Federal agency studies blocked signals
The recent spate of natural disasters in the U.S. once again has brought to light a glaring failure of current wireless communications technologies — their inability to penetrate shielded or complex environments such as the basements and elevator shafts of buildings.
This is not the first time the spotlight has focused on this particular inadequacy. When terrorists took down the World Trade Center on Sept. 11, 2001, their actions not only shocked the entire world but also served as a call to action for individuals determined to improve communications capabilities of first responders who often lose signals in buildings.
Case in point: Engineers from the National Institute of Standards and Technology (NIST) have spent the last two years radio mapping large buildings and placing transmitters in old buildings before their implosion to study how waves behave inside buildings — both intact and demolished. NIST not only wants to improve communications in dense buildings but to also study ways to detect radio signals through the dense rubble of a building that has collapsed as a result of a natural disaster or terrorist attack.
“We’ve been going around the country looking for buildings that are being imploded and putting RF signals and transmitters in to measure the radio frequency,” said Chris Holloway, NIST electrical engineer.
The Departments of Justice and Homeland Security are funding the project. So far, the team — which includes electrical engineers Holloway and Kate Remley — has found that radio waves behave in unpredictable ways inside buildings, and any small change to a building, such as the addition of Mylar window coverings, can dramatically impact radio wave propagation characteristics.
The Washington (D.C) Convention Center and Veteran’s Stadium in Philadelphia, both scheduled for demolition, were among a series of buildings around the country that NIST used for radio propagation experiments. Typically, NIST engineers placed a set of battery-operated transmitters located in strong boxes at various locations in a building prior to demolition. The transmitters send signals near the frequency bands used by emergency personnel and mobile telephones. The strength of the signals is then monitored and mapped outside the building before, during and after the building is imploded.
NIST researchers have generated a large amount of data regarding differences in signal reception at emergency communications frequencies for different types of building environments. For example, the early findings indicate that metal debris acts as a conductor to boost signals that otherwise would be blocked by piles of rubble. NIST hopes such information can be used to improve the communication capabilities of first responders and even change the way buildings are constructed. They plan to release the data by the end of the year.
“Some of the data is already being used,” Holloway said. “The idea is for people to look at buildings and do some type of modeling of signals” based on the properties of the materials from which the buildings are constructed.
The next series of tests NIST will undertake is unclear at this moment, Holloway said. Engineers either will examine triangulation methods to determine where RF signals originate or study the idea of ad hoc networks. Valuable information already has been derived simply from where NIST has placed the RF test signals, Holloway said. This might prove valuable for building construction and ad-hoc network scenarios. For instance, a building might include small transmitters that activate after the power fails to create a backup communications network.
“Looking at smoke detectors, every room in a house and every building have smoke detectors in every room,” Holloway said. “I can almost envision a similar thing where you can build portable devices and put them in every room, and they lay dormant until there is an emergency.”
In addition, researchers hope the information leads to the development of 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 in a building.
“The idea is that future radios could send out low-power signals such as chirps,” Holloway said. “This is based on what is used in deep space communications.”
Joe Miller, CEO of Vital Alert Communication, envisions the same concept, but with a twist. He said his company has developed a way for text and voice signals to travel through steel, concrete buildings, rocks and other debris by using age-old electromagnetic (EM) frequency transmissions.
Vital Alert’s technology, called the Emergency Broadcast Network (EBN), was first developed in the late 1980s under a research and development project that involved improving emergency evacuations of mines thousands of feet below the surface. The U.S. Bureau of Mines was convinced that EM frequencies could penetrate the earth since the U.S. Navy already had been using such frequencies to communicate with submarines. Miller undertook the program and in 1991 proved EM frequencies not only could penetrate the earth but could send communication signals to depths of 9000 feet.
Tuning to a resonant frequency, which ranges from 2500 Hz to 4000 Hz, creates a unique system that discriminates against electromagnetic noise, while still accepting the signal in the warning frequency range, Miller said.
Despite winning the prestigious 1993 R&D 100 Award — which was shared by the fax machine and anti-lock brakes — the technology never caught on with the mining industry, Miller said.
“The mining industry is ultraconservative with existing laws and procedures,” he said. “They really don’t have to look at other technologies. It was an uphill battle trying to get into there.”
After 9/11, however, Miller pushed the idea to another level, forming Vital Alert to focus on emergency communications for homeland security and other disaster situations. The company recently entered into an exclusive developmental license option agreement with Los Alamos National Laboratory in New Mexico, using the scientists to enhance the network in urban applications such as subway systems, skyscrapers, airports and industrial buildings.
Today, EBN consists of a transmitter, software and personal receivers for each individual connected to the system. Voice and text messages can be sent from a wireless phone, while text messages can be sent from a PC connected to a transmitter or by activating one of a variety of pre-programmed warning messages. Messages also can be sent to specific individuals carrying a small personal phone or receiver, or to an entire network of individuals. Miller said the system can be deployed quickly in emergency situations with a large broadcast area, transmitting data hundreds of miles.
So far, Miller has found it difficult to convince the skeptics.
“This technology has been around for years as a hospital paging system. Even the average person understands it,” Miller said. “But it has been an uphill battle trying to get anyone to listen.”
Miller said Vital Alert — which is targeting government entities at the state, local and federal level — is in a few discussions with interested parties, and the company is searching for a cooperative relationship with a major manufacturer that can mass produce the technology.
“I can’t just sit on this technology, knowing I have it my possession,” said Miller, who has invested millions of his own money into developing EBN. “This is about saving lives. I can’t stop until I see it in the marketplace.”
