Broadband Over Powerline

The Technology
Broadband over power line (BPL) is another high speed data service available to consumers. It uses medium and low voltage power lines to carry broadband data at speeds between 500 Kbps and 3 Mbps. At these data rates BPL is equivalent to and competes with cable and DSL. Access BPL and In-home BPL are both used to deliver data to the consumer over power lines. Access BPL is used to carry data over the medium voltage and low voltage power lines to the customer’s premises. Power companies also use Access BPL to monitor power grids. In-home BPL defines the technology that is used in side the customer premises to transport data. Many devices are available now that can network your home using the electrical wiring in your house.

BLP data can use either Orthogonal Frequency Division Multiplexing (OFDM) or Direct Sequence Spread Spectrum (DSSS) to deliver its signal. OFDM transmits multiple data signals over a wired or wireless system. It uses a spread spectrum technique that “distributes data over a large number of carriers that are spaced apart at precise frequencies”(OFDM Tutorial). ODFM is commonly used in digital broadcasting in Europe, Japan and Australia (OFDM Tutorial). It is also a world-wide standard for asymmetrical digital subscriber line (ADSL). DSSS is a popular and widely recognized form of spread spectrum. The process multiplies a radio frequency carrier and a pseudo-noise digital signal or chipping code. The chipping code, which is a redundant bit pattern for each bit that is transmitted, makes it possible to recover data if it is damaged during transmission (DSSS).

Regardless which method is used to modulate the signal, data has to be delivered to a point where it can be injected into a medium voltage power line. High voltage transmission lines must be bypassed because they are too noisy to carry data reliably (Valdes). Initial data delivery occurs over a traditional telecommunications data network using a T1 or fiber-optic line. Once the data has reached the point of entry, a BPL injector is used to transfer the data signal to the power line. Data is converted into the OFDM signal format and coupled into one phase of the medium voltage power line (Potential Interference) . Data can be transferred to the low voltage lines by either going through the transformer or by using a BPL extractor that bypass the low voltage transformers. Passing data through a transformer limits available bandwidth that can be delivered to the home. The BPL extractor converts the data between access and in-house BPL signals. A third option is for the power company to create a wireless hotspot near each transformer. This method can create a mesh wireless network that provides users with multiple wireless service areas (Bahlmann 2004). An entire city can be made into a hotspot using this method.

Two different schemes that employ OFDM are used to transmit data over power lines. One converts data from the Internet backbone into the OFDM signal and couples it into one phase of the medium voltage line and vice versa. Data is then converted to the low voltage line using an extractor that bypasses the medium to low voltage transformer. The signal is then accessed in-house using BPL devices (Potential Interference). Another scheme converts the signal from the medium voltage power line to an 802.11b WiFi signal instead of low voltage BPL. In this scheme BPL is not used on the low voltage line. Radio frequency bands are used to separate upstream from downstream BPL signals (Potential Interference).

Another scheme uses DSSS to transmit data over medium voltage power lines. All users within a BPL cell share a common frequency. Contention management on the line is done using carrier sense multiple access (CSMA). Each cell includes an injector (concentrator) that links to the T1 of fiber-optic Internet link, extractors (repeaters) and customer premises BPL equipment. Injectors can service many premises.

BPL Standards
In-Home BPL is for use in residences. The HomePlug 1.0 specification was developed by the HomePlug Powerline Alliance (HomePlug 2004) and is a standard that defines how devices are networked over power lines. The standard specifies a connection speed of 14 MBps. HomePlug AV is the successor to the 1.0 specification. This new specification initially called for a connection speed of 100Mbps. It is targeted at devices like TVs; DVD and CD players; high resolution monitors; and set-top boxes (Kistner 2002). The creators of the specification made a conscious decision to append AV instead of 2.0 to the name. According to their reasoning they want HomePlug technology to be identified with devices rather than networking technology (Kistner 2002). The HomePlug AV specification was anticipated to be completed by the end of this year. In an October 13, 2004 press release the HomePlug Alliance stated that the specification is nearing completion and invited other networking and home electronics companies to join the alliance and contribute to the specification (HomePlug AV). As stated in the press release the current details of the HomePlug AV specification are:

* 200-Mbps class networking.
* An advanced Physical Layer that offers near-capacity throughput performance and exceptional coverage for robust communications over noisy power line channels.
* A high-efficiency MAC layer that incorporates both scheduled access (TDMA) with Quality of Service (QoS) guarantees, and contention access (CSMA).
* Advanced Network Management functions and facilities capable of supporting plug-and-play, user and service provider set-up and configuration.
* Co-existence modes enabling Broadband over Powerline (BPL) co-existence, multi-network operation, hidden node service, and backward compatibility with HomePlug 1.0 (HomePlug AV).

