Non-binary SOVA algorithms for decoding of block codes on a sectionalized trellis

摘要

In this paper, we explore computationally efficient implementations of the soft output viterbi algorithm (SOVA) applied to Soft-Input Soft-Output (SISO) decoding of linear block codes. In order to simplify the trellis-based decoding of binary block codes with SOVA, we use the technique of sectionalization of the trellis, which has been successfully applied to the simplification of the MAP and Max-Log-MAP algorithms. Due to the branch complexity of the sectionalized trellis, we define a generalization of a non-binary version of SOVA. However, the computational complexity of directly applying this approach remains too high for efficient implementation; we thus introduce the concept of non-binary SOVA (NSOVA) with propagation of bit-level reliabilities (BLR). This new algorithm is analyzed from a computational complexity viewpoint. Both serial and parallel implementations are explored. Finally, optimal sectionalizations are derived for selected codes; since the normal SOVA decoding is a particular case of NSOVA with BLR, we show that our approach is more efficient than a bit-level trellis by showing that, for all the codes tested, the optimal trellis is a sectionalized one.