Author Van de Vegte, Joyce.
Title Fundamentals of digital signal processing / Joyce Van de Vegte.
Publisher Upper Saddle River, NJ : Prentice Hall, c2002.
unit impulse ( delta[n] ) and unit step functions ( u[n] )--we can use unit impulse signals ( delta[n] ) as basic building blocks for the construction and representation of other signals.
The discrete-time unit impulse ( delta[n] ) is the first difference of the discrete-time step :
delta[n] = u[n] - u[n-1]