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The September 9, 2002 Issue Provided by System Dynamics Inc.
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HomePlug Powerline Networking - Getting ready for prime time

In our previous issue, we introduced powerline networking and HomePlug. Despite our concern about market confusion in introducing yet another home networking technology, we believe that since most devices are already plugged into electrical outlets, this technology makes a lot of sense for the mass market and the stationary devices in the home. One of our questions was how well these products actually work and so we tested a sampling of HomePlug products in our own home to gain anecdotal experience. We also interviewed representatives from the HomePlug alliance to understand how they intend to promote HomePlug products, given the mind share and shelf space already occupied by Wi-Fi.

We've subjected HomePlug products from three companies to a series of in-home tests - in fact, we wrote part of this article on a desktop machine connected to our server and the Internet through HomePlug. We also interviewed many of the key players developing and marketing this technology.

We came away from our testing and discussions with the strong belief that HomePlug could play a major role in consumer networking. Our tests confirmed our initial conclusion that HomePlug would be "a good solution for connecting multiple PCs to a cable or DSL modem"; indeed, we think HomePlug is a good fit for additional applications, including telephony and audio distribution. It falls short for video distribution, but that's still several years away as a mass-market requirement.

We ran into several problems during our testing and interacted with many of the vendors about them. From the responses we got we are assuming that most should be resolved in the next generation of chips that are already being integrated into products for later this year. The most serious problem - assuring seamless interoperability between "HomePlug"-branded products - is being studied by the HomePlug organization and we hope it will be resolved soon.

Although we were impressed with HomePlug even when testing first-generation products, we are not convinced that the market can absorb yet another approach to "no new wires" networking. Now that HomePlug products are becoming available, the participants face a major challenge to get attention in a very crowded market.

HomePlug PowerLine Alliance

The HomePlug Powerline Alliance was formed more than two years ago to create a common specification so that products from different companies would be interoperable and so they could be marketed with a common logo. The Alliance released its HomePlug 1.0 specification in June 2001 and the consortium members have been working to develop consumer products.

We interviewed Tom Reed, the President of the Alliance, several times by telephone and in person. We also interviewed Larry Yonge of Intellon, chair of the HomePlug technical group; Christian Joly, Intellon's Senior VP of Marketing and Business Development; and Brad Warnock, Director of Marketing at Phonex Broadband. Our previous issue summarized our interview with Graham Wilson of Cogency, chair of the HomePlug marketing group.

We discussed the interoperability issue with technical and marketing people. They want the "HomePlug" label on a product to connote "interoperability" and said that they plan to take action to assure that devices from different vendors will work together seamlessly.

We were told that the initial positioning for HomePlug will be for sharing the broadband connection and for audio distribution, and that later generations will support higher speeds and will handle home video distribution. We were also told that HomePlug products would be price competitive with other approaches to home networking, and would be available through many distribution channels including online, retail, and through service providers. Retail will be initially focused on several key markets.

We asked the marketing people how they intend to sell HomePlug products against Wi-Fi wireless, which has achieved substantial market acceptance as a workable solution for connecting one or more remote PCs to a broadband modem. We were told that the positioning might well be "HomePlug works where wireless doesn't".

Summary Of Our Test Results

We tested HomePlug products from three companies - Asoka USA, Phonex Broadband, and ST&T xNetworks - and also examined a product from Valence Semiconductor. Other HomePlug products are currently on the market from Linksys, Netgear and others. Since all current products are based on the same chip from Intellon, the results from our tests should be representative of other current products. Our preliminary evaluation of a pre-release product based on a Cogency chip suggested that products based on this chip will provide comparable results.

We tested in only one home, so our conclusions should be considered as indicative but not definitive; we wouldn't be surprised if tests in another home were different. We understand that the HomePlug organization will publish the results of its extensive home testing, and we're looking forward to comparing the results.

