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[ISN] DOD, wireless LAN industry debate 802.11a standard



Forwarded from: William Knowles <wk@xxxxxxx>

http://www.nwfusion.com/news/2002/1217dodwirel.html

By Tom Krazit and Ephraim Schwartz
IDG News Service, 12/17/02

The Department of Defense (DOD) and various industry groups are
discussing ways to avoid interference between the next generation of
wireless LAN (WLAN) devices and military radars that operate at
frequencies above 5GHz, said various industry sources Tuesday.

One of the fastest growing segments of technology has been wireless
Internet access devices based on the 802.11b standard, commonly known
as Wi-Fi. This standard operates on the 2.4GHz frequency of the
electromagnetic spectrum, and allows users to download data from the
Internet at speeds up to 11M bit/sec.

However, another WLAN standard is coming into vogue. The 802.11a
standard was also developed by the IEEE and operates at frequencies
between 5GHz and 6GHz. It allows data to be exchanged at faster rates,
up to 54M bit/sec, but has a shorter operating range than the 802.11b
standard.

Because the DOD operates a number of radar systems in the same
frequencies as the 802.11a standard, the DOD is worried that increased
adoption of 802.11a devices will cause interference between radar
signals and the WLAN signals, said Badri Younes, director of spectrum
management at the DOD at the Pentagon in Arlington, Va.

Concerns that the DOD was trying to reduce the spread of WLAN
technologies in general was fueled by a report in the New York Times
Tuesday that didn't distinguish between the fast-growing 802.11b
technologies and the just-emerging 802.11a standard.

The DOD has no issues with the 802.11b standard, as it doesn't operate
any radar equipment on that frequency, Younes said.

"But if the 5GHz frequency is compromised, there's no more spectrum"  
in which that radar equipment can operate, he said.

The debate boils down to the sensitivity of DFS (dynamic frequency
selection) technology that currently exists in 802.11a devices to
detect the presence of radar beams. When DFS detects a radar beam on a
certain channel, it switches to another channel to avoid interfering
with the radar beam. The DOD and the industry disagree on exactly how
sensitive those devices should be, with the industry concerned about
the ability of the device to operate correctly if they are constantly
switching between channels.

"If the DFS technology is not sensitive enough, military radar may not
be adequately protected from interference. On the other hand, if the
DFS technology is too sensitive, the communications equipment won't
work. The trick is to find the 'sweet spot' where radar is adequately
protected and the communications equipment will work effectively,"  
said Scott Harris, an attorney with Harris, Wiltshire & Grannis in
Washington, D.C. Harris represents Microsoft, Intel and Cisco on
technology matters before the government.

One IT expert in the military who asked not to be named spoke of the
modern-day logistics of warfare where military engagements are more
likely to occur in heavily populated civilian locations and not on
isolated battlefields. In such cases, there is more likelihood of
civilian infrastructure interfering with the military infrastructure.

However, this is more of a battle over turf than over technology, said
Barclay Jones, vice president for field operations for wireless
infrastructure company Flarion Technologies, in Bedminster, New
Jersey.

"This comes up all the time and they (DOD) throw their weight around
at the cost to business and consumers," said Jones.

The DOD has been giving testimony for some time over conflicts between
public and private access to wireless technology, and not just with
the 802.11a standard.

In testimony last June, Steven Price, deputy assistant secretary for
Spectrum, Space, Sensors and C3 Policy with the DOD testified over the
use of another technology, called UltraWideband. The U.S. Federal
Communications Commission earlier this year opened up that technology
for public use.

Price testified that UWB "degraded the ability to use GPS to navigate
and land military aircraft and commercial airliners" and also degraded
"the operation of government airport radars."

The DOD is working with the WLAN industry in hopes of reaching a
compromise over the 802.11a technology before the June meeting of the
World Administrative Radio Conference in Geneva, said both Harris and
Younes. The WARC recommends spectrum allocation policies to regions
around the world, which are not enforceable, but are generally
followed by most countries, according to a source.

Two U.S. senators will propose a bill in the next session of Congress
seeking to dedicate no less than 255MHz of spectrum below the 6GHz for
the exclusive use of Wi-Fi devices. The bill will stipulate that the
dedicated spectrum must not interfere with military uses.

Ephraim Schwartz is a correspondent with InfoWorld


 
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