G.hn, the home networking standard whose physical architecture was adopted by the International Telecommunication Union (ITU) earlier this month, is not getting rave reviews from some broadband service providers because of concern that the standard lacks backward compatibility with existing home network technologies, particularly HomePlugAV, the powerline home network.

Even G.hn backers are saying that the technologies currently in use by service providers, including Home Phoneline Networking Alliance (HomePNA) , Multimedia over Coax Alliance (MoCA) , and HomePlugAV, are likely to remain in use for some time to come, and even incorporated into hybrid solutions with G.hn. (See ITU Touts G.hn Standard.)

"There are telecom service providers who are adamant that what they are using now can’t simply disappear," says Kurt Scherf, VP and principal analyst with Parks Associates . "And there is still some confusion, I think, about how G.hn will be adopted.

"What G.hn supporters say is that there is nothing to stop chipset vendors from adding interoperability, but they won’t mandate it. And, they seem to be pretty comfortable that they have the worldwide support of service providers to go ahead and push through under that mindset. But, it seems odd to me that some huge players are pushing back. If G.hn was supposed to be the best thing since sliced bread, why isn’t this as cut-and-dried as it might appear?”

Those pushing back are staying anonymous for now, but the resistance is coming mainly from the HomePlugAV and MoCA camps. AT&T Inc. (NYSE: T) and BT Group plc (NYSE: BT; London: BTA) are among the major service providers that have indicated support for G.hn. (See Chip Firms Prepare for Home Networking Faceoff .)

An executive for a major U.S. company using MoCA said, on condition of anonymity, that his company is happy with what it has now and has no plans to deploy G.hn, unless and until the in-home devices are available at volumes that lower the pricetag to what MoCA devices now cost. That same executive said he was concerned that there is harm to be done if adopting G.hn drives up costs of in-home devices.

Leaders of the HomeGrid Forum , which is backing G.hn, say coexistence of home networking technologies is to be expected for some time to come.

"The real theory behind G.hn is to unify the industry around a single standard that allows the next-gen network to operate on three wires," says Mario Finocchiaro, director of business development for Aware Inc. "We expect as we are developing G.hn we are going to be coexisting with other technologies. G.hn was designed with the intent of enabling dualmode devices to bridge between the two."

In addition to approving the Physical, or PHY, Layer of the G.hn standard in October, the ITU-T has also advanced the Data Link Layer, expected to be approved in 2010, and reached consent in a third area, creating G.9972, a separate standard from G.hn, which Finocchiaro says is "specifically designed to allow coexistence between G.hn and other powerline technologies, so they could coexist on the same wires, and it would do that by assigning time slots."

The powerline problem
Powerline technology advocates have expressed their frustration over the decision within ITU-T to adopt a forward error correction approach within G.hn that specifically clashes with HomePlugAV, the most widely deployed powerline technology, especially popular in Europe.

Rob Ranck, president of the HomePlug Powerline Alliance , which announced progress on its own powerline standard within IEEE (P1901) this month, points out, however, that the coexistence standard is optional, not mandatory. “There’s only one vendor talking about doing both G.hn and HomePlugAV on a single chip,” Ranck says. “I think that’s over-simplifying a complex issue -- you have all sorts of things to think about relevant to interoperability.”

With home networking products now available at retail, in addition to service provider sales, it will be harder to control deployments, Ranck feels, making compatibility issues a larger problem.

”You go into any retail shop, there are tons of HomePlug AV products,” he says. “Will a service provider deploy a product that can be shut down if a neighbor plugs in another HomePlugAV product that they can buy at BestBuy?

"Our position continues to be the same: We are disappointed that they think it’s a good idea to create a standard that is incompatible with what’s out in the market.”

Michael Weissman, VP of North American marketing for CopperGate Communications Inc. , one of the few technology companies straddling the market, with both HomePNA and HomePlugAV products, says his company is backing G.hn because of the functionality it will bring to the market. Weissman believes that HomePNA and HomePlugAV products are going to be around for a long time to come. CopperGate was among those arguing that G.hn should be compatible with HomePlugAV, he says, but having lost that argument, it's now backing the global standard.

“HomePlugAV is going to be around for a long time,” Weissman argues. “So is HomePNA. It won’t be a dominant standard, but it will still be bought 10 years from now. Markets tend to stop much later than you expect. We are a huge supporter of G.hn, but that doesn’t make us anti-HomePlug. G.hn is going to win, and let me tell you why: It’s a better technology. It’s all three wire types. It’s going to be a global ITU standard, which means that telecom service providers are going to adopt it.”

One of the challenges for the HomeGrid Forum will be to address real-world deployment and interoperability issues, notes Aware's Finocchiaro.

”ITU is about the development of the standard itself and technical underpinnings,” he contends. “HomeGrid picks that up and brings that standard to market where we can develop compatibility and an interoperability test suite and logo-ing program that goes along with that. We will be rolling that out early next year to all members as a mechanism for insuring interoperability for all devices. We think we can solve a huge problem on the consumer’s side, with ongoing tech support, ease of installation, and ease of purchase as well.

"From the service provider standpoint, regardless of what technology you have chosen, you never have the outlet you need in the place that you need it for that last TV install, or even the first TV install. G.hn will solve that issue because you can have one SKU [in-stock item] that will run on any wire in the house.”

— Carol Wilson, Chief Editor, Events, Light Reading