The Federal Communications Commission last month ordered Towerstream, a 4G wireless services company, to pay $202,000 for generating RF interference to Doppler radar systems used by the Federal Aviation Administration.
According to the commission, the company’s Unlicensed National Information Infrastructure (U-NII) transmission systems in New York and Florida were responsible for the interference, which is potentially life-threatening.
The agency, which released its order Aug. 6 as part of a Notice of Apparent Liability for Forfeiture, also gave the company 30 days to submit a signed statement under penalty of perjury that it is in compliance with the agency’s U-NII rules. In its order, the FCC found “Towerstream operated radio transmitters without a license and caused harmful interference, in apparent willful and repeated violation” of sections of the Communications Act.
U-NII devices operate on an unlicensed basis in spectrum (5.15GHz to 5.35GHz, 5.47GHz to 5.25GHz and 5.725GHz to 5.825GHz) allocated by the FCC in 2003. They are required to comply with rules aimed at preventing interference. In the event that U-NII radios do cause interference, they are required to cease operation upon notification of harmful interference and not resume operation till the interference has been resolved.
According to the order, the FCC recently “has dealt with a number of situations in which U-NII devices have caused harmful interference to Terminal Doppler Weather Radar (TDWR) systems.” TDWR operate in the 5.6GHz to 5.65GHz band at 45 U.S. and Puerto Rican airports and play an important role in identifying wind shear conditions.
FCC rules require U-NII devices operation in the 5.25GHz to 5.35GHz as well as the 5.47GHz to 5.725GHz bands to be equipped with Dynamic Frequency Selection radar detection functionality. Thus, by detecting the presence of radar the U-NII radios operating on these bands can avoid generating harmful interference to the radar systems.
The FCC’s Enforcement Bureau began getting reports of interference from U-NII devices in 2009, several of which involved U-NII devices used by Towerstream, the order said. In June 2009, the bureau found Towerstream U-NII transmitters located on the Empire State Building in Manhattan that operated on or adjacent to 5.647GHz were causing harmful interference to the TDWR radar system for John F. Kennedy International Airport in New York. The agency informed the company to cease operation of the U-NII devices causing the interference in a Notification of Harmful Interference issued in July 2009.
Similar, instances of interference involving Towerstream’s use of U-NII in Chicago, Miami and Fort Lauderdale, FL, and TDWR systems serving major airports in fall 2009, prompting the company to take steps to retune devices to cease the interference and put in place a monitoring system to send instant alerts to the company of frequency changes in markets where TDWR systems operate so that its engineers could modify U-NII operating frequency.
In July 2010, the FCC Office of Engineering and Technology and Enforcement Bureau released a Memorandum outlining the steps U-NII operators should take to eliminate interference to TDWR. This action was informed by the earlier experience of Towerstream, the order said.
Following the Memorandum, the company met with the agency and said it would “self police” 105MHz in the 5.4GHz band to protect TDWR systems. As part of the effort, the company said it would enter the locations and operating parameters of the TDWR system in a company-wide engineering database to make sure future U-NII system changes would not interfere with TDWR.
However, according to the order, the company failed to avoid frequencies adjacent to TDWR frequencies, resulting in additional interference to TDWR systems in use by JFK, Miami and Fort Lauderdale airports. The order found instances in which Towerstream did not operate according to the rules laid out in its Memorandum on Aug. 7, 2012, with respect to the TDWR serving JFK; Sept. 13, 2012, with respect to Fort Lauderdale; and Oct. 2, 2012, with respect to Miami. In all, the FCC found 13 “distinct violations” involving the use of seven different devices.