BPL is back
|Jul 20th 2011, 12:17|
Super ModeratorJoined: Apr 4th 1998, 00:00
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An ARRL member inquired of ARRL:
> How may we help you?: Here is an atricle I spotted and thought
> you should see it _ BPL is a bad idea that just won't go away.
> Networking over power line: Will next-generation technologies
> stumble or shine?, part 1
Actually, BPL has never gone away. Although there has not been as much news about it of late on the ARRL web pages, the technology is still very much in use. There is, of course, still an unresolved FCC rulemaking and continuing development in the technical standards arena.
The article is mostly focused on what is known as in-premise BPL. This is intended to use residential and building wiring to carry broadband signals. This can actually work to a degree, as most electrical wiring would function as a fair transmission line into the VHF range. There are, of course, problems, notably caused by all of the devices and loads connected to the electrical systems, some of which can also be quite noisy on the same frequencies used by in-premise BPL. Other losses come from the inherent losses of the electrical wiring at HF and from the various branches, switches and lights, etc. Some of those losses are radiation, which is the very reason for the concerns of HF and VHF radio users.
Today's in-premise BPL can operate at backbone speeds of nearly 1 gigabit per second. To do this, it uses frequencies as high as 200 MHz. However, it must be noted that this high speed is achievable on power lines for only very short distances. At greater distances, the losses add up and noise predominiates, so these modem adjust their speed downward to accomodate the nature of the communications channel.
Fortunately, most of the in-premise BPL in the United States is operating under the HomePlug specification. HomePlug has several protocols, extending over different frequency ranges. They all have one important thing in common -- HomePlug systems do not use the HF ham bands! Their protocols have a spectral mask that protects Amateur Radio.
This was well documented in the year 2000 by ARRL and HomePlug:
Newer HomePlug specifications do extend into VHF, and the 6- and 2-meter Amateur bands are not specifically masked, but the permitted operating level of VHF BPL systems is at the same low level as the HF protection for Amateur Radio, so additional spectral masks were not used.
The power lines have high losses on VHF, so just as the distance range on the lines is short at high speeds, the interference potential of the modems is also short at VHF. Although it is possible (and probable) that an Amateur could cause interference by installing BPL in his or her own house, significant protection is offered for interference from the house next door.
This appears to be a successful model. Although interference is always possible, the use of spectral masks and low operating levels on VHF has reduced the likelihood of interference to a very small number of potential cases. It would be practical and appropriate to handle these on a case-by-case basis. (The FCC rules require that the operator of an unlicensed emitter of RF signals correct any harmful interference to licensed radio services.)
The end result has also been successful. With many millions of HomePlug devices deployed in the US, ARRL has received zero reports of harmful interference to Amateur Radio from HomePlug devices. Interference to shortwave broadcast, WWV, etc, can and does occur from HomePlug (and other) BPL devices, but to date, this has not resulted in many reports of inteference in the US.
There is equally good news on other fronts. Although there are other BPL specifications other than HomePlug, the Panasonic "wavelet Orthogonal Frequency Division Multiplexing (OFDM) version of BPL similarly notches the Amateur bands. The DS2/UPA BPL system, now owned by Marvell, does not specifically protect Amateur Radio at the chipset level, but ARRL has established good dialogue with Marvell and hopefully the successful models used by HomePlug can be extended to the chipset level within the UPA specification, as well.
There is also a lot of good industry standardization and international work at hand as well. The IEEE P1901 standard specifies that for the wavelet OFDM and HomePlug specifications, the two technologies covered by the standards, signals "shall not be output at any time" in the Amateur bands.
CENELEC is also in the process of balloting a European specification that would also protect the Amateur bands. ARRL has also taken the position with the FCC that these successful models should be turned into equally successful rules.
The same principles that have been successful for in-premise BPL can also be successful for access BPL deployed on overhead distribution lines. As most of the industry adopted notching of the Amateur bands, I went to about a dozen BPL areas and investigated this notching.
The results were mostly good. In all areas where the BPL system was not operating above the FCC limits, the notching was successful. In those areas, I could park a mobile station underneath an overhead BPL coupler and although the BPL noise was loud and clear outside the ham bands, in the ham bands, there was no BPL noise. The noise from the BPL system was now on a par with other noises.
The industry was moving firmly into implementing Amateur notches in all US deployments. IBEC, a company installing BPL in rural areas, primarily with government subsidy and loads, informed ARRL that it was going to notch the Amateur bands in its installations. They prepared a system in central Virginia and invited ARRL to see the notching. They demonstrated that the Amateur notches were implemented in the entire system. Overall it was pretty successful.
Unfortunately, that communication and promise did not continue much past that demonstration and the resultant good publicity. At some point, ARRL learned later that they had discontinued the notching of the Amateur bands and were going to correct interference to fixed stations on a case-by-case basis. An amateur in central Virginia that complained of interference to his fixed station was given some relief -- again and again and again as new modems were installed --- but told that there was nothing that would be done for interfence to his mobile station.
ARRL performed extensive measurements of the system and after giving more than enough time for the involved company and electric utility, the Central Virginia Electric Cooperative (CVEC) to resolve the issue, the League filed formal complaints with the FCC:
Thanks for the report of the the article. Although some BPL, such as HomePlug, appears to have been succesfully designed and implemented, until those successful models are made into equally successful rules, ARRL will stay the course and continue to work with this industry, industry standards committees and the FCC to, ironically, help BPL be sucessful.
Ed Hare, W1RFI
ARRL - The national association for Amateur Radio
ARRL Laboratory Manager
225 Main St
Newington, CT 06111
Member: IEEE, Standards Association, Electromagnetic Compatibility Society
Vice Chair: IEEE, Connecticut Chapter
Secretary: IEEE EMC Society Standards Development Committee Member: ASC C63 EMC Committee, Vice Chair: Subcommittee 5, Immunity
Vice Chair: IEEE P1775 BPL EMC Committee
Board of Directors: QRP Amateur Radio Club International
|Aug 7th 2011, 03:05|
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One thing about BPL and its brethren like HomePlug is that expanding the bandwidth gets to be very hard to do as the expectations of users keeps going up. BPL itself was doomed because of the increasing demands for higher and higher speeds. Do you think you can push UHF and SHF down those widely space electrical distribution lines? Even for in-the-home use, look at the cable type being used (NM and UF type electrical power cabling you can see at home building supply store). They made Cat5 and Cat6 cable with twists at varying pitches for a reason. The power cable in the walls is just not going to go very high reliably.
Electrical power distribution companies really need to consider putting fiber on their existing right-of-ways, and take it all the way into the customer premise. They could be very competitive in the internet market that way, rather than being left behind in the BPL dust as other companies keep moving ahead.