Today, in my lecture on intersymbol interference (ISI), there was a discussion on postcursor ISI, and precursor ISI. Postcursor ISI is caused by the past bits, whereas, precursor ISI is caused by the future bits on the present bit. I could not understand how precursor ISI can occur. I was told that it is because of the delay of the channel. What does it mean? Isn't there a causality violation? What am I missing?
Can someone please explain? Thanks.