We tested two-node networks with HomePlug Ethernet bridge adapters from the same company; two- and three-node networks mixing different company's adapters; and a network with a USB adapter and an Ethernet bridge. These networks all used one HomePlug Ethernet bridge as the "master" adapter - connected to the Ethernet switch sitting between our broadband modem and our desktop PCs - and one or more "mobile" adapters connected to remote portable and desktop PCs. The master adapter was plugged into a "good" outlet after several false starts (see below) and we carried a portable PC with a mobile adapter around our house to test at a variety of outlets.

We performed quantitative measurement of network speed by creating a diagnostic to precisely time the transfer of a large file between PCs. This gives transfer rates substantially lower than "raw" network speed but we believe provides a realistic comparison between different networking technologies.

More information about the tested products, the details of our testing approach and results are available on our website at

Here's a summary of what we found:

Performance and Speed

  • HomePlug worked very well in our house for sharing a broadband modem between an existing primary PC and a remote PC. While slower than Ethernet over structured wiring, it worked in places in our home where our Wi-Fi equipment did not.
  • The outlet chosen for the master HomePlug adapter can have a substantial impact on HomePlug performance -- an "impaired" outlet will result in lower-speed or lost transmission. We discarded our first series of tests after concluding that the original outlet was badly impaired.
  • With the master adapter plugged into a "good" outlet, the mobile adapter worked in all fourteen outlets we tested, many of them quite far from the main electrical panel.
  • The measured network speed varied from 5 Mbps (with the mobile adapter plugged into the same "good" outlet with the master) down to about 1 Mbps at the most "impaired" outlet we tested; the next worst outlet was about 2.5 Mbps. The average across all fourteen outlets we tested was 3.4 Mbps.
  • We obtained substantially identical performance results from the three sets of Ethernet adapters we tested and from the one USB adapter. This was not surprising since all are based on the same Intellon chip. (See the detailed test results on our website.)
  • HomePlug somewhat reduced the speed of Internet downloads. The speed through HomePlug was slower than through Ethernet; we consistantly measured somewhat slower Internet download speeds than the internal file transfer speed which we used for comparison.

What Makes Outlets "Good" or "Bad"?

We spent a lot of effort trying to understand why some outlets worked much better than others. We read the product manuals, discussed this with many vendors, and tried to decipher our test results for clues. We wanted to read the HomePlug specifications, but they are considered proprietary and were not available to us. In the absence of understanding just how the technology works, it's pretty hard to deduce why some outlets were particularly bad.

  • It's especially important to find a "good" outlet for the "master" adapter. The most obvious outlet -- where you've already plugged in a broadband modem, the primary PC and its peripherals, and perhaps a cable/DSL router -- is probably one of the worst outlets for HomePlug. Manufacturers provide little help in identifying a good outlet for the master.
  • Circuits seemed to be most impaired by the type of equipment hard-wired to the circuit or plugged in to outlets. "Brick" transformers of the type that power many small electronic devices appeared to be among the worst. Several of these are typically plugged in with the primary PC - that's why that outlet and probably nearby outlets on the same circuit are so bad for the master adapter.
  • Manufacturers recommend not plugging HomePlug adapters into surge protectors. We found that it's very important to follow this recommendation -- the better the surge protector, the worse the HomePlug performance. A really good surge protector completely blocks HomePlug.
  • We saw some impairment from vacuum cleaners and hair dryers plugged into the same outlet, especially if the outlet was already impaired (as indicated by a low data transfer rate). Just plugging in one vacuum cleaner reduced the HomePlug data transfer rate substantially, and turning it on effectively stopped data transfer.
  • Outlet distance from the main electrical panel had much less impact on measured speed than we expected; the attached equipment and the wire gauge and routing through the walls had a much larger impact. Some of the longest circuits - including one that passed through a secondary electrical panel at least 75 feet from the main panel - performed much better than short circuits with the "wrong" type of equipment.
  • HomePlug crossed AC phases very well. We saw little difference in performance between circuits on different phases.
  • We saw little effect from fluorescent lights plugged into the same outlet.


