Application of Soft-In/Soft-Out Viterbi Algorithm to Turbo Trellis-Coded Modulation

Tadashi MINOWA  Haruo OGIWARA  

IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences   Vol.E81-A   No.10   pp.2047-2054
Publication Date: 1998/10/25
Online ISSN: 
Print ISSN: 0916-8508
Type of Manuscript: Special Section PAPER (Special Section on Information Theory and Its Applications)
Category: Coded Modulation
turbo codes,  SOVA,  TCM,  iterative decoding,  

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Soft-in/soft-out Viterbi algorithm (SOVA) originally proposed for rate 1/n code is applied to rate m/(m+1) trellis-coded modulation (TCM). In TCM, 2m branches merge into a node in a code trellis. After pruning the branches on path with less path-metric until two best paths remain, SOVA is applied to the pruned trellis. Based on the pruned trellis, an iterative decoding algorithm of turbo TCM is developed. Effects of path memory length and scaling of a value transferred between decoding stages are investigated through simulation. Turbo TCM over 8 PSK and 16 QAM channel with Gaussian noise realize a bit error rate (BER) of 10-5 within 1 dB from the Shannon limit.