Soft-output turbo code decoder and optimized decoding method

摘要

Turbo codes used in digital communication systems are decoded by successive iterations of a maximum likelihood algorithm. The turbo code decoder is a modular apparatus with each module comprising two or more serial constituent decoders. The output a constituent decoder or a module is part of the input to the next constituent decoder or module, respectively. The progress of the decoding can be monitored by establishing a limit for the output of the constituent decoders and monitoring the numbers of outputs of one or more constituent decoders that approximately equaling that limit. When the numbers of outputs approaching the limit or saturating is unchanged for successive iterations or successive serial decoders no further progress is being made in decoding the message. The performance of the turbo code decoder can be optimized by terminating iterations of the decoding process when the numbers of constituent decoder outputs that have saturated is unchanged for successive iterations or decoder operations.