Powerline Networking

  • Marcelo Reimer
    Participant
    Post count: 4
    #147 |

    Posted by Chris Hecht

    While Powerline networking is not wireless, it does not require additional network cabling since it uses existing power cables to form the network. What started this project were several requests about extending wireless networking through thick concrete walls or to non-adjacent offices in the same building.
    I tested a couple of Netgear XAV5001 single port adapters (now replaced by XAV5101) and a D-Link DHP-540 four port switch, all 500Mbps units with gigabit Ethernet connections. Bottom line is that these do work over local power cables (the signal will not cross a transformer) but not at the speeds advertised. These units have a maximum speed of 500Mbps but the real maximum I was able to get was about half that on adjacent outlets on the same electrical circuit. Speed depends on the distance and state of the wiring as well as interference from other devices that are plugged into the same circuits and how many network connections are running concurrently since all connections share the same wiring. In some tests, I was able to get only 32Mbps BUT that is still a lot better than a poor wireless connection. I did not conduct detailed throughput tests as my concern was whether they might be usable as a solution to a given problem. The distance and speed you get will depend on your environment. It has been noted that some kinds of Ground Fault Interrupt (GFI) circuit breakers can reduce or even block the signal.
    The units I tested are universal power accepting (100-240VAC, 50-60Hz) so can be used almost anywhere with the appropriate plug. Note, these units need to be plugged directly into the outlet – they cannot be used through a surge protector or UPS so they are not suitable for all locations. In addition, since they are plugged directly into the outlet, they are dependent on that power to work; that is, if the mains power goes off, the Powerline networking equipment will not work. Also, I do not know how robust these units are and what spikes and over voltages they can cope with; there is no mention of that in the manufacturers’ literature.
    The units are plug and play in that you plug them into the outlet and plug the computer or router into the Ethernet jack and it will work. You will, of course, need at least two units to make a working connection. Once you have two units, you can add more connections one at a time. My tests had one XAV5001 connected to my router and the other XAV5001 connected to a computer. I added the DHP-540 with a single computer on the other side of the building and up one floor and then replaced the computer with an IPTV box and added a ‘smart’ Blu-ray player to it. Everything worked although the speed on one particular electrical circuit was not great (32 Mbps)
    There is security in that a passphrase is needed to connect all the units in your network as they use 128-bit AES encryption between the units. The passphrase is set to a standard phrase from the factory – all units default to the same standard passphrase which is why they will interoperate. You can either physically click a button on the side of each unit within two minutes to change the passphrase (same as connecting to a wireless network if your router allows for WPS (Wi-Fi Protected Setup)) or you can use software loaded on a PC to make the change. Before you can change the passphrase, you need to know the current passphrase and each unit’s password that is hardcoded into the unit and stamped on it along with the serial number.
    While the units from different manufacturers interoperate (there are standards – initially HomePlug and now IEEE 1901), the software provided with each unit does not work as well on other manufacturers’ units. The software that comes with the Netgear units sees the D-Link switch and can change the passphrase on it but it isn’t able to give any details about the switch other than the transmit and receive speeds. I had difficulty getting the D-Link software to run and there is no support for it that I could find.
    Standards
    These units use the HomePlug AV2 standard (incorporated into IEEE 1901-2010). There are several other incompatible standards for Powerline networking, the most important of which is the G.hn/HomeGrid standards developed by the International Telecommunications Union (ITU); however, the G.hn/HomeGrid standards appear to be more related to industrial/commercial use (that is, for equipment supplied by telecommunications providers) whereas the HomePlug AV standard is designed for home use. I have yet to see G.hn products although a chipset is available. Note that HomePlug AV2 is backward compatible with HomePlug AV (previous standard) but not compatible with the original HomePlug 1.0 standard.
    How they work
    Powerline networking uses a high frequency signal superimposed on top of the AC. The signal is in the low megahertz band (2 – 86 MHz) so it is susceptible to electrical noise and there is a concern that it can interfere with amateur radio frequencies. There are internal notch filters to reduce radio interference. This is not something I have tested. The signal is created using sophisticated coding techniques similar to Wi-Fi to get the bandwidth and security. The units are power saving in that they will power down to standby when there is no traffic passing through for a few minutes. For more detailed information about Powerline networking, see:
    http://en.wikipedia.org/wiki/HomePlug
    http://en.wikipedia.org/wiki/IEEE_1901
    http://en.wikipedia.org/wiki/G.hn
    https://www.homeplug.org/home/
    There are a number of manufacturers of Powerline networking equipment but, based on the reviews I have read, the most recommended ones are Netgear and D-Link. There are also a number of configurations: single port units, two port units, four port switches, ones with built in Wi-Fi (ideal for extending the range of a Wi-Fi network) and D-Link has a combined router, Wi-Fi access point and Powerline network switch. Some of the single port units also have a pass-through electrical plug if you are limited in power outlets. The equipment is not cheap, ranging from about $70 for a single port unit to about $150 for the D-Link combo unit. You can buy ‘kits’ that contain two units for significantly less than twice the price of a single unit. I have found deals on some of the units and, occasionally, some of the older versions (still 500 Mbps) are available refurbished at significant savings. Manufacturer websites (these are the major ones):
    http://www.netgear.com/home/products/powerline-and-coax/default.aspx
    http://www.dlink.com/us/en/home-solutions/connect/powerline
    http://www.trendnet.com/products/products.asp?cat=65
    http://www.belkin.com/networking/powerline/
    http://www.zyxel.com/us/en/products_services/home-wired_lan_adapter
    http://www.tp-link.com/us/products/?categoryid=206&ref=pline

  • Marcelo Reimer
    Participant
    Post count: 4
    #148 |

    Reply by Marcelo Reimer
    Hi Chris
    Great info! I have been thinking about the use of inline power, but i kept reading reviews on slower performance. I guess it depends a lot on what you want to do there too.
    Thanks for putting this page up.

    Reply by Paul Federwitz
    Chris, thanks for the research on this. As I think about using this overseas though, I wonder how much trouble it would be? Our power issues can be mind blowing (or equipment blowing). Has anybody tried this in Africa?

    Reply by Marcelo Reimer
    Paul
    I am with you on the power issues. i wonder what kind of stable electricity they need. My power in Tanzania fluctuates from 270 volts down to 190 sometimes. Not sure, anyone got a test unit that we could try down here?

    Reply by Chris Hecht
    I agree that power quality is a concern. Under-voltage should not be much of an issue as the units will work down to about 100VAC but I would be concerned about spikes and sustained over-voltage. The units I have look reasonably robust but I did not open them up to look at the components. Unfortunately (for this test any way) my power here is good – it is either on at the proper voltage and frequency or it is off (not very often) so I wasn’t in a position to check on reliability. All the reviews I have read were from North America or Western Europe and did not mention power issues!

    Reply by Paul Federwitz
    I am more concerned about just simply bad wiring. I know that several outlets in my house are wired backwards which I am sure would cause some problems. Also we have serious grounding issues. It is not uncommon for me to get shocked by appliances that are supposed to be grounded if I am not wearing shoes.

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