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Sequential Decoding
Recognised by John Wozencraft, sequential decoding is a limited memory technique for decoding tree codes. Sequential decoding is mainly used as an approximate decoding algorithm for long constraint-length convolutional codes. This approach may not be as accurate as the Viterbi algorithm but can save a substantial amount of computer memory. It was used to decode a convolutional code in 1968 Pioneer 9 mission. Sequential decoding explores the tree code in such a way to try to minimise the computational cost and memory requirements to store the tree. There is a range of sequential decoding approaches based on the choice of metric and algorithm. Metrics include: *Fano metric *Zigangirov metric *Gallager metric Algorithms include: *Stack algorithm *Fano algorithm *Creeper algorithm Fano metric Given a partially explored tree (represented by a set of nodes which are limit of exploration), we would like to know the best node from which to explore further. The Fano metric (named a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
John Wozencraft
John McReynolds "Jack" Wozencraft (September 30, 1925 – August 31, 2009) was an electrical engineer and information theorist, professor emeritus at the Massachusetts Institute of Technology. One of the pioneers of coding theory, Wozencraft developed the sequential decoding techniques for convolutional codes that made error-free communication possible with relatively low computing power. Biography He attended the U.S. Military Academy at West Point, NY. Following graduation in 1946, he joined the United States Army Signal Corps Engineering Laboratory. He received his Sc.D. at MIT in 1957. From 1957 to 1976, when he retired, he served on the faculty of MIT's department of Electrical Engineering. While on a leave of absence from MIT (1972–1974), he served as Dean of Research at the Naval Postgraduate School in Monterey, California. Following his retirement from MIT in 1976, he returned to the Naval Postgraduate School as professor of electrical engineering and the foundin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tree Codes
In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, e.g., including only woody plants with secondary growth, only plants that are usable as lumber, or only plants above a specified height. But wider definitions include taller palms, tree ferns, bananas, and bamboos. Trees are not a monophyletic taxonomic group but consist of a wide variety of plant species that have independently evolved a trunk and branches as a way to tower above other plants to compete for sunlight. The majority of tree species are angiosperms or hardwoods; of the rest, many are gymnosperms or softwoods. Trees tend to be long-lived, some trees reaching several thousand years old. Trees evolved around 400 million years ago, and it is estimated that there are around three trillion mature trees in the world currently. A tree typically has many secondary branches supported clear of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
