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60GHz spec conflicts remain unsettled

Posted: 10 Jul 2008 ?? ?Print Version ?Bookmark and Share

Keywords:60Hz spec? Wi-Fi? personal area network? wireless PAN?

Despite two meetings, the standards groups that aim to establish separate Gbit-class nets at 60GHzone for Wi-Fi and the other for high-speed personal area network (PAN)are apparently still at loggerheads.

The 802.11 study group on very high throughput (VHT) will seek permission from the IEEE at a meeting in Denver the week of July 14 to officially start work on a standard for a Gbit network at 60GHz as a follow on to 802.11n. It must show that the 802 group management it will use is a significantly different technology for different applications than the 802.15.3c group on wireless PANs, which will report at the Denver meeting voting results on a first draft of its standard.

The two groups held phone conferences on June 19 and July 7 to iron out issues such as how they will differ and how they will avoid interference. A summary of unofficially feedback from members of the 3c group after the calls suggests the VHT group has not yet satisfied their concerns.

Unresolved issues
According to the 3c document a "seamless roaming" feature the VHT group proposes "may be the only perceived advantage that VHT has over 3c," the document states. The document goes on to say the 3c standard already includes a handover capability and it foresees a roaming capability as a logical follow on to its work.

The document also suggests some of the ways the VHT proposes to make its standard different are still unclear, including how its applications and range will be unique. The 3c standard aims to cover up to 10m, which is about all a 60GHz solution can handle, according to one 3c proponent.

The 3c group also requested the VHT adopt both the PHY chip and the scheme of using four 2160MHz channels over 9GHz of bandwidth defined by the 802.15 group. The 3c members also sketched out some methods to avoid data collisions for the VHT to consider.

Standards coexistence
"We asked them some questions about coexistence and their PHY which they are answering," said Reed Fisher, chairman of the 3c group. He declined to provide his own opinions on the state of the talks, noting the 3c only learned of the Wi-Fi effort in May. "We are in an exploratory phase trying to figure out what they are doing," said Fisher.

"Life might be simpler if they use our PHY, but we can't tell them what to do," he added. "If you have another standard in the same space you have to be careful about coexistence."

In a last-minute effort to resolve outstanding issues the two groups aim to have their first face-to-face meeting in Denver on the evening of July 14, France's Bastille Day. There may be some fireworks at that meeting, said one source close to the talks.

According to minutes of VHT meetings, at least two members have proposed using the 802.15 PHY. Several engineers involved in the VHT effort were not immediately available for comment.

In an earlier story one member of 802.15.3c said the threat of interference between products using 60GHz technologies is low because at that data rate products typically need to focus their signals on a narrow range of targets.

- Rick Merritt
EE Times

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