially degrade — the performance of critical radar systems, said Marine Lt. Gen. Robert Shea, the Joint Staff's director of command, control, communications and computer systems.

DOD units need to better coordinate radio frequencies before fielding systems that could cause conflicts, Shea said during a speech at the Army Knowledge Management/Directorate of Information Management conference last week in Fort Lauderdale, Fla.

Joint Staff officials, who spoke on the condition of anonymity, said Shea's remarks were based on a test conducted earlier this year in which four RFID readers degraded the performance of a radar. One staff member said the purpose of Shea's comment "was to make the point that when you put equipment into the field and turn it on, there are often unintended consequences."

Lt. Col. Beth Rowley, product manager of DOD's Joint-Automatic Identification Technology Office, said Shea's remarks should serve as a wake-up call to conduct frequency coordination tests before fielding systems.

Before hearing Shea's speech at the conference, Rowley said she was unaware of a conflict between RFID systems fielded by the office and military radar systems. She said neither Shea nor his staff had shared the test's results with her, including information about the types of readers or radars they used.

Joint Staff officials declined to provide any details about the test because they could aid a potential enemy. Another official indicated that active battery-powered tags and readers that operate at the 433 Mhz frequency caused the degradation in radar performance. Passive tags operating in the 868-956 MHz frequency range did not cause similar degradation.

Craig Mathias, a technology analyst at Farpoint Group, said the military services operate radar systems in the 420-450 MHz frequency band, adding that the potential exists for interference caused by active tags. To Mathias' knowledge, Shea's comments were the first confirmation of such a problem.

The military uses Savi Technology active tags and readers to track materiel in Iraq. The company has shipped more than 1 million tags to DOD units. The company's contract value increased from $90 million to $207 million in 2004.

Fraser Jennings, Savi's vice president of standards and regulatory activities, said the company has reviewed frequency issues with the Federal Communications Commission, DOD's Joint Spectrum Office and ID technology office, and the National Telecommunications and Information Administration (NTIA).

"We have conducted testing with specific radar systems, and we have confirmed that implementations of active RFID operating at 433 MHz do not interfere with those systems," Jennings said.

Those tests, however, did not include the tests performed by the spectrum office, Rowley said.

"In more than a decade of deployments of our RFID solutions, we have had zero incidences of interference with any other [radio frequency]-based system, much less a system as sophisticated as radar," Jennings said.

In 2002, NTIA said it could not support Savi's request to the FCC to increase the operating cycle of its tags and readers or the peak field-signal strength. Such increases would cause interference with military radars that perform critical missions.

Following NTIA's objection, Savi agreed to an FCC ruling last April that shaved power levels and cut a minute off the two-minute operating cycle that Savi had proposed. Jennings said Savi has not manufactured any systems with the higher power levels or longer operating cycle.

Despite the FCC's frequency limits for active tags, Mathias said that based on the Joint Staff's findings, DOD may decide "it is inappropriate to operate RFID on the battlefield."

Mathias added that DOD can no longer afford to field wireless systems individually and hope they can co-exist.

"It has to be done from a holistic approach," he said.

The 25-mile RFID protection zone

Active radio frequency identification tags have a nominal range of 300 feet. To prevent interference from new, higher-powered tags and readers that operate with a 60-second operating cycle, the Federal Communications Commission has barred the use of 433 MHz active tag readers within 25 miles of key military radar systems used for missile tracking.

Those massive-phased array radar systems, which operate in the 420 to 450 MHz frequency band, are located at the following military facilities:

  • Beale Air Force Base, Calif.
  • Cape Code Air Force Station, Mass.
  • Cavalier Air Force Station, N.D.
  • Clear Air Force Station, Alaska.
  • Eglin Air Force Base, Fla.


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