Pulse or digital communications – Equalizers – Automatic
Patent
1996-10-29
1998-04-21
Chin, Stephen
Pulse or digital communications
Equalizers
Automatic
375348, 375350, 3647242, H03H 730
Patent
active
057426422
ABSTRACT:
A decision feedback equalizer (DFE) is controlled co equalize a current signal sample for intersymbol interference and/or other distortion caused by the communications channel. An incorrect symbol decision by the DFE is detected and corrected to prevent propagation of the error with possible adverse effects on subsequent DFE decisions. More specifically, an error threshold is determined based on an expected bit error rate and a first postcursor value h.sub.1 of the communications channel impulse response. The decision feedback equalizer determines an intersymbol interference (ISI) component in a first, current sample of the signal being processed. The ISI component is subtracted from the current sample to generate an equalized sample. A corresponding symbol value is detected using that equalized sample. A symbol error is calculated by subtracting the equalized sample from the detected symbol value. The symbol error is compared with the error threshold. If the magnitude of the symbol error is less than the equalizer error threshold, the probability of a symbol decision error is low, and no preventive or corrective action is taken. However, if the magnitude of the symbol error is greater than the error threshold, a temporary symbol value is generated in place of the detected symbol value. The next, second sample is received and its corresponding symbol value is detected using this temporary symbol value. The second symbol error resulting from the use of the temporary symbol value is then determined. Using that second symbol error, a corrected, final symbol value is determined for the first sample that ensures symbol decision errors are not propagated through the DFE.
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Chin Stephen
Deppe Betsy L.
Telefonaktiebolaget LM Ericsson
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