Digital convolution plays an important role in digital filtering. As we verified in the last section,
a linear time-invariant system can be represented using a digital convolution sum. Given a linear timeinvariant system, we can determine its unit-impulse response hðnÞ, which relates the system input and
output. To find the output sequence yðnÞ for any input sequence xðnÞ, we write the digital convolution
shown in Equation (3.15) as