Powerline Network Adapters: The Next Generation

Many system builders involved in SOHO (small office, home office) networking are aware of the two main choices for building out a network: wired or wireless. But they should also be aware of a third alternative, one that's staring them right in the face. I'm talking about AC wires—the electrical circuitry that's already inside home and office walls.

AC wires can be accessed from multiple spots in any room where a computer is in use. What's more, by deploying what are known as "powerline adapters," system builders can deploy those AC wires inside the walls to replace lengths of Ethernet cable.

Working with powerline adapters can free system builders and their clients from situations where a spot is hard to reach with an Ethernet cable, or when doing so will produce unsightly results. Bottom line: Powerline adapters offer system builders yet another class of product to resell with confidence.

ALL ABOUT POWERLINE ADAPTERS

Powerline adapters function as interfaces between an Ethernet line and an AC line. They convert the Ethernet signals to and from signals that can be sent over the AC lines at frequencies that are unaffected by the power voltage on those lines. Meanwhile, they include processors powerful enough to continually analyze the available bandwidth, to compensate for electrical noise on the AC circuit that might be generated by the electrical motors in appliances, and/or by the jitter of halogen lights.

Proprietary versions of powerline adapters have been around for a couple of decades, offering limited speeds, interoperability, and reliability. But that was then. Today, there's a new generation of powerline adapters on the market. They offer higher speeds than in the past, more robust performance, and greater interoperability.

For this recipe, I reviewed 4 examples of these new-generation powerline adapters. Three of them use the HomePlug AV specification from the California-based HomePlug Powerline Alliance, while the fourth uses a competing spec from the UK-based Universal Powerline Association (UPA). The use of non-proprietary standards can be expected to broaden the market, since users don't have to grapple with interoperability issues.

For me, all 4 worked astonishingly well. For point-to-point connections, installation was simply a matter of plugging them into the power outlet, then using an Ethernet cable to attach them to a device. After about 5 seconds of self-configuration they were working fine, and at a speed approximately equal to that of the Ethernet cable. The Ethernet cable that had previously connected the devices could now be placed in reserve.

Each adapter is quite small, about the size of a band-aid box. And each has 3 indicator lights: 1 for power, 1 for detection of a data path to another adapter, and 1 for detection of a connection to the Ethernet port.

While each adapter has a slightly different shape, all can be plugged into a standard two-plug electric outlet without blocking the second plug the way some adapters and transformers do. (All used a two-prong plug.) None of the tested units had a through-plug, so you could use the plug for power as well. But all worked just as well on an outlet expander, extension cord or power strip.

But the documentation accompanying all four brands warns against plugging them into surge protectors or uninterruptible power supplies, which would obliterate the signal. One of the brands I tested proved nearly incapable of functioning in the presence of line noise, while the others shrugged it off. When using more than 2 adapters on a circuit—that is, for more than a simple point-to-point connection--the situation was more complicated. There were even configurations that did not work well, or at all. I'll discuss in more detail on the following pages.