Lloyd R. Welch

{{Short description|American information theorist (1927–2023)}}

{{For-text|the murderer of the Lyon Sisters|Murders of Katherine and Sheila Lyon}}

{{more footnotes needed|date=February 2013}}

{{Infobox scientist

| birth_date = {{birth date | 1927|09|28}}

| death_date = {{death date and age | 2023|12|28 | 1927|09|28}}{{cite web|title=Lloyd Richard Welch|url=https://outlookvalleysun.outlooknewspapers.com/directory-listing/lloyd-richard-welch/|work=Outlook Valley Sun|date=2024-01-22|access-date=2024-01-23}}{{cite web|author1=Christian Senger|author2=P. Vijay Kumar|title=Lloyd Welch passed away at the age of 96|url=https://www.itsoc.org/news/lloyd-welch-passed-away-age-96|website=IEEE Information Theory Society|date=2024-01-23|access-date=2024-01-23}}

| awards = National Academy of Engineering, IEEE Fellow, Claude E. Shannon Award

| known_for = Baum–Welch algorithm, Berlekamp–Welch algorithm

}}

Lloyd Richard Welch (September 28, 1927 – December 28, 2023) was an American information theorist and applied mathematician, and co-inventor of the Baum–Welch algorithm and the Berlekamp–Welch algorithm, also known as the Welch–Berlekamp algorithm.

Welch received his B.S. in mathematics from the University of Illinois, 1951, and Ph.D. in mathematics from the California Institute of Technology, 1958, under advisor Frederic Bohnenblust. He worked at the Jet Propulsion Laboratory 1956–1959, Institute for Defense Analyses in Princeton, 1959–1965, and University of Southern California, 1965–1999. He was elected a member of the National Academy of Engineering in 1979 for "contributions to an understanding of possibilities, limitations, and design of communications coding for reliability, security, and synchronization".{{Cite web|url=https://www.nae.edu/28382/Professor-Lloyd-R-Welch|title = Professor Lloyd R. Welch|publisher=National Academy of Engineering}} He was also an IEEE Fellow, and received the 2003 Claude E. Shannon Award.