A Robust Detection Algorithm for the Multi-Path Channel

In contrast to the conventional Viterbi algorithm (VA) which generates hard-outputs, an optimum soft-output Viterbi algorithm (SOVA) is derived under the constraint of fixed decision delay for detection of digital signals in the presence of intersymbol interference and additive white Gaussian noise. The SOVA, a new type of the conventional symbol-by-symbol maximum a posteriori probability algorithm, requires only a backward recursion and the number of variables to be stored. From computer simulations for an application example, a significant soft-decision gain can be obtained. Simplified variants with a complexity comparable to a conventional ML decoder are presented which perform almost as good as the optimum.