.FLYINGHEAD TECHNOLOGY ANALYSIS
.TITLE Interference: is it the dark underbelly of BPL?
.AUTHOR Bill South
.SUMMARY 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.
.OTHER
.BEGIN_SIDEBAR
.H1 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.
.END_SIDEBAR
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:
.QUOTE 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?
.TEASER The scary part is other radio signals may interfere with BPL. Tap here to read what Bill has to say about it.
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.
.H1 What about interference that interrupts BPL?
This only addresses transmitted interference from BPL to other licensed services; what about receiving interference from licensed radio services? Whether you choose to believe it or not, tests by certified electrical engineers have shown that very small amounts of high frequency RF power in the proximity of a BPL installation on a power pole or even in an underground entrance in a neighborhood can render that BPL system inoperable, sometimes for a few minutes, but sometimes permanently.
Completely legal licensed operation of a radio transmitter could shut down a part or all of a BPL installation, and there is absolutely nothing the BPL operator can do about it. The BPL industry has chosen to go the unlicensed route under Part 15 rules for the same reasons the baby monitor and garage door industry has — it’s cheap. Cheap to design and cheap to build. But cheap might just be the undoing of the BPL industry, as more and more licensed radio transmitters are coming online, or being used in a mobile environment, and these could disrupt BPL systems on a wide scale.
This radio interference is no exaggeration, either. I am a technologist first, a ham operator second. I make my living on things technical (both RF and wire line communications), and I certainly wouldn’t chance my VoIP service, or my company’s, on BPL, knowing the shortcomings it has relating to receptive interference.
Hams have not made a big point of this because, to the uninitiated, logic would make it seem that the transmitter of the interfering signal would be the offender. But because these BPL devices fall under Part 15, it’s the other way around; they must accept any interference from licensed services.
But what of unlicensed services? While they have no legal standing, unlicensed services like illegal CB operation, using exceptionally high RF power amplifiers, are a fact of life. For example, if a CBer with a 500 watt (illegal) CB amplifier is driving within a few blocks of a BPL installation, it is highly likely the BPL system will be severely adversely affected. Legal or not, the BPL is still affected, and this is something the BPL providers won’t address, because it would require a lot of money be spent to "harden" their equipment. They made a choice to go the Part 15 route in the first place to save money; it isn’t likely they will spend money after the fact to harden their systems and equipment.
This isn’t late-breaking news to the BPL providers, they simply didn’t do their homework before putting money into the technology initially.
Had they done so it would have been obvious that their 3 to 30 MHz band of operation would quite likely give, and more importantly to this discussion, almost assuredly get interference.
This could have easily been avoided if they had built their technology to operate wide-band further up the radio spectrum, like maybe in the 2 to 10 GHz range. It would have been slightly more expensive to build, but virtually impervious to outside interference. So much for advance planning. I hope you have an opportunity to research this before your next installment; the ham community would very interested in how the BPL consortium responds.
Now take this to its likely conclusion, from the BPL consumer’s point of view. Say the BPL consumer gets not only his or her Internet access on the BPL, but also the VoIP (as some BPL operators are touting).
If the traditional, relatively interference-free "POTS" (Plain ol’ telephone service) phone service is removed and the BPL consumer has his only phone service on BPL, what happens in the event his or her BPL system is interfered with by a licensed transmission? It shuts down, that’s what.
Take this even further; say the BPL consumer is making an emergency call for medical or police assistance on his or her BPL phone service (over a cheap piece of equipment no more expensive to make than a cheap baby monitor) and because a licensed radio transmitter is in the area, that consumer’s BPL system shuts down? It doesn’t take a rocket scientist to see the possible outcome — is someone’s well being or even their life worth risking on a flawed technology like BPL?
.H1 The ham radio heritage
What many in the BPL consortium, and likely some consumers who read the negative comments about BPL from the ham community, fail to appreciate is that hams pioneered most, if not all, of the RF and digital communications that consumers and businesses alike take for granted.
Hams had hand-held, two-way radios capable of placing phone calls on the PSTN (Public Switched Telephone Network) over 3 decades ago. Some of the first communications to and through space satellites was done by hams. Hams have paid for (out of their own pockets), and had launched, dozens of communications satellites.
Hams have put in place vast networks of voice and digital RF repeater networks, linking large areas of the country with a powerful, and free to any licensed ham, a voice communications network. And again all of this at their own expense, as they are prohibited by FCC rule from accepting any monetary payments for their efforts.
Without question the largest private digital and voice networks in the world have been put in place by hams.
Digital packet X.25 (aka AX.25 in the ham community) systems were put in place years before either businesses or the government began using them. The ham community, seeing the future of the TCP/IP network, secured for themselves an entire class A IP addressing scheme. If you ever see a 44.xxx.xxx.xxx IP address, it originated from a ham radio digital station.
People think WiFi and wireless Internet is so cool, and it certainly is, but hams pioneered RF wireless TCP/IP networks a decade before anyone but the government and some colleges and universities knew what the Internet was — actually before it was even called the Internet (no, we didn’t invent it, but we were certainly there in it’s infancy).
So, while hams are made out be some to be these old codgers on ancient radio transmitters talking to one another about nothing in particular, most hams actually are under 50 and highly technical engineers and technologists in the RF, wireline, satellite, power transmission, and digital fields.
Much of the equipment hams use is state-of-the-art in RF communications, with the latest in digital filtering and digital frequency stability. Where BPL and baby monitors operate unlicensed under FCC Part 15, all hams must take and successfully pass a rigorous FCC technical exam, and update their license every 10 years.
My personal bio is likely the norm for many hams. I’m in my mid 50’s, have a B.S. degree from the engineering department of a large West Coast university, and have worked in many aspects of the wireline, RF and digital networking business. I hold technical certifications recognized the world over and I am currently a network engineer with one of the largest communications companies in the world, having been there for nearly 23 years.
I’ve been involved in ham radio for over 40 years and hold the highest class of license, Amateur Extra. Most of the hams I know who are also extremely concerned about BPL and its interference issues could run circles around me from an electrical and RF engineering perspective. So we are not just a bunch of old codgers with antiquated technology and training, but well-trained, up-to-date professionals working on bleeding-edge electronics networks and systems. In short, we know what we are talking about when it comes to commenting on the technical shortcomings of BPL.
Make no mistake about it, hams are definitely for technology, and the idea of a ubiquitous Internet available to everyone is exciting to them.
But technology simply for technology’s sake doesn’t make sense if it causes problems with other licensed services, and also can be interrupted so easily. The last thing the consumers want to pay for is an unreliable Internet technology; I am sure they would much rather pay for something proven and reliable. Unfortunately the current state of BPL doesn’t meet that criteria.
Concluding, I’d just ask that before putting out the glowing reports about how great BPL is, you look at the facts on all sides and give those sides a fair shot at providing those facts. There are many things about BPL that people just don’t understand, and I am sure the eventual BPL consumer would look back and have wished they would have only know those facts before paying for it.
Ultimately the consumers will decide if BPL is viable, not the BPL industry. Those potential consumers deserve all the facts up front, facts which a publication like yours should be providing.
As hams say when signing off at the end of a communications…73 (literally translated to "best wishes").
.BIO Bill South, BSEE, MCSE, MPC is a ham radio operator with Amateur Radio Extra Class License N3OH, living in Manassas, Virginia.
