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New standard sparks home net debate

Posted: 27 Mar 2009 ?? ?Print Version ?Bookmark and Share

Keywords:home network? standard debate? powerline?

A group of powerline technology supporters is proposing to create an overarching home networking standard.

The ITU G.hn standard in the works aims to create a single specification covering powerline, coax and phone line nets. But it uses a coding technique that will not interoperate with technology used by the HomePlug Powerline Alliance, said HomePlug president Rob Ranck. Members have shipped as many as 27 million units using HomePlug technology, the group claims.

"It's too strong to say we are coming out against G.hn," said Ranck. "It's more that we are worried that the performance will not be better or even up to the level of our HomePlug AV standard, and having another technology that in many ways will conflict with HomePlug is not a good thing for the market," he added.

The heart of the issue is that HomePlug uses turbo coding forward error correction while G.hn is proposing low density parity check (LDPC). The two are incompatible and supporting both techniques would make HomePlug chips large and expensive, Ranck said.

In addition, LDPC may not provide significantly more performance than turbo codes and it could be harder to license, Ranck added. "Many people would say it's debatable if you can get more performance from LDPC, and some say you can get more performance from turbo codes," he said.

The HomePlug group is working on an AV 2.0 standard that could be completed by early next year, specifying throughput of up to 600Mbit/s at the application layer and a Gbit/s at the PHY. The G.hn spec also aims at a Gbit/s PHY, although the group has not articulated an exact target for application layer throughput over noisy power lines.

Interoperability issue
The HomePlug group likely would back G.hn if the ITU standard adopts turbo codes, Ranck said.

The criticism comes a little more than three months after the ITU finished work on the PHY of the G.hn spec late last year, paving the way for work to begin on ASICs. The group expects to complete work on its media access controller architecture as early as September in hopes of shipping products in 2010.

Last month, three other home networking groups signaled their willingness to work with the ITU spec by setting up working relationships with the HomeGrid Forum, an ad hoc industry group promoting G.hn. The three groups included the Consumer Electronics Powerline Communication Alliance, the HomePNA Alliance and the Universal Powerline Association.

Ranck has raised his criticisms with the HomeGrid group led by Matt Theall, an Intel executive and former head of the HomePlug group.

In an email exchange, Theall said he would not comment on specific technical discussions in the ITU group. However, he did say that the group does have ongoing work on interoperability.

"HomeGrid believes coexistence with other technologies is a requirement for G.hn, and a coexistence mechanism is being adopted in G.hn to achieve this goal," he wrote. "Since 2006, G.hn has been designed to be a next-generation technology, and HomeGrid believes G.hn is on track to deliver next-generation performance," Theall added.

Late last year, various powerline interests ended a two-year standoff over an IEEE powerline standard. The IEEE 1901 specification basically blesses competing powerline approaches including HomePlug and G.hn, and creates co-existence mechanisms so they do not interfere with each other.

- Rick Merritt
EE Times





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