Conformity Magazine

See this article in our Digital Edition
Download a pdf of this article (right click to save the pdf)

Many home offices are setting up local networks using either wireless or wired technology. However depending on where you live there may be a third alternative: AC wires --the electrical wires that are already inside the home and office walls. But several powerline adapters instruction books warn against plugging them into surge protectors or uninterruptible power supplies because the signal would not be usable. This may be changing as DirecTV recently announced that customers who sign up for its new broadband service will have access to a HomePlug-enabled surge protector. Will this be a path to increase use of broadband over powerlines?

The future of broadband technology may still be searching for the light at the end of the tunnel as the industry, the Federal Communications Commission (FCC), and others struggle to find a common path that is acceptable to all.

Potential for Impact on Military Communications
The problems don’t start inside the home. There are potential problems outside the home as well. Broadband Over Powerline (BPL) systems use the electrical power grids (wires) as radiators of a signal to reach into the home. Some of these systems use radio frequencies below 30 MHz (HF) which are also used by the military, shortwave broadcasters, amateur radio operators, and others.

The North Atlantic Treaty Organization (NATO) has issued a report of the expected effects that widespread BPL (a.k.a. PLC or PLT) application would have on the HF spectrum. The report concluded that there is a “high probability that PLT would cause increased noise levels at sensitive receiver sites given the projected market penetration,” and that the percentages of interference are “highly influenced by assumptions on transmitter EIRP, PLT market penetration, and duty cycle.”

The NATO report further notes that “as these lines were not designed for such broadband transmissions, they will cause unintentional RF emissions which may adversely affect the established radio noise floor directly, or by cumulative propagation from many such sources. The existing HF background noise possibly may be increased via ground wave and/or sky wave propagation.”

The report continues that the “increase of the existing HF noise floor by widespread use of PLT and/or xDSL will bring up problems for Military Radio Users as well as for HF Communication Intelligence (COMINT) in all NATO countries.”

“Currently, there are no commonly accepted regulatory emission limits from PLT,” the report notes. Since NATO, by itself, has no regulatory authority over the emission limits, the report recommends “that NATO seek the implementation of this goal by working together with the national and international regulatory authorities.”

Figure 1: BPL equipment mounted on an electrical pole in Cottonwood, AZ. (Photo courtesy of Robert Shipton.)

Continued Concerns from Amateur Radio
The interference concerns are so great that the ARRL, the national association for amateur radio operators, filed a federal appeals court brief earlier this year outlining its case and requesting oral arguments in its petition for review of the FCC’s BPL rules. The ARRL petitioned the U.S. Court of Appeals for the DC Circuit to review the FCC’s October 2004 Report and Order, and its 2006 Memorandum Opinion and Order.

In its brief, the ARRL contended that the FCC’s actions in adopting rules to govern unlicensed BPL systems fundamentally alter the longstanding rights of radio spectrum licensees, including amateur radio operators.

“For the first time ever, the FCC has permitted new unlicensed devices to operate in spectrum bands already occupied by licensees, even if the unlicensed operations cause harmful interference to the licensees,” the ARRL said in stating its case. “The orders under review reverse nearly seven decades of consistent statutory interpretation and upset the settled expectations of licensees without so much as acknowledging the reversal, let alone justifying it.”

The ARRL argued that the FCC’s approach to adopting rules to govern BPL does not agree with Section 301 of the Communications Act, which requires that operators of devices that emit radio frequency energy first obtain an FCC license. According to the ARRL brief, “the FCC has consistently read Section 301 to apply to unintentional radiators, such as BPL devices, and has expressly embodied that interpretation in its rules.”

In July, the FCC replied to the court that its authority to permit BPL as an unlicensed communications service comes from Section 302 of the Communications Act of 1934, which allows it to regulate the interference potential of RF devices, as opposed to Section 301, which is the basis of Part 15 rules that generally regulated unlicensed devices. The FCC also said its rules protect mobile and fixed stations against harmful BPL interference and that there is conflicting evidence on the science involved in determining the rate at which a signal weakens with distance from a radiator.

Oral arguments were presented before a three judge panel in Washington, D.C. in late October. The ARRL argument centered on the removal of interference protection for licensed mobile stations, and the Commission’s rules for measuring interference.

