Intersymbol Interference Currently I have generated a ISDN 2B1Q signal and added a random signal to it,then I have designed a lowpass butterworth filter to remove the noise as much possible in MATLAB.


My next task is to add Intersymbol Interference to this 2B1Q signal and implement DFE using LMS algortihm to reduce this ISI.Can anybody help me as to how I can add ISI to this signal in MATLAB?
You can simulate an ISI (inter symbol interference) effect, by passing the message signal pulses through a dispersive communication channel model filter.

The dispersive channel will spread the pulses and make them overlap, hence creating ISI.

You can simulate a dispersive channel via nonlinear phase filtering or multi path effects.