The IEEE is working on developing standards for BPL. Targeted for completion in 2006 IEEE P1675 will provide a comprehensive set of standards for installing BPL hardware on above ground and below ground power lines (IEEE Starts). In addition to setting standards for installation and transmission IEEE P1675 defines safety requirements for people who work with BPL equipment. The National Association for Amateur Radio or ARRL is working with the IEEE on this standard. The ARRL has been an outspoken opponent of BPL because of the potential for interference in amateur radio transmissions (see Objections to BPL below). According to ARRL laboratory manager Edward Hare, the IEEE standard must “include the needs of the BPL industry to have a workable environment in which to manufacture and market BPL technology while addressing the need for licensed radio services to operate in an environment that does not result in harmful interference (ARRL).”

Market Impact and Benefits of the Technology
BPL technology brings to the table another competitor in the market of high speed Internet access providers. This service will compete with cable modems and telecommunications technologies like PSTN dial up connections and ADSL. Because it is another competitor in the market is an alternative to cable and ADSL Internet access, providers of this service claim BPL will help to drive down the cost of Internet access. Another benefit to power companies is BPL will allow them to diversify their services and it gives them access to a new and previously untapped revenue stream.

One of the biggest benefits usually cited is that BPL will enable the delivery of Internet access to rural residencies where high speed Internet service is not currently available. Although cable and telephone companies are building out their infrastructure to make high speed Internet access available in rural areas it could take several years before this happens in any meaningful way. Getting high speed data technologies to rural areas is not happening as quickly as telephone companies would like us to believe. Peter Morrissey’s article Telemarketing Travails (Morrissey 2001) provides a good example of telephone companies promising more than they can deliver. The infrastructure just isn’t available yet to deliver cable modem and/or ADSL service to all locations that might benefit from it. BPL seems to be a technology that can reach into every home and could be a boon for rural customers waiting to get on the information super highway. Critics question this reasoning however. BPL is a last mile technology and data still needs to travel over traditional data lines until it can be picked up by the BPL service. For this reason, critics say BPL will not benefit rural customers as much and as quickly as the proponents suggest (Reply Comments).

Another benefit of BPL is there is no need to run additional cable to the home. Virtually every residence has an electrical power line connected to it. In addition, most homes have a power plug in every room of the house. The customer merely needs to plug into an existing power outlet using specially designed devices to access the Internet or their internal network via BPL. For the provider much of the infrastructure is already in place to deliver this service. Power companies already have lines connected to residences and a power distribution grid. In fact their penetration into residences is greater than telephone and cable. This infrastructure gives power companies access to residences and a tremendous advantage over traditional telecom and cable services. The build out of BPL infrastructure will not be as costly and will not take as much time as it would if wire had to be run to all residences for them to connect to the system. For the consumer there is no cost for the wiring needed within the home for BPL.

There are many potential benefits BPL has for the end user. Existing homes can have high speed Internet access in every room where there is an electrical outlet. I can only speculate that the potential for networking appliances in every room of the house is virtually limitless. If we consider the possibilities it is clear that BPL could change the way we live. Think about being able to monitor all of your appliances from any console. Appliances could be built that would take advantage of this capability even to the point where SNMP could be built in to a device. For example, your water heater or furnace might send an alarm long enough before it dies that you can replace it before you are inconvenienced. Or you may be able to monitor your stove and know when the roast is done while working your computer instead of having to listen for an audible alarm. Or what about a pop-up notice on your TV when the clothes are ready in the dryer? You may even be able to adjust the temperature and other settings for appliances, turning them on and off at will from a central console. Home alarm systems would not require extensive wiring as they do now.

