Making MLSD decisions by thresholding the matched filter output

This paper presents an iterative detector that, by thresholding the output of the matched filter, gives maximum-likelihood sequence detector (MLSD) de cisions on binary, antipodally modulated symbols that have been corrupted b y intersymbol interference and additive Gaussian noise. The detector will m ake decisions on some, but often not all, of the symbols in a transmitted s equence, and those decisions will be the same decisions as the MLSD would h ave made. The number of symbols that are detected is stochastic, varying fr om sequence to sequence. The basis of the detector is a bound on a crosster m of the quadratic form in the log-likelihood function for the transmitted sequence. The detector is simple in structure, consisting of a matched filt er and two variable threshold values for each symbol.