Home networking Part 7: Power line connections explained

CNET editor Dong Ngo explains home power line networking and answers frequently asked questions about the technology.

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Editors' note: This post is part of an ongoing series. For the other parts, check out the related stories section below.

Power line networking basically turns a building's existing electrical wiring -- the wires that carry electricity to different outlets in the house -- into network cables, meaning they also carry data signals for a computer network. And this means virtually all households, in the U.S at least, are "wired for" power line networking. It doesn't replace a regular network, so you'll still need a router, but it's a good way to extend your existing network into new places.

Home power line networking is far less popular than Wi-Fi, or even running network cables, however, mostly because consumers are not aware of its existence and benefits. I'm going to change that.

Common applications

Power line networking is used in many ways, including in large projects such as smart grids and power line broadband service, which uses power line connectivity to provide an Internet signal, just like a DSL service that uses an existing telephone line for the same purpose. However, in this post I'll only talk about home power line networking, where the technology is used to connect either Ethernet-ready (wired) devices, or Wi-Fi (wireless) devices.

Connecting wired devices: This is the most popular use of power line networking and generally is based on power line adapters. Each of these adapters has at least one network port.

You need two adapters to create the first power line connection -- this is why most adapters are available in a kit of two.

The first adapter is connected to a router (or a switch) of an existing wired LAN (local-area network), via its network port. The second adapter is connected to an Ethernet-ready device (such as a computer or a printer). Now just plug both adapters into their wall sockets and you will add the Ethernet-ready device to the network. There's nothing else connecting the two adapters other than the electrical wiring in between the two wall sockets being used.

A typical power line adapter has at least one network port, to work as one end of a power line connection.
A typical power line adapter has at least one network port, to work as one end of a power line connection. Dong Ngo/CNET

After the first connection is created, you need another adapter for each additional network device (usually. Some power line adapters have more than one network port so they can support multiple Ethernet-ready devices at the far end of a power line connection.)

Connecting wireless devices: This is similar to connecting wired devices, but in this case the second adapter has a built-in access point to create a Wi-Fi network of its own. The LAN is extended from the first adapter to the second one, which then broadcasts a Wi-Fi signal so that wireless devices, such as laptops, tablets, and smartphones, can be part of the network.

Some networking devices, such as routers or switches, also have power line connectivity built in. Two examples are the D-Link DHP-1320 Wireless N PowerLine Router and the D-Link DHP-540 PowerLine AV 500 4-Port Gigabit Switch. This type of combo device makes sense because they need to be plugged into the wall to operate anyway.

Some power line adapters, such as this one, have more than one network port and even a built-in Wi-Fi access point to support multiple clients.
Some power line adapters, such as this one, have more than one network port and even a built-in Wi-Fi access point to support multiple clients. Dong Ngo/CNET

Power line standards

Power line networking is being developed by the HomePlug Powerline Alliance and there are two main standards that you should know: HomePlug 1.0 and HomePlug AV.

HomePlug 1.0 was first introduced back in 2001 and has a cap speed of 14Mbps. It's now becoming obsolete.

HomePlug AV, introduced in 2005, has an initial cap speed of 200Mbps, which is fast enough to carry multimedia content, hence the AV designation for Audio and Video. This standard also supports 128-bit AES encryption for security. HomePlug AV is backward-compatible with HomePlug 1.0 and is marketed as Powerline AV (or Powerline AV 200).

Powerline AV adapters have a real cap of just 100Mbps as they also support the regular 10/100 Ethernet standard. In testing, the actual sustained speed of these adapters is somewhere from 20Mbps to 60Mbps.

Examples of Powerline AV/200 devices are the Netgear Powerline Av 200 Wireless-N Extender Kit, the D-Link DHP-1320 Wireless N PowerLine Router, and the WD Livewire Powerline AV Network Kit.

HomePlug AV got a boost with the ratification of the IEEE 1901 specification in 2010. Whereas previously Powerline was an independent standard, this brought it under the same umbrella as the other networking standards and protocols. This specification guarantees interoperability between adapters from different vendors, and on top of that the cap speed is now increased to 500Mbps. This much faster HomePlug AV is marketed as Powerline AV 500.

Powerline AV 500 offers real-life cap speeds of either 100Mbps or 500Mbps depending on the type of network port the adapter device supports, be it regular 10/100 Ethernet or Gigabit Ethernet. In real-world testing, Powerline AV 500 indeed offers significantly higher sustained speed than Powerline AV, giving speeds ranging from 90Mbps to 200Mbps.

