Pulse or digital communications – Equalizers – Automatic
Patent
1997-04-08
1999-07-27
Chan, Jason
Pulse or digital communications
Equalizers
Automatic
H03H 730, H03H 740, H03K 5159
Patent
active
059302968
ABSTRACT:
Disclosed are bidirectional equalizer arrangements in which the outputs of the forward and reverse equalizers are combined using low complexity processing to yield a single output sequence. In each disclosed arrangement of the invention, the low complexity processing utilizes the equalizer error outputs of the forward and reverse equalizers, which are then zero-delay lowpass filtered to provide relative reliability estimates. In one arrangement of the invention, these reliability estimates are used to select, on a symbol-by-symbol basis, either the forward or the reverse equalizer output. In another arrangement of the invention, a single linear lowpass filter is used to filter the difference of the equalizer error signals. In another arrangement of the invention, the relative reliability estimates are used to form a weighted average of the forward and reverse equalizer pre-decision signals. This weighted-average complex-valued signal then acts as a new equalized signal, and is fed to a constellation decision device to form a symbol decision. The arrangements of the invention can provide the majority of the gain offered by schemes that optimally (in a maximum-likelihood sense) consider all possible sequences formed from the bidirectional equalizers, while avoiding the optimal scheme's complexity which exhibits an exponential dependence on the duration of the channel impulse response.
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Chan Jason
Corrielus Jean B
Glenayre Electronics, Inc.
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