Multichannel WLAN chips look toward the sky

By , IDG News Service |  Mobile & Wireless

Chipsets from startup Engim Inc. that allow one Wi-Fi access point to carry data on multiple channels may end up in networks optimized for high-density environments, including multipurpose wireless infrastructures on airliners.

The Acton, Massachusetts, company is set to introduce on Tuesday its new generation of both silicon and access points for vendors to incorporate into wireless LAN offerings. Engim's EN-3001 Wideband Wireless LAN chipset and access point reference designs for 802.11b and 802.11g are designed to use three channels at once, allowing more clients within a single area to simultaneously use Wi-Fi, according to Scott Lindsay, vice president of marketing at Engim.

Engim is adding to its lineup a thin access point, priced to system makers at about US$100, in which the processing of packets takes place in the chipset rather than on a separate processor. Also new is a feature in Engim's radio chip called "transmit cancellation," which can prevent interference that an access point's transmitting antenna can cause to the same access point's receiving antenna, Lindsay said. The feature subtracts the transmit antenna's interfering signals for the receiving antenna.

At the heart of Engim's approach is multichannel capability. The 802.11b and 802.11g standards use spectrum in the 2.4GHz band that offers at least 11 bands, but generally only three of those can be used because of interference from channel overlap. Each access point typically can only use one of those channels, and simply putting three access points in one location with each on a different channel -- or just building an access point with three chips on different channels -- won't provide good performance because they will interfere with each other, Lindsay said.

That means the zone covered by an access point, typically about 300 feet, can only be served by one channel, leaving two channels unused, said analyst Craig Mathias, founder of Farpoint Group, in Ashland, Massachusetts. That's a waste of spectrum, he said, one that is not a big problem today but is likely to become one in the future, Mathias said.

"Imagine you had a TV set with only one channel. You'd be able to watch whatever they had on that channel at that time," he said. As more clients in a given space start to use Wi-Fi, access points increasingly will have to make use of those other two channels, he said.

Engim built the silicon for three channels into a single chip, with technology that can find the interference on a channel and subtract it out for a clear signal, Lindsay said. A radio for 802.11a, due in two or three months, will allow the use of three 802.11a channels simultaneously.

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