We can see the wavelet transform (WT) as a decomposition of a signal
f(
x) onto a set of basis functions called wavelets to obtain a series expansion of the signal. So far there are two kinds of WT, the first-generation wavelets (
Mallat, 1989;
Rioul and Vetterli, 1991;
Unser and Blu, 2003) and the second-generation wavelets (
Sweldens, 1998). In the first-generation wavelets, the basis functions are obtained from a single mother wavelet by dilations and translations. Then, the signal
f(