SOVA Based on a Sectionalized Trellis of Linear Block Codes

The use of block codes is a well known error-control technique for reliable transmission of digital information over noisy communication channels. However, a practically implementable softinput soft-output (SISO) decoding algorithm for block codes is still a challenging problem. This thesis examines a new decoding scheme based on the soft-output Viterbi algorithm (SOVA) applied to a sectionalized trellis for linear block codes. The computational complexities of the new SOVA decoder and of the conventional SOVA decoder based on the bit-level trellis are theoretically analyzed and derived. These results are used to obtain the optimum sectionalization of a trellis for SOVA. The optimum sectionalization of a trellis for Maximum A Posteriori (MAP), Maximum Logarithm MAP (Max-Log-MAP), and Viterbi algorithms, and their corresponding computational complexities are included for comparisons. The results confirm that SOVA based on a sectionalized trellis is the most computationally efficient SISO decoder examined in this thesis. The simulation results of the bit error rate (BER) over additive white Gaussian noise (AWGN) channel demonstrate that the BER performance of the new SOVA decoder is not degraded. The BER performance of SOVA used in a serially concatenated block codes scheme reveals that the soft outputs of the proposed decoder are the same as those of the conventional SOVA decoder. Iterative decoding of serially concatenated block codes reveals that the quality of reliability estimates of the proposed SOVA decoder is the same as that of the conventional SOVA decoder.