Convolutional code: Difference between revisions

Revision as of 16:23, 28 October 2005

Revision as of 01:55, 1 December 2005

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===Design Issues===

Longer constraint length codes are more practically decoded with any of several <b>sequential</b> decoding algorithms, of which the [[Shannon-Fano_coding|Fano]] algorithm is the best known. Unlike Viterbi decoding, sequential decoding is not maximum likelihood but its complexity increases only slightly with constraint length, allowing the use of strong, long-constraint-length codes. Such codes were used in the [[Pioneer program]] of the early 1970s to Jupiter and Saturn, but gave way totoo shorter, Viterbi-decoded codes, usually concatenated with large [[Reed-Solomon error correction]] codes that steepen the overall bit-error-rate curve and produce extremely low residual undetected error rates.

===Turbo Codes: replacing Convolutional Codes===