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By Carmen Nobel  |  Posted 2003-02-10 Email Print this article Print
 
 
 
 
 
 
 


FCC Chairman Michael Powell applauded the affected organizations for sharing the band.

"Consistent with the recommendations of the Spectrum Policy Task Force, the proposal would make additional unlicensed spectrum available to promote [WLAN] deployment while protecting radars vital to our national security," said Powell in a statement last week. "The parties involved are to be commended for their efforts to reach this hard-fought compromise."

Additional channels give 802.11a a certain leg up on competing standards. The reigning standard, 802.11b, and the upcoming 802.11g offer only three channels each in the lower 2.4GHz band. But prospective customers pointed to other issues.

"Tests have shown that 802.11gs lower frequency of 2.4GHz has potentially better range due to its ability to penetrate obstructions better than a transmitter operating at 5GHz," said John Ashcraft, electronic formats coordinator at the Marston Science Library at the University of Florida, in Gainesville, which operates 185 802.11b access points and is evaluating 802.11a and 802.11g.

Until now, the United States has limited allocation of unlicensed spectrum in the 5GHz band to the area between 5150MHz and 5350MHz. The new agreement includes the 5470MHz-to-5725MHz spectrum. This puts the United States in line with most of Europe, which is allowed to use those additional bands.

But theres a rub in that the Defense Department insisted on new ground rules. Under the agreement, the military increased the required sensitivity of the access points. If an access point detects military signals at a certain decibel, it must get out of the way by hopping to a new channel.

The Defense Department required that the threshold be lowered from minus-67 decibels to minus-64 decibels for 1-watt-to-200-megawatt devices and to minus-62 decibels for devices that run less than 200 megawatts. This rule applies to the 5250MHz-to-5340MHz spectrum and the new 5470MHz-to-5725MHz spectrum.

"The debate has been about how sensitive you have to be," Atheros Redelfs said. "The industry is worried about having to jump channels even when its just [radio] noise. Every time you jump channels, it slows things down a little bit. And now theres a slightly higher probability that we will view noise as radar. Theres not a lot of military radar in our neighborhoods."

Existing 802.11a products wont be forced to adhere to the new rules, which arent likely to go into effect for several months and certainly not before the WRC meeting, according to NTIA officials.

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