Skeptics question FCC's ability to control interference
FALLS CHURCH, VA.
Despite the FCC's latest endorsement of broadband-over-power-lines industry watchdogs continue to express doubts over whether the wireless technology-targeted to rural broadband deployments-can steer clear of interfering with broadcast signals.
The latest development in the three-year-old "not in my backyard" Access Broadband-over-Power-Lines saga is an FCC order dated Aug. 3, 2006. In the order, the commission reaffirmed its rules for BPL systems "while maintaining safeguards against harmful interference to existing radio services."
The FCC denied requests from the television industry and the amateur radio community to limit or prohibit BPL operations. The order also denied a request from the aeronautical industry to exclude BPL from frequencies reserved for certain aeronautical operations, and further denied a request by the gas and petroleum industry to be considered as public safety entities.
BPL has its roots extending back several decades. The technology is known as "carrier current" communications and involves coupling audio or data modulation onto ordinary power lines. Its uses include unlicensed AM college radio stations (with coverage limited to on-campus buildings), power company internal communications and control functions, wireless intercoms and home control systems.
The latest extension of carrier current technology involves data modulation for high-speed Internet service to homes and businesses. The first rollouts of BPL in the United States were in Manassas, Va. and Emmaus, Pa., where field tests were conducted.
That testing continues and has produced mixed results. On the one hand, Internet users are generally pleased with the service. However, as the band of frequencies used for BPL spans 1.7 to 80 MHz, some of the stakeholders in that spectrum have been displeased.
Licensed radio frequency services operating in the affected area begin at the top of the AM broadcast band, and include international shortwave broadcasters, public service radio, low-band VHF TV broadcasters, CB radio, HF aeronautical services and the amateur radio community. It is the latter group that has been most upset about the theoretical and proven potential for interference to licensed communications.
The amateur radio community was first to raise a flag, and was close by when the Manassas system was deployed for testing. The road has been anything but smooth since the equipment was first activated, with a nearly constant stream of complaints, promises to address the complaints, and more complaints.
The American Radio Relay League, the organization that represents U.S. radio amateurs in legislative matters, has been tracking BPL developments. Allen Pitts, media and public relations manager for the ARRL, said the Manassas BPL deployment "has problems." He also said systems in Briarcliff Manor, N.Y., and Cottonwood, Ariz. are beset with problems.
ARRL records indicate the Cottonwood system was shut down. According to Pitts, "It had unresolved interference reports or complaints that were completely resolved only when the system was shut down."
Yet Pitts said BPL doesn't have to be all bad.
"There doesn't need to be these problems," he said. "Hams want broadband as much as anyone; they just don't want interference."
Pitts gave high marks to BPL equipment from Motorola and Current Technologies.
"These systems haven't caused any problems," Pitts said. "We've even had the Motorola equipment deployed [for testing] here at the ARRL headquarters and it's not causing problems. It's really kind of a neat deal-we're not in a big hurry to get it out of here."
Regarding the FCC order, Pitts said there weren't a lot of improvements.
"From reading the actual document, my immediate feeling is that nothing has changed," he said.
Pitts did cite a comment made by Commissioner Michael Copps concerning complaints from amateur radio operators. Copps said "amateurs shouldn't have to wait for months to get complaints resolved-they deserve better."
MSTV: NOTHING NEW
Joining in the ARRL's concern is the Association for Maximum Service Television (MSTV) and the NAB. The organizations filed a joint reply comment to the FCC in August 2004 that emphasized frequencies used for BPL should not extend past 50 MHz. (TV Channel 2 operates between 54 and 60 MHz.)
The reply stated that BPL systems operating in this range "pose serious risk of interference to television Channels 2 through 5, especially the 11 stations currently transmitting a digital broadcast signal on those channels, as well as several stations who are likely to elect lower VHF channels at the end of the digital television transmission."
The joint statement concluded with a request to the commission not to authorize BPL above 50 MHz.
David Donovan, MSTV president, said the FCC's reaffirmation of the BPL order is nothing new.
"It's essentially the same position as in the past and is not surprising," Donovan said. "Our concern is with the systems operating above 50 MHz. We would have preferred that that segment would have been carved out. However, most systems that are in place don't operate there right now."
Donovan acknowledged that the potential for interference to existing and future television operations does exist.
"Our analysis on this was submitted in the original petition," Donovan said.
That petition stated that existing BPL modulation techniques have a spectral profile resembling impulse noise, and that studies on file with the FCC indicate that DTV reception is severely impaired by impulse noise in the low-VHF band.
According to the petition, the studies "revealed that the interleaver in DTV receivers reacts badly to impulse noise resulting in the inability of the TV set to produce a picture."
Donovan agreed, however, that BPL probably had a place in the growing demand for broadband communications.
"BPL is certainly another option to get broadband out to rural areas served by power lines," he said.
NTA NOT CONVINCED
The National Translator Association was not pleased with the FCC action. Dr. Byron W. St. Clair, NTA president, issued a statement on behalf of that organization.
