Intersil Sings of Duette

By Eric Griffith

June 05, 2002

The wireless silicon maker has announced a dual-band chip supporting 802.11a and g, with backwards compatibility to 802.11b: expect the PRISM Duette by early 2003.

Irvine, CA,-based WLAN chip maker Intersil has announced PRISM Duette, a dual-band 802.11a and 802.11g solution for future wireless network products. Because of the chip's support for 802.11g, the 54Mbps chip will be backwards compatible with the existing and ubiquitous 802.11b standard, which is limited to 11Mbps speeds. The chip will not be available until early 2003.

Duette will be 100% backwards compatible with Wi-Fi according to Jim Zyren, Intersil's Director of Strategic Marketing, Wireless Networking Products. "A fundamental requirement of g is that it must be able to fall back and communicate with b. You can't claim g compliance unless you can talk with an existing b or Wi-Fi."

Duette will utilize Intersil's integrated Baseband Processor and Medium Access Controller (BBP/MAC) and direct down conversion (ZIF) architecture to eliminate the intermediate frequency (IF) stage found in most wireless radios, reducing manufacturing complexity and overall cost. This technology is also found in the company's current PRISM 3 chip for 802.11b. The Orthogonal Frequency Division Multiplexing (OFDM)-based technology it will use to talk with both 2.4 GHz (802.11g) and 5 GHz (802.11a) WLAN devices is borrowed from the Indigo 802.11a chipset that will ship this summer.

A final standard for the 54Mbps 802.11g specification has not been finalized yet, but is expected in late 2002 or early 2003, which would coincide with release of the PRISM Duette. Even if the ratification of 802.11g by the IEEE is late, Zyren doesn't see that holding up shipment of the Duette, however.

"Before the IEEE can ratify the standard, it still becomes pretty stable," he says. "They've got a 75 percent approval already. Once you have that majority, any changes to the standard require another 75% vote, so it's hard to make significant changes. We don't expect a lot of change going forward. We know what the standard looks like, what gets ratified won't impact us going forward."

Even if there were changes at the last minute, products that ship with early Duette chips can be upgraded, say Zyren.

"Any change at [that] point would be software or firmware upgradeable. With OFDM using the same parameters for A, there's not a lot of enthusiasm for making a lot of hardware level changes."

"We were shipping B before it was formally ratified," he noted.

In February, Intersil partnered with Cisco Systems to begin work on 802.11g reference designs for OEMs using the company's PRISM GT chip, all while the specification is still in the draft stage. Zyren says that announcement was a first step, and calls PRISM Duette the next.

Intersil hopes those who wait to use products based on the single-chip, dual-band Duette will find connecting to any type of 802.11-based network easier.

"Duette is suitable for access points, but it's meant for a client -- it guarantees you being able to connect," says Zyren.

Jim Zyren of Intersil will be speaking next week at the 80211 Planet Conference & Expo in Philadelphia on June 11 on the panel "The 54Mbps Revolution: 802.11b vs.The Newcomers."



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