University of Rochester

Engineering Student Wins AT&T Fellowship

May 17, 1994

An electrical engineering graduate student at the University of Rochester is one of 18 students nationwide who have been named AT&T Bell Laboratories Ph.D. fellows.

Mark Hahm, who finished first in his class as an undergraduate last year at the University, will receive for the next four years paid tuition, a yearly stipend of $13,200, funds to cover books, fees, and travel to conferences, and the opportunity to work summers at AT&T.

Hahm, a native of Hilton, N.Y., graduated from the University with a perfect 4.0 grade point average; he earned both his bachelor's and master's degrees in electrical engineering in four years.

As an undergraduate Hahm worked on a variety of projects, including development of a gravity wave detector, a voice recognition system, a microprocessor-based weather station, and a cable-less optical communication link using a modulated infrared beam. Hahm, who graduated as a member of Phi Beta Kappa and is a member of the Tau Beta Pi National Engineering Honor Society, was awarded the Robert L. Wells Prize for Outstanding Scholarship and the Donald M. Barnard Prize at graduation.

As a graduate student he is working with Edward Titlebaum and Eby Friedman, faculty members in the Department of Electrical Engineering, to develop a new type of receiver suitable for decoding a novel type of signal developed by Titlebaum and colleagues.

The signals are different from conventional radio signals, where each channel occupies a certain frequency. Hahm is working with spread-spectrum code-division multiple-access (CDMA) signals, which share a large number of frequencies and hop rapidly from one frequency to another. Each signal has a unique hop pattern that allows a receiver to separate one from another.

"It's similar to selectively listening to one person at a crowded cocktail party," says Hahm. "By concentrating on that one person and listening for the unique features of his or her voice, you can tune out all the other interfering voices. We're developing receivers to do the same thing, only using electronics to listen for the signals."

The codes could be used to boost cellular telephone service, for example, or allow more computer users to fit on a network. But first engineers like Hahm must find a way to implement the new coding technology so that it is profitable for manufacturers to switch to the new technology. tr