What is linear and non-linear equalizer?

88. What is linear and non-linear equalizer?

Linear equalizer:

the current and past values of the received signal are linearly weighted by the filter coefficients and summed to produce the output. No feedback path is used. Simple and easy to implement. Not suitable for severely distorted channel. Noise power signal is enhanced.

Nonlinear equalizer:

If the past decisions are correct, then the ISI contributed by present symbol can be cancelled exactly, feedback path is used. Suitable for severely distorted channel. Noise power signal is not enhanced. Complex in structure. channels with low SNR. Suffers from error propagation.