The "Most Sought-After Class"

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Pioneering Wireless Communications
Andrew Viterbi didn't make it to the Life photo shoot in Lobby 7, but he vividly recalls the climate for aspiring young engineers at the time. "It was marvelous," he says. "Everything was wide open, and there were all sorts of opportunities." After finishing an electrical-­engineering master's degree at MIT in June 1957, Viterbi joined Caltech's Jet Propulsion Laboratory (JPL). On October 4, Sputnik was launched, and the space race was on. Viterbi was part of a team working feverishly to develop "phase-locked loop" signal-tracking technology. A key component of most digital communications receivers today, the technology was critical then because it helped enable the successful launch of Explorer 1, the first U.S. satellite, in January 1958. From the very beginning, it seemed, Viterbi was destined to be a pioneer.

He spent six years at JPL, completing a PhD in electrical engineering at the University of Southern California along the way. In 1963 he joined the faculty of the University of California, Los Angeles, where he taught communications theory. But he found it difficult to teach his students the principles governing "convolutional codes," error correction codes that enable the recovery of data transmitted through a noisy communications channel. So in 1966, he spent three months devising a mathematical model that better explained the material. "One of my favorite expressions is ‘Research is to teaching as sin is to religion; without the one, you have nothing to talk about in the other!'?" Viterbi says. One feature of his model is what is now known as the Viterbi algorithm, a method for decoding convolutional codes.

At the time, Viterbi regarded the algorithm as just a pedagogic tool. It wasn't until the 1970s that its practical uses became clearer, he says, as integrated circuits grew more sophisticated. Because the algorithm shares structural features with the Markov chain--a broadly applicable mathematical model of discrete-state systems--it has proved to be remarkably versatile. "There's a whole bunch of applications that have come out, many of which I had nothing to do with," Viterbi says with a laugh. Four international standards for digital cellular telephony now employ the algorithm, which is also used in such disparate applications as voice recognition and DNA sequence analysis.

In 1973, Viterbi decided to focus on cultivating the algorithm's practical applications, so he cofounded Linkabit in a converted dentist's office. The company initially worked on satellite communications subsystems for the military and later developed commercial products, such as a scrambler to prevent nonsubscribers from viewing Home Box Office programs. Viterbi went on to cofound Qualcomm, a provider of digital wireless-communications products and services, in 1985. The company pioneered the commercial application of CDMA (code division multiple access), a digital wireless-­communications technology that allows more users to share a given bandwidth. Although it took about three years for Qualcomm to persuade the industry to adopt CDMA, now some 335 million of the more than two billion cell-phone subscribers worldwide own phones that are CDMA-based.

Viterbi retired from Qualcomm in 2000, but he hardly stopped working. He and his daughter cofounded a venture capital firm; she focuses on biotech, and he covers the electronics and wireless-technology markets. He's also involved in a literacy initiative and in philanthropic pursuits at his alma maters--Boston Latin School, MIT, and USC. He is particularly proud of the literacy program, which enables parents serving in the armed forces overseas to make video­tapes of themselves reading stories aloud and send them to their kids. "It both serves to connect the family and to inspire children to read," Viterbi says.