Pulse or digital communications – Equalizers – Automatic
Patent
1994-10-13
1996-04-30
Chin, Stephen
Pulse or digital communications
Equalizers
Automatic
3647242, 375231, H04L 2701
Patent
active
055132162
ABSTRACT:
A hybrid type of decision feedback equalizer (DFE) structure that approaches optimal DFE performance is described. The hybrid DFE includes both an intersymbol interference DFE (ISI-DFE) and a noise predictive DFE (NP-DFE). The hybrid DFE structure is designed so that one form of tap values dominates over the other. This allows only the dominate tap values to be used by the transmitter during precoding and reduces the transmitter complexity. In particular, a hybrid DFE is designed so that the I(z) coefficient values dominate over the N(z) coefficient values, where the notation I(z) and N(z), as known in the art, represent the resulting coefficient values after adaptation of the ISI-DFE and the NP-DFE, respectively. A respective Tomlinson precoding scheme in the transmitter uses only the I(z) values. Since only the I(z) values are used in the precoder of the transmitter, the NP-DFE of the receiver is kept active during the communications phase. Conveniently, the continued use of the NP-DFE in the receiver allows the receiver to track small changes in the channel.
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IEEE, "Approximate maximum likelihood sequence estimators for time dispersive channels", N. A. Zervos, et al., 1983 International Electrical, Electronics Conference Proceedings, pp. 62-5, vol. 1; Publication Date: 1983.
ISCAS, "Design and Performance of an All-Digital Adaptive 2.048 MBIT/S Data Transmission System Using Noise Prediction", Graf et al., ISCAS 1989, pp. 1808-1812.
Gadot Shlomo
Im Gi-Hong
Langberg Ehud
Wang Jin-Der
AT&T Corp.
Chin Stephen
Gluck Jeffrey W.
Opalach Joseph J.
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