Broadband over power lines (BPL)

by Chris Woodford. Last updated: February 13, 2022.

High-speed Internet access anywhere, anytime—that's what we've increasingly come to expect in the 21st-century information age. But what if you live in a rural area where it's too expensive for a telecoms company to provide broadband? Or what if your house has old telephone wiring or the room you want to work in doesn't have a telephone access point? Worry not! The solution could be BPL (broadband over power lines), also called EOP (Ethernet over power)—a way of piping broadband to your home and channeling it from one room to another using the standard electricity supply. BPL is also known as HomePlug (the name of an alliance of manufacturers who make the equipment) and, in the UK, as "networking over the mains." Let's take a closer look at how it works!

Photo: Powerlines like this run almost everywhere, so why not use them to carry broadband Internet as well as electricity? Photo by Ryan Quijas courtesy of US Space Force and DVIDS.

Sending two signals down one line

If you know something about broadband Internet already, you're probably aware that it works by splitting your ordinary telephone line into a number of separate channels. Some of them carry your phone calls, as usual, some carry downloads (information coming from the Internet to your home), and some handle uploads (information going the opposite way). Broadband uses low-frequency electric signals (the equivalent of low-pitched sounds) to carry ordinary phone calls and higher-frequency signals (like high-pitched sounds) to carry Internet data. Electronic filters separate the two kinds of signal, with the low frequencies going to your telephone and the higher frequencies to your Internet modem.

Does that sound so strange? It's really not so hard to use a single medium to carry more than one thing. People work this way all the time. If you've ever stood quietly in a corner of a cocktail party tuning in on different conversations, you'll know how easy it is to do. The air in the room is like a giant pipe carrying many different sounds to your ears. But, using something called selective attention, your brain can tune into one conversation or another depending on whom you find most interesting. Broadband Internet works a bit like this too. A single piece of telephone cable carries both phone calls and Internet data. Your telephone listens just to the calls; your modem lists only to the data.

Access BPL: bringing broadband to your home

Photo: With BPL, your modem takes its signal from your domestic electricity socket rather than your telephone socket.

If you can send computer data down a phone line, there's no reason why you can't channel it down a power line as well. Some Internet service providers (ISPs) are already using overhead and underground power lines to carry broadband data long distances to and from their customers in what's called access BPL. It's exactly the same principle as sending broadband over a phone line: a high-frequency signal carrying the broadband data is superimposed on the lower-frequency, alternating current that carries your ordinary electric power. In your home, you need to have slightly modified power outlets with an extra computer socket. Plug in a special BPL modem, plug that into your computer, and your broadband is up and running in no time.

Photo: The basic concept of powerline broadband: electric power lines can be used to bring broadband Internet to your home (or carry it from one room to another). That's because you can do more than one thing with the same electricity cable at the same time. Note that this is just an illustration: real-world BPL uses low- and medium-voltage lines, not the very high voltage lines that dangle between pylons.

In-house BPL: carrying broadband within your home

You can also use BPL with traditional telephone or cable broadband to bring Internet access to all the different rooms in your home. You simply plug the Ethernet lead from your normal modem into a special adapter that fits into one of the power outlets. Your home electricity circuit then takes the broadband to and from every room in your house as a high-frequency signal superimposed on top of the power supply. If you want to use broadband in a bedroom, you simply plug another Ethernet adapter into one of the ordinary power outlets in that room and plug your computer into it. In-house BPL, as this system is known, is a great way of getting broadband in any part of your home. It's particularly useful if you have a big house with thick walls that make wireless Internet impossible.

Hybrid approaches

Another approach to BPL is to use powerline infrastructure—either above or below ground—as a kind of physical backbone for entirely separate fiber-optic cables, so the Internet cables simply run alongside existing power cables without actually sending signals through them. This saves the considerable expense of acquiring land and digging trenches for fiber, and also avoids the technical challenges of trying to combine two separate signals in a single cable. It's similar to the idea of running cables alongside railroad tracks, down the middle of highways, and so on, but doesn't really have anything else in common with what we think of as BPL.

Smart homes of the future?

BPL opens up an even more exciting possibility for the future. If we can connect computers using the ordinary power lines in our home, there's nothing to stop us connecting up domestic appliances both to one another and to the Internet. Smart homes (in which appliances are switched on and off automatically by electronic controllers or computers) have used this basic idea for years—but BPL could take it much further and make it far more widespread. Imagine a future where you can use a Web browser on your computer at work to switch on the electric cooker in the kitchen at home, ready for when you arrive. Or how about using the Web browser on your cellphone to turn your home lights on and off when you're staying in a hotel, to give added protection against intruders? Just imagine the possibilities: BPL could take remote control to an amazing new level!

Advantages and disadvantages of broadband over power lines

Advantages

• Electricity power lines are ubiquitous in most developed countries.
• Access BPL may be quicker, cheaper, and simpler to deploy in rural areas than higher cost, high-speed broadband over telephone lines or cable.
• Access BPL technology is relatively simple.
• Power companies who already supply electricity could also provide inexpensive broadband to existing customers over the same lines, which could help to push down the cost of broadband across the board.
• In-house BPL is perfectly compatible with Wi-Fi and helps to overcome distance and reliability limitations in existing wired and wireless networks.

