Konvolutional code decoding circuit to perform the storage and tracking step of the surviving paths of a Viterbi algorithm

摘要

This decoding consists in backtracking over a plurality of paths of a grid representing a graph of the possible transitions resulting from a coding by a coder with nu flip-flops, each node of the grid being represented by one word with N = 2 nu bits. …??The circuit works so as to select, from a plurality of possible surviving paths, the one having the smallest metric, so as to thus reconstruct the path of the grid actually described during the coding and retrieve the sequence of data bits which caused this path to be travelled. …??According to the invention, the circuit comprises a memory (20) storing a plurality of the said words (D') with N = 2 nu bits, and, at the output of this memory, a cascaded layout of nu groups of 2-into-1 multiplexers (21, 22, 23, 24, 25, 26) progressively reducing the 2 nu outputs of the memory to a single output, one D flip-flop (31, 32, 33, 34, 35, 36) being arranged at the output of each multiplexer. …??The single, final flip-flop furthest downstream (36) sequentially delivers the data bits (S(t-6)) corresponding to the path sought and the selection signal of each multiplexer is given directly by the output from this final flip-flop. …IMAGE…