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section heading icon     overview

This page considers use of domestic and other power lines for internet traffic.

It covers -

  • introduction - 'broadband over power line' technologies as a panacea or a second-rank solution
  • making sense of the technologies - access and inhouse BPL
  • status - is BPL an 'also ran' technology that was too late to move from the laboratory to the market?
  • issues - key impediments to uptake, including interference, competition from other technologies, consumer anxieties and indifferent industry support

The following pages discuss the uncertain business case for BPL, exploration of broadband powerline communication in Australia, and trials overseas.

subsection heading icon     introduction

As the name suggests, digital powerline communication (PLC) - or broadband over power lines (BPL), Power Line Telecommunications (PLT) or Power Line Broadband (PLB) - uses existing electrical power grids rather than dedicated telephone wiring or television cable to provide access to the net.

BPL is a label for a group of technologies that have been promoted
as a mechanism for freeing consumers from "the tyranny of the telephone company". Enthusiasts have characterised BPL as potentially offering broadband connectivity that is unavailable through existing telephone lines, that drives improvement in the performance of incumbent connectivity providers such as Australia's Telstra and that provides substantial new revenue for utility companies.

Others have forecast use of BPL in bridging digital divides in the Third World, "bringing broadband to isolated village and farms". It is acclaimed because the infrastructure is "already there", so that there is ostensibly no need to deploy fibre, satellite, WiMAX or other new communication infrastructure.

It has however been criticised as technologically problematical, commercially unviable and over-sold.

Technological criticisms centre on interference with existing users of the radio frequency (RF) spectrum. Although those users are sometimes dismissed as 'ham radio operators' they encompass emergency service agencies, aviators, commercial broadcasters and other entities. RF transmissions are licenced because space in the spectrum is finite. Adoption of BPL in most jurisdictions accordingly requires permission by telecommunication regulators. That permission often has not been forthcoming, because regulators have not been satisfied during technical trials.

Commercial criticisms centre on the uncertain business case for BPL. Interference problems arguably can be fixed through reengineering the infrastructure, for example by 'notching' urban and rural powerlines and by relying on underground cabling. However, the investment required for that reengineering and for ongoing maintenance erodes the commercial competitiveness of BPL.

Observers have noted poor performance in some trials, with loss of connections and erratic speeds, and consumer anxieties that their personal computer will become a toaster. They have accordingly suggested that utilities, consumers and regulators might get greater value through rollout of fibre or other infrastructure.

The BPL industry has been marketing-driven, with advocates claiming that digital powerline technology has a range of benefits including -

  • the theoretical potential to "provide every home with a fast internet connection, given that almost all homes are on an electricity supply grid"
  • use of wiring within buildings means that "every power socket is an internet access point".
  • provision of an always-on service with the same characteristics as DSL and cable modem connectivity
  • surveillance - "Monitor your children and people who are in need of regular help from any internet connection"
  • improved "safety and efficiency of the power network", with remote control and monitoring of appliances via power lines.

In practice those claims have not been tested on a large scale in a commercial environment. There has probably been more writing about BPL than implementation, particularly because it has been seen as hyped as revolutionary, freedom from telecommunication providers or as a low-cost mechanism for bridging divides in environments with inadequate phone/cable infrastructure ("broadband for everyone").

Assessment of BPL is complicated by confusion over particular technological offerings, the absence of published information about real costs and disinformation from some enthusiasts, who have tended to misrepresent small scale technical trials as large scale commercially viable implementations or who have simply dismissed concerns about interference.

There have been no commercial trials that strongly demonstrate BPL as a business case that is markedly superior to other technologies. Typically utilities in the northern hemisphere either have not initiated technical trials, have decided on business grounds not to embark on major commercial implementation or have shutterdsmall scale trials.

Some of the more mordant critics have accordingly characterised BPL as an unproven 'faith-based' solution.

subsection heading icon     making sense of the technologies

BPL essentially takes two forms -

  • to the household (sometimes labelled as 'longline PLC', 'access BPL' or BPL-to-the-home)
  • within the household ('inhome BPL' or 'in-house PLC' and using standards such as HomePlug).

Both involve conversion of digital content to a radio frequency signal that shares the same copper wire used to deliver electricity to commercial/residential buildings and to points within those buildings. That content might be a sound recording, video recording, a web page, email or a telephone call. Accessing the content involves converting the BPL signal, whether on a 'whole of building' or 'socket by socket' basis, back to a format for a personal computer or similar device.