Disadvantages

• Access BPL is still relatively uncommon. At the time of writing, it's failed to gain momentum in countries such as the United States, the UK, and Australia. In-house BPL is much more popular, however, and still widely available.
• Only low and medium voltage power cables can be used for access BPL.
• Different countries use different power voltages, which would make it harder to sell equipment internationally and push up the cost.
• Signals need booster equipment to make them travel long distances. Transformers, circuit breakers, and surge protectors can interfere with broadband signals.
• Most people already use DSL (traditional broadband) or wireless systems and own routers, modems, and other equipment compatible with it. They'll be reluctant to buy new equipment unless there's a compelling reason to do so.
• More of us use mobiles to go online than desktop computers, which arguably makes BPL less relevant—at least if people are using cellphone networks to browse with. The huge, rapid growth of mobile (cellphone) broadband in developing countries (coupled with the lower availability of conventional electricity power networks) makes it unlikely that BPL will ever catch on there. Worldwide, mobile broadband grew at over 20 per cent per year between 2012 and 2017 alone (according to the ITU-T's ICT Facts and Figures 2017); the number of connections increased 20-fold between 2007 and 2020, from 268 million to 5.83 billion (according to Statista); BPL hasn't caught on at anything like the same rate.

Find out more

On this website

• Broadband and mobile broadband
• Internet
• Wireless Internet

Manufacturers and suppliers

• HomePlug Powerline Alliance: An industry group promoting a standardized approach to powerline technology. The website has some useful background information and a comprehensive catalog of certified products from manufacturers such as Belkin, devolo (dLAN), Netgear, and ZyXEL.

Books

These are detailed technical guides mainly aimed at electronic engineers or undergraduate students:

• Understanding Broadband over Power Line by Gilbert Held. Taylor & Francis, 2019.
• Power Line Communications: Principles, Standards and Applications from Multimedia to Smart Grid by Lutz Lampe, Andrea M. Tonello, and Theo G. Swart (eds). John Wiley & Sons, 2016.
• Broadband Power Line Communication Systems: Theory and Applications by J. Anatory and N. Theethayi. WIT Press, 2010.
• Broadband Powerline Communications Networks: Network Design by Halid Hrasnica, Abdelfatteh Haidine, and Ralf Lehnert. Wiley, 2004.

Articles

• With New Tech, Panasonic Aims to Revive Interest in Delivering Broadband Over Power Lines by John Boyd, IEEE Spectrum, 14 October 2019. Could HD-PLC (high-definition power line communications) rekindle interest in BPL?
• Whatever happened to Broadband over Power Line? by Martin Courtney, Engineering and Technology, 15 October 2013. Explores why access BPL has largely failed to take off.
• Significant Broadband over Powerline Standard Is Approved by Bill Sweet, IEEE Spectrum, 23 October 2010. A short news item about the ratification of IEEE1901, the BPL standard.
• The US broadband battle by Drew Clark, BBC News, 27 May 2009. How a variety of different broadband technologies, including BPL, are competing for the lucrative US market historically dominated by telephone and cable companies.
• IBM Delivers Rural Broadband Over Power Lines by Saul Hansell, The New York Times, 19 February 2009. IBM sees an important role for delivering broadband to rural areas using existing powerlines, especially where the terrain blocks wireless.
• Plugging Into the Net, Through the Humble Wall Outlet by Tom McNichol. The New York Times, October 28, 2004. Can BPL speed up American access to the Internet?
• Broadband Over Power Lines?: Wired News, 9 February 2003. This old article shows how huge early enthusiasm for BPL has, so far, failed to live up to expectations.

Patents

This is a small selection of BPL patents you can find on the USPTO database (or Google Patents); they offer much greater technical detail than the general articles above, but are somewhat harder to understand:

• US Patent 7,492,245: Broadband over power lines (BPL) coupling system by Bruce A. Renz et al, Amperion Inc, February 17, 2009. Describes an inductive coupler that can transmit broadband over a medium-voltage power line simply by being clamped around it.
• US Patent 7,349,325: Broadband over low voltage power lines communications system and method by Andrzej Trzeciak et al, Motorola Inc, March 25, 2008. Describes a system for sending broadband over lower voltage lines (110–600 volts).
• US Patent 7,671,701: Method and device for providing broadband over power line communications by William O. Radtke, Current Technologies, Llc, March 2, 2010. Describes transmit and receive circuits for BPL systems.

Standards

• IEEE Std 1901-2010 — IEEE Standard for Broadband over Power Line Networks: Medium Access Control and Physical Layer Specifications
• IEEE Standard for Broadband over Power Line Networks: Medium Access Control and Physical Layer Specifications —Amendment 1: Enhancement for Internet of Things Applications