Feature: In sensors smaller may be smarter

By LIDIA WASOWICZ, UPI Senior Science Writer  |  July 14, 2003 at 3:05 PM
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BERKELEY, Calif., July 14 (UPI) -- Electrical engineers and computer scientists have tested successfully the latest and smallest incarnation of a "smart dust" sensor, whose Lilliputian size belies the envisioned enormity of its potential capabilities.

From instant assessments of the structural soundness of earthquake-jarred buildings to life-saving forewarnings of impending heart attacks to stealthy surveillance of enemy troops, the micro-sized device shows promise in a wide variety of fields.

The new wireless chip, dubbed Spec, integrates sensors and transmitters -- including a micro-radio, analog-to-digital converter, temperature sensor and an operating system called TinyOS -- into a piece of silicon that measures a mere 5 square millimeters. As a point of reference, the micro-machine is small enough to fit within Abe Lincoln's nose on the back of a penny.

The fourth generation wireless sensor culminates six years of research at the University of California, Berkeley, the birthplace of smart dust, a term coined in 1996 by Kris Pister, professor of electrical engineering and computer sciences who pioneered the airborne, speck-size snoopers that can sniff out everything from light to vibrations.

The project, which falls under the auspices of Berkeley's Center for Information Technology Research in the Interest of Society, has the stated goal of creating low-powered, low-cost remote sensor devices, or motes, about the size of a grain of sand.

In ground-breaking tests at the Intel Research Laboratory, also in Berkeley, the infinitesimal device -- successor to commercial motes slightly larger than the two AA batteries that keep them running -- was able to transmit radio signals at 902 megahertz some 40 feet at 19200 kilobits per second. That approximates the frequency of a cell phone, an instrument 50 times larger and 1,000 times more voracious in its power consumption.

"Whereas traditional radios consume as much as 3 watts in transmitting just half a watt, the total power consumption of the Spec transmitter is a mere .001 watts," noted Jason Hill, primary developer of TinyOS and architect of Spec.

The smart chip's success marks a key advance in combining communication, computation and sensing into a single, tiny, dirt-cheap, easily deployable and exceptionally versatile package, researchers said in interviews with United Press International.

"Spec is our first mote to integrate radio frequency communication and custom circuits onto a chip that runs the TinyOS operating system," Pister said. "It's a major step towards sensors that cost less than a dollar a piece and that are integrated into the products that we own, the buildings that we live and work in, and the freeways we drive on."

Such a life-altering, potentially intrusive technology likely will raise newfound concerns, particularly in the areas of privacy and security, researchers conceded. They pointed out, however, they already are conducting encryption work to minimize unauthorized access to mote-collected information.

"We are now coming into an era of evaluating the technology's aesthetic utility," CITRUS Director Ruzena Bajcsy said in an interview. "It will take another 5 years before this technology really gets the bugs out."

Pister, who has taken an industrial leave of absence to launch a startup company named Dust, Inc., based upon smart dust, plans to develop Spec into a commercial product within a year.

The device, including battery and casing, would be no larger than an aspirin and cost no more than a movie ticket ($5 to $10, compared to the current $50 to $100 per mote), he estimated.

"The potential for such sensor networks is momentous," he said, noting it runs the gamut from meteorological to medical to military uses.

In one scenario, the self-organizing motes tossed into the turbulence of a gathering storm could monitor and give a heads up on the whims of weather.

"If we can get funding, we'll release 1,000 sensors into a hurricane approaching the Gulf Coast and do a baby demonstration to show we can monitor weather conditions inside a hurricane, like in (the feature film) 'Twister,'" a fictional depiction of high-tech tornado chasers, Pister said in an interview.

Or, enclosed in jewelry, the smart sensors could keep tabs on the wearer's vital signs, giving instant notice of bodily distress.

Or, scattered like pixie dust across the field of battle, they also could track and report on advancing enemy battalions or an ambush attack.

In a test two years ago, dozens of second generation motes, called Rene, dropped from a plane alongside a Southern California road, tracked the speed and direction of passing vehicles based upon ground vibrations.

