If you live an old home or building, you already know the limits of WiFi. Despite the improved range of 802.11n coupled with improved throughput at greater distances‚ WiFi doesn't work magic. Buildings with brick or stucco-over-chicken-wire walls resist the charms of wireless networks, as do houses with thick wooden beams, cement elements, or with rooms spread out over many levels or floors.

Don't get me wrong. I've been extolling the virtues of WiFi as a way to avoid tedious wiring and pointless tethering since 2001. But in most cases WiFi works best in environments in which it's an obvious solution. When you start to layer floors, walls, and obstructions between a user (in a home or office) and the closest access point, you bypass the utility of easy and fast connections.

Speed may also be an issue. The fastest WiFi gear on the market, so-called 3x3x3 (three receiving and three transmitting antennas coupled with three radio chains) may be able to deliver 450Mbps of raw throughput in the 5GHz band using wide (40MHz) channels. But in practice, with other devices on a network, and not all of them very close to a base station, true throughput still tends to stabilize below 100Mbps. With more ordinary modern 802.11n equipment, or even extraordinary gear in 2.4GHz (with 20MHz channels), 30 to 50 Mbps may be more typical not too far from the access point.

Wired home networking alternatives can consistently perform from 25 to 95 percent of raw data rates of 85Mbps up to 1Gbps, depending on the technology and other factors, even with multiple simultaneous users. Once, there were three such wired alternatives, plus Ethernet. Now, we're down to Ethernet and one other, as we describe next.

The contenders for home wiring

There used to be four alternatives to WiFi, which have gradually faded and specialized as wireless issues were solved. HomePNA (once just phone wiring), MoCA (multimedia over coaxial cable), and powerline (electrical) networking were in contention as supplements or backbones for a home. The fourth, of course, is Ethernet.

Ethernet remains the gold standard. Gigabit Ethernet (1Gbps) works over long runs in homes and offices. Unmanaged (dumb) switches are cheap, and built into mid-level and above WiFi and other home and office gateway boxes. And Ethernet can deliver raw TCP throughput of over 950Mbps bidirectionally to every distinct pair of devices attached to a switch.

Of course, if your home or office isn't wired for Ethernet, you suddenly have an expensive problem. It can cost hundreds to thousands of dollars to pull wiring to multiple rooms unless you've got easy access to drops or inside walls. Even if you had Ethernet wiring put in several years ago, it might not be up to snuff (with Cat 5E or Cat 6) to handle GigE. The expense, and the lack of flexibility as to where you can plug in, is why other alternatives have sprung up. (I spent about $100 to get a single long Ethernet cable pulled from one end of my house to another when work was going on in our basement and the ceilings were open.)

All three of the other approaches rely on existing in-home wiring to bypass WiFi's relative slowness and Ethernet's expense in installation. HomePNA looked originally to the phone wires that used to be installed in every room in a house, and in newer homes may be less available. MoCA works via coax, the wire type used for terrestrial cable television, and many homes were and still are wired for this flavor, too. (Some offices have coax installed as well.) Powerline networking has the most ubiquitous potential footprint, in that every electrical outlet in the same panel is a potential network drop.

We found in researching this story that the consumer market has mostly decided on powerline networking. HomePNA morphed from just phone wiring to phone wiring or coax a few years ago, and the trade group that manages the standard now lists almost entirely coaxial-based gear from its members.

MoCA is a separately managed standard that works only over coax. There's little or no interoperability among coax HomePNA and MoCA gear, and it's actually rather difficult to purchase either HomePNA or MoCA hardware. Why? Because it's designed for the IPTV (Internet Protocol Television) installation market.

IPTV encompasses all video delivered in channel form essentially on demand to set-top boxes placed in customer homes. AT&T uses this for its U-Verse fiber-backed (but DSL over the final mile) video and Internet service, while Verizon uses a mix of IPTV and other video technology for its all-fiber FiOS. Many smaller providers outside major cities also deliver IPTV as a mix of broadband and separately provisioned video services using DSL and fiber.

The firms that offer this service had a quandary. WiFi was too slow and unreliable to deliver video around a home when IPTV started to roll out in a substantial way six to seven years ago. Installing Ethernet was far too expensive. Putting a cable terminal at each location in a home would also prove pricey.

That explains both HomePNA's initial and subsequent developments and MoCA. An installer could come in, and depending on the existing home wiring, set up a distributed network for computers and video from a single set-top terminal. Verizon FiOS terminals, for instance, include a MoCA connector. Today, it appears that most such products are sold only into the installer and provider market, and very little of it is available or sold in any quantity to home users. A few firms that made or make coax-based gear confirmed this for us as well.

Powerline networking remains an option for IPTV, but it's always been widely available for consumers, too. There are specialized powerline products for apartments and the like (hilariously called "multiple dwelling units" or MDUs) to distribute broadband through a building, but it's not substantially different in function or speed.

Thus, in this article, we focus on powerline, because it's the only thing we can recommend you go out and buy if WiFi isn't performing as you need, and you don't want to—or can't—rewire your home for Ethernet drops.

By the way, standards in the works‚ G.Hn and IEEE P1905‚ are attempting to provide a common ground under which powerline, coaxial, Ethernet, and WiFi could all be aspects of a network, with the hardware not caring over which path data went at any given time. Thus multiple solutions could be in place with a single system, appearing identical to the routing hardware.

Get the power

Powerline network encompasses a couple of very different approaches, and we're talking about just one of them. Broadband over powerline (BPL) is a way to encode data on low-, medium-, and high-voltage power transmission lines around an electrical utility's distribution system. The technology seems to work fine, but it's never proven to be the right commercial fit. Many promising BPL deployments have been abandoned, and the technology is considered more or less dead in the developed world. (I wrote an obituary for BPL back in October 2008.)

But the other approach is in-home powerline networking, of which the HomePlug Alliance certifies certain flavors. We'll use the term powerline generically, as certain manufacturers make equipment out of compliance using similar standards, while others have pushed ahead of the alliance's process for new flavors.

In practice, home powerline replaces Ethernet wiring with your electrical system's wires. Adapters feature Ethernet plugs, and some also sport WiFi gateways. But you use powerline just like you might use a home Ethernet network. Devices work together more like an Ethernet hub, in which a single pool of bandwidth is coordinated among the various devices that are plugged in, rather than an Ethernet switch, in which separate connections between devices have full-speed access to the medium.

The key limit is that all powerline devices must be on the same circuit back to the breaker. If your house is divided into zones, you can't cross those with powerline networking. (If you're clever, you could use Ethernet to bridge circuits between adapters, though, if they're not too far apart.) The system also won't work with power filters and uninterruptible power supplies (UPSes), and manufacturers advise against using plain power strips, too. Conversely, you can even have multiple powerline networks plugged into the same electrical circuit: the devices, depending on their vintage, work out amongst themselves divvying up available signal "time" on the circuit.

Powerline networking works on a very simple concept, and is remarkably similar to the technology used for WiFi. Instead of using a radio to push data wirelessly, powerline networks encode using from 2 to 28 megahertz (MHz), or 2 to 50 or even 70 MHz with newer gear. (You might note that these frequencies overlap with those used for a variety of radio purposes, licensed and unlicensed. That's fine within a wire, although some frequencies have to be "notched out," or specifically filtered from use to avoid interference.)