Companies Involved in BPL
The HomePlug Alliance is a not for profit standards organization whose purpose is to develop standards for BPL and BPL devices. Membership in the organization is free to anyone who wants to contribute. Many of the same companies that are involved in other forms of data communications and networking are part of the alliance. Those companies include LinkSys, Siemans, Belkin, and NETGEAR among others. HomePlug is an industry standard that is designed to provide connectivity to cable or DSL and distribute it throughout the home over existing power lines. Using the HomePlug specification devices can be connected to the Internet from any electrical outlet in the home. The HomePlug standard defines a throughput rate of 14Mbps. It uses a variant of CSMA/CA at the MAC layer. At the Physical layer HomePlug uses OFDM.

The utility company for Manassas Virginia has made a commitment to BPL. Manassas aims to be the first US city to deliver BPL to every home in their city (Bore). Manassas is located within 35 miles from Washington DC so it isn’t exactly rural. However, according to the 2000 Census, Manassas has a population of 35,135 which makes it an ideal size for a full BPL deployment within a reasonable shore period. They are charging $30.00 per month for access to this service. The city estimates that they will receive 4.5 million dollars over the life of their contract with Prospect Street Broadband (Bore).

Amperion is a manufacturer of BPL products with a focus on PowerWifi (Amperion). Amperion manufactures injectors to interface between the data network and a medium voltage power line. It also manufactures extractors and repeaters for delivery of the data signal to the premises. Amperion’s equipment is standards based and links the power line network to an 802.11b compliant connection (Amperion).

Objections to BPL
The group most vocal about their concerns over BPL is the AARL. They are concerned about the interference that BPL may cause with amateur radio broadcasts and reception. They have found allies in the National Telecommunications Information Administration (NTIA) and the Federal Emergency Management Agency (FEMA) who generally agree with them over this issue.

BPL delivers data over medium and low voltage power lines and uses a range of frequencies between 1.7 and 80 megahertz (MHz) (Broadband over). Power lines are not shielded and are not designed to prevent radio frequency (RF) radiation. As a consequence, the ARRL argues that BPL presents a huge source of interference for radio services using this frequency range. Because radio frequencies natural tendency is to radiate, interference not only occurs in close proximity to a BPL power line but has the potential of causing interferences at great distances. It has been observed to cause interference up to one mile away. Some say that BPL’s radio waves can potentially travel even greater distances.

The NTIA agrees with the ARRL. It issued a warning to the FCC that BPL could cause interference with government users of shortwave frequencies (Coursey 2004). In its report (Potential Interference) the NTIA suggests several means by which BPL interference can be reduced. It also urges that the FCC not relax Part 15 of the FCC regulations with respect to BPL. The NTIA suggests mandatory registration of the parameters of deployed systems and to require devices to be capable of power reduction to eliminate interference. Other recommendations include requiring devices to operate at the minimum power needed, avoiding locally used radio frequencies, and filters and terminations to remove BPL signals that are not needed on a power line (Potential Interference).

FEMA also expressed what they called grave concerns about BPL. FEMA said BPL also could negative impact services like the Radio Amateur Civil Emergency Service (RACES), the Military Affiliate Radio System (MARS) and the Civil Air Patrol (Fema Says). However, in April of 2004 FEMA softened its stance on BPL and said that there may be ways to provide BPL service and not compromise emergency systems (Fema Appears). FEMA seems willing to compromise and is not as concerned as they originally were. But the AARL is still adamantly opposed to BPL without some regulatory requirements over and above those specified in Part 15 of the FCC rules.

Gary Box in his paper BPL: The RFI Challenge I think accurately states that BPL is a challenge for everyone. Because BPL operates as an unlicensed radio frequency BPL providers must meet FCC Part 15 requirements that address the requirements limiting harmful interference.

FCC’s Position on BPL
On October 14, 2004 the FCC issued rules that limit interference to certain radio frequencies. This has cleared the way for major deployments of BPL. The FCC took into account the concerns of the ARRL, the NTIA and FEMA when issuing its rules. The new rules require devices that can switch frequencies to avoid interference. Proximity to certain locations such as airports and coast guard installations are forbidden in the rules. The FCC is encouraging companies to move forward with BPL and is excited about its potential.

The chairman of the FCC was excited when he made the announcement of the FCC’s ruling about this new technology and pledged to protect the amateur radio users from interference caused by BPL. However, in its BPL Report and Order the FCC does not consider amateur radio operators in the same class as aeronautical and maritime operators. The FCC places the responsibility on ARRL to properly plan their installations to avoid interference from power lines (FCC BPL). As a result, the FCC has made no changes to Part 15 of its rules and will treat BPL interference the same as it would any other type of interference.

