Powerline Networking 101

What Is Powerline Technology?

Powerline is a networking communications technology adapted for use over existing electrical power lines, hence the name. The Institute of Electrical and Electronics Engineers (IEEE) and HomePlug Alliance organizations created working groups and standards for Powerline technology that can be applied to electrical grids as well as in-home circuits. In fact, when you hear the terminology Smart Grid, many of the proposed industrial applications utilize Powerline technology. On the consumer front, we would most likely recognize the application of Powerline technology by the electricity industry in the form of smart meters. While not every smart meter uses Powerline, those that do are an example of the electricity industry utilizing existing power lines to exchange data, such as utility companies receiving updates from your smart meter regarding your electricity usage. That is if you opt in to such a service, of course.

When you pause and think about that though, the potential for using power lines to transmit data could mean that, eventually, electric utility companies may become an alternative to Internet service providers in providing connectivity to households. While it may not come to pass in more densely populated areas, providing Internet via Powerline to rural households is much more likely. I have several friends who live in such areas; they've mentioned that ISPs are hesitant, if not downright unwilling, to bring fiber or cable to their homes. While that may be frustrating from a consumer point of view, to the ISP, the return on investment just isn't as high on providing Internet to one remote family compared to wiring up a neighborhood. The alternatives are usually satellite or DSL.

Although it might be exciting to discuss combining your electricity and Internet delivery, for the purpose of this article, let's bring the focus back to in-home applications. Using Powerline allows you to take advantage of existing electrical wiring for your networking requirements, circumventing the need to place an Ethernet drop in every room for wired connectivity. Take a quick look around and count how many electrical outlets you see. Each one of those is a potential network uplink if you use Powerline!

Slow down a minute, though. You can't just pop in a Cat 5e or Cat 6 cable into an electrical outlet and start watching YouTube videos. There has to be a Powerline adapter in place to convert the 802.3 Ethernet protocol into the newest Powerline standard, called HomePlug AV2, for transmission over the electrical wiring.

“Wait,” you say, “What happened to the first specification for HomePlug AV?” For that answer, we can glean the history of the standard from the master observer of all things related to use of communications signals, the National Security Agency.

In a 2001 article titled Data Communications via Powerlines, long before the HomePlug standard, there were four Powerline protocols battling for contention to be the High Speed Powerline Communications (HSPLC) solution. The protocols and the companies backing them included PowerPacket by Intellon, Plug-In PLX by Intelogis, Digital Powerline and AN1000 Powerline from Adaptive Networks. All were developed to transmit data at high speeds, while compensating for inherent issues with using electrical wiring for transmission like high attenuation, interference and signal mismatches.

A committee was formed under the name HomePlug Alliance, composed of the computer and networking equipment industry's big players. In the first year of the 21^st century, two weeks before the summer solstice, the coin toss showed "heads" and thus, PowerPacket was chosen to be the power-line communication standard. In reality, the decision was most likely based on PowerPacket's usage of Orthogonal Frequency Division Multiplexing (OFDM) for better performance and more resilient signal transmission, but we'll cover OFDM in depth in the next section.

Presumably for consumer and industry brand recognition, the PowerPacket name was dropped in favor of HomePlug 1.0. At that stage, real-world data transmission rates capped out at around 5Mb/s (even as they were marketed up to the theoretical max of 14Mb/s), and transmissions operated between the 4 and 20MHz frequency range.

But was 5Mb/s enough to watch the 10-hour loop of Nyan Cat in 1080p HD while playing Call of Duty 2? Of course not! I'm sure the HomePlug Alliance realized this as well. Thus, they established the next Powerline specification in 2005, HomePlug AV.