Personal Area Network Technology Permits Individuals to Pass Identifying
Information to Other People and to Machines Simply by Touching Them
In Brief:
Technology under development at IBM's Almaden Research Center is designed to
pass digital information between two individuals or between an individual and a
device via a simple touch. To develop such personal area networks, or PANs,
Almaden scientist Thomas G. Zimmerman developed technology that, in effect,
transforms the human body into a copper cable. Zimmerman foresees initial use
of
PANs to identify people to devices that they own, such as automobiles and
telephones.
A gentle touch. A firm handshake. A pat on the back. A lingering caress. All
can communicate an enormous amount of emotion, understanding and compassion
from
one person to another. Now, Thomas G. Zimmerman, a scientist at IBM's Almaden
Research Center, has demonstrated how a touch can also be used to communicate
unemotional digital information.
When businessmen equipped with Zimmerman's technology shake hands, tiny
computers in their pockets automatically exchange business cards across a
fleshy
personal area network, or PAN. As part of a PAN, a person would be instantly
known to properly equipped cars or telephones, eliminating the need for keys or
coins. Merely touching the telephone receiver or the car's door handle would
establish a data link across which identifying information could flow.
"Imagine a world," Zimmerman says, "where everything is open
to you and available to you." PANs make this a possibility by allowing the
human body to be a network across which electronic devices can freely
communicate.
Wacky world of electronic invention
Zimmerman has been musing about the interaction of humans and computers
since 1982 when, as he puts it, he "first surfaced in the wacky world of
electronic invention." His debut invention was spectacular: the data glove,
the staple of virtual reality that first allowed humans to reach into
cyberspace. He worked for Atari for a while before going off to found several
companies, including the virtual reality pioneer VPL Research, which he started
up with Jaron Lanier. Eventually, he was drawn to MIT's Media Lab, where "all
these cool things were happening under one roof." There, he would be
serendipitously led to the invention of the personal area network.
Some of the coolest things, Zimmerman soon discovered, were taking place in
Neil Gershenfeld's Physics and Media Group. Gershenfeld had been working with
the renowned cellist Yo Yo Ma on ways in which technology could expand the
expressive capabilities of his instrument. Gershenfeld was searching for a way
to measure the details of Ma's bowing and fingering without interfering with
his
instrument.
Gershenfeld hit on a method known as near-field coupling. In essence he
placed electrical antennas on Ma's cello and bow. Pairs of these antennas
formed
capacitors. As Ma moved his bow across his instrument, he changed the
capacitance of the circuit. By measuring the capacitance it was possible to
determine the position of Ma's bow accurately.
In effect, Gershenfeld converted Ma's bow into a computer mouse. The only
problem was that a hand placed between the antennas also affected the
capacitance, interfering with the position measurement. The interference
problem
had Gershenfeld baffled. At this point Zimmerman joined the group and
discovered
the source of the interference. With the help of a rubber glove stuffed with
hamburger meat, he demonstrated that some of the signal was passing through the
human body.
This human interference proved advantageous when the magicians Penn and
Teller came to the Media Lab looking for some high-tech tricks. Penn wanted to
baffle his audiences by playing a set of "air drums." Zimmerman and
Gershenfeld decided to use Penn's body as one of the antennas in the system by
having him sit on a chair with an electrode built into its seat. Four antennas
suspended in front of the chair allowed Penn to play 128 different, invisible
drums. The audience was amazed.
Making devices communicate
The final inspiration came when another group at the Media Lab asked
Zimmerman and Gershenfeld to help develop a network that could connect all the
devices a gadget-hungry person might carry. As electronic devices have become
steadily smaller and cheaper, many people now walk around adorned with a half
dozen or more information and communication devices - pagers, cell phones,
personal digital assistants (PDAs), wristwatches and electronic games.
"None of these devices can talk to any of the others, which is both
inconvenient and inefficient. A page comes in and the silicon-laden recipient
has to reach into a pocket, read the number, perhaps punch it into a PDA to
find
out who is calling and then punch it into a cellular phone. In effect, he or
she
is devoting considerable mental capabilities to emulating an extremely
low-bandwidth communication network."
Zimmerman and Gershenfeld saw that modulating the electrical signal flowing
through Penn's body in the air drum trick - for example, turning it on to
represent a 1 and off to represent a 0 - could enable the body to carry
digital information. Using low frequency and low power would ensure that the
signal would not propagate very far beyond the body; thus, only devices worn by
the user, or by people or devices in direct contact with the user, could detect
it. The current involved is extremely tiny and totally unnoticed by the user,
whose body has been transformed into a meaty version of a copper cable: a
personal area network.
"The near-field effect used to make PAN possible has many advantages over
other methods of short-range wireless communication. Even low-powered radio
waves travel far enough to make eavesdropping and interference a real problem.
Since the human body acts like a bag of salt water and shadows radio waves, a
device on your lapel might not be able to communicate with one in your back
pocket. In addition, the radio spectrum is already crowded, and the licensing
requirements for radio communications are complex and vary from country to
country. Infrared communication is limited by line of sight."
Zimmerman understood that security is a serious problem for PANs. Touching a
person equipped with a PAN is like tapping a phone line. This is an advantage
when an exchange of information is desired, but a problem when privacy is
important. Since coming to IBM in 1995, Zimmerman has collaborated with
Almaden's Prabhakar Raghavan and Don Coppersmith of the Thomas J. Watson
Research Center to develop a security method using encryption that makes the
PAN
data look like a stream of random bits to would-be eavesdroppers.
CEOs holding hands
The version of the PAN that Zimmerman has been showing off is about the size
of a pack of cigarettes. On the back of the PAN devices are metal plates, one
of
which must face the body while the other faces outward to establish a ground
connection with the earth. The bandwidth of the PAN is relatively small, about
that of a low-speed modem. That's not sufficient to transmit video but more
than
enough to carry identification, financial or medical information.
At a recent show, Zimmerman enlisted several CEOs from some of the world's
largest corporations to hold hands, forming one of the highest-priced data
networks in history. Information on the card of the CEO on one end of the
network flowed through the intervening bodies and was detected by the card at
the far end.
High-tech business cards are unlikely to be the first applications of PANs.
For that to catch on, it will be necessary for almost everyone to be equipped
with the cards. Instead, Zimmerman believes that PANs will be used to identify
people to devices. "Imagine a thing like this," he says, fishing a
credit-card-sized device from his pocket. "It just sits in my wallet and I
never take it out. I pick up a pay phone and it autodials my calling card
number. So I dial the phone just as if it were my home phone. An ATM machine is
just my top drawer at home with the cash in it. You just grab your car door and
open it. It's really locked; but as soon as you grab it, the PAN uploads your
ID, the car acknowledges that it's you and it unlocks."
Information, in Zimmerman's vision, will become contagious, flowing freely
from person to person and computer to computer. By doing so, it will give a new
twist on what it means to keep in touch.
Bruce Schechter is a science writer based in Los Angeles. He is
currently writing a book on the life and times of Paul Erdös.
