Error Probability Analysis in Reduced State Viterbi Decoding
Carlos VALDEZ, Hiroyuki FUJIWARA, Ikuo OKA and Hirosuke YAMAMOTO
- The performance evaluation by analysis of systems employing Reduced State Viterbi decoding is addressed. This type of decoding is characterized by an inherent error propagation effect, which yields a difficulty in the error probability analysis, and has been usually neglected in the literature. By modifying the Full State trellis diagram, we derive for Reduced State schemes, new transfer function bounds with the effects of error propagation. Both the Chernoff and the tight upper bound are applied to the transfer function in order to obtain the bit error probability upper bound. Furthermore, and in order to get a tighter bound for Reduced State decoding schemes with parallel transitions, the pairwise probability of the two sequences involved in an error even is upper bounded, and then the branch metric of a sequence taken from that bound is associated with a truncated instead of complete Gaussian noise probability density function . To support the analysis, particular assessment is done for a Trellis Coded Modulation scheme.
- Key words: reduced state decoding, viterbi algorithm, feedback equalization, intersymbol interference, trellis coded modulation
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