1. A method for performing a frequency-domain transform on a time-domain signal having a sequence length N, wherein the method is executed by a processor, the method comprising decomposing the time-domain signal to a plurality of decomposed signals, wherein each of the plurality of decomposed signals includes a sequence length less than N; performing a transform on the plurality of decomposed signals to obtain a transformed signal; composing the plurality of transformed signals to obtain a composed signal, including a substep of scaling at least one of the transformed signals.