  • Installing the USB adapters was much more difficult than the Ethernet adapters. We were on the telephone several times with vendors to figure out how to get USB adapters working properly in our network. Even when a PC seemed to be networking properly, we encountered problems reading files from it. Our network is more complex than that in a typical home -- we operate with a Windows NT domain and have an existing network with lots of PCs -- so our installation and operating experience may be atypical.
  • We observed a very odd interaction with Internet Connection Sharing under Windows; when ICS was enabled on a PC to share an Ehernet-based HomePlug connection by wireless, it appeared to cut the HomePlug file transfer speed in half.
  • The first generation of HomePlug Ethernet bridges has problems when a network has more than two Ethernet Bridge adapters; with three adapters, we saw interrupted transfers and slow transfer speeds. Intellon told us that this is a known problem in their first-generation chip. Adapter manufacturers have taken different approaches to work around this problem; their approaches are not compatible with each other and do not appear to interoperate, and we were unable to get any three-adapter network to work properly. Networks built with a single vendor's adapters and installed following the vendor's instructions might not manifest the problems we saw with multi-vendor networks. Intellon told us that this problem has been resolved in the next generation of chips, which should appear in products later this year.
  • Manufacturers have used different approaches to setting the encryption keys to establish a higher level of network security. Several products use PC software to set the key in each unit, while the Phonex units let the user set the keys with pushbuttons and blinking lights on the adapter. The Phonex approach is more user-friendly, but we were unable to create a secure network combining Phonex adapters with devices using the other approach.
  • These problems are indicative of a more general issue: the lack of comprehensive interoperability testing between different implementations of HomePlug. While we were told that interoperability testing had been done, our experience indicates that the testing is not as rigorous as that used for DOCSIS cable modems or Wi-Fi wireless adapters.

Since the tested HomePlug devices are all based on the same Intellon chip, it's not surprising that they were largely compatible. Later this year, devices based on Cogency's chips will appear on the market, and products will come to market with Intellon's new chip; this offers plenty of opportunities for additional compatability issues. Consumers will be very disappointed if the HomePlug logo fails to fulfill its promise of product interoperability.

HomePlug Products Tested

We thank the HomePlug PowerLine Alliance for coordinating our contacts with vendors, the manufacturers for providing adapters and telephone support during our testing, and the chip vendors for their help in reviewing our test plan and explaining why some outlets worked better than others.

Asoka USA

Asoka Ethernet Bridge --> Click for larger pictureAsoka USB Adapter --> Click for larger pictureWe tested both Ethernet and USB adapters from Asoka USA - the PlugLink Ethernet Bridge PL9610-ETH shown on the left and PlugLink USB Adapter PL9710-USB on the right. See our previous article for background on Asoka.

Phonex Broadband

Phonex Ethernet Bridge --> Click for larger pictureWe tested two Ethernet adapters from Phonex Broadband - the QX-201 NeverWire 14 Ethernet Bridge.

ST&T xNetworks

ST&T Powerline Ethernet Bridge --> Click for larger pictureST&T U21 Powerline USB Bridge --> Click for larger pictureWe also tested both Ethernet and USB adapters from ST&T xNetworks - the iPower Point EtherFast 10/100 Bridge M51 shown on the left and iPower Point PLC USB Adaptor U21 on the right.

ST&T U22 USB Wall Adaptor --> Click for larger pictureJust before going to press, we received a pre-release product made by ST&T - a USB Wall Adaptor U22. Unlike the other units, this is designed to plug directly into the wall; it is the first production unit based on the Cogency chip. We will report on our tests of this unit in the next issue.

Valence Semiconductor

Valence PCI Board and power cord --> Click for larger pictureWe received a PCI Evaluation Kit VK6001-EVB1 from Valence Semiconductor, but ran out of time before we were able to evaluate it. Unlike the other units, this is configured as a PCI card to be installed in a desktop PC; a power cord connects it to an outlet.

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More details of these products and our tests are posted on our web site at .