By Bruce Schechter
Personal Area Network Technology Permits Individuals to Pass Identifying Information to Other People and to Machines Simply by Touching Them
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.
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