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Heading into the golden age of wireless 2.0
Newly minted PicoRadios sport
ambient intelligence and disappear into the environment
by David Pescovitz
photos by Bart Nagel
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Jan
Rabaey's PicoRadio is a small hidden computer that can endow
our daily environment with "ambient intelligence."
A native of Belgium, Rabaey envisions a world in which all
electronics disappear into the environment.
BART NAGEL PHOTO |
In Jan Rabaey's vision for the future of computing, the most
powerful PCs are the ones you cannot see. These computers will
be invisible, but alert. Small and inexpensive, they will be woven
into the tapestry of our lives—hidden in our pockets, clipped
to our prized possessions, embedded in our home appliances. They
will sense our behavior and sometimes act on our behalf.
Rabaey, Berkeley professor of electrical engineering and computer
sciences (EECS), calls this paradigm “ambient intelligence.”
Science fiction enthusiasts know it as the smart home.
Inside Rabaey's imagined smart home, surround sound music follows
him wherever he walks, shifting from speaker to speaker. The refrigerator
knows when it’s running low on milk and eggs, automatically
e-mailing an order to a grocery delivery service. A smart power
meter informs the thermostat when it’s least expensive to
run the air conditioner to maintain the desired temperature, reducing
energy consumption and the monthly utility bill. If Rabaey misplaces
his car keys, he pushes a tiny icon painted on his wall and a
flat panel display comes alive with a video image of his living
room. A bull’s eye graphic appears superimposed on the sofa
cushion where his key chain lies hidden. Authentication algorithms
embedded in the system ensure that information flows in an unobtrusive
and a need-to-know basis, avoiding Big Brother scenarios and unauthorized
snooping.
“Today’s consumer electronics world consists of individual
gadgets,” says Rabaey, who is also a researcher at the Berkeley-based
Center for Information Technology Research in the Interest of
Society (CITRIS), as well as director of the Gigascale Systems
Research Center (GSRC), a multi-university research center sponsored
by the semiconductor industry. “But ambient intelligence
means that the gadgets form networks so they can communicate with
one another.”
And that brings Rabaey to the PicoRadio, the tiny, inexpensive,
low-power communications technology that he and his students—among
them doctoral candidate Brian Otis—have developed over the
last five years at the Berkeley Wireless Research Center (BWRC),
where Rabaey serves as scientific codirector. The idea is that
a PicoRadio costing less than $1 could be slapped on any object,
from a washing machine to a keychain, enabling it to join ad hoc
wireless networks and share information with its neighbors. Outfitted
with myriad sensors to detect light, temperature, and motion,
the PicoRadio creates a distributed network that understands its
environment and reacts to it. The prefix pico, meaning
one-trillionth, isn’t to be taken literally, but rather
serves as a reminder of the research group’s mission: creating
new generations of ever smaller, cheaper, lower-powered devices.
“The big questions we ask are how much simpler can our radios
be than today’s off-the-shelf technology?” says Rabaey.
“How little energy do they need? How small can they be?”
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| By
using a "simplify, simplify, simplify" approach,
Rabaey and colleagues have stripped the PicoRadio's necessary
radio frequency electronics down to bare bones. The wireless
device pictured here is just a few square millimeters in size. |
The tiny device in Rabaey’s hand holds the answers, at
least for the moment. Just a few millimeters square, the most
recent generation of PicoRadio chips has just returned from the
chip fabrication facility. This one, called a “Quark”
node in reference to the subatomic building blocks of matter,
draws just 100 microwatts of power. That’s 10 times less
than the energy needed by the commercial radios on UC Berkeley's
Smart Dust, small wireless sensor nodes that monitor everything
from a building’s seismic stability to the environmental
conditions in a redwood forest canopy. Even devices based on Bluetooth—a
popular technology for wireless communications between nearby
devices—require a comparatively huge 70 milliwatts of power
to provide short-range connectivity so you can wirelessly synch
your computer and cell phone address books or even replace the
wires on a hands-free headset for your cell phone.
To hit such low power and small size with the PicoRadio, Rabaey
and Otis adopted a mantra of “simplify, simplify, simplify!”
They stripped the necessary radio frequency (RF) electronics down
to its bare bones. The Quark node consists of two custom chips:
a digital signal processor and a two-channel radio transceiver.
