Xirrus joins 802.11n product parade

Xirrus is the latest of the wireless LAN vendors to announce an access point that supports the most recent draft of the IEEE 802.11n high-throughput standard.

The company’s 802.11n Radio Module will pack four radios, each based on an Atheros 11n chipset, which can support 11a/b/g wireless clients, and each delivering a data rate of more than 300Mbps, with usable throughput of about 180Mbps, according to Xirrus executives.

Those numbers are based on the three-antenna chipset configuration from Atheros, and on using the 11n option of combining two standard 20MHz channels into one 40MHz channel. That will cut the number of available channels in half, on both the 2.4 and 5Ghz bands where 11n can operate. That may or may not be problem depending on the traffic and number of users. The 11n performance compares to an 11a or 11g data rate of 54Mbps and throughput, typically, of about 24Mbps.

The 11n module will fit into the Xirrus Wireless LAN Array, essentially an oversized “smoke detector”-style device that can be fitted with four, eight or 16 radios, has a built-in controller, and a special antenna design that assigns each radio a sector of 360-degree coverage. Software adjusts the radio for optimal range and performance in its sector.

The company, in Westlake Village, Calif., joins rivals Colubris, Ruckus and Trapeze in announcing draft 11n products targeted at enterprise wireless LANs. The vendors are betting that the Draft 2 IEEE standard is stable enough that only minor changes will need to be made in software between now and final ratification in late 2008.

In June 2007, the Wi-Fi Alliance will begin interoperability testing and certification of these and other Draft 2 11n products. The WFA stamp of approval could persuade some enterprises to deploy these products instead of waiting for the final IEEE standard.

Intel has included 11n Draft 2 support in its just-released Santa Rosa version of its Centrino mobile processor and radio chipset bundle, and notebook manufacturers are announcing or shipping new portable PCs based on the bundle.

Xirrus also announced what executives say is the first power-over gigabit Ethernet product, capable of delivering 60 watts over power over about 300 feet of either Category 5e or 6 cabling. The power injector is available as either a single-port module and an eight-port one-unit rack-mounted module.

The added power is needed, says Alan Amrod, Xirrus vice-president of marketing, because the current PoE standard tops out at about 15 watts. “For 11n , the wattage goes up sharply,” Amrod says. A future upgrade of the power injectors will boost power to 80 watts.

Because of the greater throughput for 11n compared to existing wireless nets, the WLAN controller to have the horsepower and interfaces to support it. Xirrus’ existing controller in the array already has two gigabit uplinks to link with a Gigabit LAN. The arrays can also do Layer 2 switching on their own, without tunneling the whole volume of traffic back to a central controller.

Xirrus plans to beta test the new 11n module in late 2007 and ship it in early 2008. The price per radio will be US$999 compared with $749 for the current 11a/b/g radio, reflecting the premium vendors are charging for the greater range and far greater throughput that 11n makes possible. The power over gigabit Ethernet injectors will be available in June, but pricing has not yet been decided.

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