Conclusion
Broadband over Power Line is poised to be the next great thing in high speed Internet access. The objections over the problems caused by the technology seem minor as compared to the potential benefits. The ability to manage devices within the home seems to me to be the most promising new benefit this technology will provide. The benefit to rural customers remains to be seen. Since BPL is a last mile technology it is questionable whether or not rural customers will see the benefits as quickly some suggest. As is true with most new technologies, there will continue to be controversy and there will continue to be improvements that will mitigate the concerns of those objecting to the technology. I see BPL as another technology that will help, along with cable modems and ADSL, make high speed Internet access universally available. I doubt that cable or DSL will be displaced in any significant way by BPL. For the consumer it will not be a matter of whether the technology is available. It will be a matter of choosing which technology to use.

References

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ARRL Participating in IEEE, BPL Industry Efforts to Set BPL Standards. retrieved December 14, 2004 at 8:38 a.m. from http://www.arrl.org/news/stories/2004/11/15/2/?nc=1.

Bahlmann, B. (2004). Broadband Over Power Lines (BPL) retrieved December 12, 2004 at 8:48 p.m. from http:://www.birds-eye.net/article_archive/broadband_over_power_lines_bpl.htm.

Bore, K. Urban Electrified Broadband, Manassas, VA nations first BPL wired city. retrieved December 13, 2004 at 8:09 p.m. from http://www.dslreports.com/shownews/34735.

Broadband over Power Line: Why Amateur Radio is Concerned about Its Deployment. retrieved December 11, 2004 at 8:08 a.m. from http://www.arrl.org/tis/info/HTML/plc/bpl-deployment.html.

Coursey, D. (2004). Why broadband over power lines is a bad idea. ZDNet Anchordesk. retrieved December 12, 2004 at 4:50 p.m. from http://reviews-zdnet.com.com/AnchorDesk/4520-7298_16-5123406.html.

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FCC BPL Report and Order Stresses Avoidance, Resolution of Harmful Interference retrieved December 14, 2004 at 11:52 A.M. from http://www.arrl.org/news/stories/2004/10/28/100/?nc=1.

FEMA Says BPL will Severely Impair HF Operations. retrieved December 13, 2004 at 10:05 p.m. from http://www.eham.net/articles/7196.

FEMA Appears to Backpedal in BPL “Clarification” Letter. retrieved December 13, 2004 at 10:13 p.m. from http://www.arrl.org/news/stories/2004/04/01/101/?nc=1.

HomePlug AV Specification Enters Final Stage retrieved December 14, 2004 at 11:14 a.m. fromhttp://www.homeplug.org/news/press101304.html.

HomePlug Powerline Alliance (2004) retrieved December 12, 2004 from http://www.homeplug.org/faq/.

IEEE Starts Standard to Support Broadband Communications over Power Lines. retrieved December 14, 2004 at 8:23 a.m. from http://standards.ieee.org/announcements/pr_p1675.html.

Kistner, T. (2002) HomePlug shares its vision. retrieved December 14, 2004 at 11:00 a.m. from http://www.nwfusion.com/net.worker/columnists/2002/1028kistner.html.

Morrissey, P. (2001). Telemarketing Travails, retrieved December 13, 2004 at 7:31 p.m. from http://www.nwc.com/1209/1209colmorrissey.html.

OFDM Tutorial. retrieved from http://www.wave-report.com/tutorials/OFDM.htm.

Potential Interference From Broadband Over Power Line (BPL) Systems to Federal Government Radio communications at 1.7 – 80 Mhz. Volume 1. US Department of Commerce: National Telecommunications and Information Administration. Donald Evans, Secretary, Michael D. Gallagher, Acting Secretary For Communications and Information. retrieved December 12, 2004 at 7:14 p.m. from http://www.ntia.doc.gov/ntiahome/fccfilings/2004/bpl.

Reply Comments to Notice of Proposed Rule Making (04-37) retrieved December 12, 2004 at 11:36 p.m. from http://www.cot.net/~n6mrx/ares/bpl.htm.

December 2004 © Ronald M. Denby