Powerline Networking - A Cabled Network Without Ethernet Cables

When it comes to networking your home or small office, I like to say "Ethernet for security and stability, WiFi for convenience". Unfortunately, you'll occasionally have a problem where you can't run Ethernet cables, and WiFi won't do the job either. Fortunately, any building with computers, and most without, has a third possibility - one that uses cables already installed - the power cables in the walls.

Ethernet Over Power, or Powerline Networking, is pretty simple. At each location where you need a network connection, you plug an EOP bridge into the wall, and an Ethernet cable connects to that. The other end of the Ethernet cable you connect to a single computer, or to a hub, switch, or router.

There are several vendor choices for EOP bridges, and here are 3 examples.

Ethernet Over Power has its disadvantages, of which you must remain aware.
  1. They have a limited market, so you'll have less choices and you'll find them relatively pricey, as compared to WiFi.
  2. They are proprietary - each of the 3 choices above will only work with others in the same product line.
  3. They use the 120V power circuits, and on a typical 240V service you will have to ensure that all units are plugged in to the same 120V half of the 240V.
  4. Like WiFi, they are half duplex. All EOP devices, even if they will not network together, will still have to share the powerline signal spectrum.

Issue 1 is simple economics. More WiFi components are sold than Powerline Networking / Ethernet Over Powerline. More sales volume = more competition = lower prices = more sales volume. Look at the choices for WiFi, and compare that to EOP.

Issue 2 is unfortunate. The HDX101 and the XE102, even with both made by Netgear, will not participate in a network.
An HDX101 may coexist with HomePlug 1.0 products, but is not compatible nor interoperable with NETGEAR’s XE104, XEPS103, XE103, XE102 or WGXB102 Powerline products.

Issue 3 is a fascinating concern. In a typical domestic wiring system in the USA, you'll have a 240V service, which includes 2 hot leads providing the 240V. There will be a third lead, neutral, such that the neutral and either one of the hot leads, in combination, provides 120V. This is a 240V split service, providing 2 "legs" of 120V each.

Small appliances and light bulbs, in the USA, use 120V. With a 240V split service, half of the appliance / lighting circuits will be on one hot lead (1 "leg" of the service), and the other half on the other leg, providing a balanced load. When you setup your EOP bridges, they will all have to be on the same 120V leg, or there will be no signal between the bridges.

Essentially, you could (unreliably) have two EOP broadcast domains. All EOP devices on one leg will irregularly receive signals from the EOP devices on the other leg. When you turn on your kitchen stove, or other 240V appliance, you may get signals from one leg to the other; at other times, both legs will be isolated. If you don't plan for this to happen, you will learn it the hard way.

To identify which legs your prospective EOP bridge locations are on, examine your circuit breaker box. First, identify the breaker servicing each location. Verify the proper breaker, by plugging a lamp into the outlet, flipping the breaker, and watching the lamp go off then on. Having verified the breakers, examine their relative locations. Most breaker boxes will have the breakers arranged in two vertical columns, with alternating rows of breaker slots on different legs.

If you have two breakers vertically adjacent (in either column), it's likely that the two circuits will be on different legs. With breakers separated by 1 breaker slot, they will be on the same leg. With breakers separated by 2 breaker slots, they will be on different legs. And so on.

Note that two breakers, separated by a double width breaker (240V circuit, occupying 2 slots), will still be on opposite legs. Two slots (one double width breaker) is the same as two slots (two single width breakers); and the two breakers on opposite sides of the two slots will be on different legs.

Issue 4 is similar to WiFi. All EOP devices on the same service will have to asynchronously share the powerline signal spectrum, regardless of product line, and only one device can transmit at any time. The more EOP devices you have, the less efficient your powerline network will be. Despite different product lines being incompatible with each other, they all still have to share the powerline spectrum, as peers.

Despite the above problems, though, Powerline networking is a good solution when you can't run Ethernet cables, and when you can't get a WiFi signal to reach.

Note that EOP, for computer networking, is a relatively new technology. X-10 Remote Control Appliances / Lighting, which also sends signals over the AC power grid, is not. The problem of signal propagation on a 240V split service has been a long time problem for X-10 owners. There may be X-10 solutions that are usable in EOP scenarios. It's also likely that EOP and X-10 may be incompatible, on the same service or in the same neighbourhood. X-10 also makes remote (wireless) stereo speaker systems, which may present the same challenge.

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