Access BPL - sometimes mooted as an answer to the 'last mile' problem - involves existing grids used by power utilities to deliver electricity from generators to consumers.

Typically digital content is converted to radio frequency transmissions at gateways located at major nodes of the power grid, for example at a power station or a distribution substation. The gateways link the PLC network to conventional high-speed communication links - usually optical fibre - with the internet and public subscriber telephone network. At the edge of the power network (eg individual houses, schools, commercial buildings or office suites) the radio transmissions are filtered by a device for delivery through a conventional local area network (eg the "blue cable" found in many office buildings) that does not reticulate power for airconditioning, toasters, personal computers or other devices.

Inhome BPL - sometimes characterised as powerplug communication - uses the same principles to deliver content via existing electrical wiring within a building.

Proponents argue that the technology means that "every power plug can be an internet access point". A gateway device at a house's perimeter might, for example serve as a bridge between the phone network and the building's internal grid - the fuses, wires and sockets that are used to run the lights, heating and domestic appliances. One or more devices - ideally small, resilient and cheap - could be plugged into that grid, converting the signal back into the form expected by a conventional phone, a personal computer or a wifi station.

Data about performance outside laboratory environments is contentious. Some t
ests suggest that data transmission rates with powerline technology might be above most ISDN connections, with for example claims of 6Mbit/s in both directions. Others indicate that performance would be lower.

The Cinergy/Current access BPL trial in Cincinnati for example was promoted as offering 6 megabits per second download but typically has been capable of only 2-4 megabits per second sustained transfer (and sometimes worse). 

Residents of older buildings in inhome BPL trials have reported that some existing wiring proves to be inadequate, with vendors accordingly advising that only particular points be used - advice that erodes the attractiveness of "broadband from any power socket".

subsection heading icon     status

BPL technology has attracted some industry and government attention, in some instances with tangible funding, but essentially has not moved from pilot installations to 'real world' use across a range of households and organisations and with a range of equipment.

Major telecommunication and consumer product manufacturers have been reluctant to make a commitment to production of powerline gear. Certification by standard-setting bodies has been exploratory rather than concerned with day to day implementation. In the marketplace PLC appears to be less competitive than wifi and wimax and thus is attracting less support than those technologies.

Major groups such as Nortel, Siemens, RWE, E.ON and Norweb have not proceeded beyond small-scale trials in Europe. Trials in the US have typically been short-lived and involved under 300 consumers. A 2005 NewsForge item noted that US utilities giant TXU apparently

doesn't have enough confidence in BPL to risk investing its own money in it, or else it feels there is no cure for those interference blues - or both.

In April 2007 Motorola was reported to have suspended development of its Access BPL products.

The German government's 2003 response to the European Commission Working Document On Broad Band Communication Through Power Line similarly commented that

The German Government does not regard a European legal framework which results in general freedom to use PLC as desirable at the present time, because Germany has a lot of negative experience with the compatibility of radio networks and line-bound networks. Initial findings about PLC applications suggest that, despite contrary assurances by the manufacturers, the ceilings in force nationally cannot be adhered to

Overall, like some other technologies, BPL appears likely to be

the technology of the next generation ... and always going to be.

Critics have argued that BPL faces substantial consumer (and regulatory) resistance, is over-sold and under-supported or is a solution looking for a problem.

That is consistent with the basket of potential uses identified on the Powerline Communications Association site - including home automation, surveillance and - of course - gaming.

It is also consistent with problematical claims that internet/phone access will be free because electricity providers will not need to charge, an echo of 1990s claims that by 2000 most telephone companies would not charge for internet access.

Projects include the EU Opera (Open PLC European Research Alliance) initiative, which has concentrated on technical aspects. Two recent outputs are its 2005 Internet Over PLC White Paper (zip) and Reference guide on implementation, installation, management and operation of PLC distribution networks (zip) - rather than in-depth examination of technology + business case. Opera is allied with the PLC Utilities Alliance (PUA), which released a broader White Paper (zip) on BPL in 2004.

subsection heading icon     issues

BPL advocates face at least five issues -

  • commercial attractiveness relative to other internet delivery mechanisms
  • interference problems
  • network performance and maintenance
  • uncertain user support and consumer demand
  • fallout from flawed marketing and advocacy.

The first, and arguably most critical, is competition from existing and emerging network technologies that are not encumbered by interference problems and may require a lower investment (upfront and ongoing).

