Using your electrical wiring for networking
As I mentioned in yesterday’s post, I needed to do some investigation into using your home’s electrical wiring for an easy high-throughput networking solution. So, I did a little research on the topic. I’ve not had the chance to actually experiment with this technology, nor have I thoroughly investigated it. However, with that disclaimer out of the way, this is what I’ve figured out.
Powerline Networking — What is it?
Powerline networking is the generic name for setting up networking using existing electrical wiring. A more common name is the industry alliance name HomePlug. The concept is to leverage existing electrical lines along with their ubiquitous plugs to get high-speed networking to the various devices and computers in the home or office.
Basically, one plugs an adapter into a wall plug (not a power strip since many power strips filter out the networking signals) for one or more devices, with another adapter getting attached from another wall plug to an existing network router or switch. There are a number of methods for attaching from the adapter to your computer or device, but in most cases, either using an ethernet or USB connection will suffice.
For home networking, it promises to provide networking speeds comparable to hard ethernet connections. These speeds are crucial given the increasing bandwidths required by high-def television and other high bandwidth applications.
What are the advantages?
The are two primary advantages to powerline networking. The first are all those electrical outlets in your home and just as important, the fact that at least one outlet needs to be near every computer and plugged in device in your home or office. The other is the speed, which run from 400 Mbps to 1 Gbps with the newer standards. You can get those speeds without the need to run ethernet CAT6 cable.
Additionally, networking through your power lines doesn’t effect delivery of power, nor put a drain on the electrical system effectively piggy-backing on the wiring for free.
What are the disadvantages?
There are several disadvantages which need to be considered:
- Wired — It is a wired solution. If you’re getting reliable and sufficient bandwidth from WI-FI, then is it worth it to be wired?
- Cost — For each computer or device, you’ll need access to an adapter than can service from 1-4 devices.
- Electromagnetic “noise” — Since electrical lines are not shielded, it tends to be “noisy”, which can effect other wireless technologies. More on this topic below.
- Interference from electrical load — Depending on the solution, washing machines, dryers, window A/C units and other appliances can impact data throughput on powerline networks. The newer technologies just coming out seem to have adapted, but time will tell whether this issue has been resolved.
- Encryption — HomePlug networks must be encrypted since it’s trivial to tap into the network. HomePlug uses AES-128 encryption, which is probably strong enough for the home, but not the office. I’d have preferred that they support AES-256.
So, what’s the issue around electromagnetic noise?
Ham-radio operators have complained to the FCC that existing powerline network solutions interfere with the radio frequencies that ham-radio uses. The National Association for Amateur Radio (ARRL.com) has been able to measure the interference caused by HomePlug. They also been able to demonstrate that a home with HomePlug can disrupt a ham-radio in the home next door. Apparently, the FCC is also investigating.
So, how is this caused? All electrical and electronic devices tend to throw off electromagnetic artifacts or “noise” which has the potential of interfering with other devices. Network signaling is particularly prone to noise. One example is “cross-talk” when you have two phone lines nearby and you can hear the other conversation. This noise can effect other wireless applications such as wireless phones, as well as TV and radio reception, which is why in the US the Federal Communications Commission (FCC) regulates how much noise a given device is permitted to emit. The rule-of-thumb is that no device should interfere with any other device.
To avoid network signaling noise, ethernet and phone wiring is shielded. The most rudimentary form of shielding is the twisted pair, where every 2 wires is twisted around each other for the length of the cable. Twisted pair shielding is the method used by traditional phone wiring and ethernet CAT5 or CAT 6 wiring (called unshielded twisted-pair (UTP) since a separate shield isn’t required). Another method of shielding is to wrap the wires in metal foil. In some particularly sensitive applications, twisted-pairs are also wrapped in fold (shielded twisted-pair).
Home electrical wiring consists of two “hot” wires and a ground wire which are neither twisted or shielded. To avoid the interference from electrical appliances on the network, newer powerline network signaling uses the ground wire to carry the signal, but as you can see, there is no shielding to prevent electromagnetic noise from being emitted.
If you’re one of the lucky few that have CAT5 or CAT6 in your home, then that certainly is a better solution for devices that need to be wired. With the advent of IEEE 802-11n, WI-FI has become more than sufficient for throughput even with high-definition TV, as long as your router and devices are actually “n” devices and you have enough signal. If any of your devices or router are still running 802-11b, then I believe you’re better off upgrading your wireless infrastructure than using HomePlug.
The one application for HomePlug that is intriguing is to help bridge your WI-FI connection. In my home, I have an Apple Airport Express on the other side of my house to get WI-FI signal to the master bedroom which is a dead spot. I happen to have a CAT6 connection, but if I didn’t, HomePlug might be a productive method to make that connection. Bridging is more effective than “extending” your WI-FI network, since it connects to the router via a high-speed hard connection. I’d only advocate this solution if you don’t have a ham-radio operator nearby. Also, you should be sensitive to any interference that the solution may cause.