ARRL Chief Executive Officer David Sumner, who was in court, said “the judges sounded skeptical that interference to mobile stations couldn’t simply be regarded as ‘not harmful’ because it was temporary.” He said that Judge Tatel responded to an FCC statement that ‘mobile stations could simply move,’ by saying that in the case of BPL in Manassas, Virginia for example, you can only get away from the interference by leaving Manassas.’ It wasn’t, he went on to say, like a garage door opener.

Sumner added. “In the course of the argument, the FCC’s attorney had to acknowledge that the Commission’s explanations in the BPL proceeding were deficient in a number of respects, although it wasn’t clear that administrative agencies are held to a very high standard in that regard.”

The FCC attorney was interrogated by the judges on the Commission’s premise that “a mobile station in a licensed service should not be afforded complete protection from harmful interference just because it can just move away from the interference.” He was also questioned about redacted material from the FCC’s response to the ARRL’s Freedom of Information request. A decision in the case could take three or more months.

Interference Enforcement in Question
In July, FCC Commissioner Jonathan S. Adelstein testified at a House Subcommittee on Telecommunications and the Internet hearing that “three of the many urgent priorities we face” include the need for “a national broadband strategy to ensure the ubiquitous deployment of affordable, high speed broadband infrastructure to this country.” He said “we must take a hard look at our successes and failures.”

In a letter to Adelstein, ARRL CEO Dave Sumner said called the Commission’s “inexplicable favoritism of BPL in the face of contrary evidence” one of those “failures.” Sumner noted that, according to the Commission’s latest publicly released figures, “of 64,600,000 ‘high-speed’ lines, only about 5000 are BPL. This is a share of 0.008 percent, a share that actually declined in the six-month period between reports.”

ARRL’s concern, Sumner said, is that “even at the very low level of deployment that exists to date, the FCC’s enforcement efforts have proved to be woefully inadequate to address ongoing cases of harmful interference from BPL systems.”

Sumner pointed to one example of documented interference caused by Ambient Corporation’s Briarcliff Manor, New York installation, where interference problems have persisted for more than three years without correction and without penalty to the system operator.

“If the Commission is unable to protect its licensees from harmful interference from BPL now, it is difficult to imagine how it will be able to do so should BPL be more widely deployed in the future.”

Sumner concluded his letter by saying “we respectfully submit that BPL has not earned a place in the much-needed national broadband strategy to benefit all Americans. Resources are better devoted elsewhere, to more promising technologies that do not pose a threat to the Commission’s radio service licensees.”

Figure 2: Amperion CEO Phillip Hunt gives former FCC Chairman Michael Powell a look at some of his company’s hardware at the Progress Energy trial BPL installation near Raleigh, NC.

Different BPL Implementations Yield Different Results
The ARRL has indicated that its only concern with BPL is interference. In fact it has offered to work closely and effectively with some companies involved with BPL technology.

According to ARRL Laboratory Manager Ed Hare, ARRL and representatives of the Current Group, a BPL provider, “have communicated regularly over the past few years. Current has been an early leader in carefully choosing its design to avoid interference to Amateur Radio. They don’t operate below 30 MHz on overhead lines at all, and use HomePlug technology, which doesn’t use the ham bands, in customers’ premises. To date, ARRL has no amateur radio interference reports involving Current or HomePlug equipment.”

Current’s approach to BPL deployment is to limit its use of the medium-voltage lines to 30-50 MHz, and to rely on the HomePlug standard to avoid the HF ham radio bands on the low-voltage drop.

Current is building out broadband networks in Cincinnati and Dallas-Fort Worth and is in talks with a number of utilities around the world. And, as noted above, a recent agreement with DirecTV will give approximately 1.8 million homes access to broadband over power lines in the next several years.

On the other hand, other BPL systems have the potential to cause interference to licensed radio services. One such system that has come under scrutiny is Ambient Corporation’s BPL pilot project in Briarcliff Manor, New York. Ambient operates the Briarcliff Manor BPL pilot program under Experimental license WD2XEQ, but ARRL testing as recent as late May indicated the system was operating outside of the parameters of its FCC authorization.

According to the ARRL’s Hare, tests conducted showed that Ambient “continues to operate well above the Part 15 emission limits that are stipulated as a condition of its Experimental license.” Hare said their visit to Briarcliff Manor in May marked the third time that emissions testing showed the system to be operating significantly above Part 15 emissions limits.