In other applications, affordable armies of the tiny gatherers and transmitters of information could monitor seabird nests in remote habitats, pinpoint structural weaknesses in buildings damaged by nature or man, warn of the presence of biochemical toxins, catch manufacturing defects in industrial equipment, evaluate the soundness of the nation's bridges, more than half of which have outlived their designated lifetime and may pose a potentially deadly threat to unsuspecting travelers.

Already, matchbox-size motes are helping conserve energy in some UC buildings.

"Everything is fully functional," reported Bajcsy, who has temperature and light measuring motes pasted on the walls of her CITRUS office.

Outfitted with the TinyOS operating system, the motes automatically organize themselves into ad hoc wireless networks, passing on information bucket-brigade style to a central computer for processing.

Rather than wearing out batteries with an endless flow of transmissions, a mote activates just long enough to send its readings by way of a two-way band radio to its neighbors, which then take up the communication gauntlet.

"The goal is to get years of operations off of dime-size batteries," Hill told UPI.

Electronics giant Panasonic is working on millimeter-scale, Spec-fitting batteries, he noted. Also, Front Edge Technology, established in 1994 to develop, manufacture and market next-generation, ultra-thin rechargeable batteries for card-type applications, has designed an autonomous power source thinner than a piece of paper.

The cost and power advantages of such miniaturization may be offset by certain drawbacks, Bajcsy noted.

"Even if you make them cheap and energy-efficient, you still have to ask about the environmental impact and how many of these things you want to have around before the environment gets cluttered," she told UPI.

Despite such concerns, Pister anticipates Spec taking a sizeable bite out of the growing wireless sensor revenue pie. A recent report predicted a four-fold increase, to $101.1 million, in sales by 2008.

"I think there's easily tens of millions of dollars of market potential just with the existing product," Pister told UPI. "Over the next year or two, you'll see the first real deployments of this technology in commercial applications."

Spec products will be available at Crossbow Technology Inc. of San Jose, a supplier of digital sensor products that carries the sensor's predecessors.

The company, which has taken three generations of mote technology from laboratory to market, has shipped more than 10,000 of the units -- primarily to research and development customers -- since it began selling the products in earnest in 2001.

"Our customers are every major university in the United States," John Crawford, Crossbow vice president of sales and business development, said in an interview. "We have DARPA (Defense Advanced Research Projects Agency, the research and development arm of the Defense Department) programs using the technology for various types of applications, including seismic and environmental monitoring."

To promote the technology, Crossbow is sponsoring a series of training seminars for new users, including two-day workshops later this month and in mid-October. Participants bring their own laptops and $895 mote kits to learn how to build and deploy simple wireless sensor networks using the technology.

"The temptation is to keep some of this proprietary in an attempt to lock customers in," said Mike Horton, Crossbow chief executive officer. "However, we think our support of the community generates business for us and keeps us in the loop."

Spec brings together years of smart dust and TinyOS research headed by Pister and David Culler, professor of computer sciences. Pister led research into miniaturizing the hardware parts while Culler and his team developed the operating system that allows the mini-motes to communicate with one another.

Their work led to generations of wireless sensor motes slightly bigger than pocket change. The breakthrough came when Hill, a former graduate student who worked with both men, combined the two sets of components on the ultra-small sliver of silicon.

"Single chip integration makes the mote very cheap because it reduces post-assembly requirements," Culler explained. "This opens the path to very low-cost deployments of a large number of motes."

Within the next seven to 13 years, Pister envisions some wondrous applications of his brainchild:

--Clothing, jewelry, cars, stereos and other personal valuables turn off or signal their location when stolen or misplaced;

--lighting, heating and other home and office comforts adjust to suit personal preferences;

--child monitors prevent death from SIDS or drowning by alerting caregivers to brewing trouble;

--motes find and reserve in advance parking space at the shopping mall;

--chronic sensor implants monitor a body's circulatory systems to provide early, life-saving warning of cancer or other disease.

"Wireless sensor talk has been around for a long time," Pister said, "Now we've got the technology to realize some of the dreams people have -- and to do it economically!"

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