Register Account

Login Help


FCC Continues BPL Debate


On July 17, the FCC issued a Request for Further Comment and Further Notice of Proposed Rulemaking (FNPRM), addressing the issues remanded to them by the US Court of Appeals. In October 2007, the ARRL took the Commission to court concerning the Commission's Orders adopting rules governing broadband over power line (BPL) systems. In April 2008, the Court agreed with the ARRL on two major points and remanded the rules to the Commission. Writing for the three-judge panel of Circuit Judges Rogers, Tatel and Kavanaugh, Judge Rogers summarized: "The Commission failed to satisfy the notice and comment requirements of the Administrative Procedure Act ('APA') by redacting studies on which it relied in promulgating the rule and failed to provide a reasoned explanation for its choice of the extrapolation factor for measuring Access BPL emissions."

New Information?

The Court found, among other things, that the FCC not only withheld the internal studies until it was too late to comment, but had yet to release portions of studies that may not support its own conclusions regarding BPL. The FCC claimed that the studies were "internal communications" that it did not rely upon in reaching its decision to adopt the BPL rules. In its April 2008 ruling, the Court ordered the FCC to release the studies. In March 2009, when the FCC still had not released the redacted portions of the studies as ordered by the court, the ARRL filed a Freedom of Information Act request for the studies. Six weeks later, the FCC released the redacted portions of the studies.

To contend with the Court's ruling, the Commission is now requesting comment on the information in those studies as it pertains the FCC's BPL decisions. The Commission is "also placing into the record certain additional materials that contain preliminary staff research and educational information" that was not previously made available. It is these records that concern ARRL Laboratory Manager and BPL expert Ed Hare, W1RFI.

"At the same time the FCC released the new FNPRM, it also released 800 MB of previously unseen FCC internal staff reports and videos on BPL," Hare said. "Although the FCC tries to downplay the work of their own staff by saying that these reports are only the opinion of one FCC staffer, these conclusions about BPL from the FCC Lab were made by FCC technical people with strong experience in measurement techniques and interference assessment. This is generally good engineering, with a clear objective of providing the Commission with accurate technical information about BPL."

According to Hare's preliminary review of the FNPRM, the FCC's own technical findings clearly spell out that BPL operating at the FCC limits has a very strong potential to cause interference to licensed radio users: "These reports show that BPL causes interference to a number of licensed services for significant distances from BPL noise sources and that the noise from BPL at antennas that are about 100 feet from wires carrying BPL operating at the FCC limits will represent an increase in noise of about 30 dB in most cases."

Hare said that other slides show that radiated noise from overhead power lines increases significantly above the noise at ground level. "Based on these internal FCC technical analyses, the present rules and test methods -- when coupled with inappropriate distance extrapolation -- simply do not protect licensed users from interference," he said. "The Commission was well aware of the content of these presentations when it issued a BPL Report and Order that discounted ARRL when the League made many of the same technical points in its filings."

Extrapolation Factor: FCC Looking for Compromise?

One of the major points of difference between ARRL and the FCC has been the measurement extrapolation factor below 30 MHz that is applied to measurements made at distances from power lines or other radiating sources to determine what the value of that measurement would be at a distance of 30 meters. This is the distance in the FCC rules for which maximum permitted emission are specified. The FCC believes that this factor should be 40 dB/distance decade.

Hare explained why this is incorrect: "The FCC's test method measures BPL emissions at ground level, using a loop antenna located 1 meter off the ground. Amateurs know that a low horizontal antenna radiates more energy upward than it does toward the horizon, and that a measurement made of a radiating power line at 1 meter off the ground is not a good indicator of the noise levels that will be present at angles upward from that same power line, where HF antennas are most apt to be located. The 40 dB extrapolation factor and the lack of any correction for height result in a BPL system that will significantly exceed the FCC emission limits at the very point where most Amateur HF antennas are located."

In response to its remand of a portion of BPL measurement procedure, the FCC is "also providing an explanation of our reasons for selecting 40 dB per decade as the extrapolation factor for frequencies below 30 MHz. We further explain why we believe the studies and technical proposal submitted earlier by the ARRL do not provide convincing information that we should use an extrapolation factor that is different from that which we adopted," noting the existence of "more recent studies" that prove their point.

In the FNPRM, the FCC states that they are "re-examining the current extrapolation factor in light of the recently issued technical studies addressing the attenuation of BPL emissions with distance and efforts by the IEEE to develop BPL measurement standards." Using these studies and older ones, the FCC said that "there can be considerable variability in the attenuation of emissions from BPL systems across individual measurement sites that is not captured in the fixed 40 dB per decade standard."

Based upon this "considerable variability," the FCC has opened a 30 day comment period, asking if they should change their rules to "adjust the extrapolation factor downward to 30 dB or some other fixed value and, as an alternative, also allow use of a special procedure for determining site-specific BPL extrapolation values using in situ measurements."

Hare notes that the FNRPM is creating a complex way to look for a simple solution to a complex problem. "It's ironic that the FNPRM discusses the 'considerable variability' in attenuation at BPL sites, then proposes that a measurement of a mere four points within that variability can determine the supposedly actual extrapolation. The NTIA Phase II study that is the 'newer study' that the FCC is relying on for part of its justification for 40 dB/decade shows an environment extremely more complicated than that. Trying to apply any measurement of extrapolation to this complex environment is a recipe for failure -- and possible 'cherrypicking' of results that will allow those making measurements of BPL systems to provide any value of extrapolation they want, in either direction. I serve on the IEEE committee that developed the draft for this extrapolation-measurement method and I did not stand alone in not supporting the approach that the P1775 Working Group has sent to ballot. At this point, the working group is in the process of resolving and rebutting the numerous comments received in the still-unresolved IEEE ballot."

Even though the FCC is inviting comments, they state that they "do not believe that the studies and technical proposal submitted earlier by the ARRL provide convincing information that we should use an extrapolation factor that is different from (and, specifically, less than) 40 dB. We believe that [other] studies [we have relied on] further validate the use of 40 dB as the extrapolation factor. In addition, the sufficiency of our rules for ensuring compliance is further validated by the fact that we have not had any new complaints of interference for more than two years."

Hare has worked extensively with the BPL industry to help it address interference. "If the FCC thinks that the falling off in BPL complaints is due to the sufficiency of its rules, it is mistaken," he said. "In response to ARRL's input and offers of help, the industry has essentially stopped using the amateur bands in US deployments. The FCC's own video documentation of interference from BPL that is operating under the rules the FCC put forward should be more than sufficient to show that the rules as written are not good ones. The industry has reduced the interference from BPL by doing more than the rules require. By not using the amateur bands and by improving the filtering of BPL systems well beyond the inadequate requirements of the present rules, the industry and ARRL have shown that it is possible to operate BPL systems without widespread interference problems involving Amateur Radio."

Hare said that what is needed now "are good rules and industry standards that reflect this successful model. That is not seen in this FNPRM. Rules that reflect the industry practice of not using the amateur bands and that specify state-of-the-art filtering could protect the Amateur Radio Service and support this still-nascent BPL industry."



Instragram     Facebook     Twitter     YouTube     LinkedIn