| Summary: | 碩士 === 國立清華大學 === 電機工程學系 === 88 === Turbo codes, which achieve near Shannon-limit error correction
performance, are a combination of parallel concatenated coding and
iterative decoding. For the coding part, the reasons why the
parallel concatenated coding structure could
produce very good codes are now well understood. However, for the
decoding part, although a number of researchers have shed a great
deal of light on how the turbo decoding algorithm works, there is
still no satisfactory theoretical explanation of the excellent
performance of the low-complexity, iterative, turbo decoding
algorithm. In this thesis, we study the turbo decoding algorithm
using Max-Log-MAP instead of MAP as the soft-input/soft-output
decoding algorithm for the constituent decoders. It is shown that
this iterative decoding algorithm is suboptimal and may not even
converge. Moreover, the existence of the fixed points of this
iterative decoding algorithm is proved. Finally, we give some
sufficient conditions for the convergence of the turbo decoding
algorithm using Max-Log-MAP.
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