AT&T's LTE network impaired by salon's fluorescent light

AT&T's (NYSE:T) cellular network has faced myriad challenges over the years, such as the overwhelming capacity crunch that hit when Apple's (NASDAQ:AAPL) first iPhone rolled out. But the latest threat to AT&T's network is particularly illuminating, because the problem is being caused by a common fluorescent light fixture.

The fixture is located inside the Perfect Cuts Salon in a San Antonio, Texas, strip mall. By simply flicking the salon's lights on and off, AT&T representatives were able to confirm that the salon's interior fluorescent lighting was the source of interference impacting a neighboring AT&T cell site.

An FCC agent subsequently visited Perfect Cuts in July, according to a citation and order adopted Oct. 25 by the commission. The agent used a spectrum analyzer and handheld antenna to reconfirm that the salon's overhead light fixture emanates a stray signal at 705 MHz, causing interference to AT&T's Band Class 17 LTE network.  

The salon's owner, Ronald Bethany, refused to allow the FCC agent to conduct any further on/off testing of the fluorescent lighting, however.

Bethany contacted General Electric, the light fixture's manufacturer, which said it would replace the problematic lighting. However, when Bethany asked for cash instead so he could handle the replacement and installation himself, GE would not comply.

According to the FCC agent, Bethany said that since the lighting was not causing him any problems, he saw no reason to repair or replace the fixture unless he is paid to do so.

However, it appears the light fixture has led to a serious legal predicament for Bethany, who was cited by the FCC for causing radio interference via an "incidental radiator." If the situation remains unresolved, the FCC may fine Bethany up to $16,000 for each violation or each day of a continuing violation, and up to $112,500 for any single act or failure to act. The commission could also seize the offending light fixture, and Bethany could ultimately face jail time.

CommLawBlog noted that this type of incidental interference is not unique to AT&T or this particular light fixture. Other light fixtures and even a well pump have recently being fingered for causing cellular network interference.

In addition, FM radio stations operating in the 88-108 MHz band have interfered with wireless networks using high-gain LTE antenna systems and high gain LTE receivers in the 700 MHz band. While that might seem unlikely, CommLawBlog explained last summer that "stations operating anywhere from 88.1 MHz to 100.5 MHz will generate 8th harmonics somewhere in the 700 MHz wireless band," with those signals potentially interfering with LTE networks using that band.

For more:
- see this FCC document (PDF)
- see this CommLawBlog article

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