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Unformatted text preview: previously decided symbols (output from the decision device) provided
that we have made correct decisions on them. This approach is called decision feedback equalization.
With decision feedback, we can think of the equalizer to contain two parts — a feedforward part and a ½ ½ ½ ½ ½ ¡ ½ ½
6 Assuming all the required invertibilities, ´
Of course, we need to have knowledge of Þ ´µ µ · to be able to do so. 4.17 . Wong & Lok: Theory of Digital Communications 4. ISI & Equalization feedback part. Suppose that the feedforward ﬁlter is of order Ä½ · ½ and the feedback ﬁlter is of order Ä¾ . Then ¼ Á Ä½ · Á Ä¾ ½ Á (4.46) where Á are the decided symbols. Again, the ﬁlter coefﬁcients can be found by minimizing the MSE. In general, signiﬁcant improvement over linear equalizers can be obtained with the decision
Consider a DFE with a feedforward ﬁlter of order Ä½ ·½ and a feedback ﬁlter of order Ä¾ . Assume
perfect decision feed...
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- Spring '08