By carefully manipulating the filtering characteristics of the channel
(and any TX or RX processing), it is possible to control the intersymbol interference such
that it does not degrade the bit
error rate performance of the link. This is achieved by making sure that the overall
channel filter transfer function has what is termed a Nyquist
frequency response.
A Nyquist channel response is characterized by the transfer function having a transition band between passband and stopband that is symmetrical about a
frequency equal to 0.5 x 1/Ts.
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