The antenna is printed directly onto the circuitboard with the
electronics that drive the microchip. In fact, Rabaey gets a kick
out of linking every component in an electron micrograph of the
PicoRadio RF chip to its counterpart in a photo of a vintage 1949
wireless set.
“In the 1920s and ‘30s, they only had a couple of
vacuum tubes to play with so they used a lot of passive components,”
he says. “In the same way, rather than use hundreds or thousands
of transistors, we really minimize the number of active components
that require the most power. The underlying assumption of the
ambient intelligence concept is that the complexity of the system
lies not in the individual nodes, but in the collection of connected
nodes.”
Still, wireless communication is notoriously power hungry. That’s
why cell phones are limited to a few hours of talk time before
you have to recharge their batteries. Of course, the smart home
applications that Rabaey foresees require sensor nodes with a
range of only a few meters. For longer transmissions, the nodes
pass data across the network, bucket-brigade style. And in an
innovative approach to power conservation, the radio only “wakes
up” when it has to send and receive. Given those constraints,
batteries would seem like the perfect approach to power the PicoRadios.
And they are, Rabaey explains, until it comes time to charge them.
The diminutive size and low cost of the PicoRadio nodes means
that they can be deployed by the thousands in every nook and cranny,
from light switches to milk cartons to keychains. But the sheer
number of nodes makes changing batteries or manually recharging
the devices completely impractical. That’s why the PicoRadios
were built from the bottom up to be self-sufficient. “They
scavenge energy from their environment,” Rabaey says.
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Rabaey
and Otis (left) have recently found a way to shrink the PicoRadio’s
antenna to a mere trace wire, reducing cost as well as the
radio’s diminutive mass. “Now we hope to bring
the power down, maybe even by a factor close to 10,”
says Otis.
BART NAGEL PHOTO |
The Quark PicoRadios are outfitted with small solar panels. With
sufficient illumination, either from the sun or indoor light bulbs,
the solar cells trickle power into two rechargeable coin batteries
that keep the node alive when light is scant. For deployment in
total darkness, the team hopes to outfit PicoRadios with the ability
to convert natural vibrations—the hum of computer monitors,
the continuous shudder of heating and cooling ducts—into
electricity. In collaboration with mechanical engineering professor
Paul Wright and his group, the team built devices that harness
this kinetic energy. Fabricated with the same processes used to
manufacture computer chips, the vibration-based generators could
eventually be integrated into the PicoRadios.
Right now though, Rabaey, Otis, and the other students on the
team are honing the PicoRadio design to further reduce power consumption.
One way to conserve juice, Otis explains, is to integrate even
more of the external circuitry into the custom chips—from
the electronics that control the power flow to the onboard clocks
that provide the “heartbeat,” synchronizing the execution
of software instructions. To that end, they are collaborating
with the Berkeley Sensor and Actuator Center on tiny micro-electromechanical
systems (MEMS) devices that can be built directly on top of the
Quark chips.
“The exciting part for me is doing work that contributes
to my field of RF design while also pushing forward the capabilities
of sensor networks,” Otis says.
Meanwhile, the first PicoRadio application is already in development
within CITRIS. Supported by the California Energy Commission,
Rabaey, Otis, and Wright are working with researchers at UC Berkeley's
Center for the Built Environment to cut utility bills by combining
PicoRadios with “demand-response” energy pricing.
A demand-response cooling system involves PicoRadio sensors that
monitor temperature in various parts of a house or apartment and
relay data to a networked thermostat. Simultaneously, sensors
coupled to electrical circuits in breaker boxes monitor the power
consumption of other appliances. As energy prices shift hourly,
those numbers are transmitted wirelessly from the utility company
to a smart meter at the residence. Sophisticated computer algorithms
running on the thermostat will keep the house cool without turning
on the air conditioner at peak times.
“This kind of closed-loop control could save you 10 to 15
percent on your power bill,” Otis says. The user’s
only responsibility would be to program temperature preferences
into a familiar thermostat. The network would take care of the
rest. The power behind the curtain, Rabaey says, is what ambient
intelligence is all about.
“My vision is for all electronics to disappear into the
environment,” Rabaey says. “This technology will help
change the way we interact with the information flowing around
us so that it’s much more natural.”
DAVID PESCOVITZ writes Lab Notes, the College
of Engineering’s online research digest, and contributes
to Popular Science, TheFeature.com, and Business
2.0. His writing on science and technology has been featured
in Wired, Scientific American, IEEE Spectrum, and the
New York Times.
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