BPL may be technically feasible but is being beaten by wireless alternatives, fibre and even old-fashioned twisted-pair. There is little sign of strong consumer demand. It is unlikely that there will be substantial consumer demand in the absence of perceived major advantages, industry support and greater comfort with 'hot wires'. That is one reason why utilities trialling BPL have typically made a greater investment in fibre or wireless at the same time.

From a technical perspective radio frequency signals over power grids -

  • are affected by interference from non-communication devices that are on the same network, eg domestic blenders, sanders, milling equipment
  • encounter problems with bandwidth when there are major demands for access at peak periods in a local loop

Those performance problems are similar to difficulties explored in our discussion of wireless networking. They are significant because, despite some visions of "plug & play" at any power point (contrasted with "plug & pray" with modems), the technology has definite limitations.

Critics note that domestic filters are vulnerable to lightning strikes or other power surges and that the environment in utility substations is unfriendly (eg high temperatures, dust, substantial electromagnetic noise).

A third issue is indifferent industry support and the absence of major commercial and regulatory champions. Powerline communication is often seen as "out there" or a curiosity, rather than a commercially credible product that is likely to gain the traction of wifi and wimax. There is no consensus about standards; there is disagreement about both technical and commercial feasibility. There is uncertainty about the cost of components, with criticism for example of the more upbeat projections about access BPL equipment costs and maintenance expenses.

Irrespective of network construction, some critics have asked whether power companies have the appetite or mindset for establishing 'back office' functions such as spam control, security, abuse and help desks. Others have responded that some power utilities currently have ISP subsidiaries (eg CountryEnergy in NSW, which in June 2005 hyped the "first VOIP call made over powerline"), have the resources to acquire an ISP or - as noted below - can outsource operations to a third party.

Figures about the cost of infrastructure for 'to the household' delivery in Australia, North America and Europe are contentious. It has variously been claimed the configuration of power grids in much of Europe means that costs would be somewhat lower than in the US (or instead higher) and that the cost of measures to reduce interference in the EU mean that BPL is not economic. Benefits for utility operators - notably remote telemetry of consumer power usage - might be more cost-effectively achieved through wireless-enabled meters.

One of the few publicly accessible economic analyses is Rahul Tongia's 2003 Promises & False Promises of PowerLine Carrier (PLC) Broadband Communications - A Techno-Economic Analysis (PDF), complemented by Osorio Urzúa's 2004 Bits of Power: The Involvement of Municipal Electric Utilities in Broadband Services (PDF) and the technical discussion in Broadband Powerline Communications: Network Design (New York: Wiley 2004) by Halid Hrasnica, Abdelfatteh Haidine & Ralf Lehnert. The latter supersedes Klaus Dostert's Power Line Communications (Upper Saddle River: Prentice Hall 2001).

In Europe there has been increasing concern over interference, with comments that PLC is inconsistent with the Digital Radio Mondiale (DRM) standard - discussed in our note on digital radio - which uses compression to deliver near-FM quality digital sound over existing AM broadcast frequencies. DRM has been recognised by the European Telecommunications Standards Institute (ETSI), the International Electrotechnical Committee (IEC) and International Telecommunications Union (ITU) Radio Regulations Board.

Studies in the UK during 2004 suggested that there is significant degradation of DRM signals through interference from access BPL systems. That is consistent with inhouse BPL studies on the continent in 2002 and 2003. Deutsche Telekom advised the European Commission that

The deployment of millions of inhouse PLC modems throughout Europe is a nightmare to any radio operator and to administrations which will have to solve numerous cases of interference. We have measured inhouse PLC modems: interference fieldstrengths up to "NB30 plus 30/40 dB", with the capability of jamming all radio reception in the frequency band between 2 and 30 MHz (sometimes with "notches" to protect some amateur bands, but no protection/notches for the broadcasting bands); the jamming range is estimated about 100 meters

Some studies suggest that that longline BPL can result in short-wave signal mirroring at the ionosphere, affecting reception of civilian shortwave transmissions (including long distance emergency communications) and communication of interest to national security agencies.

It is likely that some technology enhancements such as better and closer repeaters on longlines (eg 'notches' every 100 to 250 metres) will reduce interference problems. However, at least for the moment, those fixes appear distinctly uneconomic. The cost of reducing/removing RF interference problems appears to render access BPL uncompetitive.

One 2006 report (PDF) by Mark Connolly, Pat Cooney & Mati Cleary of the Irish Electricity Supply Board thus commented that

despite significant hype and R&D spending by vendors and certain utilities, Broadband Power Line Technology is nowhere near an appropriate state of development required for commercial ‘mass market’ rollout.


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version of April 2010
© Bruce Arnold