OPTIMAL SEQUENCE ESTIMATION FOR CONVOLUTIONALLY CODED SIGNALS WITH BINARY DIGITAL MODULATION IN ISI CHANNELS

Decoding convolutional codes with binary digital modulation in intersy mbol interference (ISI) channels is studied. The receiver structure is a whitened matched filter (WMF) whose transfer function is determined by the ISI channel. Decoding of the output sequence can be performed in two steps or one step. The two-step decoding first decodes the ISI corrupted coded sequence back to the ISI free coded sequence which is then decoded back to the ur?coded message sequence. For one-step decod ing, the entire encoder-channel-receiver system is modeled as a new en coder with combined memory length of the memory lengths of the origina l encoder and the channel, and followed by a weighted summation mappin g from the binary symbols to real number symbols. The weighting coeffi cients are determined by the channel characteristic. In both two-step and one-step decoding, the Viterbi algorithm (VA) is used to perform t he maximum likelihood decoding. Decoding error probability and complex ity of both methods are analyzed, simulated and compared.