“The spectral masks in this system intended to protect some radio services from interference work poorly enough in this generation-1 equipment, but when the system is operated at excessive levels, strong interference is an inevitable outcome,” he commented. “By operating this system above the Part 15 emissions limits, Ambient is making it impossible for any electric utility to use results from this experiment to reach any conclusions about the technical and commercial viability of BPL.”

The FCC has called on Ambient to demonstrate its compliance with all terms of a Part 5 experimental license authorizing the system, or face possible enforcement action. But, in a letter to the Commission, ARRL’s General Counsel Chris Imlay contended that “interference has repeatedly occurred, and it has been witnessed and verified by a member of the Commission’s Enforcement Bureau staff. Yet no action has been taken whatsoever to terminate this experimental authorization over a period of more than two and one-half years.”

Ambient has responded to the FCC, indicating that they have identified an equipment failure in Briarcliff Manor that was the cause of the problems encountered. As of press time, they have removed the generation-1 equipment and replaced it with FCC certificated generation-2 technology. Hare reported that follow-up testing on the site showed that, although the upgrade was a work in progress, the partial reinstallation was no longer using the amateur bands, which were noise-free at the time of his visit. He plans another visit when the rebuild is complete.

Hare also said that he and Ambient staff have been discussing ways to work together effectively to ensure that future problems are unlikely. Allen Pitts, an ARRL spokesman, says that the FCC could have taken effective action in this case years ago, offering much more timely benefit to all of the parties.

Figure 3: ARRL’s Ed Hare checks for interference at a BPL installation in Cottonwood, AZ.
(Photo courtesy of Robert Shipton.)

BPL and Television
The National Association of Broadcasters (NAB) is also concerned about BPL systems. The NAB says that BPL systems could pose serious risk of interference to television channels 2-5, especially the eleven stations currently transmitting a digital broadcast signal on those channels, as well as several stations which are likely to elect lower VHF channels at the end of the digital television transition. Thus, to ensure that the public’s free over-the-air television service remains clear of any interfering signals, NAB and MSTV strongly oppose any BPL operations in the television broadcast bands.

Some of the digital TV stations currently in operation on channels 2-5 (54 - 82 Mhz) include: WBBM-TV, Chicago, Il; WKYC-TV, Cleveland-Akron (Canton), OH; WHMT, Grand Rapids-Kalamazoo-Battlecreek, MI; WHP-TV, Harrisburg, Lancaster, Lebanon-York, PA; KVBC, Las Vegas, NV; WDKY-TV, Lexington, KY; WBRA-TV Roanoke-Lynchburg, VA; WTWC, Tallahassee, FL-Thomasville, GA; WMAZ-TV, Macon, GA; KOTA-TV, Rapid City, SD; and KTVM, Butte-Bozeman, MT.

The NAB does not oppose BPL as a technology per se. However, it says there is insufficient technical data upon which the broadcast industry and the Commission can fully and properly evaluate BPL’s potential to interfere with free-over-the-air broadcast television stations operating on the low VHF frequencies, including DTV signals.

According to the NAB, “the low VHF TV band is already heavily polluted with man-made impulse type background interference, attributed in part to leaky power lines. BPL systems radiating RF energy in the television broadcast bands are likely to lead to a further increase of the noise floor, and may result in significant analog television picture disruption and total degradation of DTV signals.”

What’s the Future of BPL?
The answer to this question depends on whom you talk to. For example, officials at Connecticut Light & Power say that, with wireless technology taking off in the United States, there isn’t likely to be much of a demand for Internet access through the local utility wire network. BPL may be more prevalent in other countries, they say, but that could be a reflection of the American marketplace rather than foreign sophistication.

On the other hand, DirecTV say that its subscribers will soon have access to Current’s BPL network. Access will be initially available in the Dallas/Fort Worth area, but will eventually cover approximately 1.8 million homes and businesses over the next several years. Further, DirecTV says that its agreement with Current will allow BPL expansion as Current builds out its network.

But unlike cable or WiFi systems, BPL providers have to rely on the power grid of electrical companies. In the end, it’s the electrical companies that may decide whether BPL expansion continues, or has its plug pulled.

Bob Josuweit is a freelance writer who reports on public service and emergency communications. He can be reached at bjosuweit@verizon.net.