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TECHNOLOGY ANALYSIS
Interference: is it the dark underbelly of BPL?
By Bill South
About this series
We continue our in-depth coverage of the broadband over powerline (BPL) controversy. Is it a benign technology that can bring broadband to the unwired masses or is it a disaster waiting to happen? Here at Computing Unplugged, we honestly don't know. The manufacturers have a heck of a story to tell, but if you read analysis by technical experts, like this one from engineer Bill South, you get an entirely different perspective.
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I must comment on Computing Unplugged's recent interview with Mr. Gomez of DS2 and the general tone of the article boasting of BPL (broadband over powerline). As has been the norm with "reporting" on BPL in the past 3 years, articles such as that focus only on the limited benefits of BPL and don't touch on any of the negatives.
With rose-colored glasses on, any technology can look like a panacea -- until the glasses come off and the real details are studied. What the interview failed to mention is that BPL devices operate under FCC Part 15 rules. Part 15 regulates those RF devices that are unlicensed, like baby monitors and garage door openers; so too is BPL.
With Part 15 regulation comes a host of potential interference issues, both on the transmitted side as well as on the received side. The FCC rules are quite clear about interference with these unlicensed devices, they can never cause any harmful interference to any licensed radio services, and must accept any interference from any licensed radio services.
Harmful interference is described as:
Harmful interference. Any emission, radiation or induction that endangers the functioning of a radio navigation service or of other safety services or seriously degrades, obstructs or repeatedly interrupts a radiocommunications service operating in accordance with this chapter.
What does all this mean for the BPL consumer, the ones paying the bills to have their broadband Internet access (and in some cases even their phone service via VoIP) come across the power line on an unlicensed device?
It means the BPL system, any and all parts of it, can never interfere with any licensed radio service. These are services like low-band business radio, short wave radio broadcasting, amateur radio, government and military operations, and even CB legal operation.
BPL can never cause harmful interference to these, or any other licensed radio services. If it does, it must immediately mitigate the interference, and if it can not, it must cease operation. Field studies have proven that BPL does, in fact, cause this interference to licensed services. Even the Vice President of a local BPL provider stated in print that his BPL system interferes with licensed radio operations, so there is no denying this interference occurs. As stated earlier, this interference is strictly forbidden by FCC Part 15 rules.
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