Subject: [NEXTEL-1] Interference Temperature Causes Some Friction

From: NEXTEL-1
Date: Sun, 27 Jun 2004 13:40:29 -0400

Interference Temperature Causes Some Friction

Will the FCC’s New Rules Take the 
‘Fear’ out of ‘Interference’? 
Some Holders of Licensed Spectrum Appear Wary

By Annie Lindstrom

The Federal Communications Commission (FCC) is 
exploring the merits of a new means of managing 
interference in wireless environments. The concept, 
called interference temperature, was introduced by 
the Spectrum Policy Task Force in late 2002 with the 
hope that it might foster more efficient use of 
available spectrum. 

In November of 2003, the FCC formally issued a Notice of Inquiry (NOI)
and Notice of Proposed Rulemaking (NPRM). 
(ET Docket 03-237
http://svartifoss2.fcc.gov/prod/ecfs/retrieve.cgi?native_or_pdf==pdf&id_document=e15292549)  
Slated for official publication in February, the FCC is taking comments
on both notices from all interested parties until 
late spring.

Today, rules intended to limit interference take a transmitter-centric
approach that may not adequately protect license holders as the wireless
industry grows, according to FCC spokespersons.

“As radio spectrum is used more intensely, the FCC is looking for ways
to improve its toolbox for managing interference,” said Lauren Van
Wazer, special counsel to the Chief of the FCC’s Office of Engineering
and Technology. “Interference temperature is one possibility that offers
a lot of promise.”

Initial Concept

In a nutshell, interference temperature would involve measuring the
level of interference in a given chunk of spectrum, in a given
geographical area, in real time, explained Gary Thayer, electronics
engineer and attorney at the FCC’s Office of Engineering and Technology
Policy and Rules Division. 

“Once a measurement is taken, a cap could be set for that area in that
frequency,” Thayer said. “Depending on where that cap is, the margin
between it and the noise floor may, or may not, allow for unlicensed
operators to operate in that area.”

The NOI seeks comments on nearly every aspect of the concept itself.
This includes who or what would take the measurements, engineering
concerns and establishing a global idea of how interference temperature
might work, Thayer said.

The NPRM seeks to begin exploring the concept in the 6525-6700 MHz and
12.75-13.25 GHz satellite bands. These bands were chosen because
operators using them employ high-powered transmitters and the services
they provide are robust and fairly immune to interference from undesired
signals, he added. 

“The NPRM is a simplified version of interference temperature that helps
us get the ball rolling,” Thayer said.

Sorting Out the Details

One of the most obvious questions the NOI seeks to answer is who, or
which devices, would be responsible for making interference temperature
measurements. Thayer describes three potential approaches. 

In one scenario, intelligence could be built into wireless receivers of
unlicensed or licensed devices that would enable them to “sniff” the
environment in real time. Based on the amount of interference in that
environment at that moment, the device would determine whether to, and
how to, transmit and receive signals.

“The simplest decision is ‘do or do not transmit,’ but a refined answer
might be ‘transmit, but at low power’,” Thayer explained.

In a second scenario, central monitoring sites scattered around a given
geographical area could continuously sniff the environment and relay
information to devices seeking information. A third possibility could be
to use satellites to monitor the environment and disseminate information
to end devices.

A potential drawback to interference temperature is that end devices
will have to be smarter, and, as a result, they will likely be more
complex and more expensive, said Marc Goldburg, chief technology officer
at ArrayComm Inc. 

“There are a lot of open technical issues on how to build such devices
and debate as to whether it is practical to make end devices responsible
for sensing the environment,” he added. 

The answers to questions such as what responsibility operators would
have and who would be charged with enforcing interference temperature
depends on what the rules turn out to be, Thayer said.

“That’s why we are asking the questions we are asking in the NOI,” he
added.

Boon or Bane for License Holders?

Van Wazer and Thayer couch the NOI and NPRM as initial efforts designed
to flush out what the FCC sees as a nascent concept. However, some are
wary of how fast interference temperature will move from concept to
reality, as well as the actual impact that the new rules will have on
owners of licensed spectrum. 

In a January letter to its members, the Wireless Communications
Association (WCA) stated that the FCC is “proposing to adopt rules
without knowing whether the ideas will actually work.” Further
clarification of that statement was unavailable as WCA spokespersons
declined requests for an interview. 

The WCA’s letter warns that absent an aggressive response by WCA, the
consequences of these two proceedings could be “dire” and create an
unprecedented amount of interference, which could lead to degradation of
service and ultimately to devaluation of operators’ licenses. The letter
also states that vendors may find that their equipment won’t work in the
new environment being contemplated and ends with a call to WCA members
to “strongly consider” participating in a task force formed by the
group’s Engineering Committee. The task force will “prepare the
extensive and complex technical studies we will need to develop our
positions and make WCA’s case effectively before the FCC.”

Donald L. Herman Jr., associate attorney with Bennet and Bennet PLLC,
said that “if adopted, The FCC’s interference temperature will
fundamentally change the way spectrum is utilized. Licensees and
unlicensed operators should pay close attention to the proceedings to
ensure that their existing spectrum rights are not impaired.”

First, Do No Harm

Operators can consider the interference temperature issue with either a
“glass-is-half-empty or a glass-is-half-full approach,” said Paul
Kolodzy, professor and director of the Wireless Network Security Center
(WiNSeC) at Stevens Institute of Technology in Hoboken, N.J. Prior to
his work at the Institute, Kolodzy was director of the Spectrum Policy
Task Force and senior spectrum policy advisor at the FCC.

“The concern is that once a temperature value is allowed, even if it is
zero, then it provides an easy mechanism to raise the allowable amount
of interference, and thus reduce the capacity of a license-holder’s
system,” Kolodzy explained. “The glass-is-half-full scenario states that
the temperature will provide a limit to any potential interference —
current or future — and thus, it will provide more certainty of the RF
environment for the license holder.”

Kolodzy, who said that interference temperature’s origins lie in radio
astronomy, multiuser detection and spectrum occupancy, believes that
interference temperature will make the United States more competitive
internationally because it will spawn new technology, devices and
consumer products. Some will build cheaper equipment that does less,
while others will focus on more expensive devices with more
functionality.

On the positive side, interference temperature would likely enable
entrepreneurs to bring new low-power wireless services — that don’t need
a lot of spectrum or geography — to market quickly and at less expense,
said Dennis Miller, president and CEO at Midwest Wireless in Mankato,
Minn. However, he added, potential negatives go along with the
positives.

“The debate over how much interference will be tolerable has to take
place first,” he cautioned. “Our customers are too important. I don’t
want someone creating an interference temperature at a threshold that
interferes with my ability to serve customers with the best possible
service.”

Thayer and Van Wazer both assert that the FCC is taking a win-win
approach to the concept. While interference temperature would allow
others to operate in licensed spectrum, the FCC’s first order of
business is to “do no harm to licensed facilities,” they said.

About the Author: Annie Lindstrom is a free-lance writer based in
Florida. She writes for several leading telecommunications publications
and has been covering telecom for 15 years. Her articles have covered
the full range of technologies and issues within the industry, including
fiber optics, central office switching, outside plant, DSL, cable modems
and wireless access. She can be reached at annielindstrom @aol .com

Broadband Wireless Business Magazine
Vol. 5, No. 2 
March/April 2004 
http://www.shorecliffcommunications.com/magazine/volume.asp?Vol=D&story==402

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