Experiments
aimed at improving emergency radio communications will be
performed by researchers from the Department of Commerce's
National Institute of Standards and Technology (NIST) at the
old Washington Convention Center in downtown Washington, D.C.,
before, during and after its demolition on Dec. 18, 2004.
The NIST
work, which supports public safety programs of the U.S. departments
of Homeland Security and Justice, is intended to help improve
the communications capabilities of first responders. First
responders who rely on radio communications often lose signals
in shielded or complex environments such as the basements
or elevator shafts of buildings. It also is very difficult
to detect radio signals through the dense rubble of a building
that has collapsed as a result of natural disasters or terrorist
attacks.
To simulate
disaster environments, NIST is using real-world “laboratories”—buildings
that are scheduled to be imploded as part of construction
and recycling projects. The old Washington Convention Center
is among a series of buildings around the country that NIST
is using for radio propagation experiments. Among its tasks,
NIST is investigating new tools to improve communications,
such as methods for detecting very weak radio signals and
the use of improvised “antennas” made of metal
found in debris to boost signals.
"We're
trying to understand the whole radio propagation process in
these huge buildings both before and after a collapse,"
says Chris Holloway, the researcher from NIST's Boulder, Colo.,
laboratories who is heading up the experiments. "We're
specifically looking at very large buildings because that's
where you're likely to have communications problems and large
numbers of people involved in an emergency situation."
The NIST
team will place a set of about 25 battery-operated transmitters
at various locations in the convention center prior to demolition.
The transmitters send signals near the frequency bands used
by emergency personnel and mobile telephones. Scientists will
monitor and map the strength of signals sent by the transmitters
to receivers outside the building before, during and after
the building is imploded. After the implosion, NIST researchers
will study various schemes for detecting signals by searching
with directional antennas and by connecting detectors to metal
debris found within the rubble of the building.
The researchers
will be using a variety of techniques, including a method
for measuring received signal strength and detecting very
weak signals (see at right). NIST researchers hope to develop
reliable, cost-effective tools that can be retrofitted to
existing radio systems to assist emergency personnel in locating
and perhaps communicating with rescuers and other survivors
trapped inside a collapsed building. For example, using software
that turns sounds into visual images, first responders may
be able to receive and see simple patterns—like Morse
code—from a survivor repeatedly turning a radio or phone
on and off, in cases where the signal was too weak to receive
audible voice messages.
The research is
funded in part by the Department of Homeland Security and
the Department of Justice’s Community Oriented Policing
Services.
As a
non-regulatory agency of the U.S. Department of Commerce’s
Technology Administration, NIST develops and promotes measurement,
standards and technology to enhance productivity, facilitate
trade and improve the quality of life.
For additional
information on NIST Emergency Communication projects see
this fact sheet.
Background
on NIST Radio Propagation Experiments
Other NIST Tests
NIST
performed its first set of building implosion experiments
at the 13-story Fischer Public Housing Project in New Orleans
in January 2004. A second set of experiments was performed
at Veterans Stadium in Philadelphia in March 2004. The old
Washington Convention Center is the third site in this series.
To complement the
implosion experiments, NIST also is performing radio-propagation
studies in existing public buildings that will remain standing.
This work involves mapping signal strength throughout the
buildings to identify potential weak-signal “dead spots”
that might hinder emergency rescue efforts. Ultimately, the
researchers plan to generate a large set of public-domain
data on differences in signal reception at emergency communications
frequencies for different types of building environments.
During the week
of Nov. 29, 2004, the NIST crew carried out such tests in
Maryland in cooperation with the Montgomery County Fire Department.
Previous signal-strength mapping tests were performed at an
office building in Arizona in May 2004 with members of the
Phoenix Fire Department; at a hotel in Colorado Springs, Colo.,
in June 2004; and at a supermarket in Boulder, Colo., in August
2004.
Detecting Weak Radio Signals
NIST researchers
are using a reliable, inexpensive method that improves detection
of weak radio signals for first responders in emergency situations.
Based on an approach used in deep-space communications, the
method may improve signal detection sensitivity by several
orders of magnitude over a standard handheld radio receiver.
When a radio signal
is weak, a person listening to a radio receiver hears only
static but may be able to see the signals if they are converted
to a visual display. A visual pattern becomes even easier
to see when the signals are confined to a narrow frequency
spectrum, as in the NIST application.
The method uses
a standard communications receiver to receive a very narrow
band of high-frequency radio signals and convert them to lower
frequencies. A sound card connected to a personal computer
digitizes signals in this band of frequencies. Computer software
uses signal-processing techniques to amplify and/or graphically
display the digitized signals. The system is calibrated using
a new NIST-developed technique, so that the strength of the
radio signals can be displayed in absolute units (electric
field strength). These calibrated measurements are made possible
by NIST laboratory characterizations of antennas and other
components. Calibration of the equipment also allows comparison
of signal strength measurements made with different receiver
systems and may allow manufacturers to verify their product's
performance.
The NIST
researchers have applied this variety of tools to the specific
needs of the public safety community, where systems must be
reliable, inexpensive and easy to implement and use in emergency
scenarios. The radio receiver is a type already used by many
first responders, the sound card is commercially available,
and the required audio-recording software is widely available
for a nominal charge. In the field, the method could be used
to detect faint patterns of data signals (such as Morse code)
sent by emergency responders unable to communicate through
voice signals. A radio transmitter also might be programmed
to emit such signals automatically to help locate a first
responder who has collapsed or fallen.
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