"The National Translator Association feels it is unfortunate that the FCC did not protect the low-band VHF TV channels by limiting the top frequency to 54 MHz," he said. "A disproportionate number of translators have low- band VHF inputs because these signals are available further out from metropolitan areas and the three original commercial networks tend to be found on Channels 2 to 6. We feel a safer approach would have been to gain experience on frequencies below 54 MHz before allowing the use of frequencies that are in conflict with the low-band VHF channels."
In a statement issued in connection with the order, Copps said, "...the commission must be available and positioned to respond to interference complaints with alacrity."
St. Clair was asked if he believed that the FCC could honor such a commitment.
"I'm very skeptical that they have the resources-the field people are spread pretty thin right now," St. Clair said. "Asking them to take on this additional problem of protecting consumers is unrealistic."
As indicated by the ARRL's Pitts, deployment of BPL technology doesn't necessarily have to include interference problems. According to Jim Dondero, vice president of marketing for the Current Communications Group, a major manufacturer and service provider in the BPL arena, there have been no complaints received at all in connection with systems using Current gear.
"We have the largest deployment in the U.S. and one of largest in the world," Dondero said. "The system in Cincinnati passes 50,000 homes and has been in service for more than two years. There have been no complaints from radio amateurs, TV broadcasters, or anyone."
Dondero acknowledged that he was aware of the sensitivity to BPL in the amateur radio community.
"Some systems interfere. Ours does not," he said. "It never has."
Dondero pointed out that the Cincinnati BPL system and other installations were not really field trials.
"These are live deployments with paying customers," he said.
Current is in the process of building a network in Texas in cooperation with TXU Electric Delivery to serve 22 million subscribers, he said.
Dondero cited a high rate of satisfaction from broadband customers and the electric utilities, saying that the utility had received a substantial number of customers defecting from established DSL providers. He reported that utilities are pleased with Current's Smart Grid technology, as it allows them to perform such tasks as grid management and remote customer meter reading.
"Hey, guess what-this works and works quite well," he said.
Motorola is offering a competing system that is hybrid wireless/power line in nature, and is designed not to raise any interference issues.
In Motorola's backhaul portion of broadband delivery, data is transmitted in the high-UHF and SHF portions of the spectrum to omnidirectional repeater sites, referred to as Access Point Clusters using the company's Canopy technology.
These repeater sites have a range of several miles, and each has the potential to reach utility step-down transformers feeding as many as 1,200 customer homes or businesses. The HF carrier for the data signals is coupled into the low voltage (120 to 240 V) secondaries of these transformers, located a relatively short distance from user-access points.
"Our state of the art is focused on having a wireless link all the way to the low-voltage transformer," said Richard Illman, principal staff engineer at Motorola. "We're using HomePlug-based technology to get into the house. This already has the carriers turned off in the amateur radio portion of the spectrum, and we've also added some filters to prevent interference to and from amateur radio operations."
According to Motorola, interference to off-air television reception is not possible with the company's BPL equipment, as data signals are only placed on relatively low-voltage AC lines directly at the customer's home or place of business, and the portion of the spectrum used extends from 4.5 to 21 MHz.
Next-generation system enhancements are in the works, but even in that iteration, spectrum usage will only extend to 28 MHz. The Motorola BPL system has been deployed in South Carolina for more than a year with no interference complaints.
Charles Rhodes, TV Technology columnist, had a slightly different take on BPL television interference issues.
"Analog [television] will die before BPL can become important," Rhodes said. "As for digital, DTV shouldn't be in the low-VHF band anyway. Man- made noise levels are increasing with the increasing consumption of electrical energy in this country. The high-tension lines have 'creeping' electricity leaking across dirty insulator surfaces. This generates a lot of noise."
Rhodes explained this source of noise particularly affects low-band VHF television frequencies and that broadcasters really shouldn't consider staying in, or relocating to, this part of the spectrum.
"Man-made noise will only grow higher as time goes by," Rhodes said. "More and more people will give up on watching low-band VHF DTV. Low-band VHF antennas will wear out and not be replaced. The public is not aware of what is going on, BPL or not."
Rhodes said even though BPL is marketed as a panacea for extending broadband to those living in rural America, this probably will not happen for some time.
"I think that some people are exerting political influence by saying that we can provide practically free Internet linkage to those in rural areas who are not connected yet," Rhodes said. "Actually, it will be deployed in the urban areas because that is where you will be making money.
"The pitch is that it will help the people in the rural areas. I see the money to develop it going in to the urban areas where there are a lot of people and a lot of money to pay for it. It's disingenuous to think that Wyoming is going to get it and not New York.
"If you were a businessman, which would you rather invest in, BPL in Wyoming or BPL in New York City? It all boils down to the number of customers."
James E. O’Neal has more than 50 years of experience in the broadcast arena, serving for nearly 37 years as a television broadcast engineer and, following his retirement from that field in 2005, moving into journalism as technology editor for TV Technology for almost the next decade. He continues to provide content for this publication, as well as sister publication Radio World, and others. He authored the chapter on HF shortwave radio for the 11th Edition of the NAB Engineering Handbook, and serves as editor-in-chief of the IEEE’s Broadcast Technology publication, and as associate editor of the SMPTE Motion Imaging Journal. He is a SMPTE Life Fellow, and a Life Member of the IEEE and the SBE.
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