The Viterbi School of Engineering (formerly the USC School of Engineering) is located at the University of Southern California. It was renamed following a $52 million donation by Andrew Viterbi.

The Viterbi School of Engineering is ranked No. 6 nationally by U.S. News and World Report (and No. 4 among private institutions.)

Viterbi’s inventions — led by his influential algorithm — are just one aspect of what has long been a major strength of USC’s Andrew and Erna Viterbi School of Engineering: digital information technology.

Since the early 1960s, researchers at or connected to USC have played a central role in the transmigration from the old radio world of analog signals to the digital domain we inhabit today.

USC engineers have made vital contributions to the theoretical understandings and science of computers and to the basic tools computers depend on to operate and communicate. Such everyday items as the compact disc, fax machine and cell phone use technology rooted in USC research. Interplanetary communication signals from Voyager to the Mars Rovers are kept pristine with error correction systems created at USC.

Critical elements of the Internet began at USC, including the powerful system for robustly coding and decoding digital signals. Also born here: the now-familiar technologies and Internet fundamentals of jpeg and mpeg, used by computers worldwide to store, transmit and restore still and video images.

The digital ancestry of today’s Andrew and Erna Viterbi School of Engineering was fixed in the early 1960s by that era’s legendary dean, Zohrab Kaprielian. Under his leadership, three great mathematical and information theorists joined the USC electrical engineering faculty. Solomon Golomb, Irving Reed and Lloyd Welch were all young scientists at the beginning of their careers when Claude Shannon of MIT published his landmark 1948 paper on signals. All three, and Dr. Viterbi, would eventually win the Shannon Award, the highest honor from the Information Theory Society of the Institute of Electrical and Electronics Engineers.

At a time when information was transmitted using continuous analog waveforms, Shannon conceived that all signals — whether for use on a telephone, radio or television — could be decomposed into zeros and ones, encoded, transmitted and decoded at the other end. Shannon determined a maximum rate of transmission on a single channel and posited that adding enough redundancy to the transmitted signal would enable receivers to decode the message accurately no matter how noisy the channel.

Shannon’s insights were theoretical. But, to a remarkable degree, Golomb, Reed, Welch and their students and colleagues — including Andrew Viterbi — turned theory into working signaling systems. That work continues today with a new generation of USC electrical engineers such as Alan Willner and Keith Chugg. Here are some of the landmark contributions by USC-associated researchers to the digital revolution:

Baum-Welch algorithm

• The Baum-Welch algorithm developed by Lloyd Welch in collaboration with Leonard Baum is, like the Viterbi Algorithm, a powerful tool for examining and analyzing the results of continuing processes that proceed regularly in stepwise fashion — so-called Markov processes. It has become an important tool in many fields, led by speech recognition, and gained recent additional celebrity as a key component of the turbo-decoding systems that functions, as the name indicates, with unparalleled speed.

Domain name system (DNS)

• The Internet depends on a flexible, stable system to regularize, distribute and store names. In 1983, at USC’s Information Sciences Institute, Paul Mockapetris devised a system to solve this problem, with the potential to add an almost unlimited number of new addresses. In addition to organizing numerical addresses, Mockapetris and the late Jon Postel introduced the now-ubiquitous .com, .gov, .edu, .org, suffixes, as well as country codes.

Image compression & recognition

• William Pratt was among the first to study methods of analyzing and storing data that recorded visual images in compressed form. Harry Andrews explored methods of recognizing shapes — initially, printed letters — in digital files. The work of Pratt, Andrews and subsequently Andrew G. Tescher led to today’s jpeg compression system for still images. The parallel mpeg system, which compresses video images, also has USC roots. Jay Kuo and Antonio Ortega are continuing USC research into video compression, while Irving Reed created his own system of image compression, adopted by AOL.

Pseudorandom sequences/shift register sequences

• In 1967, Solomon Golomb published the first book devoted exclusively to pseudorandom sequences, also known as shift register sequences. As the technology of digital communications has evolved, these sequences have played a central role in many applications, including digital CDMA cell-phone systems and “direct-sequence spread spectrum” secure military communications. They are widely used in limited-access security systems, “streamcipher” cryptography, and jam-resistant missile guidance systems (for generating efficient, continuous wave radar signals), as well as in implementing the encoding and decoding of many error correcting codes, including Reed- Solomon codes.

Quaternary (z4) error correction codes/3G

• In 1994, Vijay Kumar, working with his Ph.D. student, Roger Hammons, Jr., discovered a hidden regularity in existing error codes, which led directly to improvements and added efficiency in CDMA cell coding. Rather than encoding binary messages, Kumar’s codes employ quaternary (1,2,3,0) values, which are at the basis of sophisticated new “third generation” (3G) signal equipment, that carry information four times as efficiently.