## Pulse shaping for zero ISI: Nyquist channel filtering (cont)

#### By sampling the symbol stream at the precise point where the ISI goes through zero, it can be seen that the energy spreading from adjacent symbols does not affect the value of the present symbol at that sampling point. It is also evident that the sample timing must be very accurate to minimize the ISI problem. One of the major challenges in modem design, particularly in noisy or high distortion links, is the recovery of accurate symbol timing information. Inaccuracy in symbol timing is usually referred to as timing jitter. |