Wicker's focus: networks of people and communications

Associate Professor Stephen Wicker talks with electrical engineering graduate student Noah Henyon in the Duffield Laboratory of Rhodes Hall. Frank DiMeo/University Photography

By Bill Steele

It's all about networking.

Associate Professor Stephen Wicker studies communication networks, and he's much more successful at it, he says, because he's been able to join a network of other faculty members and students. It was the opportunity for that kind of collaboration that persuaded him to leave a tenured post at Georgia Tech and come to Cornell two years ago.

Wicker was born to be an engineer but didn't know it right away. "I come from a family of doctors," he explains, "so I was going to be a cardiac surgeon. I would read books about that and tell my friends that was what I was going to do, but all the while I was building radios. I rewired the house; I took apart the television."

Nevertheless, he entered the University of Virginia as pre-med. "But," he says, "I decided there was no way on earth I wanted to spend a lot of time in hospitals. I wanted to build things."

It took one more step to put him on the path to a professorship: "When I got into graduate school I realized I wasn't fit for a real job. I wanted to be an academic."

He did take a "real job" for a while, designing satellite communications systems for Hughes Aircraft. But his self-evaluation was accurate: He didn't like having other people tell him what kind of research to do, and he didn't like having to work only on projects with short-term, market-driven goals, so in 1987 he went to Georgia Tech. It seemed a good choice, since his family was originally from the south.

"My students and I did some nice work there," he recalls. But surrounded by an electrical engineering faculty of about 100, he still found no one who wanted to collaborate. "I had my little empire at Georgia Tech," Wicker recalls. But so, too, he found, did everyone else. "I heard that Cornell was building a wireless program and had already hired two new faculty in the area. I have always been impressed by Cornell, and I thought that Ithaca would be a better place for my family."

He wasn't disappointed. "There were already several very strong, very senior people in telecommunications at Cornell, but there were also several new faculty to work with. It was an ideal mix. We have done some nice things here, together, in the last two years."

Among others, Wicker works with the "wireless group," researching methods to make wireless communications systems, like cellular phones and commercial two-way wireless data systems, more reliable. The group includes electrical engineering faculty colleagues Zygmunt Haas, Venugopal Veeravalli and Sheila Hemami.

Partly because their work has so many practical applications, it has brought in unprecedented support. Shortly before Wicker's arrival, David Duffield, alumnus and president of PeopleSoft, donated $1 million for a joint Electrical Engineering/Computer Science laboratory focusing on information technology. Wicker and his colleagues used these funds to develop a state-of-the-art facility for simulating real wireless networks in real time.

This facility is now the focal point for several collaborative projects, including a joint electrical engineering/computer science effort to study the application of artificial intelligence to communications networks. Wicker calls the subject of this study "Cognitive Engineering"; it is his favorite example of the benefits of faculty collaboration. The initial results from this study led to a $900,000 grant from the National Science Foundation for Wicker, Terrence Fine (electrical engineering) and Joseph Halpern (computer science).

Although Wicker's work involves sophisticated computers and esoteric math, it still boils down to the basic challenge faced by most engineers: how to do a better job with what you've got.

Cellular phone companies, for example, pay enormous fees for the use of a small number of radio frequencies. "Having spent all this money, and being in debt up to their eyeballs," Wicker explains, "the companies want to cram as many users as possible into a small number of channels."

They do that by dividing the world into small areas, or cells, so people in several cells can be talking on the same channel at the same time. Computers can switch users from one frequency to another as they move between cells.

Part of Wicker's work is to make these computers more sophisticated, introducing artificial intelligence (AI) techniques to deal with questions like, "We expect 55 active users to arrive in Cell A in 90 seconds. How do we rearrange our channel allocation to handle them?" For communications networks, Wicker says, these systems will have to be "probabalistic," making guesses about what's going to happen and acting accordingly.

To keep users from interfering with one another, you also have to keep the power of the signal quite low. "Cellular phone users want to carry on their conversations in elevators, walking down the street or even riding in trains going several hundred miles an hour. By the time the signal, which was weak to begin with, bounces off a few buildings and vehicles and arrives at its destination, it is in sad shape," Wicker says. Much research goes into developing technology that can sort out these signals and correct errors, using special codes built into the transmissions that tell the receiver what the signal ought to look like.

The future, Wicker says, belongs to "turbo codes," which decode the information several times, compare the results to arrive at a consensus, then recalculate whatever can't be resolved. "It's like a turbocharged engine where you take incompletely combusted material and run it around and burn it some more," he explains.

This allows for the transmission of data with extraordinarily weak signals. Turbo codes developed by one of Wicker's friends at NASA's Jet Propulsion Laboratory are already being used to verify data from the Cassini spacecraft, which has flown by the planet Venus and will eventually orbit Saturn. Wicker and Cornell faculty colleague Chris Heegard will publish a book on turbo codes (the first ever) in the fall.

Wicker teaches both graduate and undergraduate courses in networking, wireless communications and expert systems, including the very popular "Introduction to Telecommunications" for freshmen. He was awarded Cornell's Michael Tien College of Engineering Teaching Award for 1997-1998.

He is a member of the board of governors of the Institute of Electrical and Electronics Engineers (IEEE) Information Theory Society, and he is the author of Error Control Systems for Digital Communication and Storage (Prentice Hall, 1995), co-author of Turbo Coding (Kluwer Academic Press, to appear in 1998), co-editor of Reed-Solomon Codes and Their Applications (IEEE Press, 1994) and editor for coding theory and techniques for the IEEE Transactions on Communications. The last, a monthly journal, is the premier publication in the field of telecommunications research.