Most power line adapters come in a kit of two.
Most power line adapters come in a kit of two. Dong Ngo/CNET

Examples of Powerline AV 500 devices include the ZyXel PLA4231 500 Mbps Powerline Wireless N Extender, the Trendnet Powerline 500 AV Nano Adapter Kit, and the D-Link DHP-501AV PowerLine AV 500 Adapter Starter Kit.

There's also a new standard called HomePlug AV 2 that promises real Gigabit Ethernet network speed via a power line connection. This new standard is compliant with the IEEE 1901 specification and will be backward-compatible with existing HomePlug AV devices.

Pros of power line networking

The biggest advantage of power line networking is convenience, especially when compared with a regular wired network. Instead of having to run network cables, you just plug the adapters into the wall sockets. You can build a home power line network off your original network in a matter of minutes.

When compared with a Wi-Fi signal, the second advantage of a power line connection is you can extend a network to the far end of a house or a basement easily, which a Wi-Fi signal might have a hard time reaching, especially in homes with thick walls. On top of that, a power line connection is very similar to a regular wired connection in terms of latency, meaning you can access the Internet with almost no lag at all.

Thirdly, compared with Wi-Fi extenders, a power line connection is so much better since you can easily add another Wi-Fi network in the far end of a house independently from the existing Wi-Fi network. In fact, using a power line Wi-Fi extender such as the ZyXel PLA4231 is the best way to extend a home network for both wired and wireless clients.

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And, finally, power line technology is now quite affordable, with adapters costing just around $50 for a kit of two. This costs much less than the parts you need to run cable properly.

Cons of power line networking

Power line networking has a few drawbacks.

First, power line adapter devices need to be plugged directly into a wall socket; they don't work well, or at all, if plugged in a surge protector or power strip. This plus the fact that they are generally large and don't come with a power pass-though socket (though a few do) means they can be a hassle to use at the place where there is just one wall outlet, or outlets that are close to one another.

Second, power line adapters require standard 110v electrical outlets and the data signal between them depends on the quality of the electrical wiring itself. On top of that, improper wiring and circuit breakers can also negatively affect the performance.

Third, power line adapters' performance can be degraded by the noise that certain home appliances generate in the power grid. Examples of these appliances include motorized devices (fans, vacuum cleaners, washer and dryers), switch power supplies (AC-to-DC converter used in phone chargers), and fluorescent lamps.

And finally, using power line connections in an apartment building might lead to a security risk. As the wiring is connected, people living in other apartments could tap in to your network by using an adapter of their own. This is similar to using an open Wi-Fi network. However, all power line adapters come with a security feature to prevent this from happening (note that adapters from different vendors generally don't work well together with security turned on, so you'll be better off with adapters from the same vendor).

If you live in a home, you don't have to worry about your next-door neighbor being able to access your network. Power line signals can't cross a transformer, which is generally what separates street-side power connections.

FAQ

Q. Does power line networking work with Macs?

A. Yes. Starting with HomePlug 1.0, power line networking works just like Ethernet cables, meaning you can use it to provide a network for devices of any platform.

Q. I have a power line connection at home. Can I add a switch to the far-end adapter to add more devices to the network?

A. Yes. This is similar to using a power line adapter with multiple network ports, such as the D-Link DHP-540 or the WD Livewire Powerline.

Q. Can I add a second router to the far-end adapter to add more devices to the network?

A. Yes and no, depending on the router.

Generally, if you connect the second router's WAN port to the power line adapter, it will create a new LAN at the far end, and devices connected to this second router (both wired and wireless if a Wi-Fi router is used) can't see devices connected to the first router. All devices, connected to both routers, can share the same Internet connection, however.

Some Wi-Fi routers, such as the Asus RT-N66U or RT-AC66U, can work as an access point (AP) and when set to AP mode their WAN (wide-area network) port will work like another LAN port. If you use one of these routers as the second router, all devices connected to both routers will be part of the same LAN network.

Q. How do I use power line to extend a Wi-Fi network?

A. You can either:
1) Get a kit of two power line adapters with the second adapter having a built-in Wi-Fi access point, such as the NetGear Powerline XAVNB2001 kit or the ZyXel PLA4231 Wi-Fi Extender. Or,

2) Get a kit of two regular power line adapters and a separate Wi-Fi access point. After that, connect the Wi-Fi access point to the second adapter at the far end of the connection.

That's it for now. Note that you can always find the latest top power line products at this page. If you have more questions, send them my way via Facebook, Twitter, or Google+, or just post them in the comments section below.

 

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